bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric studies of dorsal horn neurons responding to tactile stimulation
Authors: Brown P. B. , Fuchs J. L. , Tapper D. N.
Published: December 2017

Dorsal horn neurons responding to tactile input were recorded in segments L3-S2 of unanesthetized, low-spinal cats. Single units were characterized with regard to receptive field (RF) location, RF size and shape, spontaneous discharge rate, central delay, and convergence of four tactile afferent types. 1. RF size increased from the toes to the calf region. 2. Length-width ratio increased from the toes to the calf and declined from the calf to the hip. 3. The relation between RF size and position on the limb was independent of segmental and laminar location of the neurons. 4. RF size was positively correlated with spontaneous discharge rate. 5. The relation between RF size and shape and RF position can be interpreted in terms of regional variations in the magnitude of the gradient of representation in the dorsal horn somatotopic map. 6. Central delay was negatively correlated with both RF size and rate of ongoing discharge. 7. There were no statistically significant differences among the laminae with respect to central delay, RF size or shape, ongoing discharge, or convergence combinations of the four tactile afferent systems. 8. Data presented were at variance with Wall's laminar cascading model for laminae IV-VI. Our results suggest that the model should be modified, at least to emphasize monosynaptic tactile input to all three of these laminae.
Morphological and functional identifications of catfish retinal neurons. II. Morphological identification
Authors: Naka K. , Otsuka T.
Published: December 2017

In this study the morphological origins of the responses from the catfish retinal neurons evoked by step inputs were determined by injecting intracellularly a dye, Procion yellow. A method was devised to view the dye-injected neurons in flat mount to study their dendritic expansion; later the same neurons could be sectioned radially to locate the levels of their somata or dendritic expansion. The results of this study show the inherent danger of identifying dye-injected neurons only in a radial or tangential view. Bipolar cells could be identified functionally without any ambiguity by changing widely the stimulus parameters, because the stimulation of their receptive-field center and surround gave rise to responses of opposing polarity. We found no exception to this rule. The neurons in the proximal layers produced a large variety of responses which could not be segregated into two such classes as the amacrine and ganglion cells. In this part II they were classified into three broad categories: neurons giving rise to sustained, transient, and spiking responses. The demarcation among the three types, morphologywise and functionwise, was vague and not well established. The sustained responses were recoreded from the starburst and spaghetti neurons (part I (9)) which correspond to Ramon y Cajal's (2) amacrine cells. The transient responses, whose patterns were largely invariant of the changes in the stimulus parameters, were recorded from a class of neurons with spindle-shaped somata in the INL. We do not know whether they had axons or not, but we will not be surprised if a future study defines them as a class of ganglion cells. Responses with or without spike discharges were recorded from a class of neurons which were identified as ganglion cells. Observations made on a large number of Procion-injected neurons in both flat-mount preparations and radial sections show that finer dendritic arborizations were not seen in the dye-injected neurons although the presence of such branches was proved in the Golgi preparations. Probably this was due to the weak contrast of the Procion-injected cell against the tissue background, rather than the failure of the dye to diffuse into finer branches. We recognize the severe difficulty involved in the traditional approach of identifying a class of neurons based on typical but subjectively selected functional and structural samples. Neurons have to be classified statistically according to their (quantitative) parameters. (cont'd)
Afferent new fiber activity responding to temperature changes of scrotal skin of the rat
Authors: Pierau F-K. , Torrey P. , Carpenter D. O.
Published: December 2017

The discharge patterns of single afferent fibers from rat pudendal nerve were studied as a function in temperature of the scrotal skin, an area known to function in temperature regulation. In a number of respects the population of temperature-sensitive afferents here differ from most previously described; 75% of temperature-sensitive afferents were also sensitive to mechanical stimulation. Of the 25% nonmechanosensitive units, half showed dynamic and static responses to cooling, while most of the remaining fibers gave only static discharges to warming. The most frequent thermal reaction of the mechanosensitive units was a dynamic-static cold response or a pure static warm response. However, fibers were also present with only dynamic or only static cold responses. Of the bimodal units, 20% had a dynamic cold response, but showed a minimal static discharge at intermediate temperatures (about 35 degrees C) and an increased discharge on both warming and cooling from that temperature. One unit had static and dynamic warm responses. Whereas a bursting discharge in the cold has previously been considered to be a distinguishing characteristic of specific cold receptors, in the pudendal afferents a bursting discharge on cooling or at low temperatures is common both in mechanosensitive and specific cold fibers. This observation and the identical discharge patterns and mechanisms underlying the thermosensitivity argue for the view that the mechanosensitive afferents participate in thermal sensation and/or regulation along with the specific temperature receptors. Hellon and Misra (7) have concluded that there is processing of thermal information from the scrotal skin at the level of the first synapse in the cord. However, in this study, we have found peripheral afferents which have most of the discharge properties that led Hellon and Misra to conclude that processing had occurred. The unusual characteristics of thermosensitive afferents of the pudendal nerve suggest that there is probably organ specificity of neuronal discharge properties.
Responses of cats to sudden falls: an otolith-originating reflex assisting landing
Authors: Watt D. G.
Published: December 2017

