bluuebunny/crossref_metadata_2025 huggingface dataset:
Topographic and directional organization of visual motion inputs for the initiation of horizontal and vertical smooth-pursuit eye movements in monkeys
Authors: Lisberger S. G. , Pavelko T. A.
Published: December 2017

1. The goal of our study was to determine the properties of the visual inputs for pursuit eye movements. In a previous study we presented horizontal target motion along the horizontal meridian and showed that targets were more effective if they moved across the center of the visual field. We have now analyzed the topographic weighting of the inputs for pursuit in greater detail, using targets that moved in all directions and across a wide area of the visual field. 2. Monkeys were rewarded for tracking targets that started at 48 positions in the visual field. The initial positions were spaced equally around 4 circles that were centered at the position of fixation and had radii of 3, 6, 9, and 12 degrees. Targets moved horizontally or vertically at 30 degrees/s. We measured the smooth eye acceleration in the first 80 ms after the initiation of pursuit, before there had been time for visual feedback to affect the position or velocity of the retinal images from the target. 3. For both horizontal and vertical target motion, there were major differences between the early and late intervals in the first 80 ms of pursuit. In the first 20 ms eye acceleration was largely independent of initial target position. In later intervals eye acceleration decreased sharply as a function of initial target eccentricity. The later intervals also showed a pronounced toward/away asymmetry such that the initiation of pursuit was more vigorous for target motion toward than for motion away from the horizontal or vertical meridian. 4. Comparison of the topographic organization of the middle temporal visual area (MT) with our data on pursuit suggests that the topography of cortical maps is smoothed when the visual signals are transmitted to the pursuit system. For example, the superior visual hemifield is underrepresented in cortical motion processing areas, but target motion in the superior and inferior visual hemifields is equally effective for the initiation of pursuit. 5. We investigated the directional organization of the visual inputs for pursuit by presenting targets that started at 6 degrees eccentric and moved in 16 different directions. Horizontal target motion always evoked larger eye accelerations than did vertical target motion. Target motion in oblique directions evoked intermediate values of eye acceleration. 6. Our data show two classes of variation in pursuit performance. First, some subjects showed ideosyncratic variations that were restricted to one hemifield or one direction of target motion. We attribute these variations to differences among subjects in the physiology of visual pathways.(ABSTRACT TRUNCATED AT 400 WORDS)
The contribution of articular receptors to proprioception with the fingers in humans
Authors: Clark F. J. , Grigg P. , Chapin J. W.
Published: December 2017

1. Whether joint receptors contribute demonstrably to proprioception has remained uncertain. Therefore, we tested whether an articular contribution to movement sense could be revealed if the total sensory input available to signal joint movement were reduced by eliminating movement signals from muscles. With a reduced sensory input, whatever contribution articular receptors made to proprioception ought to assume a greater-than-normal importance, and any effect of eliminating articular inputs should become more apparent. The distal interphalangeal joint of the middle finger was used, because the muscles could be decoupled from this joint by positioning the fingers to slacken the tendons. 2. To further enhance the possibility for observing an effect of eliminating articular contributions, we planned to test movement sense at positions of the joint in which the articular receptors would be most active. However, the response properties of receptors in primate finger joints were unknown, so we examined activity of receptors in finger joints of monkeys prior to testing humans. 3. Activity of receptors in interphalangeal joints of monkeys was measured over a wide range of positions before and during local anesthesia of the joint. Little response was seen over intermediate positions, but activity increased as the joint approached full flexion or full extension in much the same manner as responses previously observed with receptors in the knee, elbow, wrist, and hip joints. Local anesthetic injected into the joint space abolished the nerve activity. 4. Proprioception was tested in humans before and during local anesthesia of the joint using a movement-detection paradigm.(ABSTRACT TRUNCATED AT 250 WORDS)
Thalamocortical response transformation in the rat vibrissa/barrel system
Authors: Simons D. J. , Carvell G. E.
Published: December 2017

