title: John Paul Jones

text: After making the necessary preparations, Jones sailed for France on November 1, 1777, with orders to assist the American cause however possible. The American commissioners in France were Benjamin Franklin, Silas Deane, and Arthur Lee, and they listened to Jones's strategic recommendations. They promised him the command of , a new vessel being constructed for America by the Netherlands in Amsterdam. Britain, however, was able to divert "L'Indien" away from American hands by exerting pressure to ensure its sale to France instead (which had not yet allied with America). Jones was again left without a command, an unpleasant reminder of his stagnation in Boston from late 1776 until early 1777. It is thought that during this time Jones developed his close friendship with Franklin, whom he greatly admired.


title: John Paul Jones

text: On February 6, 1778, France signed the Treaty of Alliance with America, formally recognizing the independence of the new American republic. Eight days later, Captain Jones's "Ranger" became the first American naval vessel to be formally saluted by the French, with a nine-gun salute fired from Captain Lamotte-Piquet's flagship. Jones wrote of the event: "I accepted his offer all the more for after all it was a recognition of our independence and in the nation". On April 10, Jones set sail from Brest, France, for the western coasts of Great Britain.


title: John Paul Jones

text: Jones had some early successes against British merchant shipping in the Irish Sea. He persuaded his crew on April 17, 1778, to participate in an assault on Whitehaven, the town where his maritime career had begun. Jones later wrote about the poor command qualities of his senior officers (having tactfully avoided such matters in his official report): "'Their object', they said, 'was gain not honor'. They were poor: instead of encouraging the morale of the crew, they excited them to disobedience; they persuaded them that they had the right to judge whether a measure that was proposed to them was good or bad". As it happened, contrary winds forced them to abandon the attempt and drive "Ranger" towards Ireland, causing more trouble for British shipping on the way.


title: John Paul Jones

text: On April 20, Jones learned from captured sailors that the Royal Navy sloop of war was anchored off Carrickfergus, Ireland. According to the diary of "Ranger"s surgeon, Jones's first intention was to attack the vessel in broad daylight, but his sailors were "unwilling to undertake it" (another incident omitted from the official report). Therefore, the attack took place just after midnight, but the mate responsible for dropping the anchor to halt "Ranger" right alongside "Drake" misjudged the timing in the dark (Jones claimed in his memoirs that the man was drunk), so Jones had to cut his anchor cable and run. The wind shifted, and "Ranger" recrossed the Irish Sea to make another attempt at raiding Whitehaven.


title: John Paul Jones

text: Jones led the assault with two boats of fifteen men just after midnight on April 23, hoping to set fire to and sink all of the ships anchored in Whitehaven's harbour, which numbered between 200 and 400 wooden vessels and consisted of a full merchant fleet and many coal transporters. They also hoped to terrorize the townspeople by lighting further fires. As it happened, the journey to shore was slowed by the shifting wind, as well as a strong ebb tide. They successfully spiked the town's big defensive guns to prevent them being fired, but lighting fires proved difficult, as the lanterns in both boats had run out of fuel. To remedy this, some of the party were sent to raid a public house on the quayside, but the temptation to stop for a quick drink led to a further delay. Dawn was breaking by the time they returned and began the arson attacks, so efforts were concentrated on the coal ship "Thompson" in the hope that the flames would spread to adjacent vessels, all grounded by the low tide. However, in the twilight, one of the crew slipped away and alerted residents on a harbourside street. A fire alert was sounded, and large numbers of people came running to the quay, forcing the Americans to retreat and extinguishing the flames with the town's two fire-engines. The townspeople's hopes of sinking Jones's boats with cannon fire were dashed because of the prudent spiking.


title: John Paul Jones

text: Jones next crossed the Solway Firth from Whitehaven to Scotland, hoping to hold for ransom Dunbar Douglas, 4th Earl of Selkirk, who lived on St Mary's Isle near Kirkcudbright. The earl, Jones reasoned, could be exchanged for American sailors impressed into the Royal Navy. The earl was discovered to be absent from his estate, so his wife entertained the officers and conducted negotiations. Canadian historian Peter C. Newman gives credit to the governess for protecting the young heir to the Earldom of Selkirk, Thomas Douglas, and to the butler for filling a sack half with coal and topping it up with the family silver, in order to fob off the Americans. Jones claimed that he intended to return directly to his ship and continue seeking prizes elsewhere, but his crew wished to "pillage, burn, and plunder all they could". Ultimately, Jones allowed the crew to seize a silver plate set adorned with the family's emblem to placate their desires, but nothing else. Jones bought the plate when it was later sold off in France, and he returned it to the Earl of Selkirk after the war.


title: John Paul Jones

text: The attacks on St Mary's Isle and Whitehaven resulted in no prizes or profits which would be shared with the crew under normal circumstances. Throughout the mission, the crew acted as if they were aboard a privateer, not a warship, led by Lieutenant Thomas Simpson, Jones's second-in-command.


title: John Paul Jones

text: Jones led "Ranger" back across the Irish Sea, hoping to make another attempt at "Drake", still anchored off Carrickfergus. Late in the afternoon of April 24, the ships, roughly equal in firepower, engaged in combat. Earlier in the day, the Americans had captured the crew of a reconnaissance boat and learned that "Drake" had taken on dozens of soldiers with the intention of grappling and boarding "Ranger", so Jones made sure that did not happen, capturing "Drake" after an hour-long gun battle in which British captain George Burdon was killed. Lieutenant Simpson was given command of "Drake" for the return journey to Brest. The ships separated during the return journey as "Ranger" chased another prize, leading to a conflict between Simpson and Jones. Both ships arrived at port safely, but Jones filed for a court-martial of Simpson, keeping him detained on the ship.


title: John Paul Jones

text: Partly through the influence of John Adams, who was still serving as a commissioner in France, Simpson was released from Jones's accusation. Adams implies in his memoirs that the overwhelming majority of the evidence supported Simpson's claims. Adams seemed to believe Jones was hoping to monopolize the mission's glory, especially by detaining Simpson on board while he celebrated the capture with numerous important European dignitaries. Even with the wealth of perspectives, including the commander's, it is difficult to determine what occurred. It is clear, however, that the crew felt alienated by their commander, who might well have been motivated by his pride. Jones believed his intentions were honorable and his actions were strategically essential to the Revolution. Regardless of any controversy surrounding the mission, "Ranger"s capture of "Drake" was one of the Continental Navy's few significant military victories during the Revolution. "Ranger"s victory became an important symbol of the American spirit and served as an inspiration for the permanent establishment of the United States Navy after the revolution.


title: John Paul Jones

text: In 1779, Captain Jones took command of the 42-gun , a merchant ship rebuilt and given to America by the French shipping magnate, Jacques-Donatien Le Ray. On August 14, as a vast French and Spanish invasion fleet approached England, he provided a diversion by heading for Ireland at the head of a five-ship squadron including the 36-gun , 32-gun USS "Pallas", 12-gun , and "Le Cerf", also accompanied by two privateers, and "Granville". When the squadron was only a few days out of Groix, "Monsieur" separated because of a disagreement between her captain and Jones. Several Royal Navy warships were sent towards Ireland in pursuit of Jones, but on this occasion, he continued right around the north of Scotland into the North Sea. Jones's main problems, as on his previous voyage, resulted from insubordination, particularly by Pierre Landais, captain of "Alliance". On September 23, the squadron met a large merchant convoy off the coast of Flamborough Head, East Yorkshire. The 44-gun British frigate and the 22-gun hired armed ship placed themselves between the convoy and Jones's squadron, allowing the merchants to escape.


title: John Paul Jones

text: Shortly after 7 p.m. the Battle of Flamborough Head began. "Serapis" engaged "Bonhomme Richard", and "Alliance" fired from a considerable distance at "Countess". Quickly recognizing that he could not win a battle of big guns, and with the wind dying, Jones made every effort to lock "Richard" and "Serapis" together (his famous, albeit apocryphal, quotation "I have not yet begun to fight!" was said to have been uttered in reply to a demand to surrender in this phase of the battle). After about an hour, he succeeded, and he began clearing the British decks with his deck guns and his Marine marksmen in the rigging . "Alliance" sailed past and fired a broadside, doing at least as much damage to "Richard" as to "Serapis". Meanwhile, "Countess of Scarborough" had enticed "Pallas" downwind of the main battle, beginning a separate engagement. When "Alliance" approached this contest, about an hour after it had begun, the badly damaged "Countess" surrendered.


title: John Paul Jones

text: With "Bonhomme Richard" burning and sinking, it seems that her ensign was shot away; when one of the officers shouted a surrender, believing his captain to be dead, the British commander asked, seriously this time, if they had struck their colours. Jones later remembered saying something like "I am determined to make you strike", but the words allegedly heard by crew-members and reported in newspapers a few days later were more like: "I may sink, but I'll be damned if I strike". An attempt by the British to board "Bonhomme Richard" was thwarted, and a grenade caused the explosion of a large quantity of gunpowder on "Serapis" lower gun-deck. "Alliance" returned to the main battle, firing two broadsides. Again, these did at least as much damage to "Richard" as to "Serapis", but the tactic worked to the extent that "Serapis" was unable to move. With "Alliance" keeping well out of the line of his own great guns, Captain Pearson of "Serapis" accepted that prolonging the battle could achieve nothing, so he surrendered. Most of "Bonhomme Richard"s crew transferred to other vessels, and after a day and a half of frantic repair efforts, it was decided that the ship could not be saved. "Bonhomme Richard" was allowed to sink, and Jones took command of "Serapis" for the trip to the island of Texel in neutral (but American-sympathizing) Holland.


title: John Paul Jones

text: In the following year, King Louis XVI of France honoured Jones with the title "chevalier". Jones accepted the honour and desired the title to be used thereafter: when the Continental Congress in 1787 resolved that a medal of gold be struck in commemoration of his "valour and brilliant services" it was to be presented to "Chevalier John Paul Jones". He also received from Louis XVI a decoration of "l'Institution du Mérite Militaire" and a sword. By contrast, in Britain at this time, he was usually denigrated as a pirate.


