bluuebunny/crossref_metadata_2025 huggingface dataset:
Afferent fibers from mystacial vibrissae of cats and seals
Authors: Dykes R. W.
Published: December 2017

1. Studies of vibrissae of cats and seals revealed minor species-specific differences in functional characteristics of the afferent fibers: vibrissal fibers from the seal showed a significantly higher rate (P smaller than 0.05) and frequency of occurrence (P smaller than 0.01) of spontaneous activity, and a significantly greater percentage (P smaller than 0.01) responded to vibrations greater than 256 Hz. None of these differences could be interpreted as an adaptation to the aquatic environment. 2. Of 455 afferent fibers obtained from the infraorbital nerve, a large proportion (66% in cats and 85% in seals) served vibrissae. A population study of 357 such fibers showed that two-thirds were rapidly adapting (RA) and the remainder were slowly adapting (SA). Neither group displayed preferential directional sensitivity, but for 75% of the individual fibers in cats and 71% in seals, a particular direction elicited maximal response. 3. On the basis of their tuning curves, the RA fibers were divisible into three major groups: insensitive, sensitive, and those with frequency-dependent tuning curves. Single RA fibers provided little information about vibratory stimulus amplitude. However, it is postulated that the range of thresholds in the RA fiber group within each follicle represents a mechanism of encoding the intensity of vibratory stimuli. 4. By contrast, single SA fibers encoded precisely the intensity of steady stimuli. The average fiber conveyed 2.7 bits of information about the magnitude of vibrissal deflections of smaller than 17 degrees (1.5 mm, at 5 mm from skin). 5. Each type of fiber abstracted one or more features from the environment, and conveyed these abstractions by its individual pattern of neural activity. It is postulated that vibrissae provide fine textural information about surfaces.
Neuronal and glial activity during spreading depression in cerebral cortex of cat
Authors: Sugaya E. , Takato M. , Noda Y.
Published: December 2017

1. Extra- and intracellular potentials were recorded from neurons and glia during spreading depression (SD) in cerebral cortex of cats. The glial membrane depolarized during SD and the time course of depolarization was concurrent with the surface DC change of SD. The glial depolarization evoked by 20-Hz repetitive cortical stimulation disappeared during the negative DC shift of SD. Simultaneous recording of the extra- and intracellular potentials from a single glial cell with a coaxial microelectrode showed that the extracellular DC potential change was of opposite polarity to the glial intracellular potential, which suggests that the slow glial depolarization concurrent with SD is not the field potential. In contrast to glial cells, the neuronal burst discharges as well as the neuronal membrane depolarization associated with SD did not show a close relationship to SD: the neuronal membrane depolarization and discharge were frequently delayed by 10-3- s from the onset of the SD slow wave. Sometimes SD was observed without accompanying neuronal depolarization. The degree of neuronal depolarization was not always correlated with the amplitude of the negative wave of SD. 2. The effect of tetrodotoxin (TTX) on the negative DC potential of SD was examined. Simultaneous recording of glial membrane potential and the neuronal unit activity as well as extracellular DC potential and surface DC potential during SD was performed and the TTX-treated cortex was compared with the normal state. TTX did not change the DC level of the cerebral cortex. SD could be evoked by KCl when neuronal discharge was completely abolished by TTX application...
Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space
Authors: Mountcastle V. B. , Lynch J. C. , Georgopoulos A. , Sakata H. , Acuna C.
Published: December 2017

Experiments were made on the posterior parietal association cortical areas 5 and in 17 hemispheres of 11 monkeys, 6 M. mulatta and 5 M. arctoides. The electrical signs of the activity of single cortical cells were recorded with microelectrodes in waking animals as they carried out certain behavioral acts in response to a series of sensory cues. The behavioral paradigms were one for detection alone, and a second for detection plus projection of the arm to contact a stationary or moving target placed at arm's length. Of the 125 microelectrode penetrations made, 1,451 neurons were identified in terms of the correlation of their activity with the behavioral acts and their sensitivity or lack of it to sensory stimuli delivered passively; 180 were studied quantitatively. The locations of cortical neurons were identified in serial sections; 94 penetrations and 1,058 neurons were located with certainty. About two-thirds of the neurons of area 5 were activated by passive rotation of the limbs at their joints; of these, 82% were related to single, contralateral joints, 10% to two or more contralateral joints, 6% to ipsilateral, and 2% to joints on both sides of the body. A few of the latter were active during complex bodily postures. A large proportion of area 5 neurons were relatively insensitive to passive joint rotations, as compared with similar neurons of the postcentral gyrus, but were driven to high rates of discharge when the same joint was rotated during an active movement of the animal...
Organization of cat striate cortex: a correlation of receptive-field properties with afferent and efferent connections
Authors: Singer W. , Tretter F. , Cynader M.
Published: December 2017