1. Extracellular single-unit recordings and controlled whisker stimuli were used to compare response properties between cells in the "barreloids" of the thalamic ventrobasal complex and those in the cytochrome oxidase-rich centers of the "barrels" in the first somatic sensory cortex. Individual vibrissae were deflected alone or in paired combination involving the neuron's maximally excitatory whisker and an adjacent one in the same or neighboring whisker rows. Quantitative data were derived from 135 thalamocortical unit's (TCUs), 242 "regular-spike" barrel units (RSUs), and 16 "fast-spike" barrel units (FSUs) recorded in 26 normal adult rats. 2. Compared with TCUs, RSUs displayed lower rates of spontaneous activity and responded less vigorously to whisker stimuli. Proportionally, more than twice as many TCUs as RSUs responded in slowly adapting fashion to at least one angular direction of whisker displacement. Discharges of slowly adapting TCUs were approximately 3.5 times greater than those of slowly adapting RSUs. 3. Proportionally, about twice as many TCUs than RSUs responded selectively to whisker movements in different angular directions. 4. Cells in the thalamus responded more vigorously to a larger number of whiskers than RSUs in the cortex. Depending on the stimulus conditions, two to three times more TCUs than RSUs were excited by two or more whiskers. 5. Following displacement of an adjacent whisker, unit discharges to subsequent deflections of the maximally excitatory whisker were reduced in a time-dependent fashion. The time course of response suppression was similar in TCUs and RSUs, but inhibitory interactions between adjacent whiskers were observed much less often in the thalamus. A cyclic pattern of stimulus-evoked excitation/inhibition characterizes responses in the cortical barrels but is considerably less pronounced in the thalamic barreloids. 6. The presence and/or degree of response suppression depended on which adjacent whisker was stimulated and on the angular direction of that whisker's movement. For individual TCUs, some adjacent whiskers evoked inhibition, others did not. The vast majority of RSUs displayed response suppression to all adjacent whiskers. Unlike receptive fields of TCUs, those of RSUs have small--i.e., single-whisker--excitatory centers with potent and symmetrical inhibitory surrounds. 7. Fast-spike units in the barrels displayed the greatest spontaneous and stimulus-evoked activities and were the least selective for whisker movements at different angular directions. FSUs had the largest excitatory receptive fields; 100% responded to two or more vibrissae.(ABSTRACT TRUNCATED AT 400 WORDS)
Differential effects of baclofen on sustained and transient cells in the mudpuppy retina
Authors: Slaughter M. M. , Bai S. H.
Published: December 2017

1. Baclofen, a gamma-aminobutyric acid (GABA)/B receptor agonist, was bath applied while recording the responses of second- and third-order neurons in the mudpuppy retina. Baclofen receptors were largely restricted to amacrine and ganglion cells. 2. Baclofen hyperpolarized the membrane potential of many, but not all, third-order neurons. This involved an increase in input conductance, probably associated with an opening of potassium channels. 3. The maximal increase in input conductance associated with the activation of GABA/B receptors was approximately one-third of that produced by activation of GABA/A receptors. 4. Baclofen suppressed sustained responses but enhanced transient responses. The net effect was that responses throughout the inner retina became more transient in the presence of baclofen. 5. In sustained cells baclofen not only suppressed the sustained responses but also revealed large transient responses. Thus baclofen converted the light responses of these cells from sustained to transient. This suggests that sustained cells receive significant transient excitation which is normally masked by the sustained inputs. 6. The role of the GABA/B receptor in controlling response characteristics and information content of amacrine and ganglion cells is discussed.
Evidence that repetitive seizures in the hippocampus cause a lasting reduction of GABAergic inhibition
Authors: Kapur J. , Stringer J. L. , Lothman E. W.
Published: December 2017

1. A method was developed to quantify paired-pulse depression of population spikes in the CA1 region of the hippocampus of urethane-anesthetized rats with paired stimuli to the contralateral CA3 region at various states of excitability of pyramidal cells. This method was applied to measure changes following recurrent seizures, a single seizure, or long-term potentiation (LTP). 2. In naive animals paired-pulse depression was highly variable at low stimulus intensities, but constant above a certain "threshold" stimulus intensity. The potency of paired-pulse depression also depended on the time between paired stimuli, being maximal at an interpulse interval of 20 ms. The general relationships of paired-pulse depression to stimulus intensity and to interpulse interval were unaltered after LTP, after a single seizure, and after recurrent seizures, but there were quantitative changes in the last two cases. 3. A variety of pharmacologic agents known to interact with GABAergic inhibition were studied for their effect on paired-pulse depression. These agents affected earlier phases of paired-pulse depression (interpulse intervals less than or equal to 100 ms). The GABA agonist muscimol and the benzodiazepine diazepam enhanced paired-pulse depression whereas the GABA antagonist bicuculline decreased it. 4. Repeated seizures elicited by trains (50-Hz, 10-s durations every 5 min) of electrical stimuli to the hippocampus were associated with progressive lengthening of afterdischarges. 5. Recurrent seizures caused a statistically significant reduction in the potency of earlier phases of paired-pulse depression. There was an increase in the potency of later phases of paired-pulse depression after recurrent seizures, but this was not statistically significant. These changes were present for at least 2 h after the last seizure. 6. An antidromic-orthdromic paired-pulse protocol was used to exclude slow conductance changes as the cause of paired-pulse depression. Paired-pulse depression measured with this method was also decreased by recurrent seizures. 7. A single seizure caused a small reduction in paired-pulse depression that dissipated in less than an hour. 8. A single seizure caused LTP of stimulus intensity versus population spike curves whereas recurrent seizures attenuated or even reversed the potentiation, leading to a rightward shift of the curves relative to control curves. When LTP was produced by a less intense stimulus train (50-Hz, 400-ms duration), there were no associated seizures nor was there any change in paired-pulse depression.(ABSTRACT TRUNCATED AT 400 WORDS)
Monkey primary motor and premotor cortex: single-cell activity related to prior information about direction and extent of an intended movement
Authors: Riehle A. , Requin J.
Published: December 2017