title: John Paul Jones

text: Jones was also admitted as an original member of The Society of the Cincinnati in the state of Pennsylvania when it was established in 1783.


title: John Paul Jones

text: In June 1782, Jones was appointed to command the 74-gun , but his command fell through when Congress decided to give "America" to the French as replacement for the wrecked "Le Magnifique". As a result, he was given assignment in Europe in 1783 to collect prize money due his former hands. At length, this too expired and Jones was left without prospects for active employment, leading him on April 23, 1787, to enter into the service of the Empress Catherine II of Russia, who placed great confidence in Jones, saying: "He will get to Constantinople". He was granted name as a French subject Павел де Жонес ("Pavel de Zhones", Paul de Jones).


title: John Paul Jones

text: Jones avowed his intention, however, to preserve the condition of an American citizen and officer. As a rear admiral aboard the 24-gun flagship "Vladimir", he took part in the naval campaign in the Dnieper-Bug Liman (an arm of the Black Sea, into which flow the Southern Bug and Dnieper rivers) against the Turks, in concert with the Dnieper Flotilla commanded by Prince Charles of Nassau-Siegen. Jones (and Nassau-Siegen) repulsed the Ottoman forces from the area, but the jealous intrigues of Nassau-Siegen (and perhaps Jones's own ineptitude for Imperial politics) turned the Russian commander Prince Grigory Potemkin against Jones.


title: John Paul Jones

text: Jones was recalled to St. Petersburg for the claimed purpose of transfer to a command in the North Sea. Other factors may have included the theoretical resentment of rival officers, some of whom were several ex-British naval officers also in Russian employment, who regarded Jones as a renegade and refused to speak to him.


title: John Paul Jones

text: In April 1789, Jones was accused of raping a 10-year-old girl named Katerina Stepanova. She testified to the police that she had been summoned to his apartment to sell him butter, when he punched her in the face, gagged her with a white handkerchief, and vaginally penetrated her; a regimental surgeon and a midwife both examined her and found evidence to substantiate these physical and sexual assaults. There had been a delay on one day in reporting the rape, which meant the case would ordinarily not continue, due to Russian statutory codes considering any such delay evidence of consent, but Catherine intervened directly to allow the legal proceedings to continue.


title: John Paul Jones

text: Jones responded to the allegations by claiming that he had paid the girl for sex several times, denying that he had deprived her of her virginity, and suggesting she was older than 10. However, Jones would later change his story and claim the accusation was entirely false, stemming from the supposed desire of Katerina's mother, Sophia Fyodorovna, to gain financially from a prominent man. He involved the Count de Segur, the French representative at the Russian court (and also Jones's last friend in the capital), who investigated the accusation and suggested to Potemkin that it was false, and that Jones was the victim of a plot by Prince Charles for his own purposes. Jones went on to gather evidence, producing Katerina's father, Stephan Holtszwarthen, to testify in court that his daughter was 12 and that his wife had left him for another man, lived in a brothel, and was herself promiscuous.


title: John Paul Jones

text: The international pressure applied by American and French connections via the Count de Segur exerted a softening influence on Catherine. She granted him two years leave abroad, a de facto exile. According to Jacob Bell:


title: John Paul Jones

text: On June 8, 1788, Jones was awarded the Order of St. Anne, but he left the following month, an embittered man. In 1789 Jones arrived in Warsaw, Poland, where he befriended Tadeusz Kościuszko, a veteran of the American Revolutionary War. Kościuszko advised him to leave the service of the autocratic Russia and serve another power, suggesting Sweden. Despite Kościuszko's backing, the Swedes, while somewhat interested, in the end decided not to recruit Jones. Catherine, who retained a personal enmity for Jones, had blocked his appointment to not just the Swedish navy, but the Danish navy also.


title: John Paul Jones

text: In May 1790, Jones arrived in Paris. He still retained his position as Russian rear admiral, with a corresponding pension which allowed him to remain in retirement until his death two years later. During this time he made several attempts to re-enter the service in the Russian navy. However, Catherine did not respond to his letters, explaining to their go-between Baron von Grimm that Jones' service record was not exceptional and that Russian seamen refused to serve under him, because he had raped a girl.


title: John Paul Jones

text: By this time, his memoirs had been published in Edinburgh. Inspired by them, James Fenimore Cooper and Alexandre Dumas later wrote their own adventure novels: Cooper's 1824 novel "" contains fictionalised accounts of Jones's maritime activities, and Dumas' "Captain Paul" is a follow-up novel to "The Pilot", published in 1846. According to Walter Herrick:


title: John Paul Jones

text: In June 1792, Jones was appointed U.S. Consul to treat with the Dey of Algiers for the release of American captives. Before Jones was able to fulfill his appointment, he was found dead lying face-down on his bed in his third-floor Paris apartment, No. 19 Rue de Tournon, on July 18, 1792. He was 45 years old. The cause of death was interstitial nephritis. A small procession of servants, friends and loyal family walked his body for burial. He was buried in Paris at the Saint Louis Cemetery, which belonged to the French royal family. Four years later, France's revolutionary government sold the property, and the cemetery was forgotten.


title: John Paul Jones

text: In 1905, Jones' remains were identified by U.S. Ambassador to France General Horace Porter, who had searched for six years to track down the body using faulty copies of Jones's burial record. After Jones's death, Frenchman Pierrot Francois Simmoneau donated over 460 francs to mummify the body. It was preserved in alcohol and interred in a lead coffin "in the event that should the United States decide to claim his remains, they might more easily be identified." Porter knew what to look for in his search. With the aid of an old map of Paris, Porter's team, which included anthropologist Louis Capitan, identified the site of the former St. Louis Cemetery for Alien Protestants. Sounding probes were used to search for lead coffins, and five coffins were ultimately exhumed. The third, unearthed on April 7, 1905, was later identified by a post-mortem examination by Doctors Capitan and Georges Papillault as being that of Jones. The autopsy confirmed the original listing of cause of death. The face was later compared to a bust by Jean-Antoine Houdon.


title: John Paul Jones

text: Jones's body was brought to the United States aboard the , escorted by three other cruisers. On approaching the American coastline, seven U.S. Navy battleships joined the procession escorting Jones's body back to America. On April 24, 1906, Jones's coffin was installed in Bancroft Hall at the United States Naval Academy, Annapolis, Maryland, following a ceremony in Dahlgren Hall, presided by President Theodore Roosevelt who gave a speech paying tribute to Jones and holding him up as an example to the officers of the Navy. On January 26, 1913, the captain's remains were finally re-interred in a bronze and marble sarcophagus at the Naval Academy Chapel in Annapolis.


title: John Paul Jones

text: Jones was given an honorary pardon in 1999 by the port of Whitehaven for his raid on the town, in the presence of Lieutenant Steve Lyons representing the U.S. Naval Attaché to the UK, and Yuri Fokine the Russian Ambassador to the UK. The U.S. Navy was also awarded the Freedom of the Port of Whitehaven, the only time the honour has been granted in its 400-year history. The pardon and freedom were arranged by Gerard Richardson as part of the launch of the series of Maritime Festival. Richardson's of Whitehaven, a wine and coffee merchant in the town, is now the honorary consulate to the U.S. Navy for the Town and Port of Whitehaven. The consul is Rear Admiral (retired) U.S. Navy Steve Morgan, and the deputy consul is Rob Romano.


title: RGB color model

text: The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.


title: RGB color model

text: The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB color model already had a solid theory behind it, based in human perception of colors.


title: RGB color model

text: RGB is a "device-dependent" color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual red, green, and blue levels vary from manufacturer to manufacturer, or even in the same device over time. Thus an RGB value does not define the same "color" across devices without some kind of color management.


title: RGB color model

text: Typical RGB input devices are color TV and video cameras, image scanners, and digital cameras. Typical RGB output devices are TV sets of various technologies (CRT, LCD, plasma, OLED, quantum dots, etc.), computer and mobile phone displays, video projectors, multicolor LED displays and large screens such as the Jumbotron. Color printers, on the other hand are not RGB devices, but subtractive color devices typically using the CMYK color model.


title: RGB color model

text: To form a color with RGB, three light beams (one red, one green, and one blue) must be superimposed (for example by emission from a black screen or by reflection from a white screen). Each of the three beams is called a "component" of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture.


title: RGB color model

text: The RGB color model is "additive" in the sense that the three light beams are added together, and their light spectra add, wavelength for wavelength, to make the final color's spectrum. This is essentially opposite to the subtractive color model, particularly the CMY color model, that applies to paints, inks, dyes, and other substances whose color depends on "reflecting" the light under which we see them. Because of properties, these three colors create white, this is in stark contrast to physical colors, such as dyes which create black when mixed.


title: RGB color model

text: Zero intensity for each component gives the darkest color (no light, considered the "black"), and full intensity of each gives a white; the "quality" of this white depends on the nature of the primary light sources, but if they are properly balanced, the result is a neutral white matching the system's white point. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, more or less saturated depending on the difference of the strongest and weakest of the intensities of the primary colors employed.


title: RGB color model

text: When one of the components has the strongest intensity, the color is a hue near this primary color (red-ish, green-ish, or blue-ish), and when two components have the same strongest intensity, then the color is a hue of a secondary color (a shade of cyan, magenta or yellow). A secondary color is formed by the sum of two primary colors of equal intensity: cyan is green+blue, magenta is blue+red, and yellow is red+green. Every secondary color is the complement of one primary color: cyan complements red, magenta complements green, and yellow complements blue. When all the primary colors are mixed in equal intensities, the result is white.


title: RGB color model

text: The RGB color model itself does not define what is meant by "red", "green", and "blue" colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green, and blue primaries are defined, the color model then becomes an absolute color space, such as sRGB or Adobe RGB; see RGB color space for more details.