The purposes of this study were 1) to relate the receptive-field characteristics of area 17 cells to their afferent and efferent connections, and 2) to obtain quantitative data from area 17 neurons for later comparison with area 18 cells. Intra- and extracellular recordings were obtained in paralyzed preparations which were anesthetized with nitrous oxide. The connectivities of the recorded cells were determined from responses to electrical stimulation of afferent and efferent pathways. In parallel to the classification of units as simple and complex cells, the receptive fields were grouped in four classes according to the spatial arrangement of on- and off-areas; class I, fields with exclusive on- or off-areas; class II, fields with spatially separate on- and off-areas; class III, fields with mixed on-off areas; class IV, fields which could not be mapped with stationary stimuli. The results from electrical stimulation suggest two major classes of cells: cells in the first group are driven mainly or exclusively by LGN afferents. They rarely receive additional excitation from intrinsic or callosal afferents and rarely possess corticofugal axons. Cells in the second group receive either converging inputs from LGN afferents and further intrinsic afferents or only from intrinsic afferents. They frequently received additional input from callosum and from recurrent collaterals of corticofugal axons. They project subcortically more often than cells in the first group. Cells in both groups can be driven either by X- or Y-type afferents. Cells in the first group have mainly class I and class II fields or simple fields, whereas the neurons in the second group have mainly class III and class IV fields or complex fields. Thus, simple and complex cells differ in their connectivity patterns, but the discriminative parameter is neither the selective connection to the X- or the Y-system nor, in a strict sense, the synaptic distance from subcortical input. From the combined consideration of receptive-field properties and connectivity patterns it is concluded that class I and class II cells or simple cells are concerned mainly with the primary analysis of subcortical activity, whereas class III and class IV cells or complex cells perform a correlative analysis between highly convergent activity from extrinsic and intrinsic afferents.
Modification of auditory and somatosensory system activity during pupillary conditioning in the paralyzed cat
Authors: Oleson T. D. , Ashe J. H. , Weinberger N. M.
Published: December 2017

The role of sensory systems in the development of behavioral conditioned responses was investigated by recording multiple-unit activity in the auditory and somatosensory pathways during Pavlovian conditioning of the pupillary-dilation responses of paralyzed cats. Establishment of conditioned pupillary-dilation responses to a white noise CS+, pupillary discrimination between the CS+ and a tone CS-, and subsequent discrimination reversal provided the behavioral foundation for examining neural changes related to behavioral learning. Multiple-unit responses to the acoustic CS+ were significantly enhanced in the auditory cortex, cochlear nucleus, and somatic cortex, but not in the cuneate nucleus. The possibility that these effects could be due to changes in stimulus intensity at the sensory receptor, to mo-ement artifacts, or to feedback from skeletal responses were ruled out because the animals were immobilized. Nor could these neural changes be attributable to sensitization, as those brain areas which showed conditioned enhancement to the CS+ exhibited significantly larger responses to the CS+ than to the CS-. Furthermore, the changes in neural activity followed the significance of the CS; after reversal of the reinforcement contingencies, the amount of multiple-unit activity evoked by the stimuli gradually reversed too. Although the somatic cortex showed conditioning and discrimination, greater stimulus specificity was found in the auditory system. Only in the somatic cortex was there a significant increase in responses to the CS- as well as the CS4. Furthermore, both somatosensory loci exhibited enhanced responses to those tactile probes presented during the acoustic CS, suggesting a phasic increase in neural excitability to all stimuli. Analysis of the number of trials required to attain an acquisition criterion indicated that the neural changes occurred first in the auditory cortex, then the cochlear nucleus, followed in turn by the somatic cortex, and finally the cuneate nucleus. However, none of these neural changes preceded acquisition of conditioned pupillary dilations. These results suggest that sensory system changes are not essential for the initial associative process. These findings indicate that the study of autonomic conditioned responses may prove beneficial in seeking the critical neural events which underlie the initial association between two stimuli. A hypothetical model, which explains the development of pupillary and sensory system conditioned responses, was also presented.
Unit activity in vestibular nucleus of the alert monkey during horizontal angular acceleration and eye movement
Authors: Fuchs A. F. , Kimm J.
Published: December 2017

Single units were recorded from the vestibular nuclei of unanesthetized monkeys that were rotated in the horizontal plane while simultaneously pressing individual buttons in a controlled array which turned with hem. Using this behavioral paradigm, it was possible to 1) determine the relationship of unit discharge to eye movements measured by the DC-coupled electrooculogram and calibrated by the button-press task, and 2) determine the relationship of unit discharge to horizontal acceleration, either with or without the compensatory eye movements evoked by vestibular stimulation. Based on their responses during vestibular stimulation and/or eye movements, neurons in the vestibular nuclei (77% of our sample was in the medial nucleus) could be divided into four groups...
Inferior colliculus. II. Development of tuning characteristics and tonotopic organization in central nucleus of the neonatal cat
Authors: Aitkin L. M. , Moore D. R.
Published: December 2017