1. This study was devoted to the neuronal processes underlying the construction of the motor program. Two monkeys were trained in a choice reaction time task to perform precise wrist flexion and extension movements of small and large extent. During a trial, the first visual signal, the preparatory signal (PS), informed the animal completely, partially, or not at all about direction and/or extent of the forthcoming movement. After a constant waiting period, a second visual signal, the response signal (RS), was illuminated calling for execution of the requested movement. 2. Reaction time (RT) and movement time (MT) measurements during the training as well as the recording sessions revealed that providing prior information about movement parameters strongly affected RT, but only slightly affected MT. Reaction time decreased in relation to the amount (number of movement parameters precued) and the type of prior information. Providing information about movement direction shortened RT much more than providing information about movement extent. Behavioral data support a parametric conception of motor programming, i.e., that the programming of the different movement parameters results from assembling separate processes of different duration. These results are compatible with the model in which programming processes are serially and hierachically ordered, movement direction being processed before movement extent. 3. Single-cell recording techniques were used to study neuronal activity of the primary motor (MI) and the premotor (PM) cortex, contralateral to the active arm. The activity of 155 neurons of MI and 158 neurons of PM was recorded during performance of the task. Of these 313 neurons, only 14 neurons did not change their activity during execution of the task. Two hundred and seven neurons whose activity changes were related to movement direction and/or movement extent have been selected for the further study. They were classified into three main groups: 1) execution-related neurons (49 in MI, 27 in PM), 2) preparation- and execution-related neurons (48 in MI, 54 in PM), and 3) preparation-related neurons (8 in MI, 21 in PM). 4. Directionally selective, execution-related neurons were found to be more frequently located within MI (81/105, 77.1%) than within PM (55/102, 53.9%), whereas directionally selective, preparation-related neurons appeared tobe more frequently located within PM (47/102, 46.1%) than within MI (24/105, 22.9%).(ABSTRACT TRUNCATED AT 400 WORDS)
Activity of hippocampal formation neurons in the monkey related to a conditional spatial response task
Authors: Miyashita Y. , Rolls E. T. , Cahusac P. M. , Niki H. , Feigenbaum J. D.
Published: December 2017

To analyze neurophysiologically the functions of the primate hippocampus, the activity of 905 single hippocampal formation neurons was analyzed in two rhesus monkeys performing a conditional spatial response task known to be impaired in monkeys and in man by damage to the hippocampus or fornix. In the task, the monkey learned to make one spatial response, touching a screen three times when he saw one visual stimulus on the video monitor, and a different spatial response, of withdrawing his hand from the screen, when a different visual stimulus was shown. Fourteen percent of the neurons fired differentially to one or the other of the stimulus-spatial response associations. The mean latency of these differential responses was 154 +/- 44 (SD) ms. The firing of these neurons was shown to reflect a combination of the particular stimulus and the particular response associated by learning in the stimulus-response association task and could not be accounted for by the motor requirements of the task, nor wholly the stimulus aspects of the task, as demonstrated by testing their firing in related visual discrimination tasks. Responsive neurons were found throughout the hippocampal formation, but were particularly concentrated in the subicular complex and the CA3 subfield. These results show that single hippocampal neurons respond to combinations of the visual stimuli and the spatial responses with which they must become associated in conditional spatial response tasks and are consistent with the suggestion that part of the mechanism of this learning involves associations between visual stimuli and spatial responses learned by single hippocampal neurons.
GABA- and glutamate-mediated synaptic potentials in rat dorsal raphe neurons in vitro
Authors: Pan Z. Z. , Williams J. T.
Published: December 2017

1. Synaptic potentials were recorded with intracellular electrodes from rat dorsal raphe neurons in a slice preparation. 2. Synaptic potentials were evoked by applying electrical pulses to bipolar stimulating electrodes positioned immediately dorsal to the raphe nucleus; these arose after a latency of 0.5-5 ms and had a duration of 20-200 ms. 3. The synaptic potential was biphasic (at the resting potential) when the recording electrodes contained potassium citrate; a depolarization was followed by a hyperpolarization. The hyperpolarization reversed in polarity at -70 mV and was blocked by bicuculline. 4. The depolarizing synaptic potential was reduced to 50-90% of control by kynurenate (1-2 mM) or 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX) (10 microM) and increased in amplitude and duration by magnesium-free solution. 5. In magnesium-free solutions (with CNQX), the depolarizing synaptic potential was blocked by DL-2-amino-5-phosphonovaleric acid (APV, 50 microM). APV also blocked depolarization caused by adding N-methyl-D-aspartate (NMDA) to the superfusion solution. 6. The results indicate that raphe neurons display two synaptic potentials having a duration of 150-200 ms: one that is mediated by GABA and a second that is due to an excitatory amino acid. The component mediated by an excitatory amino acid involves, in part, a receptor of the NMDA type.
Changes in properties of the medial gastrocnemius motor units in aging rats
Authors: Kanda K. , Hashizume K.
Published: December 2017

