bluuebunny/crossref_metadata_2025 huggingface dataset:
Response properties of vibrissa units in rat SI somatosensory neocortex
Authors: Simons D. J.
Published: December 2017

1. Glass microelectrodes were used to record extracellular responses from 308 SI cortical neurons to deflections of the contralateral vibrissae in 21 unanesthetized, paralyzed rats. Controlled deflections of individual hairs were produced by means of an electromechanical stimulator. Fast green dye marks were made to aid histological reconstructions of electrode tracks. 2. TS) were observed throughout layers II--VI; "fast" cortical spikes (FS) were less frequently encountered and largely restricted to layer IV. Although both types of potentials had similar negative-positive waveforms. FSs were distinguished from RSs by their comparatively rapid time course, about half that of RSs. RS units (RSU) discharged spontaneously at rates of less than 1--15/s, whereas FS units (FSU) displayed rates of 15--50/s. The amplitudes of FSs, which were generally smaller than those of RSs, often decreased during high-frequency discharges. 3. With sinusoidal oscillations of a vibrissa FSUs responded more reliably and over a broader range of frequencies (3 to at least 40 Hz) than did RSUs , particularly in layer IV. In addition, FSUs typically responded to whisker deflections over a range of 360 degrees, whereas many RSUs in layer IV displayed sharp spatial-tuning charcteristics, responding over a restricted range of less than 90 degrees. 4. Of all units, 58% responded preferentially to stimulus transients (vibrissal movements), 32% displayed sustained responses to stimulus stead-states (fixed vibrissal displacement). For the remaining 10% of units the appropriate stimulus could not be specified; these units were particularly common in layer V. 5. Computation of quantitative stimulus-response relations showed that many units increased their rate of discharge with increasing stimulus intensities. 6. Most units were directionally selective, responding preferentially to deflections of a whisker in one or more of four quadrants. 7. In radial penetrations through the cortex there was a columnar patern so that units were activated at least by the same (i.e., the "principal") whisker. In a number of cases these could be directly correlated with the barrels. Of all units, 55% responded to deflections of single vibrissa only, the remaining 45% to 2--12 adjacently situated vibrissae. For most multiple-whiser units the responses elicited by deflection of any one hair activating the neuron was qualitatively similar to those elicited by deflection of any other hair activating it. The principal whisker of the penetration was typically associated with the most vigorous responses. 8. In layer IV, 85% of neurons responded to deflections of one hair only, the remaining 15% to two or more hairs. In layers II and III 39% of units were activated by more than one vibrissa; in layers V and VI multiple-whisker units predominated (64%). Whisker configurations in the deep layers were larger than those in other layers. 9...
Effect of auditory cortex ablation on localization and discrimination of brief sounds
Authors: Heffner H.
Published: December 2017

1. Dogs with bilateral auditory cortex lesions were tested on their ability to localize and discriminate brief sounds. In each test the animals were required to approach one of two goal boxes in order to indicate their response. 2. The results showed: a) that the operated animals could not solve the localization tasks when the goal boxes were located more than 125 cm away, but could solve the task if the goal boxes were located closer to the animal; b) that the operated animals could successfully discriminate brief bursts of click trains (i.e., 100/s versus 10/s, 0.3 s duration) even when required to indicate their discrimination by moving to goal boxes located 250 cm away, in spite of the fact that they could not successfully localize these sounds under similar conditions; c) that the operated animals tracked the source of a continuous sound instead of localizing it in a normal manner. 3. It appears that the deficit in sound localization resulting from cortical ablation is not due to any impairment in auditory attention or memory. Furthermore, the deficit cannot be ascribed to an inability to make a spatial response to an auditory cue. Instead, the deficit may be the result of a disconnection of the sound-localization mechanism from the motor mechanism necessary for some, though not all, behavioral responses.
Properties of ganglion cells with atypical receptive-field organization in retina of macaques
Authors: de Monasterio F. M.
Published: December 2017