A short-latency electromyographic response has been demonstrated in the human gastrocnemius during unexpected falls (11). The hypothesis that it is a form of otolith-spinal reflex has been tested in the cat. Electromyographic activity was measured in four muscles while suddenly and unexpectedly dropping a series of six cats from 50 cm above the ground. In normal animals, electrical activation of all muscles tested occurred in two distinct phases. An early burst commenced as early as 15 ms from the instant of release, was usually spindle shaped, and often but not always disappeared by 100 ms. This burst was totally and permanently abolished by bilateral labyrinthectomy, but not by selective inactivation of the relevant semicircular canals. A later phase of muscle activity commenced 75-140 ms after release and gradually built up and then subsided, rougly centered about the movement of landing on the ground. This activity was not greatly altered by labyrinthectomy. The present results appear to confirm that the early electromyographic response to sudden falls is due to an otolith-spinal reflex. A later component is nonlabyrinthine in origin, however. Smooth landings from short falls are not possible in the absence of either phase of the response.
Initial burst of primary endings of isolated mammalian muscle spindles
Authors: Hunt C. C. , Ottoson D.
Published: December 2017

The initial burst has been studied in primary endings of isolated mammalian muscle spindles subject to controlled ramp-and-hold stretch. Near the onset of ramp stretch the primary ending discharges at a frequency dependent on stretch velocity. The initial burst is reduced or abolished by repetitive stretch. After block of impulse activity by tetrodotoxin, the receptor potential of primary endings shows an initial component, a rapid depolarization which occurs near the onset of ramp stretch at the same time as the initial burst. This initial component depends, in rate of rise and amplitude, on stretch velocity. It is also reduced or abolished by repetitive stretch. Recording of tension development by the isolated spindle in response to ramp-and-hold stretch shows an early rise in tension associated with the initial burst and the initial component of the receptor potential. This tension rise is also dependent on stretch velocity and is reduced or abolished by repetitive stretch. The results provide direct evidence that the initial burst results from mechanical factors, probably from cross bridge formation between thick and thin filaments as has been suggested (3).
Electrical properties of frog motoneurons in the in situ spinal cord
Authors: Magherini P. C. , Precht W.
Published: December 2017

Electrical properties of the spinal motoneurons of Rana temporaria and R. esculenta were investigated in the in situ spinal cord at 20-22 degrees C by means of intracellular recording and current injection. Input resistance values depended on the method of measurement in a given cell but were generally inversely related to axon conduction velocity. The membrane-potential response to a subthreshold current pulse was composed of at least two exponentials with mean time constants of 2.5 and 20 ms. The membrance potential reached by the peak of a spike depended on the mode of spike initiation and membrane potential. Preceding a suprathreshold depolarization by a hyperpolarizing pulse could delay and eliminate spike initiation, similar to effects reported in certain invertebrate neurons. Antidromic invasion frequently failed in motoneurons of normal resting potential. Antidromic spike components (m,IS, SD) were similar to those of cat motoneurons. The delayed depolarization and the long afterhyperpolarization following an antidromic spike had many properties in common with the analogous afterpotentials of cat motoneurons. The reversal potential of the short afterhyperpolarization occurring immediately after the spike varied with resting potential and could not be used to determine potassium equilibrium potential. Sustained rhythmic firing could be evoked by continuous synaptic drive or long pulses of injected current. The plot of firing rate versus current strength had a substantial linear region. Both steady firing and adaptation properties varied markedly with motoneuron input resistance.
Postcritical-period reversal of effects of monocular deprivation on striate cortex cells in the cat
Authors: Kratz K. E. , Spear P. D.
Published: December 2017

1. The possibility that effects of monocular deprivation on cat striate cortex could be reversed after the developmental critical period by removal of the normal eye was investigated. In addition, the time course of any postcriticalperiod reversal was studied. Single-unit recording was conducted in the striate cortex of kittens anesthetized with nitrous oxide.2. Six control kittens were raised with monocular lid suture until they were 4-8 mo old (group MD). In agreement with previous investigators, from 0-10% of the striate cortex cells could be driven by visual stimulation of the deprived eye in these kittens.3. Eleven kittens were raised with monocular lid suture until they were 4-5 mo old, at which time the normal eye was enucleated. In five of these (group MD-DE-immediate), recording was conducted in striate cortex on the day of the enucleation. In these animals, 29-39% of the striate cortex cells could be driven by the deprived eye. In four kittens (group MD-DE-3 mo), the deprived eye remained closed for an additional 3 mo before recording was conducted. In these animals, 17-45% of the striate cortex cells could be driven by the deprived eye. In two kittens (group MD-DE greater than 12 mo), the deprived eye remained closed for 14-15 mo after the normal eye was enucleated. In these kittens, 26-40% of the striate cortex cells could be driven by the deprived eye. Thus, removal of the normal eye after the critical period in monocularly drprived kittens results in a rapid increase in the percent of striate cortex cells that can be driven by visual stimulation of the deprived eye, and there is no further increase in responsiveness over a period of more than a year.4. The receptive-field properties of the cells which responded to the deprived eye following enucleation of the normal eye were usually abnormal; 61% of them had nonspecific receptive fields, 39% of the responsive cells were direction selective, and only 12% were both direction and orientation selective.5. The increase in responsive cells was observed in the striate cortex of both hemispheres. However, the increase was greater in the hemisphere contralateral to the deprived eye. The responsive cells tended to occur in clusters of two to four adjacent cells separated by regions containing nonresponsive cells. These clusters were not related to the horizontal cortical layers; however, they may be related to the ocular dominance columns in striate cortex.6. Several mechanisms were considered for the present findings, including neuronal sprouting, denervation supersensitivity, and release from inhibition. It was suggested that the increased responsiveness to the deprived eye was probably not the result of rapid sprouting in the 4- to 5-mo-old kittens. If this is so, then the results indicate that functional connections from the deprived layers of the DLG to the striate cortex remain following rearing with monocular deprivation...
Analysis of passive and active electrophysiologic properties of neurons in mammalian nodose ganglia maintained in vitro
Authors: Jaffe R. A. , Sampson S. R.
Published: December 2017