Tuning curves were measured for 65 units in the inferior colliculus of seven anesthetized kittens aged from 6 to 28 days. At 2 days of age the inferior colliculus was divisible into central, pericentral, and external nuclei. Evidence was found for broader tuning curves to occur in the pericentral nucleus compared with the central nucleus, as has been observed in the adult. The middle ear was filled with serous fluid to 6 days, while the external auditory meatus remained collapsed until 10 days. Central nucleus tuning curves in kittens were relatively flat with high thresholds. Best-frequency thresholds diminished from a mean of near 100 dB SPL at 6-11 days to near 50 dB in the adult. The marked drop in thresholds between days 22 and 21 led to the adoption of the sharp form of tuning curve common for adults. Tonotopic organization of the central nucleus was clear at day 11. Speculations were advanced about the dependence of central auditory maturations on cochlear development, axon myelination in the auditory pathway, and changes in synaptic density as a function of age.
Receptive-field characteristics of single neurons in lateral suprasylvian visual area of the cat
Authors: Spear P. D. , Baumann T. P.
Published: December 2017

The visual receptive fields of 213 cells in the lateral suprasylvian visual cortex (LS, or Clare-Bishop area) were studied in cats anesthetized with nitrous oxide. Eighty-one percent of the cells were directionally selective. They responded poorly to stationary stimuli flashed on or off, but gave a directionally selective response to stimuli moving through the receptive field. Most of these had a single preferred direction and an opposite null direction. They typically responded to a range of directions of stimulus movement from 45 to 90 degrees to either side of the preferred direction. Small stimuli (1-2 degrees or smaller) typically were effective and 87% of the directionally selective cells showed spatial summation. About 32% had inhibitory mechanisms which decreased the response of the cell if the stimulus exceeded a maximum size. There was little or no evidence that LS area cells were orientation selective or sensitive to variations in stimulus shape independent of size.
Information signaled by sensory fibers in medial articular nerve
Authors: Clark F. J.
Published: December 2017

Responses of 331 individual medial articular nerve fibers innervating the cat knee joint were tested to bending the joint over its entire range and to pressing on the tissues of the joint. The 331 fibers were classified into five groups on the basis of their discharge characteristics: slowly adapting (64), phasic (103), Pacinian corpuscle-like (12), weakly activated (39), and nonactivated (113). Five of the slowly adapting and all twelve of the Pacinian corpuscle-like receptors responded at intermediate joint angles. The remainder responded, if at all, only near the extremes of joint bending or twisting. Many of these same receptors could be activated by pressing about the knee. Sometimes gentle pressure on the focus sufficed to produce a vigorous discharge. The properties of these receptors are considered to be consistent with the hypothesis that articular mechanoreceptors do not signal joint angle but are involved in deep-pressure sensations.
Mechanical factors influencing response of joint afferent neurons from cat knee
Authors: Grigg P.
Published: December 2017

The responses of 67 slowly adapting joint afferent neurons in cat posterior articular nerve (PAN) were studied in relation to mechanical stimulation of the knee. The response of most neurons could be interpreted in terms of the stretching of joint tissues resulting from angular displacement of the knee. No neurons discharged at angles intermediate between the limits of movement of the joint. The limits of movement of the joint were operationally defined in terms of displacements resulting from applied torques.
Direction selectivity of complex cells in a comparison with simple cells
Authors: Goodwin A. W. , Henry G. H.
Published: December 2017

Following our earlier study on direction selectivity in simple cells (5), the present findings on complex cells made it possible to compare the direction selectivity in the two types of striate cell. Common properties were found in the dimension of the smallest stimulus displacement giving a direction-selective response and in the role of inhibition in suppressing the response as the stimulus moved in the nonpreferred direction. However, the effectiveness of this inhibition varied in the two cell types since it suppressed both driven and spontaneous activity in the simple cell, but only driven firing in the complex cell. It is argued that direction selectivity must enter the response before the complex cell if the inhibition responsible for it's generation fails to influence the spontaneous activity of the cell. The consequences of this finding are considered in the terms of parallel or sequential processing of visual information in striate cortex.
Spatiotemporal organization of cat lateral geniculate receptive fields
Authors: Stevens J. K. , Gerstein G. L.
Published: December 2017