1. About 10% of a sample of 436 cells recorded in the retina of macaques had receptive fields lacking a center-surround organization. These cells had a diffuse extrafoveal distribution, they were less frequently found in the foveal region, and their conduction latencies overlapped with those of cells (types I, III, and IV) having a center-surround organization. Three groups were distinguished. 2. Type II cells had spectrally opponent responses mediated by mechanisms having similar or identical distributions and response latency; these cells did not respond to white light. They predominated in the central retina, they usually received input from all three types of cone, they had a linear spatial summation of incomming photo-receptor signals, they lacked rod input, they had conduction latencies that were intermediate between those of the other two groups, and they could be antidromically activated by electrical stimulation of the lateral geniculate body but not of the superior colliculus. 3. Type V cells were neurons whose common characteristic was the presence of on-off responses to both small and large stimuli. One subgroup had either excitatory or inhibitory on-off responses and a silent inhibitory surround that tended to suppress cell responses and maintained activity. They were observed throughout the central retina, including the fovea; they received input from green- and red-sensitive cones, but not from blue-sensitive cones; they had a non-linear spatial summation; they had comparatively long conduction latencies; and they could be antidromically activated by electrical stimulation of either the lateral geniculate body or superior colliculus. Another subgroup lacked spontaneous activity and any type of surround. They were encountered at a retinal depth more sclerad than that of other neurons and could not be antidromically driven from the optic tract or more central structures; these cells also lacked input from blue-sensitive cones and had a nonlinear spatial summation. 4. Type VI cells were predominantly inhibited by moving stinuli in any direction of motion and failed to respond to stationary flashing stimuli; they appeared to predominate toward the perifovea and had comparatively short conduction latencies.
Characteristics of motor programs underlying arm movements in monkeys
Authors: Polit A. , Bizzi E.
Published: December 2017

1. The experiments described here are addressed at identifying some of the processes underlying arm movements in monkeys. 2. We used three adult monkeys that were trained to point to a target light with the forearm and hold at that position for about 1 s in order to obtain a reward. During the experimental sessions the monkey was seated in a primate chair and its forearm was fastened to an apparatus that permitted flexion and extension of the forearm about the elbow in the horizontal plane. 3. We tested their performance prior to and after bilateral dorsal rhizotomy (C2--T3). Forearm movements were performed without the sight of the arm both before and after the surgical intervention. In intact animals we unexpectedly displaced the arm prior to movement initiation (150--200 ms) and observed the outcome of this displacement on movement termination. Our results indicated that the arm moved accurately to the target. The same procedure was used in the deafferented monkeys, yielding qualitatively the same results; i.e., a displacement of the initial position did not affect the attainment of the intended final position. 4. These results are relevant to the question of what is being controlled by motor commands. It appears that the controlled variable is an equilibrium point resulting from the interaction of agonist and antagonist muscles. Consequently, a change in the equilibrium leads to movement and the attainment of a new posture. The fact that both intact and deafferent monkeys display essentially similar motor behavior in our highly practiced task should not obliterate the dramatic difference in motor performance that exists between intact and rhizotomized animals. In fact, the successful execution of the learned motor performance in the deafferented animal is contingent on the animal's body being in a fixed relation to the arm apparatus. Whenever we changed the usual spatial relationship between the monkey's body and the arm apparatus, the animal's pointing response to the target was inaccurate. All of our intact monkeys, in contrast, were able to compensate quickly for any variations in their accustomed position with respect to the arm apparatus. The dramatic inability of the deafferented monkey to execute accurate pointing responses in an unusual postural setting underscores the great importance of the afferent monkey to execute accurate pointing responses in an unusual postural settiing underscores the great importance of the afferent feedback. These findings suggest that, in the performance of visually evoked learned movements, one of the major functions of the afferent feedback is in the adaptive modifications of learned motor programs.
Photoreceptor coupling in retina of the toad, Bufo marinus. II. Physiology
Authors: Gold G. H.
Published: December 2017