title: RGB color model

text: The choice of primary colors is related to the physiology of the human eye; good primaries are stimuli that maximize the difference between the responses of the cone cells of the human retina to light of different wavelengths, and that thereby make a large color triangle.


title: RGB color model

text: The normal three kinds of light-sensitive photoreceptor cells in the human eye (cone cells) respond most to yellow (long wavelength or L), green (medium or M), and violet (short or S) light (peak wavelengths near 570 nm, 540 nm and 440 nm, respectively). The difference in the signals received from the three kinds allows the brain to differentiate a wide gamut of different colors, while being most sensitive (overall) to yellowish-green light and to differences between hues in the green-to-orange region.


title: RGB color model

text: As an example, suppose that light in the orange range of wavelengths (approximately 577 nm to 597 nm) enters the eye and strikes the retina. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more. The difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the orange appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously but to different degrees.


title: RGB color model

text: Use of the three primary colors is not sufficient to reproduce "all" colors; only colors within the color triangle defined by the chromaticities of the primaries can be reproduced by additive mixing of non-negative amounts of those colors of light.


title: RGB color model

text: The RGB color model is based on the Young–Helmholtz theory of trichromatic color vision, developed by Thomas Young and Hermann von Helmholtz in the early to mid-nineteenth century, and on James Clerk Maxwell's color triangle that elaborated that theory (circa 1860).


title: RGB color model

text: The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, and involved the process of combining three color-filtered separate takes. To reproduce the color photograph, three matching projections over a screen in a dark room were necessary.


title: RGB color model

text: The additive RGB model and variants such as orange–green–violet were also used in the Autochrome Lumière color plates and other screen-plate technologies such as the Joly color screen and the Paget process in the early twentieth century. Color photography by taking three separate plates was used by other pioneers, such as the Russian Sergey Prokudin-Gorsky in the period 1909 through 1915. Such methods lasted until about 1960 using the expensive and extremely complex tri-color carbro Autotype process.


title: RGB color model

text: When employed, the reproduction of prints from three-plate photos was done by dyes or pigments using the complementary CMY model, by simply using the negative plates of the filtered takes: reverse red gives the cyan plate, and so on.


title: RGB color model

text: Before the development of practical electronic TV, there were patents on mechanically scanned color systems as early as 1889 in Russia. The color TV pioneer John Logie Baird demonstrated the world's first RGB color transmission in 1928, and also the world's first color broadcast in 1938, in London. In his experiments, scanning and display were done mechanically by spinning colorized wheels.


title: RGB color model

text: The Columbia Broadcasting System (CBS) began an experimental RGB field-sequential color system in 1940. Images were scanned electrically, but the system still used a moving part: the transparent RGB color wheel rotating at above 1,200 rpm in synchronism with the vertical scan. The camera and the cathode-ray tube (CRT) were both monochromatic. Color was provided by color wheels in the camera and the receiver.


title: RGB color model

text: More recently, color wheels have been used in field-sequential projection TV receivers based on the Texas Instruments monochrome DLP imager.


title: RGB color model

text: The modern RGB shadow mask technology for color CRT displays was patented by Werner Flechsig in Germany in 1938.


title: RGB color model

text: Personal computers of the late 1970s and early 1980s, such as the Apple II and VIC-20, used composite video. The Commodore 64 and the Atari 8-bit family used S-Video derivatives. IBM introduced a 16-color scheme (four bits—one bit each for red, green, blue, and intensity) with the Color Graphics Adapter (CGA) for its IBM PC in 1981, later improved with the Enhanced Graphics Adapter (EGA) in 1984. The first manufacturer of a truecolor graphics card for PCs (the TARGA) was Truevision in 1987, but it was not until the arrival of the Video Graphics Array (VGA) in 1987 that RGB became popular, mainly due to the analog signals in the connection between the adapter and the monitor which allowed a very wide range of RGB colors. Actually, it had to wait a few more years because the original VGA cards were palette-driven just like EGA, although with more freedom than VGA, but because the VGA connectors were analog, later variants of VGA (made by various manufacturers under the informal name Super VGA) eventually added true-color. In 1992, magazines heavily advertised true-color Super VGA hardware.


title: RGB color model

text: One common application of the RGB color model is the display of colors on a cathode-ray tube (CRT), liquid-crystal display (LCD), plasma display, or organic light emitting diode (OLED) display such as a television, a computer's monitor, or a large scale screen. Each pixel on the screen is built by driving three small and very close but still separated RGB light sources. At common viewing distance, the separate sources are indistinguishable, which tricks the eye to see a given solid color. All the pixels together arranged in the rectangular screen surface conforms the color image.


title: RGB color model

text: During digital image processing each pixel can be represented in the computer memory or interface hardware (for example, a "graphics card") as binary values for the red, green, and blue color components. When properly managed, these values are converted into intensities or voltages via gamma correction to correct the inherent nonlinearity of some devices, such that the intended intensities are reproduced on the display.


title: RGB color model

text: The Quattron released by Sharp uses RGB color and adds yellow as a sub-pixel, supposedly allowing an increase in the number of available colors.


title: RGB color model

text: RGB is also the term referring to a type of component video signal used in the video electronics industry. It consists of three signals—red, green, and blue—carried on three separate cables/pins. RGB signal formats are often based on modified versions of the RS-170 and RS-343 standards for monochrome video. This type of video signal is widely used in Europe since it is the best quality signal that can be carried on the standard SCART connector. This signal is known as RGBS (4 BNC/RCA terminated cables exist as well), but it is directly compatible with RGBHV used for computer monitors (usually carried on 15-pin cables terminated with 15-pin D-sub or 5 BNC connectors), which carries separate horizontal and vertical sync signals.


title: RGB color model

text: Outside Europe, RGB is not very popular as a video signal format; S-Video takes that spot in most non-European regions. However, almost all computer monitors around the world use RGB.


title: RGB color model

text: A framebuffer is a digital device for computers which stores data in the so-called "video memory" (comprising an array of Video RAM or similar chips). This data goes either to three digital-to-analog converters (DACs) (for analog monitors), one per primary color or directly to digital monitors. Driven by software, the CPU (or other specialized chips) write the appropriate bytes into the video memory to define the image. Modern systems encode pixel color values by devoting eight bits to each of the R, G, and B components. RGB information can be either carried directly by the pixel bits themselves or provided by a separate color look-up table (CLUT) if indexed color graphic modes are used.


title: RGB color model

text: A CLUT is a specialized RAM that stores R, G, and B values that define specific colors. Each color has its own address (index)—consider it as a descriptive reference number that provides that specific color when the image needs it. The content of the CLUT is much like a palette of colors. Image data that uses indexed color specifies addresses within the CLUT to provide the required R, G, and B values for each specific pixel, one pixel at a time. Of course, before displaying, the CLUT has to be loaded with R, G, and B values that define the palette of colors required for each image to be rendered. Some video applications store such palettes in PAL files ("Age of Empires" game, for example, uses over half-a-dozen) and can combine CLUTs on screen.


title: RGB color model

text: This indirect scheme restricts the number of available colors in an image CLUT—typically 256-cubed (8 bits in three color channels with values of 0–255)—although each color in the RGB24 CLUT table has only 8 bits representing 256 codes for each of the R, G, and B primaries, making 16,777,216 possible colors. However, the advantage is that an indexed-color image file can be significantly smaller than it would be with only 8 bits per pixel for each primary.


title: RGB color model

text: Modern storage, however, is far less costly, greatly reducing the need to minimize image file size. By using an appropriate combination of red, green, and blue intensities, many colors can be displayed. Current typical display adapters use up to 24-bits of information for each pixel: 8-bit per component multiplied by three components (see the Numeric representations section below (24bits = 256, each primary value of 8 bits with values of 0–255). With this system, 16,777,216 (256 or 2) discrete combinations of R, G, and B values are allowed, providing millions of different (though not necessarily distinguishable) hue, saturation and lightness shades. Increased shading has been implemented in various ways, some formats such as .png and .tga files among others using a fourth greyscale color channel as a masking layer, often called RGB32.


title: RGB color model

text: For images with a modest range of brightnesses from the darkest to the lightest, eight bits per primary color provides good-quality images, but extreme images require more bits per primary color as well as the advanced display technology. For more information see High Dynamic Range (HDR) imaging.


title: RGB color model

text: In classic CRT devices, the brightness of a given point over the fluorescent screen due to the impact of accelerated electrons is not proportional to the voltages applied to the electron gun control grids, but to an expansive function of that voltage. The amount of this deviation is known as its gamma value (formula_1), the argument for a power law function, which closely describes this behavior. A linear response is given by a gamma value of 1.0, but actual CRT nonlinearities have a gamma value around 2.0 to 2.5.


title: RGB color model

text: Similarly, the intensity of the output on TV and computer display devices is not directly proportional to the R, G, and B applied electric signals (or file data values which drive them through digital-to-analog converters). On a typical standard 2.2-gamma CRT display, an input intensity RGB value of (0.5, 0.5, 0.5) only outputs about 22% of full brightness (1.0, 1.0, 1.0), instead of 50%. To obtain the correct response, a gamma correction is used in encoding the image data, and possibly further corrections as part of the color calibration process of the device. Gamma affects black-and-white TV as well as color. In standard color TV, broadcast signals are gamma corrected.


title: RGB color model

text: In color television and video cameras manufactured before the 1990s, the incoming light was separated by prisms and filters into the three RGB primary colors feeding each color into a separate video camera tube (or "pickup tube"). These tubes are a type of cathode-ray tube, not to be confused with that of CRT displays.


title: RGB color model

text: With the arrival of commercially viable charge-coupled device (CCD) technology in the 1980s, first, the pickup tubes were replaced with this kind of sensor. Later, higher scale integration electronics was applied (mainly by Sony), simplifying and even removing the intermediate optics, thereby reducing the size of home video cameras and eventually leading to the development of full camcorders. Current webcams and mobile phones with cameras are the most miniaturized commercial forms of such technology.