Spatial and temporal properties of LGN receptive fields were studied by flashing a small bar of light across the field in 28 discrete steps. The flashes at each of the spatial positions were used to produce 28 PST histograms. These histograms were in turn displayed as a plane, with space on the chi axis, time on the psi axis, and probability of firing on the zota axis. These response planes demonstrate that the terms on, off, center, and surround do not adequately describe when the simplest LGN receptive field. We, therefore, introduce a new terminology describing the four major spatiotemporal components of LGN fields. The primary excitatory (PE) domain corresponds to the strongest excitatory response, the secondary excitatory (SE) domain corresponds to the second-strongest excitatory domain, the primary inhibitory (PI) domain corresponds to the strongest inhibitory domain and, finally, the secondary inhibitory (SI) domain corresponds to the second-strongest inhibitory domain. Based on the arrangement of these four domains, it is possible to divide LGN fields into four major categories: 1) homogeneous-on, on-center receptive fields which have a spatially homogeneous distribution of domains; 2) homogeneous-off, off-center receptive fields which have a spatially homogeneous distribution of domains; 3) heterogeneous-on, on-center receptive fields which have a spatially heterogeneous distribution of domains; and 4) heterogeneous-off, off-center receptive fields which have a spatially heterogeneous distribution of domains; 3) heterogeneous-on, on-center receptive fields which have a spatially heterogeneous distribution of domains; and 4) heterogeneous-off, off-center receptive fields which have a spatially heterogeneous distribution of domains. Using grating, it can be demonstrated that our heterogeneous/homogeneous fields correspond to X/Y fields, respectively. These data lead us to suggest that retinal PE domains generage LGN PE and SI domains, while retinal SE domains generate LGN SE and SI domains.
Fast and slow pyramidal tract neurons: an intracellular analysis of their contrasting repetitive firing properties in the cat
Authors: Calvin W. H. , Sypert G. W.
Published: December 2017

1. Intracellular recordings were made from an estimated 500 neurons in the sensorimotor cortex of barbiturate-anesthetized cats. Of those which were antidromically identified from the medullary pyramids, 70 were selected which also exhibited steady repetitive firing to steps of current injected through the recording electrode; 81% were "fast" (conduction velocity greater than 20 m/s) and 19% were "slow". 2. As shown by earlier workers, the spike duration is a function of conduction velocity; a spike duration of 1.0 ms is the dividing line between fast and slow. 3. Of the 57 fast pyramidal tract neurons (PTNS), 14 exhibited double spikes during otherwise rhythmic firing patterns to a step of injected current. These very short interspike intervals (usually 1.5-2.5 ms) were first seen interspersed in a rhythmic discharge (e.g., 50-ms intervals) but, with further increases in current strength, would come to dominate the firing pattern; e.g., double spikes every 40 ms. Further increases in current would typically shorten only the long intervals; e.g., 40-30 ms, but some fast PTNS developed triple spikes, etc. 4. The extra spike appears to arise from a large hump which follows most spikes in fast PTNS; while this humplike "depolarising after-potential" can also be seen in slow PTNS, it is small. Extra spikes were seen only in fast PTNS with large postspike humps; in perhaps half of the fast PTNS, extra spikes probably contributed to "adaptation." 5. Slow PTNS often had frequency-current curves which were not repeatable; a "hysteresis" phenomenon could often be seen, where the proportionality constant relating current to firing rate decreased following high firing rates. 6.The B spike was distinguishable from the A spike in differentiated antidromic spikes in 77% of the slow PTNS, in only 14% of the fast PTNS which later exhibited double spikes during current-induced repetitive firing, and in 53% of the other fast PTNS. 7. The antidromic spike heights of doublet PTNS were not significantly different from those of other repetitively firing PTNS.
Mechanisms underlying achievement of final head position
Authors: Bizzi E. , Polit A. , Morasso P.
Published: December 2017

The studies reported here are directed toward understanding some of the mechanisms whereby the central nervous system terminates a given phase in a motor sequence and maintains a newly acquired position. In particular, we investigated the extent to which the termination of a centrally initiated head movement in monkeys and the subsequent maintenance of posture depend on a readout of proprioceptive afferent input generated during the movement itself or are instead centrally programmed. We approached this question in two ways: first, using vestibulectomized, but otherwise intact monkeys, we applied load disturbances unexpectedly at the beginning and throughout centrally initiated head movements with the aim of provoking a proprioceptive response in all types of neck receptors and to observe the outcome of this stimulation on the head final position. In a second set of experiments, we interrupted the flow of afferent input by cutting cervical and upper thoracic dorsal roots and observed how the absence of proprioceptive feedback affects the achievement of final head position. The results indicated that the central pattern of neural impulses establishing final head position is preprogrammed and it is not reset by the afferent proprioceptive impulses generated during the intended movement. In addition, our findings are consistent with the view that final head position is an equilibrium point dependent on a number of factors, such as the firing rate and the recruitment of the alpha motoneurons, the length-tension properties of the muscles involved in posture, and passive elastic properties of external loads.
Effects of dorsal column stimulation on primate spinothalamic tract neurons
Authors: Foreman R. D. , Beall J. E. , Coulter J. D. , Willis W. D.
Published: December 2017