1. Intracellular recordings were made from red rods in the isolated toad retina in order to measure the extent of the rod coupling. 2. The network space constant, lambda, was determined from edge-response profile measurements on single cells (lambda = 19 +/- 7 micrometer). 3. The network input resistance was estimated to be between 45 and 100 M omega. 4. Both discrete and continuous resistance networks, which were based on the anatomical observations, were analyzed. For lambda/D greater than 1, a continuous network provides an accurate description of the discrete network (D, cell spacing for a square grid). 5. The network analysis was used to estimate the specific resistance of junction membrane (0.75--1.5 omega.cm2) and the conductance provided by a single junctional channel (2.0--3.9 X 10(-12) mho). 6. The anatomical and physiological results provide strong evidence that the rods are electrically coupled. It is concluded that photoreceptor coupling provides averaging of the voltages in adjacent cells. The consequences of this averaging are discussed.
Central and peripheral control of siphon-withdrawal reflex in Aplysia californica
Authors: Perlman A. J.
Published: December 2017

1. The defensive withdrawal reflex of the siphon of Aplysia is a local response (exhibited by the organ that is stimulated) mediated by the conjoint action of both the central and peripheral nervous systems. 2. Three independent methods were used to determine the contribution of the central and peripheral nervous systems to the siphon-withdrawal reflex: 1) acute reversible deganglionation, 2) chronic deganglionation, and 3) a selective reversible hyperpolarization. With each of these techniques, the central nervous system was found to contribute about 55% of the total reflex. 3. Seven motor neurons were identified and characterized with respect to their electrophysiological properties and the motor actions. Three of the central motor cells belong to the LD clusters of cells (LDS1, LDS2, LDS3) and one is an RD cell (RDS). These four cells all receive excitatory synaptic input from siphon stimulation, excitatory synaptic input from the activity of the respiratory command cells network (interneuron II). large spontaneous IPSPs, and exhibit hyperpolarizing responses (H response) to iontophoretically applied acetylcholine (ACh). These cells all participate in the siphon-withdrawal component of a centrally commanded fixed-action pattern: spontaneous pumping movements of the mantle organs driven by the respiratory command cells. They receive an EPSP burst during the activity of the respiratory command cells and are competent to mediate the siphon motion. Three central siphon motor cells belong to the LB cluster (LBS1, LBS2, LBS3). These cells also receive excitatory input following stimulation of the siphon, a spontaneously occurring IPSP, and have H response to iontophoretically applied ACh. These cells, however, receive an IPSP burst during spontaneous pumping movement and thus do not participate in the active contraction phase of this behavior. LBS1 and LDS1 were examined with respect to their transmitter biochemistry and were found to be noncholinergic. 4. The siphon-withdrawal reflex habituates with comparable kinetics to repeated tactile stimulation when it is under central and peripheral control and when it is under peripheral control only. Thus, not only do both systems act conjointly to produce the defensive withdrawal reflex, but also they have similar response properties and are well matched to mediate the two parts of this siphon behavior.
Inhibition of spinal neuronal responses to noxious skin heating by stimulation of mesencephalic periaqueductal gray in the cat
Authors: Carstens E. , Yokota T. , Zimmermann M.
Published: December 2017

1. Discharges of lumbar dorsal horn neurons were evoked by noxious radiant skin heating, and inhibition of the heat-evoked responses by stimulation of the mesencephalic periaqueductal gray was investigated in N2O-anesthetized cats. 2. Thirty-seven units selected on the basis of receiving afferent C-fiber input from the posterior tibial and/or superficial peroneal nerves responded vigorously to 50 degrees C heating of the plantar surface of the ipsilateral hindpaw. All discharges were inhibited by periaqueductal gray stimulation (PAGS) at current strengths of 300--900 microA; the mean threshold for inhibition was 167 microamperemeter. The mean frequency of the inhibited discharge was 39% of the control response. 3. Effective PAGS sites were distributed throughout the ventral PAG bilaterally. Stimulus current-distance estimates indicate that small (0.5--1.2 mm diameter) volumes of tissue within the PAG were stimulated. 4. A monotonic relationship between temperature and unitary discharge was found for skin heating from threshold to about 50 degrees C. PAGS resulted in a decrease in the slope of the curve plotting discharge against temperature, without altering the threshold. 5. Inhibition of the heat-evoked discharges rarely outlasted the PAGS. 6. Possible neural substrates for descending inhibition and correlates with neural mechanisms of analgesia are discussed.
Graded synaptic interactions between local premotor interneurons of the locust
Authors: Burrows M.
Published: December 2017