title: RGB color model

text: Photographic digital cameras that use a CMOS or CCD image sensor often operate with some variation of the RGB model. In a Bayer filter arrangement, green is given twice as many detectors as red and blue (ratio 1:2:1) in order to achieve higher luminance resolution than chrominance resolution. The sensor has a grid of red, green, and blue detectors arranged so that the first row is RGRGRGRG, the next is GBGBGBGB, and that sequence is repeated in subsequent rows. For every channel, missing pixels are obtained by interpolation in the demosaicing process to build up the complete image. Also, other processes used to be applied in order to map the camera RGB measurements into a standard RGB color space as sRGB.


title: RGB color model

text: In computing, an image scanner is a device that optically scans images (printed text, handwriting, or an object) and converts it to a digital image which is transferred to a computer. Among other formats, flat, drum and film scanners exist, and most of them support RGB color. They can be considered the successors of early telephotography input devices, which were able to send consecutive scan lines as analog amplitude modulation signals through standard telephonic lines to appropriate receivers; such systems were in use in press since the 1920s to the mid-1990s. Color telephotographs were sent as three separated RGB filtered images consecutively.


title: RGB color model

text: Currently available scanners typically use CCD or contact image sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. Early color film scanners used a halogen lamp and a three-color filter wheel, so three exposures were needed to scan a single color image. Due to heating problems, the worst of them being the potential destruction of the scanned film, this technology was later replaced by non-heating light sources such as color LEDs.


title: RGB color model

text: A color in the RGB color model is described by indicating how much of each of the red, green, and blue is included. The color is expressed as an RGB triplet ("r","g","b"), each component of which can vary from zero to a defined maximum value. If all the components are at zero the result is black; if all are at maximum, the result is the brightest representable white.


title: RGB color model

text: In many environments, the component values within the ranges are not managed as linear (that is, the numbers are nonlinearly related to the intensities that they represent), as in digital cameras and TV broadcasting and receiving due to gamma correction, for example. Linear and nonlinear transformations are often dealt with via digital image processing. Representations with only 8 bits per component are considered sufficient if gamma correction is used.


title: RGB color model

text: Following is the mathematical relationship between RGB space to HSI space (hue, saturation, and intensity: HSI color space):


title: RGB color model

text: The RGB color model is one of the most common ways to encode color in computing, and several different digital representations are in use. The main characteristic of all of them is the quantization of the possible values per component (technically a "sample" ) by using only integer numbers within some range, usually from 0 to some power of two minus one (2 − 1) to fit them into some bit groupings. Encodings of 1, 2, 4, 5, 8 and 16 bits per color are commonly found; the total number of bits used for an RGB color is typically called the color depth.


title: RGB color model

text: Since colors are usually defined by three components, not only in the RGB model, but also in other color models such as CIELAB and Y'UV, among others, then a three-dimensional volume is described by treating the component values as ordinary Cartesian coordinates in a Euclidean space. For the RGB model, this is represented by a cube using non-negative values within a 0–1 range, assigning black to the origin at the vertex (0, 0, 0), and with increasing intensity values running along the three axes up to white at the vertex (1, 1, 1), diagonally opposite black.


title: RGB color model

text: An RGB triplet ("r","g","b") represents the three-dimensional coordinate of the point of the given color within the cube or its faces or along its edges. This approach allows computations of the color similarity of two given RGB colors by simply calculating the distance between them: the shorter the distance, the higher the similarity. Out-of-gamut computations can also be performed this way.


title: RGB color model

text: Initially, the limited color depth of most video hardware led to a limited color palette of 216 RGB colors, defined by the Netscape Color Cube. The web-safe color palette consists of the 216 (6) combinations of red, green, and blue where each color can take one of six values (in hexadecimal): #00, #33, #66, #99, #CC or #FF (based on the 0 to 255 range for each value discussed above). These hexadecimal values = 0, 51, 102, 153, 204, 255 in decimal, which = 0%, 20%, 40%, 60%, 80%, 100% in terms of intensity. This seems fine for splitting up 216 colors into a cube of dimension 6. However, lacking gamma correction, the perceived intensity on a standard 2.5 gamma CRT / LCD is only: 0%, 2%, 10%, 28%, 57%, 100%. See the actual web safe color palette for a visual confirmation that the majority of the colors produced are very dark.


title: RGB color model

text: With the predominance of 24-bit displays, the use of the full 16.7 million colors of the HTML RGB color code no longer poses problems for most viewers. The sRGB color model (a "device-independent" color space) for HTML was formally adopted as an Internet standard in HTML 3.2, though it had been in use for some time before that. All images and colors are interpreted as being sRGB (unless another color space is specified) and all modern displays can display this color space (with color management being built in into browsers or operating systems).


title: RGB color model

text: where # equals the proportion of red, green, and blue respectively. This syntax can be used after such selectors as "background-color:" or (for text) "color:".


title: RGB color model

text: Proper reproduction of colors, especially in professional environments, requires color management of all the devices involved in the production process, many of them using RGB. Color management results in several transparent conversions between device-independent (sRGB, XYZ, L*a*b*) and device-dependent color spaces (RGB and others, as CMYK for color printing) during a typical production cycle, in order to ensure color consistency throughout the process. Along with the creative processing, such interventions on digital images can damage the color accuracy and image detail, especially where the gamut is reduced. Professional digital devices and software tools allow for 48 bpp (bits per pixel) images to be manipulated (16 bits per channel), to minimize any such damage.


title: RGB color model

text: ICC profile compliant applications, such as Adobe Photoshop, use either the Lab color space or the CIE 1931 color space as a "Profile Connection Space" when translating between color spaces.


title: RGB color model

text: All luminance–chrominance formats used in the different TV and video standards such as YIQ for NTSC, YUV for PAL, YDD for SECAM, and YPP for component video use color difference signals, by which RGB color images can be encoded for broadcasting/recording and later decoded into RGB again to display them. These intermediate formats were needed for compatibility with pre-existent black-and-white TV formats. Also, those color difference signals need lower data bandwidth compared to full RGB signals.


title: RGB color model

text: Similarly, current high-efficiency digital color image data compression schemes such as JPEG and MPEG store RGB color internally in YCC format, a digital luminance–chrominance format based on YPP. The use of YCC also allows computers to perform lossy subsampling with the chrominance channels (typically to 4:2:2 or 4:1:1 ratios), which reduces the resultant file size.


title: The Hershey Company

text: The Hershey Company, commonly known as Hershey's, is an American multinational company and one of the largest chocolate manufacturers in the world. It also manufactures baked products, such as cookies and cakes, and sells beverages like milkshakes, as well as other products. Its headquarters are in Hershey, Pennsylvania, United States, which is also home to Hersheypark and Hershey's Chocolate World. It was founded by Milton S. Hershey in 1894 as the Hershey Chocolate Company, which is a subsidiary of his Lancaster Caramel Company. The Hershey Trust Company owns a minority stake but retains a majority of the voting power within the company.


title: The Hershey Company

text: Hershey's chocolate is available across the United States, and in over 60 countries worldwide. It has three large distribution centers with modern labor management systems. In addition, Hershey is a member of the World Cocoa Foundation. It is also associated with the Hersheypark Stadium and the Giant Center.


title: The Hershey Company

text: After an apprenticeship to a confectioner in 1873, Milton S. Hershey opened a candy shop in Philadelphia, Pennsylvania. This shop was open for six years, after which Hershey apprenticed with another confectioner in Denver, where he learned to make caramel. After another failed business attempt in New York, Hershey returned to Pennsylvania, where he founded the Lancaster Caramel Company in 1886.


title: The Hershey Company

text: The use of fresh milk in caramels proved successful, and in 1900, after seeing chocolate-making machines for the first time at the 1893 World's Columbian Exposition in Chicago, Hershey sold his caramel company for $1,000,000 (equal to $ today), and concentrated on chocolate. To people who questioned him, he said, "Caramels are just a fad, but chocolate is a permanent thing."


title: The Hershey Company

text: In 1896, Hershey built a milk-processing plant so he could create and refine a recipe for his milk chocolate candies. In 1899, he developed the Hershey process, which is less sensitive to milk quality than traditional methods. In 1900, he began manufacturing Hershey's Milk Chocolate Bars, also known as Hershey's Bars or Hershey Bars.


title: The Hershey Company

text: In 1903, Hershey began construction of a chocolate plant in his hometown of Derry Church, Pennsylvania, later known as Hershey, Pennsylvania. The town was an inexpensive place for the workers and their families to live, though the factory was built without windows, so that employees would not be distracted. To increase employee morale, Hershey provided leisure activities and created what would later become Hersheypark. The milk chocolate bars from this plant proved popular, and the company grew rapidly.


title: The Hershey Company

text: In 1907, he introduced a new candy: bite-sized, flat-bottomed, conical pieces of chocolate that he named "Hershey's Kiss". At first, each was wrapped by hand in a square of aluminum foil. The introduction of machine wrapping in 1921 sped up the process and added a small paper ribbon to the top of the package, indicating that it was a genuine Hershey product. Today, over 70 million candies are produced daily.


title: The Hershey Company

text: Other products introduced included Mr. Goodbar (1925) (peanuts in milk chocolate), Hershey's Syrup (1926), semisweet chocolate chips (1928), and the Krackel bar with crisped rice (1938).


title: The Hershey Company

text: Harry Burnett Reese invented Reese's Peanut Butter Cups after founding the H.B. Reese Candy Company in 1923. Reese died on May 16, 1956, in West Palm Beach, Florida, leaving the company to his six sons. On July 2, 1963, the H.B. Reese Candy Company merged with the Hershey Chocolate Corporation in a tax-free stock-for-stock merger. In 1969, only six years after the Reese/Hershey merger, Reese's Peanut Butter Cups became The Hershey Company's top seller. As of September 20, 2012, Reese's was the best-selling candy brand in the United States, with sales of $2.603 billion, and the fourth-best-selling brand globally, with sales of $2.679 billion.