The effect of dorsal column stimulation on spinothalamic tract cells was investigated in anesthetized monkeys. The dorsal column stimuli were applied at midthoracic or at cervical levels of the cord, while the responses of spinothalamic tract cells of the lumbosacral enlargement were examined. A dorsal column volley depressed the activity of spinothalamic tract cells for about 150 ms. A similar depression was observed whether the spinothalamic tract cell was classified as hair activated, low, or high threshold, based on its response properties to cutaneous stimulation. The hair-activated and low-threshold spinothalamic tract cells were initially excited by the dorsal column volley, but often it was possible to demonstrate that a depression could be produced by stimuli which were too weak to cause excitation of these cells. Depression was produced both of the responses of spinothalamic tract cells to electrical stimulation of peripheral nerves and to mechanical stimulation of cutaneous nociceptors. A similar depression was produced by electrical stimulation of large afferents in peripheral nerves.The pathway mediating the depression of spinothalamic tract cells was shown to involve antidromic invasion of collaterals of dorsal column fibers. The best points for stimulation of the cord to produce a depression were over the ipsilateral dorsal column. A lesion interrupting the dorsal column eliminated the depression of cells below the lesion, whereas a lesion of much of the lateral column had no effect.The mechanism of the depression is likely to be complex. Apart from interactions at an interneuronal level, dorsal column volleys can be presumed to collide with sensory input from afferents which project up the dorsal column; collision would interfere chiefly with the responses of hair-activated and low-threshold spinothalamic tract cells. In addition, dorsal column volleys were shown to evoke inhibitory postsynaptic potentials in some spinothalamic tract neurons, and they also produced primary afferent depolarization, at least of large cutaneous afferemts.The excitation of hair-activated and low-threshold spinothalamic tract cells argues against their participation in signaling pain, since dorsal column stimulation in humans does not produce pain at stimulus intensities and frequencies which should activate such neurons. Alternatively, an ascending volley in the dorsal column or in other pathways may interfere with pain transmission in the brain.
Organization of monkey superior colliculus: enhanced visual response of superficial layer cells
Authors: Wurtz R. H. , Mohler C. W.
Published: December 2017

1. Cells in the superficial layers of monkey superior colliculus respond more vigorously to a spot of light falling in their receptive fields when the monkey uses that spot of light as the target for a saccadic eye movement. Our purpose in these experiments was to investigate the characteristics of this enhancement effect. While monkeys fixated, we determined the response of a cell to a stimulus falling in its receptive field. Then we determined the response of the cell to the same stimulus when the monkey made a saccade to the stimulus or near to it. 2. The enhancement of the visual response is spatially limited. The receptive field of a cell always shows enhancement throughout its extent and frequently shows a slight expansion. Saccades made near to a stimulus in the visual receptive field, but not to it, also lead to an enhancement of that visual stimulus; an area around the excitatory center of the receptive field where such enhancement occurs was referred to as the enhancement field of the cell. An enhanced response in one part of the visual field was not accompanied by depressed responses associated with saccades to other parts of the visual field. 3. The enhancement effect is temporally limited; it begins 200-300 ms before the eye movement, as determined by the increasing response to 50-ms light pulses presented at varying intervals before the eye movement. The degree of enhancement intensifies when the visual stimulus is turned on closer in time to the onset of the saccade. A buildup of the enhancement also occurs on successive trials as does the response of eye movement-related cells in the intermediate layers. 4. The enhancement response is not present in the upper quarter-millimeter of the superficial layers, suggesting that the effect is not present in retinal afferents which terminate primarily in this area of the superficial layers. The enhancement effect is seen throughout the visual field; the foveal area was not tested. 5. In order to determine the relation of the enhancement effect to the monkey's behavioral response, we required the monkey to make a hand response rather than an eye movement-response to the visual stimuli. Cells did not show a clear enhancement with such a hand response. Results of these experiments indicate that the enhancement effect is dependent on the type of response the monkey makes to the stimulus and is probably specifically related to eye movements. Since the enhancement of visual response seems likely to be related specifically to eye movements both on physiological and behavioral grounds, the response-free term "attention" is probably inappropriate for the phenomenon. 6. The hypothesis advanced in the preceding paper that eye movement-related activity from intermediate and deep colliculus layers is directed upward to converge with visually related activity in the superficial layers is extended to include an input from cells in these deeper layers (or their afferents) to the superficial layer cells...
Enhancement of visual responses in monkey striate cortex and frontal eye fields
Authors: Wurtz R. H. , Mohler C. W.
Published: December 2017

1. We have studied the visual enhancement effect in two areas of the cerebral cortex of monkeys. The response of the cells to a visual stimulus was determined both when the monkey used the visual stimulus as the target for a saccadic eye movement and when he did not. 2. In striate cortex cells with nonoriented, simple, complex, and hypercomplex receptive-field types were studied. Clear enhancement of the response to the appropriate visual stimulus was seldom seen when the monkey used the stimulus as a target for a saccade. In addition, any enhancement effect seen was nonselective; it occurred whether the monkey made a saccade to the receptive-field stimulus or some other stimulus at a point distant from the receptive field. The enhancement also occurred whether the monkey made a saccade to the stimulus or just released the bar when the stimulus dimmed. 3. This nonselective enhancement in striate cortex is in striking contrast to the selective enhancement of the visual response seen in the superior colliculus. The different characteristics of the enhancement in striate cortex and the observation of enhancement in the colliculus following ablation of striate cortex suggest that this cortical area is an unlikely source of the collicular enhancement. 4. These observations reinforce the distinction between striate cortex and superior colliculus. Striate cortex is an excellent analyzer of stimulus characteristics but a poor evaluator of stimulus significance. The superior colliculus is an excellent evaluator but a poor analyzer. 5. The area of frontal eye fields in which cells have clear visual responses has been better localized. Enhancement of the visual response of these cells also occurs and, at least for some cells, the response enhancement is selective. The response enhancement, like the visual properties of these frontal eye field cells, appears to be more closely related to the properties of superior colliculus cells than to striate cortex cells.
Integration of directional mechanosensory input by crayfish interneurons
Authors: Wiese K. , Calabrese R. L. , Kennedy D.
Published: December 2017