1. Graded synaptic interactions are revealed between pairs of nonspiking, local interneurons in the metathroracic ganglion of the locust. These interneurons drive motor neurons innervating muscles of a hindleg. 2. All the interactions found between the interneurons are inhibitory and one way. Synaptic transmission is effected by the graded release of chemical transmitter. Some of the connections are apparently direct. One local interneuron can, therefore, exert a graded control over the membrane potential of another local interneuron. 3. There are inhibitory connections between local interneurons that excite the same motor neuron, between local interneurons that excite antagonistic motor neurons, and between local interneurons that excite motor neurons to muscles moving different joints of a hindleg. 4. Other pairs of interneurons, which are not connected, may be driven by common synaptic inputs. Their outputs add together at the level of the motor neurons to produce effects that are greater than the sum of their individual effects. 5. It is proposed that graded interactions between these local interneurons are an essential element in the generation of motor patterns.
Multiple, prolonged actions of neuroendocrine bag cells on neurons in Aplysia. II. Effects on beating pacemaker and silent neurons
Authors: Mayeri E. , Brownell P. , Branton W. D.
Published: December 2017

1. A survey of identified cells of the abdominal ganglion of Aplysia was undertaken to determine the extent of bag cell influence in the ganglion. Bursts of bag cell spike activity lasting 5--40 min were elicited by brief, 0.6- to 2 s local stimulation while recording simultaneously from bag cells and other ganglion cells with intracellular electrodes. 2. Slow inhibition occurs in giant cell R2, neurosecretory cells R3-R14, and ink-gland motoneurons, L14A, B, C. The cells remain hyperpolarized for from 15 to 60 min. 3. Transient excitation occurs in mechanoreceptor cells L1 and R1. The cells are strongly depolarized by a slow excitatory potential that lasts for about 10 min and produces spike activity for 3--7 min. 4. Prolonged excitation occurs in some cells of the LB and LC identified cell clusters. The cells are depolarized and spike activity is increased for 3 h or more. 5. A biphasic response occasionally occurs in the command interneuron L10. Inhibition of this cell lasts 10--15 min and is followed by excitation for several hours. Excitation is accompanied by facilitation of synaptic potentials for 40--60 min in cells innervated by L10; the facilitation apparently results from the increase in L10 firing rate. 6. The results indicate that the bag cells have multiple types of actions and affect large numbers of ganglion neurons. All effects have the slowly graded onsets and prolonged durations to be expected of hormonally mediated interactions. 7. Previous studies have indicated that in intact animals the bag cell burst discharge initates a stereotyped egg-laying behavioral pattern that persists for several hours (3, 27). The present data support the hypothesis that certain elements of egg-laying behavior and homeostasis are regulated by a direct action of the bag cells on the central nervous system.
Different species of alpha motoneurons in same pool: further evidence from effects of inhibition on their firing rates
Authors: Harris D. A. , Henneman E.
Published: December 2017

1. Single units of the plantaris pool were isolated in ventral root filaments of decerebrate cats and their critical firing levels (CFLs) were determined. Motoneurons of similar size were compared in firing rate (FR) during repetitive stimulation of the plantaris nerve to establish control values and also during added stimulation of various inhibitory nerves (sural, hamstrings, or peroneal). 2. Criteria, based on maximal firing rate, were developed whereby certain pairs of units of similar size could be reliably classified into different types. 3. A second, independent set of criteria was formulated by which the same pair of units could be classified according to their responses to added inhibitory inputs. 4. The ability to distinguish motoneurons consistently by more than one set of criteria reinforces the evidence that different physiological types of units exist within a single motoneuron pool. 5. The findings indicate that different types of cells either receive different densities of input from certain inhibitory sources or that they react differentially to the same amounts of these inputs.
Neuronal mechanisms of human locomotion
Authors: Dietz V. , Schmidtbleicher D. , Noth J.
Published: December 2017