1. We studied the passive and active electrical properties of the soma membrane of neurons in nodose ganglia removed from cats and rabbits and maintained in vitro. The ganglia were superfused at 37 degrees C with a solution formulated to approximate the extracellular fluid of each species. The solution was buffered to pH 7.34, continuously equilibrated with 95% O2 and 5% CO2, and contained dialyzed calf serum and glucose. We also examined these properties in nodose ganglion neurons in vivo. Intracellular recordings were obtained with glass micropipettes filled with either 3 M KCl or 5 M K acetate. 2. We determined mean values for a variety of passive and active electrophysiologic properties. Values obtained in vitro did not differ significantly from those obtained in vivo. Based on the passive electrical properties of the soma membrane, neurons in the nodose ganglion appear to be a uniform population, despite the different sensory modalities conveyed by the afferent fibers. 3. Cell bodies of neurons generated action potentials in response to impulses in their afferent fibers. Somatic spikes could be evoked by stimulation of either the supranodose or infranodose vagus nerve, and an inflection point could be seen on their rising phase. When the vagus nerve was stimulated at frequencies greater than 10-20 Hz, the generation of somatic spikes often became progressively delayed and then failed completely, leaving a smaller potential (IS spike) which was apparently generated in the initial complex. The afterhyperpolarization was associated only with the somatic spike. 4. Many neurons, both in vitro and in vivo, developed a persistent hyperpolarization when repetitive action potentials occurred in the soma. This hyperpolarization was apparent at frequencies as low as 1-2 Hz, persisted for up to 5 s after the occurrence of the last somatic spike, and sometimes caused failure of somatic spikes to be generated. 5. Neurons in both species differed in their responses to suprathreshold depolarization applied through the recording electrode. Some neurons produced a train of action potentials which lasted for the duration of the depolarizing pulse, the frequency of the train being related to the magnitude of depolarization. The trains were characterized by gradually decreasing spike amplitudes and increasing interspike intervals. Other neurons responded with only a single spike or brief burst of action potentials at the beginning of depolarization to threshold. 6. It is suggested that the adaptive properties of the soma membrane of a peripheral sensory neuron are similar to those of its sensory ending, and that electrophysiological studies of the soma membrane may provide an opportunity to examine mechanisms of receptor adaptation.
Discrimination of orientation and position disparities by binocularly activated neurons in cat straite cortex
Authors: Nelson J. I. , Kato H. , Bishop P. O.
Published: December 2017

1. We have examined and compared the ability of binocularly activated striate neurons to make both position disparity and orientation disparity discrimination in the anesthetized (N2O/O2) and paralyzed cat preparation. 2. Accurate knowledge of eye position is essential for disparity studies. Using a retinal projection technique able to detect eye drifts of less than 3' arc per retinal landmark and less than 18' arc cyclorotation disparity, we determined eye drift during the course of 2- to 4-day experiments. After the initial eye rotation due to the anesthesia and the onset of paralysis (see below), rotational drift thereafter was mainly excyclorotatory and, from all causes, rarely totaled more than 4 degrees disparity. All our data have been corrected for this residual cyclorotatory drift. 3. Optimal stimulus orientation disparities were determined from quantitative monocular orientation tuning curves for 74 binocularly activated striate cells (37 simple, 3 hypercomplex I, 31 complex, 3 hypercomplex II) from nine cats. Without exception, the mean optimal stimulus orientation disparity in each of our animals showed a departure from zero disparity equivalent to an incyclorotation of the eyes (mean, 9.2 degrees; range, 2.7 degrees-15.9 degrees). 4. We attribute this mean optimal stimulus orientation disparity shift to ocular cyclorotation as a result of the initial anesthesia and paralysis. Assuming equal intortion, incyclorotation for each eye averages 4.6 degrees. On the assumption that the mean optimal stimulus orientation disparity is zero in normal life, we pooled results from the nine animals about their individual means. For the 74 cells the resulting distribution of the optimal stimulus orientation disparities had a range of about +/-15 degrees (simple cells: SD 4.9 degrees; complex cells: SD 7.4 degrees). 5. We examined the relationship of the sharpness of the orientation tuning curves to ocular dominance, to absolute orientation preference, and to other unit properties. The striking observation was the high correlation between the sharpness of orientation tuning curves for the two eyes of a binocular neuron. For simple cells the mean difference for the half-widths of half-height was only 2.54 degrees, with sharpness showing a high correlation between the two eyes (r=0.915) over half-width at half-heights ranging from 8.5 degrees to 41.8 degrees. Complex cells showed a similar, albeit weaker, correlation. 6. Having shown that, assessed monocularly binocular units show different orientation tunings in the two eyes, we undertook binocular experiments to ascertain if these differences were the optimal disparities of sharply tuned stimulus orientation disparity channels. Using a matrix stimulation paradigm to minimize the effects of spontaneous changes in responsiveness, we have simultaneously extracted bionocular stimulus orientation disparity and position disparity tuning curves from single striate neurons...
Neuromuscular transmission in dystrophic mice
Authors: Carbonetto S.
Published: December 2017