title: The Hershey Company

text: In 2022, after 59 years of stock splits, the original 666,316 shares of Hershey common stock received by the Reese family represented 16 million Hershey shares valued at more than $3.6 billion, paying annual cash dividends of $66.3 million.


title: The Hershey Company

text: Labor unrest came to Hershey in the late 1930s, as a Congress of Industrial Organizations-backed union attempted to organize the factory workers. A failed sit-down strike in 1937 ended in violence; loyalist workers and local dairy farmers beat many of the strikers as they attempted to leave the plant. By 1940, an affiliate of the American Federation of Labor had successfully organized Hershey's workers under the leadership of John Shearer, who became the first president of Local Chapter Number 464 of the Bakery, Confectionery, Tobacco Workers and Grain Millers' International Union. Local 464 still represents the Hershey workforce.


title: The Hershey Company

text: Shortly before World War II, Bruce Murrie, son of long-time Hershey's president William F.R. Murrie, struck a deal with Forrest Mars to create hard sugar-coated chocolate that would be called M&M's (for Mars and Murrie). Murrie had a 20% interest in the product, which used Hershey chocolate during World War II rationing. In 1948, Mars bought out Murrie and became one of Hershey's main competitors.


title: The Hershey Company

text: In 1969, Hershey received a license from Rowntree's to manufacture and market Kit Kat and Rolo in the United States. After Hershey's competitor Nestlé acquired Rowntree's in 1988, it was still required to honor the agreement, and so Hershey continues to make and market the products in the U.S. The license would revert to Nestlé if Hershey were sold. This became a sticking point in Hershey's failed attempt to attract a serious buyer in 2002, and even Nestlé rejected Hershey's asking price, feeling that the economics would not work.


title: The Hershey Company

text: In 1988, Hershey's acquired the rights to manufacture and distribute many Cadbury-branded products in the United States (except gum and mints, which are part of Mondelēz International). In 2015, they sued a British importer to halt imports of British Cadbury chocolate, which reportedly angered consumers. A merger between Mondelēz and Hershey's was considered but abandoned in 2016 after Hershey's turned down a $23 billion cash-and-stock bid.


title: The Hershey Company

text: In 1977, Hershey acquired Y&S Candies, founded in 1845, and became the makers of Twizzlers licorice candies.


title: The Hershey Company

text: In 1986, Hershey's made a brief foray into cough drops when it acquired the Luden's cough drops brand. By 2001, though, the brand had been sold to Pharmacia (now part of Pfizer), and Luden's eventually became a product of Prestige Brands. Hershey's kept Luden's 5th Avenue bar.


title: The Hershey Company

text: In 1996, Hershey purchased the American operations of the Leaf Candy Company from Huhtamäki. In 1999, the Hershey Pasta Group was divested to several equity partners to form the New World Pasta company (now part of Ebro Foods).


title: The Hershey Company

text: On July 25, 2002, it became known that the Hershey Trust Company was seeking to sell its controlling interest in the Hershey Foods Corporation. The value of Hershey stock rose 25% in a single day, with over 19 million shares traded. Over the following 55 days, widespread press coverage, as well as pressure from Pennsylvania Attorney General Mike Fisher, the community of Hershey, and Dauphin County Orphans' Court Senior Judge Warren G. Morgan, led to the sale being abandoned. The seven Hershey trustees who voted to sell Hershey Foods on September 17, 2002, for US$12.5 billion to the William Wrigley Jr. Company (now part of Mars Incorporated) were removed by Attorney General Fisher and Judge Morgan. Ten of the 17 trustees were forced to resign and four new members who lived locally were appointed. The former Pennsylvania Attorney General, LeRoy S. Zimmerman, became the new chairman of the reconstituted Milton Hershey School Trustees. Mr. Zimmerman has publicly committed to having the Milton Hershey School Trust always retain its interest in The Hershey Company.


title: The Hershey Company

text: In 2005, Krave Jerky was founded by Jon Sebastiani after he trained for a marathon and looked for a healthy source of energy. Alliance Consumer Growth, a private equity group, invested in Krave Jerky in 2012. Hershey's purchased the company in 2015 for $240 million. Hershey would later in 2020 sell Krave Jerky to Sonoma Brands, the food industry incubator founded by Sebastiani in 2016.


title: The Hershey Company

text: In July 2005, Hershey acquired the Berkeley, California-based boutique chocolate-maker Scharffen Berger. In November 2005, Hershey acquired Joseph Schmidt Confections, the San Francisco-based chocolatier, and in November 2006, Hershey acquired Dagoba Organic Chocolate, a boutique chocolate maker based in Ashland, Oregon.


title: The Hershey Company

text: In June 2006, Philadelphia city councilman Juan Ramos called for Hershey's to stop marketing "Ice Breakers Pacs", a kind of mint, due to the resemblance of its packaging to a kind that was used for illegal street drugs.


title: The Hershey Company

text: In September 2006, ABC News reported that several Hershey chocolate products were reformulated to replace cocoa butter with vegetable oil as an emulsifier. According to the company, this change was made to reduce the costs of producing the products instead of raising their prices or decreasing the sizes. Some consumers complained that the taste was different, but the company stated that in the company-sponsored blind taste tests, about half of consumers preferred the new versions. As the new versions no longer met the Food and Drug Administration's official definition of "milk chocolate", the changed items were relabeled from stating they were "milk chocolate" and "made with chocolate" to "chocolate candy" and "chocolatey."


title: The Hershey Company

text: In December 2011, Hershey reached an agreement to acquire Brookside Foods Ltd., a privately held confectionery company based in Abbotsford, British Columbia. In April 2015, the Hershey chocolate plant on East Chocolate Avenue in Hershey, Pennsylvania was demolished to make way for mixed-use development. In 2016, Hershey acquired barkTHINS, a New York-based chocolate snack foods company that expected to generate between $65 million and $75 million in revenue for that year, for $290 million.


title: The Hershey Company

text: An August 2016 attempt to sell Hershey to Mondelez International was abandoned because of objections by the Hershey Trust.


title: The Hershey Company

text: In 2017, Hershey acquired Amplify Snack Brands, Austin, Texas-based maker of SkinnyPop, in an all-cash transaction valued at approximately $1.6 billion. In September 2018, Hershey announced to buy Pirate Brands from B&G Foods for $420 million in an all-cash deal. In August 2019, Hershey announced it would purchase protein bar maker One Brands LLC for $397 million. In October 2019, Hershey announced a collaboration with Yuengling to produce a limited release collaboration beer titled Yuengling Hershey's Chocolate Porter, becoming Hershey's first licensed beer partnership. In June 2021, Hershey acquired Lily's for $425 million. In November 2021, Hershey announced plans to acquire Dot's Pretzels, and their co-packer, Pretzel INC for $1.2BN


title: The Hershey Company

text: Unable to have children of his own, Milton S. Hershey founded the Hershey Industrial School in 1909 for white orphaned boys. In 1918, three years after the death of his wife, Milton Hershey donated around $90 million to the boarding school in trust, as well as 40% of the Hershey Company's common stock. The school's initial purpose was to train young men in trades but eventually shifted to focus on preparation for college. The Hershey Trust Company has exercised voting rights for the school and has been a trustee since its founding.


title: The Hershey Company

text: Many of its designs resemble Hershey chocolate products, such as the Hershey Kisses street lights. Milton Hershey was involved in the school's operations until his death in 1945. The Hershey Industrial School was renamed the Milton Hershey School in 1951.


title: The Hershey Company

text: The first plant outside Hershey opened on June 15, 1963, in Smiths Falls, Ontario, and the third opened on May 22, 1965, in Oakdale, California. In February and April 2007, Hershey's announced that the Smiths Falls and Oakdale plants would close in 2008, being replaced in part by a new facility in Monterrey, Mexico. The Oakdale factory closed on February 1, 2008. Hershey chocolate factory in São Roque, Brazil, was opened in August 2002. Hershey's Asia operations were largely supplied by their plant in Mandideep, India.


title: The Hershey Company

text: Hershey also has plants in Stuarts Draft, Virginia; Lancaster, Pennsylvania; Hazleton, Pennsylvania; Memphis, Tennessee; Robinson, Illinois, and Guadalajara, Mexico.


title: The Hershey Company

text: Visitors to Hershey can experience Hershey's Chocolate World visitors center and its simulated tour ride. Public tours were once operated in the Pennsylvania and California factories, which ended in Pennsylvania in 1973 as soon as Hershey's Chocolate World opened, and later in California following the September 11, 2001, attacks, due to security concerns.


title: The Hershey Company

text: On September 18, 2012, Hershey opened a new and expanded West Hershey plant. The plant was completed at a budget of $300 million.


title: The Hershey Company

text: On March 9, 2018, Hershey broke ground to expand its Kit Kat manufacturing facility in Hazle Township, Pennsylvania. The expansion project has a $60 million budget and is expected to create an additional 111 jobs at the facility.


title: The Hershey Company

text: In October 2022, the company's Scope 1 and 2 emissions were "48% lower than they were in 2018". Scope 3 emissions had gone down 18%.These reductions were achieved by investments in three solar farms.


title: The Hershey Company

text: Hershey has made large contributions to education. One of their most notable contributions was the Elizabethtown College Honors Program. The program was established in 1999 and is funded partially through the endowment.


title: The Hershey Company

text: In 2015, Hershey announced a commitment to the Clinton Global Initiative to help build a sustainable supply chain to support basic nutrition for children in Ghana.


title: The Hershey Company

text: Hershey's long-term focus on children and families has yielded long-standing partnerships with organizations such as Children's Miracle Network, Ronald McDonald House, and United Way (UW). In 2016, the company donated more than $486,200 to those organizations.


title: The Hershey Company

text: Hershey has been criticized for not having programs to ensure sustainable and ethical cocoa purchases, lagging behind its competitors in fair trade measures.