1. Interneurons activated by mechanosensory hairs on the crayfish telson respond selectively to directional displacements of the medium; the directions of maximum sensitivity lie 180 degrees apart in approximately the rostrocaudal plane, corresponding to the directional sensitivities of the two populations of primary afferent neurons. We have examined the basis for this selectivity by intracellular recording in the interneurons, correlating subthreshold potentials with activity evoked in identified afferents by bending single hairs or by producing nearfield displacements of the medium. 2. Interneurons can usually be caused to discharge by a brief train of impulses in single sensory axons. Unitary EPEPs are associated with arriving affterent spikes in the fourth (sensory) root; each primary interneuron receives convergence from several sensory axons, all sensitive to the same direction of movement. Since each afferent axon is drawn from a pair innervating a single sensory structure, this remarkable specificity of connection is unlikely to depend on an anatomical mode of address. 3. Higher order interneurons receive from directionally sensitive lower order interneurons of the same class, as well as from primary afferents of that class. The responses of such cells may show much more decrement during a train of displacement stimuli than do those of lower order cells. Directionality does not appear to be enhanced. 4. During the "null phase" some interneurons appear to be actively inhibited: bending of single hairs 180 degrees away from the effective direction may produce membrane hyperpolarization and slow spontaneous discharges, and shocks to afferent roots produce mixtures of monosynaptic EPSPs and polysynaptic IPSPs.
Modulation of spike frequency by regions of special axonal geometry and by synaptic inputs
Authors: Spira M. E. , Yarom Y. , Parnas I.
Published: December 2017

1. Spike propagation across the nonhomogeneous section of the giant axon in ganglion T3 of the cockroach was analyzed by intracellular microelectrodes recording at the posterior and anterior ends of T3. Ascending and descending potentials were evoked by stimulation of A5-A6 and T2-T3 connectives. 2. At high frequencies, descending and ascending impulses exhibit the following: a) consecutive reduction in the spike amplitude, b) a decrease in the afterhyperpolarization; c) gradual appearance of a prepotential together with an increase in delay of spike initiation; d) failure of full spike invasion into the recording area, showing only a decremental potential. 3. The duration of a train required to block spike propagation when the whole connective is stimulated is much shorter (about 6 times) than that required when a single giant axon is stimulated. 4. The conduction block is associated with a marked decrease in effective membrane resistance, greater than that expected from depolarization and delayed rectification. 5. Synaptic potentials could be recorded in the giant axons in the caudal base of ganglion T3 after stimulation of either the ipsilateral or contralateral connectives at both ends of the ganglion. These synaptic potentials could be blocked by d-tubocurarine (d-TC) or low Ca2+-high Mg2+. 6. Activation of these synapses produces a marked increase in membrane conductance, blocking propagation of spike trains through the ganglion. 7. After these synapses are blocked by d-TC or low Ca2+-high Mg2+, high-frequency stimulation still produces a conduction block. 8. It seems that conduction of spike during repetitive stimulation is affected both by accumulation of extracellular potassium, which depolarizes the membrane and causes sodium inactivation, and by activation of synaptic inputs to shunt the membrane in this region. 8. Each of these two mechanisms by itself can produce conduction block along the giant axons in ganglion T3.
Activity of ventrolateral thalamic neurons during arm movement
Authors: Strick P. L.
Published: December 2017

1. Monkeys were trained to maintain the handle of a manipulation within a small zone despite perturbations to the handle and to perform slow and rapid arm movements triggered by a visual stimulus. The activity of neurons in the region of the ventrolateral thalamus which projects directly to the arm area of the motor cortex (VL arm area) was then examined during performance of the task and while the animal's limb was passively manipulated. 2. Thalamic units related to arm movement were confined to the VL arm area. Microstimulation (less than 25 muA) in the VL arm area could, in some instances, evoke localized contractions of shoulder, arm, and hand musculature. Thalamic units whose discharge appeared to be related to jaw, tongue, and neck muscle activity occurred only medial to arm movement-related units, and units related to spontaneous leg movements occurred only laterally. 3. Most VL arm area neurons, although well related to active arm movements, were not influenced by gentle passive manipulation of the animal's limb. Few VL arm area neurons responded at short latency to perturbations applied to the handle of the manipulandum which the animal was holding. Thus, VL arm area neurons are unlike many motor cortex arm area neurons which are responsive to passive manipulation and are influenced at short latency by similar perturbations to the animal's limb. 4. Most arm movement-related VL neurons discharge during both fast and slow arm movements. Although a few neurons varied their discharge only during fast movements, none varied only in relation to slow movements. VL arm area neurons are, therefore, unlike the neurons in one source of its input, the globus pallidus, where some neurons are preferentially related to slow movements. 5. Some VL arm area neurons vary their discharge before any change in muscle activity during a fast and slow movement. Such neurons were recorded in VL regions which project to motor cortex areas representing proximal and distal musculature. This suggests that VL neurons might play a role in initiating activity in muscles concerned with controlling body posture, as well as those involved in discrete limb movements.20
Physiology of peripheral neurons innervating otolith organs of the squirrel monkey. I. Response to static tilts and to long-duration centrifugal force
Authors: Fernandez C. , Goldberg J. M.
Published: December 2017