1. The properties of motor units were investigated in the medial gastrocnemius (MG) of old rats [27.5 +/- 1.6 (SD) mo old, n = 18]. Individual motor units were functionally isolated by ventral root fiber splitting and grading stimulus intensity. The muscle-unit portion of the motor unit was identified by the glycogen depletion method. The physiological properties of 77 motor units in 6 animals and the histological results of 7 slow-twitch (type S) muscle units were compared with data from motor units in the same muscle of middle-aged rats (12.8 +/- 1.6 mo old, n = 33). 2. The motor units were classified into four types of categories [FF (fast-twitch motor units with a fatigue index less than or equal to 0.5), FI (fast-twitch motor units with a fatigue index greater than 0.5 but less than 0.75), FR (fast-twitch motor units with a fatigue index greater than or equal to 0.75), S (slow-twitch motor units with a fatigue index greater than 0.75)] using the same criteria (i.e., presence or absence of the "sag" property and fatigability) used for middle-aged rats. No significant difference in the relative distributions of these unit types was detected, although the MG muscle in old rats exhibited a relatively high proportion of type S units and fewer type FR units. 3. The mean tetanic tensions for type FF + FI and FR units were significantly smaller than those in the middle-aged rats. On the other hand, type S motor units produced more tension than in the middle-aged rats. 4. The conduction velocity of motor axons was considerably slower in any unit type of old motor units, and the most marked change was found in type FR units. 5. The general morphological features of the old rat MG were fiber-type grouping, disseminated atrophic or angulated fibers, a decrease in the total number of muscle fibers, and an increase in the number of type I muscle fibers. The major distribution patterns of fibers of different types were the same as those in the middle-aged MG. 6. Seven type S units that produced large tetanic tension were depleted of glycogen in the muscle-unit portions. These units had a large innervation ratio compared with those in the middle-aged rats, whereas the mean cross-sectional area of muscle fibers and the calculated specific tension remained unaltered.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of 5-hydroxytryptamine on the afterhyperpolarization, spike frequency regulation, and oscillatory membrane properties in lamprey spinal cord neurons
Authors: Wallen P. , Buchanan J. T. , Grillner S. , Hill R. H. , Christenson J. , Hokfelt T.
Published: December 2017

1. Local application of 5-hydroxytryptamine (5-HT) in the area in which a dense 5-HT plexus is located in the lamprey spinal cord leads to a marked depression of the late phase of the afterhyperpolarization (AHP) following the action potential. This effect was observed in motoneurons, premotor interneurons, and giant interneurons, whereas no effect was observed in the sensory dorsal cells and edge cells. 2. The late 5-HT sensitive phase of the AHP was increased in amplitude when calcium entry was enhanced during the prolongation of action potentials caused by tetraethylammonium (TEA). Conversely, a blockade of Ca2+ entry by manganese reduced the AHP amplitude, suggesting that a calcium-dependent current, most likely carried by potassium, underlies the late phase of the AHP in these cells, as is the case in many other types of neurons. 3. The late phase of the AHP could be depressed by 5-HT although no effects were exerted on either the resting input resistance or on the shape of the action potential in 54% of the cells. The membrane conductance increase associated with the late phase of the AHP was markedly attenuated by 5-HT application. 4. In voltage-clamp experiments, Na+ currents and most K+ currents were blocked by tetrodotoxin (TTX) and TEA, respectively. Under these conditions, voltage steps elicited a slow outward current, most likely representing a Ca2+-activated K+ current, which was depressed by 5-HT application. 5. 5-HT does not appear to reduce AHP amplitude by blocking the calcium entry occurring during the action potential. No evidence was obtained for an involvement of second messengers such as adenosine-3':5'-cyclic monophosphate (cAMP), guanosine-3':5'-cyclic monophosphate (cGMP), diacyglycerol, or arachidonic acid. The effect of 5-HT on the late AHP may be due to a direct action on the calcium-dependent potassium channels or on the intracellular handling of Ca2+ ions. 6. The amplitude reduction of the AHP has a profound influence on the spike frequency regulation of any given cell; the frequency of spikes evoked by a given excitatory stimulus is therefore markedly increased by application of 5-HT. 5-HT thus increases the "gain" of the input-output relation of interneurons and motoneurons responsible for generating the locomotor rhythm. In addition, 5-HT causes a prolongation of the depolarized plateau of the N-methyl-D-aspartate (NMDA) receptor-induced membrane potential oscillations, as expected from the 5-HT-induced effects on the Ca2+-activated K+ channels that contribute to the repolarization.
Functional properties of monkey caudate neurons. II. Visual and auditory responses
Authors: Hikosaka O. , Sakamoto M. , Usui S.
Published: December 2017