1. The surface electromyogram (EMG) of human leg muscles was recorded during running at different speeds; The EMG was compared with the simultaneously recorded vertical force exerted by the foot and with the angle of the ankle joint. 2. During running, the electrical activity of the gastrocnemius muscle increased sharply 35--45 ms after ground contact and reached its maximum at the end of muscle stretch; This activity was superimposed on a slowly increasing level of activation, which began 120--180 ms before ground contact. At the end of the stance phase, gastrocnemius became inactive and, simultaneously, there was a sudden increase in tibialis anterior activity. The assumption that the steep increase in the gastrocnemius EMG reflects the spinal stretch reflex of alpha-motoneurons is supported by the following findings. 3. The peak level of gastrocnemius EMG in the stance phase of fast running was 2--3 times higher than the activity during maximum voluntary contraction. 4. With stimulation of the tibial nerve at different rates, the maximum isometric force was about 30--40% higher than the maximum voluntary isometric contraction. 5. The increase in EMG at 35--45 ms after ground contact was markedly diminished during running, after partial blockage of Ia afferents by ischemia, at a time when the strength of voluntary contraction was shown to be uninfluenced by the ischemia. 6. The gastrocnemius activity during running was simulated by electrical stimulation of the tibial nerve. The rate of stimulation was varied so as to approximate to the EMG profile during running. This indicated that a spinal stretch reflex could become mechanically effective within the shortest stance phase measured in a fast sprint (ca. 120 ms).
Luxotonic responses of units in macaque striate cortex
Authors: Kayama Y. , Riso R. R. , Bartlett J. R. , Doty R. W.
Published: December 2017

1. Single units in striate cortex were studied in alert macaques while they viewed a ganzfeld. Of the 385 well-isolated units studied for 10 min to 2 h, 24% gave "luxotonic" responses, i.e., their rate of discharge for 1 min or more in diffuse, featureless, wideangle illumination (20-450 cd/m2) was at least double that during a comparable period in darkness, or vice versa, and not attributable to eye movements of blinking. Those discharging faster in the light, "photergic" units, outnumber those responding to darkness, "scotergic" units 1 by 4:1. 2. In the lateral geniculate nucleus, on the other hand, among 46 units studied, 28% were luxotonic, but scotergic units were the more common. Both types were present in both magno- and parvocellular laminae. 3. For striate cortex two-thirds of the luxotonic units were binocular. Some showed highly similar response for either eye alone, and essentially no summation binocularly; others had grossly differing responses from each eye, and complex binocular interaction. 4. Many units of all types at striate cortex showed significant modulation of their activity consequent to saccadic eye movements made in darkness, whereas comparable modulation was not observed at the lateral geniculate nucleus. 5. On the basis of these and other findings it is concluded that luxotonic cortical activity is prominent probably only in alert primates, and that this is a consequence of the fact that all retinal ganglion cells in primates synapse in the lateral geniculate nucleus (Ref. 9). Possible functions range from mere trophic input to providing a veridical image or a scaling factor for maintenance of perceptual constancy in the face of varying levels of general illumination.
Responses of neurons in primate ventral posterior lateral nucleus to noxious stimuli
Authors: Kenshalo D. R. , Giesler G. J. , Leonard R. B. , Willis W. D.
Published: December 2017