1. Neuromuscular transmission was studied in the extensor digitorum-longus muscle of dystrophic mice (strain 129/ReJ) by means of intracellular recording techniques. 2. In a large population of normal and dystrophic muscle fibers tested, the incidence of transmission failure was about 2% and showed no significant difference between the two groups. 3. Quantal size and quantum content of dystrophic junctions were found to be normal. This was true even of nerve terminal on apparently atrophied muscle fibers. 4. The facilitation ratio at dystrophic junctions was not significantly different from normal. 5. Dystrophic neuromuscular junctions exhibited an abnormality high frequency of giant spontaneous potentials. Application of tetrodotoxin (10(-6) M) and curare (10(-6) M) indicated that these potentials were caused by impulse-independent release of acetylcholine. 6. Neuromuscular transmission in dystrophic mice was found functionally normal and unrelated to the degenerative state of the muscle.
Somatotopic projections of mystacial vibrissae on cerebral cortex of cats
Authors: Dykes R. W. , Dudar J. D. , Tanji D. G. , Publicover N. G.
Published: December 2017

1. Using classical evoked-potential techniques and 100-micron deflections of one vibrissa, at least three loci of potentials were identified in cats' cortices. 2. The relationships of these loci to cortical landmarks and to each other varied sufficiently to prevent specification of homologies between animals. 3. Attempts to differentiate the loci on functional criteria were unsuccessful. The areal extent of each locus appeared similar and there was evidence of a specific somatotopic pattern within each locus; in each locus different vibrissae were represented at different cortical points. 4. Latencies differed slightly between the loci, being shortest at the most rostral site and longest at the caudal site. In all loci, off-center latencies were longer, but this difference was detected only after complete maps of all three loci were produced. 5. The focus of potentials for an individual vibrissa was radically different, depending on the parameter measured (negative peak, positive peak, and latency). The focus of potentials could also be shifted by changing the velocity or direction of the stimulus. 6. The effects of these stimulus parameters on the cortical map suggest that a cortical focus represents more than simply a point on the skin surface.
Effect of compensatory hypertrophy studied in individual motor units in medial gastrocnemius muscle of the cat
Authors: Walsh J. V. , Burke R. E. , Rymer W. Z. , Tsairis P.
Published: December 2017

1. Compensatory hypertrophy of the medial gastrocnemius (MG) muscle was produced by denervating or removing its synergists (i.e., the lateral gastrocnemius, soleus, and plantaris muscles) in adult cats. Following survival times of 14-32 wk, intracellular recording and stimulation techniques were used to study the motor-unit population in MG. The data obtained were compared with results from MG motor units in normal unoperated cats of the same body size and weight. 2. Using criteria employed for normal motor units, the units in hypertrophic MG muscles were readily classified into the same groups (types FF, F(int), FR, and S) as in normal MG. There was no detectable difference in the distribution of motor-unit types after hypertrophy. 3. When compared with a normal motor-unit sample, there was a large increase in mean tetanic tension, but no significant change in twitch tension, for each motor-unit type in the hypertrophied muscles. The most marked increase was found among the fatigue-resistant type S and type FR motor units. There was no alteration of twitch contraction times or fatigue resistance in any unit type after hypertrophy. 4. For each motor-unit type, the mean homonymous (MG) group Ia EPSP amplitude was the same in normal and hypertrophic MG populations. There was, however, a significant increase in the average conduction velocity of MG motor axons in the animals with uncomplicated MG synergist removal and maximal MG hypertrophy. 5. On the basis of histochemical staining, muscle fibers from comparable sections of hypertrophic and contralateral (unoperated) MG muscles were presumptively identified as belonging to FF, FR, or S units. There was no significant difference between hypertrophic and contralateral MG muscles in the percentage of each fiber type, although there was some variability in muscle composition from one cat to another. One muscle pair was studied in detail for fiber cross-sectional area. In this cat, with marked hypertrophy by muscle weight, there was a modest increase in the mean fiber areas of histochemical S and FR muscle fibers, but no evident change in FF fibers, on the hypertrophic side. 6. MG motor units were examined in several cats in which synergist removal resulted in scarring and marked limitation of passive ankle mobility, and no evident weight gain in MG. Motor units of all types in these animals showed a decrease in twitch tension and in mean twitch/tetanus ratios, with little alteration in mean tetanic tensions. 7. The main effect of compensatory hypertrophy under the present conditions was a large increase in tetanic tension output from individual motor units due, at least in part, to an increase in fiber cross-sectional area. There was no evidence indicating any "conversion" of motor units or of their muscle fibers from one type to another.
Comparison of responses of warm and nociceptive C-fiber afferents in monkey with human judgments of thermal pain
Authors: LaMotte R. H. , Campbell J. N.
Published: December 2017