1. Visual responses of caudate neurons were studied in monkeys trained to fixate on a small spot of light. A visual stimulus (another spot of light) was presented in various contexts of behavior using different behavioral paradigms. Visual receptive fields were usually large and centered on the contralateral hemifield. Among 217 neurons with visual responses, 184 were further classified into subtypes. 2. Visual responses in 64 neurons were not modulated by changing the paradigms (unconditional visual responses). In the other neurons, visual responses were dependent on the behavioral contexts in which the stimulus was presented. Three types of behavioral modulation were found. 3. A saccade-enhanced visual response (n = 37) was the one that was enhanced if the monkey made a saccade to the stimulus on its appearance. The enhancement was spatially selective: the response was depressed if the saccade was directed away from the stimulus. 4. Memory-contingent visual responses (n = 36) were present preferentially when the monkey remembered the location of the stimulus and a few seconds later made a saccade to the remembered location. Responses were greater when the location of the stimulus was randomized between trials. 5. Expectation-contingent visual responses (n = 46) were present preferentially when the stimulus came on while the monkey was not fixating another spot, and the stimulus was related directly to a reward. Unlike the other types, its receptive field included both contralateral and ipsilateral hemifields without a particular preference. 6. A small number of neurons (n = 16) showed a visual response that easily habituated. 7. Latencies of visual responses were usually between 100 and 200 ms. The latencies of the memory-contingent, expectation-contingent, and habituated visual responses tended to be longer than the others and tended to be more variable between trials. 8. Among auditory responsive neurons only a small proportion were related to the tasks. The response was greater to a contralateral sound. It was enhanced if the monkey used the sound as the cue for the future target location. 9. The results suggest that sensory responses of caudate neurons could be used to guide a subsequent sequence of learned behaviors by confirming predicted environmental states, renewing memory, or establishing a motor set.
Peptidergic modulation of a multioscillator system in the lobster. I. Activation of the cardiac sac motor pattern by the neuropeptides proctolin and red pigment-concentrating hormone
Authors: Dickinson P. S. , Marder E.
Published: December 2017

1. The cardiac sac motor pattern consists of slow and irregular impulse bursts in the motor neurons [cardiac sac dilator 1 and 2 (CD1 and CD2)] that innervate the dilator muscles of the cardiac sac region of the crustacean foregut. 2. The effects of the peptides, proctolin and red pigment-concentrating hormone (RPCH), on the cardiac sac motor patterns produced by in vitro preparations of the combined stomatogastric nervous system [the stomatogastric ganglion (STG), the paired commissural ganglia (CGs), and the oesophageal ganglion (OG)] were studied. 3. Bath applications of either RPCH or proctolin activated the cardiac sac motor pattern when this motor pattern was not already active and increased the frequency of the cardiac sac motor pattern in slowly active preparations. 4. The somata of CD1 and CD2 are located in the esophageal and stomatogastric ganglia, respectively. Both neurons project to all four of the ganglia of the stomatogastric nervous system. RPCH elicited cardiac sac motor patterns when applied to any region of the stomatogastric nervous system, suggesting a distributed pattern generating network with multiple sites of modulation. 5. The anterior median (AM) neuron innervates the constrictor muscles of the cardiac sac. The AM usually functions as a part of the gastric mill pattern generator. However, when the cardiac sac is activated by RPCH applied to the stomatogastric ganglion, the AM neuron becomes active in antiphase with the cardiac sac dilator bursts. This converts the cardiac sac motor pattern from a one-phase rhythm to a two-phase rhythm. 6. These data show that a neuropeptide can cause a neuronal element to switch from being solely a component of one neuronal circuit to functioning in a second one as well. This example shows that peptidergic "reconfiguration" of neuronal networks can produce substantial changes in the behavior of associated neurons.
Physiological and pharmacological analysis of suppressive rod-cone interaction in Necturus retina [corrected]
Authors: Eysteinsson T. , Frumkes T. E.
Published: December 2017

1. Intracellular recordings were obtained from retinal neurons of the mudpuppy, Necturus, while superfusing the eyecup with various pharmacologic agents. In most experiments, the retina was continuously stimulated with a small spot of red light that was centered over the recording electrode and flickering at rates too fast for amphibian rods to follow. The retina was additionally stimulated intermittently with a dim, spatially diffuse background field of 520 nm wavelength. 2. In general, the dim background greatly enhanced flicker responsiveness. We (16) previously called this effect suppressive rod-cone interaction (SRCI) and showed it reflects a tonic suppressive influence on cone pathways that is removed by selective rod-light adaptation. 3. Lead chloride has been claimed to selectively block rod-related retinal responses (13, 35). While recording from horizontal cells lead chloride decreases responses to the dim, diffuse light flashes, enhances the frequency entrained response attributable to cones, and eliminates a background influence on flicker responses. 4. O-phospho-D-serine (DOP), kynurenic acid (KyA), and piperidine dicarboxylic acid are known to act on horizontal cells as antagonists of the photoreceptor neurotransmitter (26, 32, 33). In both depolarizing and hyperpolarizing bipolar cells, these agents enhance flicker responsiveness with no background present and prevent background enhancement of flicker. 5. Mudpuppy cones were found to have a receptive-field surround, which under our stimulus conditions is attributable to rod input. KyA, which is unknown to have any direct influence on photoreceptors, totally blocks this surround mechanism. This indicates that the cone-surround mechanism is attributable to horizontal cell feedback. The influence of KyA on SRCI in cones is similar to that observed in recordings from depolarizing bipolar cells. 6. Most sustained third-order neurons demonstrate SRCI. In these cells, SRCI is blocked by DOP or KyA. Most ON-OFF neurons fail to demonstrate SRCI under control circumstances. The ON-response of these cells is blocked by 2-amino-4-phosphonobutyric acid (31) which leaves the OFF-response intact. While their ON-response is blocked, ON-OFF neurons demonstrate SRCI. 7. The foregoing results indicate that SRCI reflects a tonic, inhibitory influence of horizontal cells on cone pathways that is removed by light-adapting rods. In part, SRCI must involve horizontal cell feedback onto cones. SRCI in third-order neurons appears to largely reflect distal retinal processing.
Efferent neurons and suspected interneurons in S-1 vibrissa cortex of the awake rabbit: receptive fields and axonal properties
Authors: Swadlow H. A.
Published: December 2017