1. The response to static tilts was studied in peripheral otolith neurons in the barbiturate-anesthetized squirrel monkey (Saimiri sciureus). Each unit was characterized by a functional polarization vector, which defines the axis of greatest sensitivity. A circumstantial criterion was used to assign units to the inferior (IN) or superior (SN) vestibular nerves. The former neurons should innervate the sacculus, the latter mainly the utriculus. Confirming pasting experiments, the polarization vectors for SN units lay near the plane of the utricular macula, those for IN units near the plane of the saccular macula. The polarization vectors for IN units were compared in two groups of animals. In one group, the vestibular nerve was intact; in the other, the superior nerve was sectioned. No differences were found and this, together with other observations, demonstrate that the sacculas in mammals functions mainly (if not solely) as an equilibrium organ. 2. The resting discharge of otolith neurons averages some 60 spikes/s, the sensitivity some 30-40 spikes/s-g. IN units tend to have slightly lower sensitivities than do SN units. IN units with upwardly directed (+Z) vectors have substantially higher resting discharges than do units with downwardly directed (-Z) vectors. The +Z units are also characterized by more linear force-response relations. 3. There is a strong positive relation between the resting discharge and sensitivity of units characterized by regular steady-state discharge patterns. A weaker, but statistically significant, relation is demonstrable for irregular units. It is suggested that the relation seen in regular units is the result of the neurons differing from one anothrer in terms of a receptor bias, a transduction gain, or both. Only the mechanism based on transduction gain is thought to be operative among the population of irregular units. 4. Centrifugal-force trapezoids were used to study the response adaptation to prolonged stimulation. Adaptation was more conspicious in irregular units and was characterized by perstimulus response declines and poststimulus secondary responses. For regular units, adaptive properties were similar during excitatory and inhibitory responses. For irregular units, response declines were larger during excitatory stimuli, secondary responses larger following inhibitory stimuli. Typically, response declines were most rapid at the start of the force plateau. A few units, all of them irregular, exhibited a delayed adaptation with response declines beginning only after a constant force had been maintained for 10-20 s. 5. Excitatory responses of regular units are almost always larger than inhibitory responses. This is so during both the dynamic and static portions of force trapezoids. A similar asymmetry is seen in the dynamic response of irregular units; static response asymmetries of the latter units are more variable.
Responses of fibers in medial longitudinal fasciculus (MLF) of alert monkeys during horizontal and vertical conjugate eye movements evoked by vestibular or visual stimuli
Authors: King W. M. , Lisberger S. G. , Fuchs A. F.
Published: December 2017

Extracellular recordings were obtained from 37 histologically identified MLF fibers near the trochlear nucleus in alert monkeys trained to perform a visual tracking task and subjected to adequate horizontal and vertical vestibular stimulation. The behavioral paradigm permitted independent quantitative assessment of a fiber's response to eye or head movements. 2. According to their discharge pattern, almost all MLF fibers were placed in one of two classes: 1) Horizontal burst-tonic fibers (n = 20). During both vestibular and visually evoked eye movements, burst-tonic fibers discharged in strict relation to horizontal eye movements, exhibiting a burst of activity prior to on-direction saccades and steady firing related to horizontal eye position during fixations. 2) Vertical vestibular plus eye-position fibers (n = 14). Vertical fibers discharged in relation to vertical head velocity in the absence of eye movements and in relation to vertical eye position in the absence of head movement, and paused with saccades in any direction. 3. The quantitative similarity of horizontal burst-tonic fiber discharge to that of ipsilateral medial rectus oculomotoneurons suggests that burst-tonic fibers provide the major excitatory synaptic drive to medial rectus motoneurons during conjugate eye movements of vestibular or visual origin. 4. The discharge pattern of vertical vestibular plus eye-position fibers is significantly different from that of oculomotoneurons, suggesting that additional neural processing of vertical fiber information must occur in the mesencephalon. 5. The functional dichotomy of horizontal and vertical MLF fibers and their contrasting discharge patterns provide new evidence for the anatomic and functional separation of horizontal and vertical eye movement mechanisms in the pons and mesencephalon, respectively.
Effect of stimulation with light on synthesis and release of acetylcholine by an isolated mammalian retina
Authors: Masland R. H. , Livingstone C. J.
Published: December 2017