1. Radiant-heat stimuli of different intensities were delivered every 28 s to the thenar eminence of the hand of human subjects and to the receptive fields (RFs) of 58 "mechanothermal nociceptive" and 16 "warm" C-fibers, most of which innervated the glabrous skin of the monkey hand. A CO2 infrared laser under control via a radiometer provided a step increase in skin temperature to a level maintained within +/- 0.1 degrees C over a 7.5-mm-diameter spot. 2. Human subjects categorized the magnitude of warmth and pain sensations evoked by stimuli that ranged in temperature from 40 to 50 degrees C. The scale of subjective thermal intensity constructed from these category estimates showed a monotonically increasing relation between stimulus temperature and the magnitude of warmth and pain sensations. 3. The mechanothermal fibers had a mean RF size of 18.9 +/- 3.2 mm2 (SE), a mean conduction velocity of 0.8 +/- 0.1 m/s, mean thresholds of 43.6 +/- 0.6 degrees C for radiant heat and 5.95 +/- 0.59 bars for mechanical stimulation, and no spontaneous activity. In contrast, warm fibers had punctate RFs, a mean conduction velocity of 1.1 +/- 0.1 m/s, heat thresholds of less than 1 degrees C above skin temperature, no response to mechanical stimulation, and a resting level of activity in warm skin that was suppressed by cooling. 4. The cumulative number of impulses evoked during each stimulation in the nociceptive afferents increased monotonically as a function of stimulus temperature over the range described by humans as increasingly painful (45-50 degrees C). Nociceptive fibers showed little or no response to stimulus temperatures less than 45 degrees C that elicited in humans sensations primarily of warmth but not pain. In contrast, the cumulative impulse count during stimulation of each warm fiber increased monotonically with stimulus temperature over the range of 39-43 degrees C. However, for stimuli of 41-49 degrees C the cumulative impulse count in warm fibers was nonmonotonic with stimulus temperature. Warm-fiber response to stimuli of 45 degrees C or greater usually consisted of a short burst of impulses followed by cessation of activity. 5. The subjective magnitude of warmth and pain sensations in humans and the cumulative impulse count evoked by each stimulus in warm and nociceptive afferents varied inversely with the number, delivery rate, and intensity of preceding stimulations. 6. The results of these experiments suggest the following: a) that activity in the mechanothermal nociceptive C-fibers signals the occurrence of pain evoked by radiant heat, and that the frequency of discharge in these fibers may encode the intensity of painful stimulation; b) that activity in warm fibers may encode the intensity of warmth at lower stimulus temperatures, but is unlikely to provide a peripheral mechanism for encoding the intensity of painful stimulation at higher stimulus temperatures.
Control of pedal and parapodial movements in Aplysia. II. Cerebral ganglion neurons
Authors: Jahan-Parwar B. , Fredman S. M.
Published: December 2017

1. Intracellular stimulation of individual neurons in the two symmetrical A neuron clusters of the cerebral ganglion evoked contractions of both the foot and parapodia. Electrical stimulation of pedal and parapodial nerves caused antidromic action potentials in A neurons. Units recorded in the nerves followed the driven somatic spike 1:1. This suggests that the A neurons are presumptive pedal and parapodial motor neurons.2. Individual A neurons evoked both bilteral and unilateral contractions of the parapodia or split foot. Contractions in the parapodia were independent of those in the foot. An individual A neuron caused contractions in either the foot or the parapodia, but not both. Sequential transection of parapodial nerves had only a slight effect until a key nerve was cut. The contractions produced by a single A neuron on one side were then abolished. These data suggest that the motor fields of the A neurons are well defined within the foot or the parapodia. 3. Parapodial contractions produced by individual A neurons are not dependent on the excitation of follower motor neurons. Blocking synaptic transmission by the addition of CoCl2 did not eliminate the contractions produced by driving individual A neurons. This is consistent with the A neurons being motor neurons. 4. Intracellular stimulation of individual neurons in the symmetrical B neuron clusters of the cerebral ganglion also evoked pedal and parapodial contractions. Electrical stimulation of the pedal and parapodial nerves elicited antidromic spikes in these neurons. Individual B neurons caused contractions in both the foot and parapodia. This suggests that the B neurons are motor neurons with very large motor fields. 5. Filling the pedal and parapodial nerves with cobalt primarily filled the cell bodies of neurons located in the pedal and pleural ganglia. The somata of A and B neurons were also occasionally filled. This is consistent with the electrophisiological results. 6. Other neurons also evoked parapodial contractions. Intracellular stimulation of neurons in the pedal and pleural ganglia caused parapodial contractions in intact animals. Some of these neurons were excited by stretching the parapodia or touching the tentacles. 7. The B neurons are strongly excited by tactile stimulation of the tentacles. Since they can cause pedal and parapodial contractions they may mediate reflex contractions elicited by tentacular stimulation. Stretching the parapodia only occasionally caused the A neurons to fire. This makes it unlikely that they make a major contribution to pedal and parapodial proprioceptive reflexes. These reflexes are probably controlled by neurons in the pedal and pleural ganglia.
Auditory nerve fiber response to wide-band noise and tone combinations
Authors: Rhode W. S. , Geisler C. D. , Kennedy D. T.
Published: December 2017