title: The Hershey Company

text: The "Raise the Bar, Hershey!" campaign was launched in September 2010 by Global Exchange, Green America, the Oasis Trust, and the International Labor Rights Forum. The purpose of the Raise the Bar Campaign was to pressure Hershey to commit "to take immediate action to eliminate forced and child labor ... from Hershey's cocoa supply"; "to sourcing 100% Fair Trade Certified cocoa beans by 2012 for at least one of its top five selling chocolate bars ... making at least one additional top five selling bar 100% Fair Trade Certified every two years thereafter"; and that "the majority of Hershey's cocoa across all products will be Fair Trade Certified by 2022". The pressure was particularly directed at Whole Foods Market, which announced on October 3, 2012, that it would cease carrying Hershey's Scharffen Berger line. The Campaign stated, "Whole Foods' decision follows more than 40 natural food retailers and coops publicly expressing concern about carrying Scharffen Berger and Dagoba products as a consequence of the giant chocolate maker's refusal to address child labor in its supply chain". The same day, Hershey's announced it would "source 100 percent certified cocoa for its global chocolate product lines by 2020 and help to accelerate its programs to help eliminate child labor in the cocoa regions of West Africa".


title: The Hershey Company

text: In 2019, Hershey announced that they could not guarantee that their chocolate products were free from child slave labor, as they could trace only about 50% of their purchasing back to the farm level. According to The "Washington Post" noted that the commitment taken in 2001 to eradicate such practices within four years had not been kept, neither at the due deadline of 2005, nor within the revised deadlines of 2008 and 2010, and that the result was not likely to be achieved for 2020.


title: The Hershey Company

text: In 2021, Hershey was named in a class action lawsuit filed by eight former child slaves from Mali who alleged that the company aided and abetted their enslavement on cocoa plantations in Ivory Coast. The suit accused Hershey (along with Nestlé, Cargill, Mars, Incorporated, Olam International, Barry Callebaut, and Mondelez International) of knowingly engaging in forced labor, and the plaintiffs sought damages for unjust enrichment, negligent supervision, and intentional infliction of emotional distress.


title: Hippocampus

text: The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation. The hippocampus is located in the allocortex, with neural projections into the neocortex in humans, as well as primates. The hippocampus, as the medial pallium, is a structure found in all vertebrates. In humans, it contains two main interlocking parts: the hippocampus proper (also called "Ammon's horn"), and the dentate gyrus.


title: Hippocampus

text: In Alzheimer's disease (and other forms of dementia), the hippocampus is one of the first regions of the brain to suffer damage; short-term memory loss and disorientation are included among the early symptoms. Damage to the hippocampus can also result from oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy. People with extensive, bilateral hippocampal damage may experience anterograde amnesia: the inability to form and retain new memories.


title: Hippocampus

text: Since different neuronal cell types are neatly organized into layers in the hippocampus, it has frequently been used as a model system for studying neurophysiology. The form of neural plasticity known as long-term potentiation (LTP) was initially discovered to occur in the hippocampus and has often been studied in this structure. LTP is widely believed to be one of the main neural mechanisms by which memories are stored in the brain.


title: Hippocampus

text: In rodents as model organisms, the hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation. Many neurons in the rat and mouse hippocampus respond as place cells: that is, they fire bursts of action potentials when the animal passes through a specific part of its environment. Hippocampal place cells interact extensively with head direction cells, whose activity acts as an inertial compass, and conjecturally with grid cells in the neighboring entorhinal cortex.


title: Hippocampus

text: The earliest description of the ridge running along the floor of the temporal horn of the lateral ventricle comes from the Venetian anatomist Julius Caesar Aranzi (1587), who likened it first to a silkworm and then to a seahorse (Latin "hippocampus", from Greek ἱππόκαμπος, from ἵππος, 'horse' + κάμπος, 'sea monster'). The German anatomist Duvernoy (1729), the first to illustrate the structure, also wavered between "seahorse" and "silkworm". "Ram's horn" was proposed by the Danish anatomist Jacob Winsløw in 1732; and a decade later his fellow Parisian, the surgeon de Garengeot, used "cornu Ammonis" – horn of Amun, the ancient Egyptian god who was often represented as having a ram's head.


title: Hippocampus

text: Another reference appeared with the term "pes hippocampi", which may date back to Diemerbroeck in 1672, introducing a comparison with the shape of the folded back forelimbs and webbed feet of the mythological hippocampus, a sea monster with a horse's forequarters and a fish's tail. The hippocampus was then described as "pes hippocampi major", with an adjacent bulge in the occipital horn, described as the "pes hippocampi minor" and later renamed as the calcar avis. The renaming of the hippocampus as hippocampus major, and the calcar avis as hippocampus minor, has been attributed to Félix Vicq-d'Azyr systematizing nomenclature of parts of the brain in 1786. Mayer mistakenly used the term hippopotamus in 1779, and was followed by some other authors until Karl Friedrich Burdach resolved this error in 1829. In 1861 the hippocampus minor became the center of a dispute over human evolution between Thomas Henry Huxley and Richard Owen, satirized as the Great Hippocampus Question. The term hippocampus minor fell from use in anatomy textbooks and was officially removed in the Nomina Anatomica of 1895. Today, the structure is just called the hippocampus, with the term "cornu Ammonis" (that is, 'Ammon's horn') surviving in the names of the hippocampal subfields CA1-CA4.


title: Hippocampus

text: The term "limbic system" was introduced in 1952 by Paul MacLean to describe the set of structures that line the deep edge of the cortex (Latin "limbus" meaning "border"): These include the hippocampus, cingulate cortex, olfactory cortex, and amygdala. Paul MacLean later suggested that the limbic structures comprise the neural basis of emotion. The hippocampus is anatomically connected to parts of the brain that are involved with emotional behaviorthe septum, the hypothalamic mammillary body, and the anterior nuclear complex in the thalamus, and is generally accepted to be part of the limbic system.


title: Hippocampus

text: The hippocampus can be seen as a ridge of gray matter tissue, elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn. This ridge can also be seen as an inward fold of the archicortex into the medial temporal lobe. The hippocampus can only be seen in dissections as it is concealed by the parahippocampal gyrus. The cortex thins from six layers to the three or four layers that make up the hippocampus.


title: Hippocampus

text: The term hippocampal formation is used to refer to the hippocampus proper and its related parts. However, there is no consensus as to what parts are included. Sometimes the hippocampus is said to include the dentate gyrus and the subiculum. Some references include the dentate gyrus and the subiculum in the hippocampal formation, and others also include the presubiculum, parasubiculum, and entorhinal cortex. The neural layout and pathways within the hippocampal formation are very similar in all mammals.


title: Hippocampus

text: The hippocampus, including the dentate gyrus, has the shape of a curved tube, which has been compared to a seahorse, and to a horn of a ram, which after the ancient Egyptian god often portrayed as such takes the name "cornu Ammonis". Its abbreviation CA is used in naming the hippocampal subfields CA1, CA2, CA3, and CA4. It can be distinguished as an area where the cortex narrows into a single layer of densely packed pyramidal neurons, which curl into a tight U shape. One edge of the "U," – CA4, is embedded into the backward-facing, flexed dentate gyrus. The hippocampus is described as having an anterior and posterior part (in primates) or a ventral and dorsal part in other animals. Both parts are of similar composition but belong to different neural circuits. In the rat, the two hippocampi resemble a pair of bananas, joined at the stems by the commissure of fornix (also called the hippocampal commissure). In primates, the part of the hippocampus at the bottom, near the base of the temporal lobe, is much broader than the part at the top. This means that in cross-section the hippocampus can show a number of different shapes, depending on the angle and location of the cut.


title: Hippocampus

text: In a cross-section of the hippocampus, including the dentate gyrus, several layers will be shown. The dentate gyrus has three layers of cells (or four if the hilus is included). The layers are from the outer in – the "molecular layer", the "inner molecular layer", the "granular layer", and the "hilus". The CA3 in the hippocampus proper has the following cell layers known as strata: lacunosum-moleculare, radiatum, lucidum, pyramidal, and oriens. CA2 and CA1 also have these layers except the lucidum stratum.


title: Hippocampus

text: The input to the hippocampus (from varying cortical and subcortical structures) comes from the entorhinal cortex via the perforant path. The entorhinal cortex (EC) is strongly and reciprocally connected with many cortical and subcortical structures as well as with the brainstem. Different thalamic nuclei, (from the anterior and midline groups), the medial septal nucleus, the supramammillary nucleus of the hypothalamus, and the raphe nuclei and locus coeruleus of the brainstem all send axons to the EC, so that it serves as the interface between the neocortex and the other connections, and the hippocampus.


title: Hippocampus

text: The EC is located in the parahippocampal gyrus, a cortical region adjacent to the hippocampus. This gyrus conceals the hippocampus. The parahippocampal gyrus is adjacent to the perirhinal cortex, which plays an important role in the visual recognition of complex objects. There is also substantial evidence that it makes a contribution to memory, which can be distinguished from the contribution of the hippocampus. It is apparent that complete amnesia occurs only when both the hippocampus and the parahippocampus are damaged.


title: Hippocampus

text: The major input to the hippocampus is through the entorhinal cortex (EC), whereas its major output is via CA1 to the subiculum. Information reaches CA1 via two main pathways, direct and indirect. Axons from the EC that originate in layer III are the origin of the direct perforant pathway and form synapses on the very distal apical dendrites of CA1 neurons. Conversely, axons originating from layer II are the origin of the indirect pathway, and information reaches CA1 via the trisynaptic circuit. In the initial part of this pathway, the axons project through the perforant pathway to the granule cells of the dentate gyrus (first synapse). From then, the information follows via the mossy fibres to CA3 (second synapse). From there, CA3 axons called Schaffer collaterals leave the deep part of the cell body and loop up to the apical dendrites and then extend to CA1 (third synapse). Axons from CA1 then project back to the entorhinal cortex, completing the circuit.