1. The behavioral tractability of the rabbit was exploited and enabled, in the fully awake state, receptive-field analysis of antidromically identified efferent neurons within the vibrissa representation of primary somatosensory cortex (S-1). Efferent neurons studied included ipsilateral corticocortical neurons (C-IC neurons, n = 56) that project to or beyond the second somatosensory cortical area (S-2) and corticofugal neurons of layer 5 (CF-5 neurons, n = 75) and layer 6 (CF-6 neurons, n = 92) that project to and/or beyond the thalamus. 2. An additional class of neurons was studied that was not activated antidromically from any stimulus site, but which responded synaptically to electrical stimulation of the ventrobasal (VB) thalamus with a burst of three or more spikes at frequencies of 600 to greater than 900 Hz. Most of these neurons also responded synaptically to stimulation of S-2. The action potentials of these neurons were much shorter (mean = 0.43 ms), than those of efferent neurons (mean = 0.98 ms). Such properties have been associated with interneurons found throughout the central nervous system, and these neurons are thereby referred to as suspected interneurons (SINs). Although SINs were found at all cortical depths, a strong peak in the distribution occurred just superficial to the peak in the distribution of CF-5 neurons. Most SINs located within this peak responded to deflection of only a single vibrissa. In contrast, SINs located in layer 6 and in layer 2-3 responded to deflection of many vibrissae (median = 11.0 and 5.5 vibrissae, respectively). In addition, SINs of layer 6 and layer 2-3 had significantly longer synaptic latencies to stimulation of VB thalamus than did SINs located at intermediate cortical depths. 3. The properties of efferent neurons and SINs differed considerably. Efferent neurons never responded to stimulation of VB thalamus with the high-frequency burst of spikes characteristic of SINs. Although greater than 70% of CF-6, CF-5 and C-IC neurons had receptive fields that were directionally selective, only 20% of SINs showed any degree of directional selectivity. Furthermore, SINs showed both much lower angular thresholds to vibrissa deflection and a much greater ability to follow high-stimulus frequencies than was seen in efferent neurons. The spontaneous firing rates of SINs had a mean value of 16.5 spikes/s, which was the highest seen in any population within S-1. 4. CF-5 neurons had a number of properties which contrasted with those of both CF-6 and C-IC neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Abducens internuclear neurons carry an inappropriate signal for ocular convergence
Authors: Gamlin P. D. , Gnadt J. W. , Mays L. E.
Published: December 2017

1. Single-unit recording studies in alert Rhesus monkeys characterized the vergence signal carried by abducens internuclear neurons. These cells were identified by antidromic activation and the collision of spontaneous with antidromic action potentials. The behavior of abducens internuclear neurons during vergence was compared with that of horizontal burst-tonic fibers in the medial longitudinal fasciculus (MLF) and to that of a large sample of unidentified abducens cells (presumably both motoneurons and internuclear neurons). 2. The results indicate that abducens internuclear neurons and lateral rectus motoneurons behave similarly during vergence eye movements: the majority of both groups of cells decrease their firing rate for convergence eye movements: a minority show no change for vergence. This finding is strongly supported by recordings of horizontal burst-tonic fibers in the MLF, the majority of which decrease their activity significantly for convergence eye movements. 3. These findings indicate that a net inappropriate vergence signal is sent to medial rectus motoneurons via the abducens internuclear pathway. Because medial rectus motoneurons increase their activity appropriately during symmetrical convergence, this inappropriate MLF signal must be overcome by a more potent direct vergence input. 4. Overall, both abducens internuclear neurons and lateral rectus motoneurons decrease their activity for convergence less than would be expected based on their conjugate gain. This implies that some degree of co-contraction of the lateral and medial rectus muscles occurs during convergence eye movements. 5. Some horizontal burst-tonic MLF fibers decrease their activity more for convergence than any recorded abducens neuron. These fibers may arise from cells in the nucleus prepositus hypoglossi or vestibular nuclei.
Deep neurons in piriform cortex. I. Morphology and synaptically evoked responses including a unique high-amplitude paired shock facilitation
Authors: Tseng G. F. , Haberly L. B.
Published: December 2017