1. Responses of single auditory nerve fibers to combinations of noise and tone were obtained. The results were found to depend on the relative effectiveness of each stimulus when presented alone. 2. When the response rate to one stimulus presented alone was considerably greater than the response rate to the other stimulus presented alone, the more effective stimulus dominated the responses when the two stimuli were combined. The more effective stimulus captured the response of the neuron. Thus, intense noise was found to mask responses to weaker tones, and intense tones were found to mask responses to weaker noise. This masking of the weaker stimulus is thought to enhance the signal-to-noise ratio of the most prominent response component. 3. When the two stimuli had similar effectiveness, complex interactions occurred. When the tone was near best (characteristic) frequency, partial summation effects occured. The tone partially suppressed the responses to the noise if other frequencies were used. Tones above best frequency caused particularly powerful suppression. 4. The bandwidth of the noise was varied somewhat. While bandwidth affected the effectiveness of the noise, it did not affect the types of interactions observed. 5. For a neuron which was essentially silent in the absence of acoustic stimuli, adding a weak level of noise lowered the threshold of responsiveness to the tone.
Transfer characteristics of neurons in vestibular nuclei of the alert monkey
Authors: Buettner U. W. , Buttner U. , Henn V.
Published: December 2017

1. In the alert monkey, 74 neurons in the vestibular nuclei were investigated during sinusoidal rotation about a vertical axis at frequencies between 0.003 and 0.5 Hz. Phase and gain were determined by a fast Fourier analysis program. 2. Phase advance, relative to turntable velocity, was small between 0.05 and 0.5 Hz. At lower frequencies phase advance increased to 45 degrees at 0.007--0.02 Hz, and 90 degrees at 0.003--0.005 Hz. In agreement with the phase characteristics, a gain decrease of -3 dB was determined between 0.007 and 0.02 Hz. Assuming a linear system, time constants of 9.5, 11.9, and 24.5 s were calculated for three different monkeys. 3. Simultaneously recorded nystagmus exhibited similar time constants as the central vestibular neurons for each monkey. 4. Frequency responses of 11 neurons were recorded from the same monkeys while they were under general anesthesia and the time constants were reduced to 4--7 s. This is the range of time constants seen in the peripheral nerve. 5. The longer time constants in the alert state are due to an integration process, which provides a low-frequency compensation, and is thought to be achieved through a feedback loop involving the reticular formation. 6. In the alert and anesthetized state, monkeys were also exposed to velocity trapezoids. Time constants of decay of neuronal activity were in good agreement with the data obtained during sinusoidal stimulation. 7. A transfer function of the primary vestibular afferents is expanded to include the described low-frequency compensation found in central vestibular neurons in the alert animals.
Acoustic response characteristics of neurons in nonspecific areas of cat cerebral cortex
Authors: Irvine D. R. , Huebner H.
Published: December 2017

1. Acoustic properties of single neurons in pericruciate, anterior lateral, and medial suprasylvian "association" areas were studied in chloralose-anesthetized cats using sealed stimulating systems incorporating probe microphone assemblies. 2. A total of 652 cells were isolated. Approximately 70% of the cells in each area were responsive to acoustic stimulation, and the majority of these cells were also driven by visual and/or somatosensory stimulation. 3. Association cortex neurons responded to tone- or noise-burst stimulation with an onset response of 16--50 ms latency. The onset response was found to be followed by a long period of suppression in those cases in which spontaneous activity was sufficiently high for this to be detected. 4. The majority of 56 units for which detailed frequency-tuning data were obtained had broad, irregular tuning curves extending over 5--6 octaves or more. A small proportion of association cortex cells exhibited sharp tuning comparable to that obtained in control recordings from cells in primary auditory cortex (AI). Although a number of broadly tuned units were rather insensitive, many cells--both broadly and sharply tuned--were of comparable sensitivity to AI cells. 5. Of the association cortex cells examined for binaural properties, 95% received excitatory input from each ear, and the dominant mode of binaural interaction in these cells was one of occlusion. The occurrence of occlusion at suprathreshold intensities reflected a tendency for monoaural and binaural intensity functions to asymptote at the same level. 6. The broad tuning, lability, and polysensory convergence exhibited by association cortex cells are similar to those of the so-called auditory lemniscal adjunct system. However, the binaural properties of association cells differ significantly from those of both the lemniscal line and adjuct components of the auditory pathway. 7. The homogeneity of acoustic and polysensory input to the three association fields is compatible with their input being derived from the single subcortical nonspecific projection system (reticular formation and medial/intralaminar thalamus) postulated by previous investigators. However, both neuroanatomical and neurophysiological evidence suggest that the lemniscal adjunct system and certain areas of periauditory cortex might also contribute to this input.
Cholinergic features of photoreceptor synapses in Hermissenda
Authors: Heldman E. , Grossman Y. , Jerussi T. P. , Alkon D. L.
Published: December 2017