1. Acetylcholine synthesis and release were studied in rabbit retinas isolated from the eye and incubated under conditions in which their electrophysiological function is maintained. ACh synthesized from exogenous [14C] choline appeared in the retina at an initial rate of 16 nmol/g wet wt-h. Incorporation of labeled choline into ACh was accelerated by stimulation of the retina with light. 2. Retinas incubated for 40 min in the presence of labeled choline and then superfused with a medium containing an anticholinesterase released radioactive ACh into the perfusate. The rate of release increased approximately fourfold during stimulation with light. 3. When retinas were incubated with labeled choline and then superfused with medium containing no pharmacological agents, stimulation with light caused an increased release of choline into the perfusate. The recovery of labeled choline following stimulation was enhanced by hemicholinium 3. 4. Neither the light-induced release of ACh (in perfusate containing anticholinesterase) nor the light-induced release of choline (in perfusate containing no anticholinesterase) occurred if the perfusate contained 20 mM Mg2+ and 0.2 mM Ca2+. 5. Synthesis of ACh by the retina at a high rate, acceleration of choline incorporation by stimulation, and Ca2+-dependent release of ACh by stimulation are each presumptive evidence that the retina contains a cholinergic synapse. If this presumption is correct, one such synapse mayx be of an amacrine or bipolar cell since these cells can depolarize during illumination, whereas the predominant response of receptor and horizontal cells is hyperpolarization.
Quantitative studies of single-cell properties in monkey striate cortex. III. Spatial frequency
Authors: Schiller P. H. , Finlay B. L. , Volman S. F.
Published: December 2017

1. The response properties of single cells in monkey striate cortex were examined using moving bars, square-wave gratings, and sine-wave gratings. 2. The moving of cells studied were not selective for bar width or for the spatial frequency of square-wave gratings. 3. Most cells responded selectively to the spatial frequency of the sine-wave gratings. 4. The spatial frequency of the sine-wave grating eliciting the optimal response could not be predicted from the organization of the receptive field of each cell as determined by stationary or moving stimuli. 5. The sharpness of spatial-frequency selectivity is only slightly more pronounced in S-type cells than in CX-type cells. 6. S-type and CX-type cells differ significantly in the temporal modulation of their discharges to gratings. S-type cells discharge in sharp bursts to each cycle which traverses the receptive field. CX-type cells discharge in a rather continuous fashion. This measure can be used reliably to classify cells as S or CS type.
Analysis of muscle receptor connections by spike-triggered averaging. 1. Spindle primary and tendon organ afferents
Authors: Watt D. G. , Stauffer E. K. , Taylor A. , Reinking R. M. , Stuart D. G.
Published: December 2017

1. The synaptic connections of 44 single identified muscle spindle Ia afferents and of 21 Golgi tendon organ (Ib) afferents from medial gastrocnemius (MG) were studied in 46 cats by the spike-triggered averaging of synaptic noise in 803 motoneurons of various types. 2. The well-known monosynaptic Ia excitatory connections were confirmed and their characteristics examined in 113 cells. The method was used at greater sensitivity than before and revealed that, in addition to the larger EPSPs of the order of 300 muV, there were many below the previously reported lower 17-muV limit. 3. By studying the Ia disynaptic inhibitory pathway with quick stretch-evoked Ia volleys and by spike-triggered averaging (STA), it was shown that the latter method can reveal disynaptic and possibly trisynaptic excitatory connections. This is believed to depend on having continuous activity in the relevant interneurons. 4. Latencies of individual connections showed broad distributions and arguments are advanced for setting working limits to mono- and disynaptic paths for Ia excitation and inhibition. Monosynaptic EPSP latency from cord entry was 0.4-1.1 ms and disynaptic inhibition was 1.2-2.4 ms. It was recognized that the boundaries are not rigid and monosynaptic Ia EPSPs may have latencies up to 1.5 ms. 5. Rise times of disynaptic PSPs were, on average, significantly longer than monosynaptic, but individual disynaptic responses could have values within the monosynaptic range. 6. A small diphasic wave shortly preceding the monosynaptic EPSPs was interpreted as a presynaptic spike. Its timing was consistent with this and, as such, permitted estimates to be made of central conduction time. 7. An early negative wave (latency less than or equal 1.1 ms) of small emplitude was sometimes detected in antagonist motoneurons when triggering from Ia afferents. It was found tha extracellular fields could be detected due to single Ia afferent excitations and efforts were made to see if the early negative wave could be explained by this. In a few cases there was evidence that a very short-latency IPSP might be occuring. This evidence and its implications are discussed with attention to the new factors which have to be considered in using the spike-triggered averaging method at very high sensitivity. 8. Ib effect were di- or trisynaptic. They were excitatory to 18% of synergists and to 28% of antagonists. They were inhibitory to 41% of synergists and to 19% of antagonists. The Ib IPSPs were larger than the EPSPs.