1. Synaptic responses of cells in layer III of the piriform cortex and the subjacent endopiriform nucleus (layer IV) were analyzed with intracellular recording techniques in a slice preparation from the rat, cut perpendicular to the pial surface. 2. Micropipettes containing Lucifer yellow (LY) were used to correlate response properties with morphology. An antiserum to LY was used to intensify staining and to prevent fading during detailed morphological study. Response properties were also examined with potassium acetate-containing electrodes. 3. Morphologically, two cell types were identified: pyramidal cells that were confined to layer III of the piriform cortex and multipolar cells that were in layer III and the endopiriform nucleus. 4. In morphology, deep pyramidal cells in layer III closely resembled superficial pyramidal cells in layer II, with the exception that primary apical dendritic trunks were longer and basal dendritic arborizations were more extensive than apical. Like superficial pyramidal cells, apical dendrites of all deep pyramidal cells stained extended through the afferent fiber termination zone in layer Ia and gave rise to local axonal arbors that were concentrated in layer III and the endopiriform nucleus. 5. Multipolar cells were morphologically indistinguishable in layer III and the endopiriform nucleus. All gave rise to nonvaricose spiny dendrites that never extended into layer II and local axonal arbors. 6. Response properties of deep pyramidal and multipolar cells were similar; responses of both of these populations were very different from those of superficial pyramidal cells. The primary difference between responses of deep pyramidal and multipolar cells was a shorter latency of postsynaptic potentials evoked in deep pyramidal cells by stimulation of afferent fibers, consistent with the extension of their dendrites into layer Ia. 7. Responses of most deep cells to stimulation of afferent and association fibers at sufficiently high strength consisted of an initial excitatory postsynaptic potential (EPSP), followed by a fast Cl- -mediated and a slow K+-mediated inhibitory postsynaptic potential (IPSP). 8. A characteristic feature of deep cells, which was only rarely observed in superficial pyramidal cells, was the presence of variable EPSPs evoked at long latencies (greater than 100 ms) by stimulation of afferent or association fibers. 9. A striking finding for deep pyramidal and multipolar cells, when studied with LY-containing pipettes, was a variable slowly rising depolarizing potential triggered at depolarized membrane potentials by stimulation of afferent or association fibers.(ABSTRACT TRUNCATED AT 400 WORDS)
The detection and perceived intensity of noxious thermal stimuli in monkey and in human
Authors: Kenshalo D. R. , Anton F. , Dubner R.
Published: December 2017

1. The magnitude of the sensations produced by small increases in thermal stimuli superimposed on noxious levels of heat stimulation was studied by the use of a simple reaction-time task. Noxious thermal stimuli were presented on the face of three monkeys, the forearm volar surface of three monkeys, and the face of four human subjects. The subject, either monkey or human, initiated a trial by pressing an illuminated button. Subsequently, a contact thermode increased in temperature from a base line of 38 degree C to temperatures of 44, 45, 46, or 47 degrees C (T1). After a variable time period lasting between 4 and 10 s, the thermode temperature increased an additional 0.1, 0.2, 0.4, 0.6, or 0.8 degrees C (T2). The subject was required to release the button as soon as the T2 stimulus was detected. Detection latency, expressed as its reciprocal, detection speed, was defined as the time interval between the onset of T2 and the release of the button. 2. The monkeys' detection speed to stimuli presented on the upper lip was dependent on the intensity of both T1 and T2. Increases in the intensity of T2 between 0.1 and 0.8 degrees C produced faster detection speeds. In general, as the intensity of T1 increased, the detection speed increased to identical T2 stimuli. The monkeys' T2-detection threshold was also dependent on the intensity of T1. 3. The psychophysical functions obtained from stimulation of the monkey's face were compared with those obtained from the volar surface of the monkey's forearm. Whereas the T2 thresholds obtained from stimulation of the monkey's forearm and face were similar, the psychophysical functions obtained from stimulation of the face were significantly steeper than those obtained from stimulation of the forearm. 4. The humans' detection speed of T2 stimuli presented on the face was monotonically related to the intensity of T2 and was dependent on the level of T1. The psychophysical functions obtained from the human's face were equivalent to those obtained from the monkey's faces. 5. A cross-modality matching procedure was used to examine the perceived intensity of pain sensation produced by T2 stimuli in human subjects. The magnitude estimates of these stimuli were dependent on the level of T1, as well as the intensity of T2. Detection speed, plotted as a function of the estimated magnitude of pain, independent of T1 and T2 temperature, was best fit by a logarithmic function.(ABSTRACT TRUNCATED AT 400 WORDS)
5-HT-mediated synaptic potentials in the dorsal raphe nucleus: interactions with excitatory amino acid and GABA neurotransmission
Authors: Pan Z. Z. , Colmers W. F. , Williams J. T.
Published: December 2017

1. Intracellular recordings from neurons within dorsal raphe nucleus in slices from rat brain were used to study an inhibitory postsynaptic potential (IPSP) evoked by electrical stimulation. 2. The IPSP was observed in approximately 70% of neurons, had a latency to onset of 40-65 ms, reached a peak in 350-400 ms, had a total duration of 1-2 s, and reversed polarity at the potassium equilibrium potential. 3. This IPSP was blocked by spiperone (1 microM) and prolonged by fluoxetine (300 nM-30 microM) suggesting that it was mediated by 5-hydroxytryptamine (5-HT). 4. Superfusion with gamma-aminobutyric acid (GABA) and excitatory amino acid receptor antagonists were used to block "fast" synaptic potentials that preceded the IPSP such that it could be studied in isolation. Blockade of the GABA-mediated synaptic potentials increased the amplitude of the IPSP by 1.3-fold. The amplitude of the IPSP was reduced by 30% after blockade of the excitatory amino acid-mediated synaptic potential. 5. The results indicate that the IPSP recorded in dorsal raphe neurons was caused by 5-HT released at least in part from indirect (synaptically induced) excitation of 5-HT-containing cells within the slice.
Sensorimotor representations for pointing to targets in three-dimensional space
Authors: Soechting J. F. , Flanders M.
Published: December 2017