1. Recordings were made from the caudal part of the ventral posterior lateral (VPLc) nucleus of the thalamus in anesthetized macaque monkeys. In additon to many neurons that responded only to weak mechanical stimuli, scattered neurons were found that responded to both innocuous and noxious stimulation or just to noxious stimulation of the skin. A total of 73 such neurons were examined in 26 animals. 2. Noxious stimuli included strong mechanical stimuli (pressure, pinch, and squeezing with forceps) and graded noxious heat (from 35 degrees C adapting temperature to 43, 45, 47, and 50 degrees C). The responses of the VPLc neurons increased progressively with greater intensities of noxious stimulation. The stimulus-response function when noxious heat stimuli were used was a power function with an exponent greater than one. 3. Repetition of the noxious heat stimuli revealed sensitization of the responses of the thalamic neurons to such stimuli. The threshold for a response to noxious heat was lowered, and the responses to supra-threshold noxious heat stimuli were enhanced. 4. The responses of VPLc neurons to noxious heat stimuli adapted after reaching a peak discharge frequency. The rate of adaptation was slower for a stimulus of 50 degrees C than for one of 47 degrees C. 5. For the six neurons tested, responses to noxious heat were dependent on pathways ascending in the ventral part of the lateral funiculus contralateral to the receptive field (ipsilateral to the thalamic neuron). In two cases, the input to the thalamic neurons from axons of the dorsal column was also conveyed by way of a crossed pathway in the opposite ventral quadrant. In another case, access to the thalamic neuron by way of ascending dorsal column fibers was demonstrated. 6. The thalamic neurons had restricted contralateral receptive fields that were somatotopically organized. Neurons with receptive fields on the hindlimb were in the lateral part of the VPLc nucleus, whereas neurons with receptive fields on the forelimb were in medial VPLc. 7. Ninety percent of the VPLc neurons tested that responded to noxious stimuli could be activated antidromically by stimulation of the surface of SI sensory cortex. It was possible to confirm that many of these cells project to the SI sensory cortex by using microstimulation. Successful microstimulation points were either within the SI cortex or in the white matter just beneath the cortex. 8. We conclude that some neurons in the VPLc nucleus are capable of signaling noiceptive stimuli. The nociceptive information appears to reach these cells through the ventral part of the lateral funiculus on the side contralateral to the receptive field, presumably by way of the spinothalamic tract. The VPLc cells are somatotopically organized, and they are thalamocortical neurons that project to the VPLc nucleus and SI cortex play a role in nociception.
Cerebellar-dependent adaptive control of primate saccadic system
Authors: Optican L. M. , Robinson D. A.
Published: December 2017

1. The ability of the central nervous system to compensate for saccadic dysmetria was demonstrated in rhesus monkeys. The behavior of this adaptive mechanism after cerebellar ablations was examined. 2. Monkeys were trained to fixate small target lights. Eye movements were monitored while the animals were seated, with their heads fixed, in a rotating magnetic field. The horizontal recti muscles of one eye were weakened by tenectomy. Saccades made by this weakened eye were hypometric and followed by postsaccadic drift. 3. When the patch was switched so that the weak eye was viewing, the hypometric saccades made by the weak eye gradually became larger, until after 3 days they were essentially orthometric. This indicated that the central nervous system could compensate for a peripheral weakness. 4. The tenectomy operation reduced the strength of the muscles, creating hypometria, and upset the ratio of viscosity to elasticity in the orbit, creating postsaccadic drift in the weak eye. The innervation required to make a saccade has both phasic and tonic components, the so-called pulse and step. The sacccadic repair mechanism increased both the pulse and the step to compensate for the hypometria and also adjusted the ratio of the pulse to the step to eliminate postsaccadic drift. 5. Total cerebellectomies were performed on two monkeys, each of which had one tenectomized eye. These ablations created an enduring saccadic hypermetria and postsaccadic drift in the unoperated eye of both animals. The total cerebellectomy abolished all adaptive repair of the saccadic system. 6. Partial cerebellectomies were performed on two monkeys, each of which had one tenectomized eye. Lesions of the vermis and paravermis (lobes IV-IX) and the fastigial nuclei created an enduring saccadic hypermetria without postsaccadic drift in the unoperated eye of both animals. These lesions abolished adaptive control of the pulse of innervation. Adaptive changes in the step of innervation still occurred, so that postsaccadic drift was always eliminated in the experienced, viewing eye. Thus the midline cerebellum (vermis, paravermis, and fastigial nuclei) appears to be important for repair of saccadic dysmetria, but not for repair of postsaccadic drift. Additional evidence that postsaccadic retinal slip cannot be compensated for in flocculectomized monkeys suggest that the adaptive control of the step may depend on the flocculus. 7. After cerebellar lesions the monkeys were able to make saccades of all amplitudes and directions. The principal deficit in these animals seemed to be that the pulse and step of innervation were no longer appropriate to the target displacement. We conclude that the cerebellum's principal contribution to saccadic eye movements is the adjustment of the gains of the pulse- and step-generating mechanisms. Hence this study supports the hypothesis that repair of dysmetria is a general function of the cerebellum.
Pharmacological dissection of pyloric network of the lobster stomatogastric ganglion using picrotoxin
Authors: Bidaut M.
Published: December 2017