title: Hippocampus

text: Basket cells in CA3 receive excitatory input from the pyramidal cells and then give an inhibitory feedback to the pyramidal cells. This "recurrent inhibition" is a simple feedback circuit that can dampen excitatory responses in the hippocampus. The pyramidal cells gives a "recurrent excitation" which is an important mechanism found in some memory processing microcircuits.


title: Hippocampus

text: Several other connections play important roles in hippocampal function. Beyond the output to the EC, additional output pathways go to other cortical areas including the prefrontal cortex. A major output goes via the fornix to the lateral septal area and to the mammillary body of the hypothalamus (which the fornix interconnects with the hippocampus). The hippocampus receives modulatory input from the serotonin, norepinephrine, and dopamine systems, and from the nucleus reuniens of the thalamus to field CA1. A very important projection comes from the medial septal nucleus, which sends cholinergic, and gamma amino butyric acid (GABA) stimulating fibers (GABAergic fibers) to all parts of the hippocampus. The inputs from the medial septal nucleus play a key role in controlling the physiological state of the hippocampus; destruction of this nucleus abolishes the hippocampal theta rhythm and severely impairs certain types of memory.


title: Hippocampus

text: Areas of the hippocampus are shown to be functionally and anatomically distinct. The dorsal hippocampus (DH), ventral hippocampus (VH) and intermediate hippocampus serve different functions, project with differing pathways, and have varying degrees of place cells. The dorsal hippocampus serves for spatial memory, verbal memory, and learning of conceptual information. Using the radial arm maze, lesions in the DH were shown to cause spatial memory impairment while VH lesions did not. Its projecting pathways include the medial septal nucleus and supramammillary nucleus. The dorsal hippocampus also has more place cells than both the ventral and intermediate hippocampal regions.


title: Hippocampus

text: The intermediate hippocampus has overlapping characteristics with both the ventral and dorsal hippocampus. Using anterograde tracing methods, Cenquizca and Swanson (2007) located the moderate projections to two primary olfactory cortical areas and prelimbic areas of the medial prefrontal cortex. This region has the smallest number of place cells. The ventral hippocampus functions in fear conditioning and affective processes. Anagnostaras "et al." (2002) showed that alterations to the ventral hippocampus reduced the amount of information sent to the amygdala by the dorsal and ventral hippocampus, consequently altering fear conditioning in rats. Historically, the earliest widely held hypothesis was that the hippocampus is involved in olfaction. This idea was cast into doubt by a series of anatomical studies that did not find any direct projections to the hippocampus from the olfactory bulb. However, later work did confirm that the olfactory bulb does project into the ventral part of the lateral entorhinal cortex, and field CA1 in the ventral hippocampus sends axons to the main olfactory bulb, the anterior olfactory nucleus, and to the primary olfactory cortex. There continues to be some interest in hippocampal olfactory responses, in particular, the role of the hippocampus in memory for odors, but few specialists today believe that olfaction is its primary function.


title: Hippocampus

text: Over the years, three main ideas of hippocampal function have dominated the literature: response inhibition, episodic memory, and spatial cognition. The behavioral inhibition theory (caricatured by John O'Keefe and Lynn Nadel as "slam on the brakes!") was very popular up to the 1960s. It derived much of its justification from two observations: first, that animals with hippocampal damage tend to be hyperactive; second, that animals with hippocampal damage often have difficulty learning to inhibit responses that they have previously been taught, especially if the response requires remaining quiet as in a passive avoidance test. British psychologist Jeffrey Gray developed this line of thought into a full-fledged theory of the role of the hippocampus in anxiety. The inhibition theory is currently the least popular of the three.


title: Hippocampus

text: The second major line of thought relates the hippocampus to memory. Although it had historical precursors, this idea derived its main impetus from a famous report by American neurosurgeon William Beecher Scoville and British-Canadian neuropsychologist Brenda Milner describing the results of surgical destruction of the hippocampi when trying to relieve epileptic seizures in an American man Henry Molaison, known until his death in 2008 as "Patient H.M." The unexpected outcome of the surgery was severe anterograde and partial retrograde amnesia; Molaison was unable to form new episodic memories after his surgery and could not remember any events that occurred just before his surgery, but he did retain memories of events that occurred many years earlier extending back into his childhood. This case attracted such widespread professional interest that Molaison became the most intensively studied subject in medical history. In the ensuing years, other patients with similar levels of hippocampal damage and amnesia (caused by accident or disease) have also been studied, and thousands of experiments have studied the physiology of activity-driven changes in synaptic connections in the hippocampus. There is now universal agreement that the hippocampi play some sort of important role in memory; however, the precise nature of this role remains widely debated. A recent theory proposed – without questioning its role in spatial cognition – that the hippocampus encodes new episodic memories by associating representations in the newborn granule cells of the dentate gyrus and arranging those representations sequentially in the CA3 by relying on the phase precession generated in the entorhinal cortex


title: Hippocampus

text: The third important theory of hippocampal function relates the hippocampus to space. The spatial theory was originally championed by O'Keefe and Nadel, who were influenced by American psychologist E.C. Tolman's theories about "cognitive maps" in humans and animals. O'Keefe and his student Dostrovsky in 1971 discovered neurons in the rat hippocampus that appeared to them to show activity related to the rat's location within its environment. Despite skepticism from other investigators, O'Keefe and his co-workers, especially Lynn Nadel, continued to investigate this question, in a line of work that eventually led to their very influential 1978 book "The Hippocampus as a Cognitive Map". There is now almost universal agreement that hippocampal function plays an important role in spatial coding, but the details are widely debated.


title: Hippocampus

text: Later research has focused on trying to bridge the disconnect between the two main views of hippocampal function as being split between memory and spatial cognition. In some studies, these areas have been expanded to the point of near convergence. In an attempt to reconcile the two disparate views, it is suggested that a broader view of the hippocampal function is taken and seen to have a role that encompasses both the organisation of experience (mental mapping, as per Tolman's original concept in 1948) and the directional behaviour seen as being involved in all areas of cognition, so that the function of the hippocampus can be viewed as a broader system that incorporates both the memory and the spatial perspectives in its role that involves the use of a wide scope of cognitive maps. This relates to the purposive behaviorism born of Tolman's original goal of identifying the complex cognitive mechanisms and purposes that guided behaviour.


title: Hippocampus

text: It has also been proposed that the spiking activity of hippocampal neurons is associated spatially, and it was suggested that the mechanisms of memory and planning both evolved from mechanisms of navigation and that their neuronal algorithms were basically the same.


title: Hippocampus

text: Many studies have made use of neuroimaging techniques such as functional magnetic resonance imaging (fMRI), and a functional role in approach-avoidance conflict has been noted. The anterior hippocampus is seen to be involved in decision-making under approach-avoidance conflict processing. It is suggested that the memory, spatial cognition, and conflict processing functions may be seen as working together and not mutually exclusive.


title: Hippocampus

text: Psychologists and neuroscientists generally agree that the hippocampus plays an important role in the formation of new memories about experienced events (episodic or autobiographical memory). Part of this function is hippocampal involvement in the detection of new events, places and stimuli. Some researchers regard the hippocampus as part of a larger medial temporal lobe memory system responsible for general declarative memory (memories that can be explicitly verbalizedthese would include, for example, memory for facts in addition to episodic memory). The hippocampus also encodes emotional context from the amygdala. This is partly why returning to a location where an emotional event occurred may evoke that emotion. There is a deep emotional connection between episodic memories and places.


title: Hippocampus

text: Due to bilateral symmetry the brain has a hippocampus in each cerebral hemisphere. If damage to the hippocampus occurs in only one hemisphere, leaving the structure intact in the other hemisphere, the brain can retain near-normal memory functioning. Severe damage to the hippocampi in both hemispheres results in profound difficulties in forming new memories (anterograde amnesia) and often also affects memories formed before the damage occurred (retrograde amnesia). Although the retrograde effect normally extends many years back before the brain damage, in some cases older memories remain. This retention of older memories leads to the idea that consolidation over time involves the transfer of memories out of the hippocampus to other parts of the brain. Experiments using intrahippocampal transplantation of hippocampal cells in primates with neurotoxic lesions of the hippocampus have shown that the hippocampus is required for the formation and recall, but not the storage, of memories. It has been shown that a decrease in the volume of various parts of the hippocampus in people leads to specific memory impairments. In particular, efficiency of verbal memory retention is related to the anterior parts of the right and left hippocampus. The right head of the hippocampus is more involved in executive functions and regulation during verbal memory recall. The tail of the left hippocampus tends to be closely related to verbal memory capacity.


title: Hippocampus

text: Damage to the hippocampus does not affect some types of memory, such as the ability to learn new skills (playing a musical instrument or solving certain types of puzzles, for example). This fact suggests that such abilities depend on different types of memory (procedural memory) and different brain regions. Furthermore, amnesic patients frequently show "implicit" memory for experiences even in the absence of conscious knowledge. For example, patients asked to guess which of two faces they have seen most recently may give the correct answer most of the time in spite of stating that they have never seen either of the faces before. Some researchers distinguish between conscious "recollection", which depends on the hippocampus, and "familiarity", which depends on portions of the medial temporal lobe.


title: Hippocampus

text: When rats are exposed to an intense learning event, they may retain a life-long memory of the event even after a single training session. The memory of such an event appears to be first stored in the hippocampus, but this storage is transient. Much of the long-term storage of the memory seems to take place in the anterior cingulate cortex. When such an intense learning event was experimentally applied, more than 5,000 differently methylated DNA regions appeared in the hippocampus neuronal genome of the rats at one hour and at 24 hours after training. These alterations in methylation pattern occurred at many genes that were down-regulated, often due to the formation of new 5-methylcytosine sites in CpG rich regions of the genome. Furthermore, many other genes were upregulated, likely often due to the removal of methyl groups from previously existing 5-methylcytosines (5mCs) in DNA. Demethylation of 5mC can be carried out by several proteins acting in concert, including TET enzymes as well as enzymes of the DNA base excision repair pathway (see Epigenetics in learning and memory).