1. A number of observations, as listed below, suggested a cholinergic basis for inhibitory interactions between photoreceptors of the eye in the nudibranch mollusk Hermissenda crassicornis. 2. The isolated eyes synthesized and accumulated acetylcholine but not other putative neurotransmitter substances. Synthesis and accumulation were determined by electrophoretic separation of products that incorporated radioactive label. Electron microscopic visualization of clear round vesicles within the photoreceptors' somata and axon hillocks was consistent with synthesis and storage of acetylcholine within these cells. 3. Pharmacologic experiments indicated the presence of cholinergic receptors on the terminal branches of the photoreceptors, which are pre- and postsynaptic to each other. Carbachol or nicotine produced hyperpolarization of the photoreceptors' membrane accompanied by a reduction of the input resistance. The reversal potential of carbachol-induced hyperpolarization coincided with the reversal potentials of the IPSPs that followed, one for one, impulses of neighboring photoreceptors. Eserine often caused blockade of the IPSPs. This blockade was associated with substantial membrane hyperpolarization and reduction of membrane resistance. 4. Neuronal endings within the optic tract in the area of the photoreceptor's terminal branches stained for acetylcholinesterase. 5. The results of these different experiments, especially when considered together, strongly suggest, although by no means unequivocally demonstrate, that the neurotransmitter of the photoreceptors is acetylcholine.
Phrenic motoneurons in the cat: subpopulations and nature of respiratory drive potentials
Authors: Berger A. J.
Published: December 2017

1. Intracellular recordings were made from 78 phrenic motoneurons (PM) in anesthetized, paralyzed, artificially ventilated cats that were slightly hypercapnic. 2. Three subpopulations of PM (types A, B, and A/B) were identified on the basis of their membrane potential trajectories during expiration (E). Type A cells exhibited wholly linear trajectories. These were rapidly hyperpolarized at the onset of E followed by a slow ramp of increasing hyperpolarization observed in 51 of 59 type A cells. Types B (13 cells) and A/B (6 cells) had nonlinear trajectories in E. Type B cells approached their end-expiratory potential levels more slowly. 3. Measurements of axonal conduction velocity, expiratory phase input resistance, initial depolarization rate, and initial spike onset during inspiration revealed that type B cells had significantly slower axonal conduction velocities, higher input resistances, greater initial depolarization rates, and earlier initial spike onsets than type A cells. The properties of type A/B were intermediate between the other cell types. These results support the hypothesis that the PM pool is not homogeneous. 4. Active E-phase inhibition of all types of PM was directly demonstrated by reversal of the increasing hyperpolarizing wave to a depolarizing wave with hyperpolarizing current injection using a bridge circuit. Thus hyperpolarization of PM during E is not merely due to a central disfacilitation. 5. During hyperpolarizing current injection the inspiratory phase membrane potential trajectory of all PM became a ramp depolarization similar to that seen during control conditions in type A cells. These results support the conclusion that all cells within the PM pool are receiving a similar central excitatory synaptic input during inspiration. The rapid initial depolarization of type B and their concomitant early spike onset is a consequence in part of a rebound excitation from their expiratory phase inhibition as well as a higher input resistance, probably due to a smaller cell size. 6. Expiratory related neural activity was recorded within the phrenic motor nucleus. It is suggested that these expiratory related neural elements, based on the temporal pattern of their activity, may be responsible for the active inhibition of PM.
Intracellular study of tonic-type enteric neurons in guinea pig small intestine
Authors: Wood J. D. , Mayer C. J.
Published: December 2017