1. The accuracy with which subjects pointed to targets in extrapersonal space was assessed under a variety of experimental conditions. 2. When subjects pointed in the dark to remembered target locations, they made substantial errors. Errors in distance, measured from the shoulder to the target, were sometimes as much as 15 cm. Errors in direction, also measured from the shoulder, were smaller. 3. An analysis of the information transmitted by the location of the subject's finger about the location of the target showed that the information about the target's distance was consistently lower than the information about its direction. 4. The errors in distance persisted when subjects had their arm in view and pointed in the light to remembered target locations. 5. The errors were much smaller when subjects used a pointer to point to the target or when they were asked to reproduce the position of their finger after it had been passively moved to the target. 6. From these findings we conclude that subjects have a reasonably accurate visual representation of target location and are able to effectively use kinesthetically derived information about target location. We therefore suggest that errors in pointing result from errors in the sensorimotor transformation from the visual representation of the target location to the kinematic representation of the arm movement.
Errors in pointing are due to approximations in sensorimotor transformations
Authors: Soechting J. F. , Flanders M.
Published: December 2017

1. We define an extrinsic frame of reference to represent the location of a point in extrapersonal space relative to a human subject's shoulder, and we define an intrinsic frame of reference to represent the orientation of the arm and forearm. 2. We examined the relations between coordinates in the extrinsic and intrinsic frames of reference under two experimental conditions: when subjects made inaccurate movements by pointing to virtual targets in the dark and when they made accurate movements by pointing to actual targets in the light. 3. When subjects made inaccurate movements, there was a close-to-linear relationship between the orientation angles of the arm (intrinsic coordinates) at its final position and the extrinsic coordinates of the target. When they made accurate movements, these relationships were more nonlinear. 4. Specifically, arm and forearm elevations depended principally on target distance and elevation, whereas the two yaw angles depended mainly on the target's azimuth. 5. We propose that errors in pointing occur because subjects implement a linear approximation to the transformation from extrinsic to intrinsic coordinates and that this transformation is one step in the process of transforming a visually derived representation of target location into an appropriate pattern of muscle activity.
Human cortical potentials evoked by stimulation of the median nerve. II. Cytoarchitectonic areas generating short-latency activity
Authors: Allison T. , McCarthy G. , Wood C. C. , Darcey T. M. , Spencer D. D. , Williamson P. D.
Published: December 2017

1. The anatomic generators of human median nerve somatosensory evoked potentials (SEPs) in the 40 to 250-ms latency range were investigated in 54 patients by means of cortical-surface and transcortical recordings obtained during neurosurgery. 2. Contralateral stimulation evoked three groups of SEPs recorded from the hand representation area of sensorimotor cortex: P45-N80-P180, recorded anterior to the central sulcus (CS) and maximal on the precentral gyrus; N45-P80-N180, recorded posterior to the CS and maximal on the postcentral gyrus; and P50-N90-P190, recorded near and on either side of the CS. 3. P45-N80-P180 inverted in polarity to N45-P80-N180 across the CS but was similar in polarity from the cortical surface and white matter in transcortical recordings. These spatial distributions were similar to those of the short-latency P20-N30 and N20-P30 potentials described in the preceding paper, suggesting that these long-latency potentials are generated in area 3b of somatosensory cortex. 4. P50-N90-P190 was largest over the anterior one-half of somatosensory cortex and did not show polarity inversion across the CS. This spatial distribution was similar to that of the short-latency P25-N35 potentials described in the preceding paper and, together with our and Goldring et al. 1970; Stohr and Goldring 1969 transcortical recordings, suggest that these long-latency potentials are generated in area 1 of somatosensory cortex. 5. SEPs of apparently local origin were recorded from several regions of sensorimotor cortex to stimulation of the ipsilateral median nerve. Surface and transcortical recordings suggest that the ipsilateral potentials are generated not in area 3b, but rather in other regions of sensorimotor cortex perhaps including areas 4, 1, 2, and 7. This spatial distribution suggests that the ipsilateral potentials are generated by transcallosal input from the contralateral hemisphere. 6. Recordings from the periSylvian region were characterized by P100 and N100, recorded above and below the Sylvian sulcus (SS) respectively. This distribution suggests a tangential generator located in the upper wall of the SS in the second somatosensory area (SII). In addition, N125 and P200, recorded near and on either side of the SS, suggest a radial generator in a portion of SII located in surface cortex above the SS. 7. In comparison with the short-latency SEPs described in the preceding paper, the long-latency potentials were more variable and were more affected by intraoperative conditions.(ABSTRACT TRUNCATED AT 400 WORDS)