title: Hippocampus

text: Studies on freely moving rats and mice have shown many hippocampal neurons to act as place cells that cluster in place fields, and these fire bursts of action potentials when the animal passes through a particular location. This place-related neural activity in the hippocampus has also been reported in monkeys that were moved around a room whilst in a restraint chair. However, the place cells may have fired in relation to where the monkey was looking rather than to its actual location in the room. Over many years, many studies have been carried out on place-responses in rodents, which have given a large amount of information. Place cell responses are shown by pyramidal cells in the hippocampus and by granule cells in the dentate gyrus. Other cells in smaller proportion are inhibitory interneurons, and these often show place-related variations in their firing rate that are much weaker. There is little, if any, spatial topography in the representation; in general, cells lying next to each other in the hippocampus have uncorrelated spatial firing patterns. Place cells are typically almost silent when a rat is moving around outside the place field but reach sustained rates as high as 40 Hz when the rat is near the center. Neural activity sampled from 30 to 40 randomly chosen place cells carries enough information to allow a rat's location to be reconstructed with high confidence. The size of place fields varies in a gradient along the length of the hippocampus, with cells at the dorsal end showing the smallest fields, cells near the center showing larger fields, and cells at the ventral tip showing fields that cover the entire environment. In some cases, the firing rate of hippocampal cells depends not only on place but also the direction a rat is moving, the destination toward which it is traveling, or other task-related variables. The firing of place cells is timed in relation to local theta waves, a process termed phase precession.


title: Hippocampus

text: In humans, cells with location-specific firing patterns have been reported during a study of patients with drug-resistant epilepsy. They were undergoing an invasive procedure to localize the source of their seizures, with a view to surgical resection. The patients had diagnostic electrodes implanted in their hippocampus and then used a computer to move around in a virtual reality town. Similar brain imaging studies in navigation have shown the hippocampus to be active. A study was carried out on taxi drivers. London's black cab drivers need to learn the locations of a large number of places and the fastest routes between them in order to pass a strict test known as The Knowledge in order to gain a license to operate. A study showed that the posterior part of the hippocampus is larger in these drivers than in the general public, and that a positive correlation exists between the length of time served as a driver and the increase in the volume of this part. It was also found the total volume of the hippocampus was unchanged, as the increase seen in the posterior part was made at the expense of the anterior part, which showed a relative decrease in size. There have been no reported adverse effects from this disparity in hippocampal proportions. Another study showed opposite findings in blind individuals. The anterior part of the right hippocampus was larger and the posterior part was smaller, compared with sighted individuals.


title: Hippocampus

text: There are several "navigational cells" in the brain that are either in the hippocampus itself or are strongly connected to it, such as the speed cells present in the medial entorhinal cortex. Together these cells form a network that serves as spatial memory. The first of such cells discovered in the 1970s were the place cells, which led to the idea of the hippocampus acting to give a neural representation of the environment in a cognitive map. When the hippocampus is dysfunctional, orientation is affected; people may have difficulty in remembering how they arrived at a location and how to proceed further. Getting lost is a common symptom of amnesia. Studies with animals have shown that an intact hippocampus is required for initial learning and long-term retention of some spatial memory tasks, in particular ones that require finding the way to a hidden goal. Other cells have been discovered since the finding of the place cells in the rodent brain that are either in the hippocampus or the entorhinal cortex. These have been assigned as head direction cells, grid cells and boundary cells. Speed cells are thought to provide input to the hippocampal grid cells.


title: Hippocampus

text: Approach-avoidance conflict happens when a situation is presented that can either be rewarding or punishing, and the ensuing decision-making has been associated with anxiety. fMRI findings from studies in approach-avoidance decision-making found evidence for a functional role that is not explained by either long-term memory or spatial cognition. Overall findings showed that the anterior hippocampus is sensitive to conflict, and that it may be part of a larger cortical and subcortical network seen to be important in decision-making in uncertain conditions.


title: Hippocampus

text: A review makes reference to a number of studies that show the involvement of the hippocampus in conflict tasks. The authors suggest that one challenge is to understand how conflict processing relates to the functions of spatial navigation and memory and how all of these functions need not be mutually exclusive.


title: Hippocampus

text: The hippocampus shows two major "modes" of activity, each associated with a distinct pattern of neural population activity and waves of electrical activity as measured by an electroencephalogram (EEG). These modes are named after the EEG patterns associated with them: theta and large irregular activity (LIA). The main characteristics described below are for the rat, which is the animal most extensively studied.


title: Hippocampus

text: The theta mode appears during states of active, alert behavior (especially locomotion), and also during REM (dreaming) sleep. In the theta mode, the EEG is dominated by large regular waves with a frequency range of 6 to 9 Hz, and the main groups of hippocampal neurons (pyramidal cells and granule cells) show sparse population activity, which means that in any short time interval, the great majority of cells are silent, while the small remaining fraction fire at relatively high rates, up to 50 spikes in one second for the most active of them. An active cell typically stays active for half a second to a few seconds. As the rat behaves, the active cells fall silent and new cells become active, but the overall percentage of active cells remains more or less constant. In many situations, cell activity is determined largely by the spatial location of the animal, but other behavioral variables also clearly influence it.


title: Hippocampus

text: The LIA mode appears during slow-wave (non-dreaming) sleep, and also during states of waking immobility such as resting or eating. In the LIA mode, the EEG is dominated by sharp waves that are randomly timed large deflections of the EEG signal lasting for 25–50 milliseconds. Sharp waves are frequently generated in sets, with sets containing up to 5 or more individual sharp waves and lasting up to 500 ms. The spiking activity of neurons within the hippocampus is highly correlated with sharp wave activity. Most neurons decrease their firing rate between sharp waves; however, during a sharp wave, there is a dramatic increase in firing rate in up to 10% of the hippocampal population


title: Hippocampus

text: These two hippocampal activity modes can be seen in primates as well as rats, with the exception that it has been difficult to see robust theta rhythmicity in the primate hippocampus. There are, however, qualitatively similar sharp waves and similar state-dependent changes in neural population activity.


title: Hippocampus

text: The underlying currents producing the theta wave are generated mainly by densely packed neural layers of the entorhinal cortex, CA3, and the dendrites of pyramidal cells. The theta wave is one of the largest signals seen on EEG, and is known as the hippocampal theta rhythm. In some situations the EEG is dominated by regular waves at 3 to 10 Hz, often continuing for many seconds. These reflect subthreshold membrane potentials and strongly modulate the spiking of hippocampal neurons and synchronise across the hippocampus in a travelling wave pattern. The trisynaptic circuit is a relay of neurotransmission in the hippocampus that interacts with many brain regions. From rodent studies it has been proposed that the trisynaptic circuit generates the hippocampal theta rhythm.


title: Hippocampus

text: Theta rhythmicity is very obvious in rabbits and rodents and also clearly present in cats and dogs. Whether theta can be seen in primates is not yet clear. In rats (the animals that have been the most extensively studied), theta is seen mainly in two conditions: first, when an animal is walking or in some other way actively interacting with its surroundings; second, during REM sleep. The function of theta has not yet been convincingly explained although numerous theories have been proposed. The most popular hypothesis has been to relate it to learning and memory. An example would be the phase with which theta rhythms, at the time of stimulation of a neuron, shape the effect of that stimulation upon its synapses. What is meant here is that theta rhythms may affect those aspects of learning and memory that are dependent upon synaptic plasticity. It is well established that lesions of the medial septumthe central node of the theta systemcause severe disruptions of memory. However, the medial septum is more than just the controller of theta; it is also the main source of cholinergic projections to the hippocampus. It has not been established that septal lesions exert their effects specifically by eliminating the theta rhythm.


title: Hippocampus

text: During sleep or during resting, when an animal is not engaged with its surroundings, the hippocampal EEG shows a pattern of irregular slow waves, somewhat larger in amplitude than theta waves. This pattern is occasionally interrupted by large surges called "sharp waves". These events are associated with bursts of spike activity lasting 50 to 100 milliseconds in pyramidal cells of CA3 and CA1. They are also associated with short-lived high-frequency EEG oscillations called "ripples", with frequencies in the range 150 to 200 Hz in rats, and together they are known as sharp waves and ripples. Sharp waves are most frequent during sleep when they occur at an average rate of around 1 per second (in rats) but in a very irregular temporal pattern. Sharp waves are less frequent during inactive waking states and are usually smaller. Sharp waves have also been observed in humans and monkeys. In macaques, sharp waves are robust but do not occur as frequently as in rats.


title: Hippocampus

text: One of the most interesting aspects of sharp waves is that they appear to be associated with memory. Wilson and McNaughton 1994, and numerous later studies, reported that when hippocampal place cells have overlapping spatial firing fields (and therefore often fire in near-simultaneity), they tend to show correlated activity during sleep following the behavioral session. This enhancement of correlation, commonly known as "reactivation", has been found to occur mainly during sharp waves. It has been proposed that sharp waves are, in fact, reactivations of neural activity patterns that were memorized during behavior, driven by strengthening of synaptic connections within the hippocampus. This idea forms a key component of the "two-stage memory" theory, advocated by Buzsáki and others, which proposes that memories are stored within the hippocampus during behavior and then later transferred to the neocortex during sleep. Sharp waves in Hebbian theory are seen as persistently repeated stimulations by presynaptic cells, of postsynaptic cells that are suggested to drive synaptic changes in the cortical targets of hippocampal output pathways. Suppression of sharp waves and ripples in sleep or during immobility can interfere with memories expressed at the level of the behavior, nonetheless, the newly formed CA1 place cell code can re-emerge even after a sleep with abolished sharp waves and ripples, in spatially non-demanding tasks.