1. Intracellular recording revealed a population of myenteric neurons with electrical behavior that appeared to be equivalent to the tonic-type mechanosensitive neurons found in earlier studies that utilized extracellular recording of single units. 2. Electrical stimulation of the interganglionic fiber tracts evoked a slowly rising excitatory postsynaptic potential (slow EPSP) that was prolonged for several seconds after termination of the stimulus in these cells. The slow EPSP was associated with increased input resistance and augmented excitability of the somal membrane. The somal membranes had relatively low excitability in the absence of fiber tract stimulation. This was indicated by: 1) failure of depolarizing current pulses to elicit spike discharge in some cells; 2) when spikes were elicited by depolarizing current pulses, one to three spikes occurred, and these were seen only at the onset of the pulse; 3) passive invasion of the soma by current from spikes in the cell's processes did not trigger spikes; 4) the spikes were followed by prolonged hyperpolarizing afterpotentials associated with decreased input resistance. 3. Characteristics of the augmented excitability during the slow EPSP were: 1) endogenous discharge of trains of spikes, 2) spike discharge throughout 200 ms duration depolarizing current pulses, 3) electrotonic spike potentials from the processes triggered somal spikes, 4) postspike afterhyperpolarization was reduced or abolished. 4. The slow EPSP was reduced or abolished in Krebs solution with 16 mM Mg+2 and in HEPES-buffered Krebs with 1 mM Mn2+. It was enhanced in Krebs solution with 3 times normal Ca2+. Spike discharge in elevated Ca2+ eliminated the increase in input resistance associated with the slow EPSP. 5. Calcium availability was an important factor in regulation of membrane conductance and excitability in the perikaryon. The slow EPSP provides a mechanism whereby the soma of a multipolar neuron gates the spread of excitation between its dendrites and axon.
Aplysia ink release: central locus for selective sensitivity to long-duration stimuli
Authors: Shapiro E. , Koester J. , Byrne J. H.
Published: December 2017

1. A behavioral and electrophysiological analysis of defensive ink release in Aplysia californica was performed to examine the response of this behavior and its underlying neural circuit to various-duration noxious stimuli. 2. Three separate behavioral protocols were employed using electrical shocks to the head as noxious stimuli to elicit ink release. Ink release was found to be selectively responsive to longer duration stimuli, and to increase in a steeply graded fashion as duration is increased. 3. Intracellular stimulation of ink motor neurons revealed that ink release is a linear function of motor neuron spike train duration, indicating that the selective sensitivity of the behavior to long-duration stimuli is not due to a nonlinearity in the glandular secretory process. 4. In contrast, electrophysiological examination of ink motor neuron activity in response to sustained head shock revealed an accelerating spike train. During the later part of the spike train, compound excitatory synaptic potentials show a positive shift in reversal potential. 5. Our results suggest a central locus for the mechanisms that determine sensitivity of inking behavior to stimulus duration. 6. In contrast to ink release, defensive gill withdrawal was found to be extremely sensitive to short-duration stimuli.
Statoacoustic properties of utricular afferents
Authors: Budelli R. , Macadar O.
Published: December 2017

1. We classified the utricular afferents on the basis of their spontaneous acitivity and responses to tilts and vibrations. 2. Type I afferents fire spontaneously in a regular pattern; their responses to tilts consist of a phasic-tonic change in firing rate. They may respond to vibrations by increasing or decreasing their rate and show no adaptation. 3. The spontaneous activity and the responses to tilts of type II are similar to those observed in type I afferents. The differences become apparent when the preparation is subjected to a vibrational stimulus, since type II neurons increase their firing rate regardless of the stimulus frequency and show adaptation. 4. Type III neurons have no spontaneous activity. They respond to tilts by firing during the transition from one position to the other. They respond to a vibrational stimulus with maintained firing and show no adaptation. 5. We studied the dynamic responses of each type of neuron. We used sensitivity curves for the study of type III afferents and proposed a statistical method to define gain curves for the study of the other types. 6. The gain curves generated by type I neurons reach their maximum at frequencies of stimulation close to the spontaneous rate of firing. 7. In the gain curves of type II afferents the maximum corresponds to frequencies higher than their spontaneous activity. 8. Sensitivity curves and gain curves give similar results for type III fibers. The sensitivity curves of these afferents were classified into four subtypes. 9. We studied the responses of the three types of afferents to bursts of sinusoidal vibrations. 10. We concluded that the properties of types I and II fibers are fit to carry information about movements and position of the head, but also transmit acoustical information. Type III fibers are more adapted to provide information about acoustical stimuli, but can also convey information about head movements.
Organization of primary somatosensory cortex in the cat
Authors: Dykes R. W. , Rasmusson D. D. , Hoeltzell P. B.
Published: December 2017

1. Multi-unit recordings were made from SI cortex of barbiturte-anesthetized cats. In four cats, multiple vertical penetrations were made at closely spaced intervals. In 12 cats, long surface-parallel penetrations were made in the rostrocaudal or the lateromedial directions with observations taken every 100 micron. 2. Evidence is presented suggesting that cytoarchitectonic area 3a receives input from deep receptors and area 3b receives input from cutaneous receptors. 3. Within area 3b there was an abrupt change in submodality such that the rostral portion of 3b was activated by slowly adapting (SA) afferents, while the caudal portion was activated by rapidly adapting (RA) afferents. 4. The change in modality from deep to cutaneous occurred at the 3a/3b border, but the change in submodality occurred within area 3b and there was no obvious anatomical correlate of the latter transition. 5. These data suggest that there are modality- and submodality-specific bands in register with the bands of cytoarchitecture that extend across the mediolateral dimension of primary somatosensory cortex (SI). 6. A particular receptor population (or populations) from all regions of the body delivers information to each functionally specific band--one map is found in area 3a and two are in area 3b. If this pattern holds for the rest of cat SI, then there must be additional maps of the body in cytoarchitectonic areas 1 and 2.