1. Picrotoxin (PTX) (10(-7)-10(-6) M) completely blocked most inhibitory synapses in the pyloric pattern generator of the lobster (Panulirus interruptus) stomatogastric ganglion. The sensitivity of synapses from most classes of identified neurons was examined. Blockade was at least partly reversible with prolonged washing. 2. The synapses from pyloric dilator (PD) neurons were the only inhibitory synapses that picrotoxin failed to block completely. 3. A correlation is derived that brief, fast-rise inhibitory postsynaptic potentials (IPSPs) are picrotoxin sensitive, whereas a slow rounded component of IPSPs from PD neurons is not picrotoxin sensitive. 4. Picrotoxin caused specific changes in the pattern of the motor rhythm produced by the 16-cell pyloric network. This sheds some light on the functional role of particular synapses in the pyloric generator. 5. The endogenously bursting neurons (PD and anterior burster (AB)), which drive the pyloric rhythm, kept a similar burst rate. 6. Under picrotoxin, the pyloric "follower" neurons all moved to later phase relative to the "driver" group. Some normally antagonistic cells, related by reciprocal inhibitor connections, became in-phase. These and other pattern changes could be related to blockade of particular synapses. 7. The pyloric rhythm was still quite recognizable under picrotoxin despite the drastically altered circuitry of the synaptic network. This supports the idea that periodic inhibition from the PD driver neurons plays a primary role in creating the pyloric pattern.
Center-surround antagonistic organization in small-field luminosity horizontal cells of turtle retina
Authors: Piccolino M. , Neyton J. , Gerschenfeld H.
Published: December 2017

1. The spatial properties of the small-field luminosity horizontal cell (L2-HC) were investigated in the retina of the turtle by using circular or annular light stimuli of varying dimensions. 2. The amplitude of the hyperpolarizing response induced by dim light spots decreased when the diameter of the spot was increased beyond about 1,000 micrometer. 3. With bright-light stimuli the peak amplitude of the light responses increased monotonically when increasing the illuminated area, but a delayed antagonistic effect appeared with spots of more than 1,000-micrometer diameter. 4. Depolarizing responses were observed if the periphery of the receptive field was stimulated with annuli of light in the presence of central background illumination. 5. The interaction of the inputs converging on the L2-HC from the peripheral and central regions of the receptive field was found to be nonlinear. The same peripheral stimulation could result either in an enhancement or in a depression of the central response according to the intensity of the central illumination. 6. By comparing the receptive-field properties of the L2-HC and the red cones a model is proposed that explains the antagonistic surround mechanism of the L2-HC on the basis of the antagonistic peripheral mechanism in cones. '
Submodality distribution in sensorimotor cortex of the unanesthetized monkey
Authors: Tanji J. , Wise S. P.
Published: December 2017

1. Neuronal responses to cutaneous and noncutaneous stimulation were examined in the hindlimb representation of the precentral motor cortex (MI) and the first somatosensory cortex (SI) of unanesthetized monkeys. 2. MI can be divided into two distinct parts of the basis of its afferent input. The rostral part receives predominantly noncutaneous inputs, while the cutaneous input is primarily confined to the caudal part of MI. Thus, a differential distribution of submodality groups exists in the MI cortex. Caudal to MI, area 3a responds mainly to stimulation of noncutaneous receptors, in marked contrast to the caudal part of MI or area 3b. 3. The finding of a differential distribution of cutaneous inputs within MI is of significance a) to hypotheses concerning the role of somatosensory input to the MI cortex, b) to studies that attempt to characterize somatosensory inputs to MI by the proportion of neurons responsive to cutaneous and noncutaneous stimulation, and c) in that they confirm and extend similar findings recently reported for the forelimb representation of an anesthetized New World monkey (43).
Effects of visual cortical lesions on receptive-field properties of single units in superior colliculus of the rabbit
Authors: Graham J. , Berman N. , Murphy E. H.
Published: December 2017

1. One hundred seventy-nine single units were studied in the superior colliculus of seven Dutch-belted rabbits following ablation of the ipsilateral visual cortex. The response characteristics of these units were compared with those of 284 single units recorded from the superior colliculus of 20 intact animals. 2. In both the upper and lower parts of the stratum griseum superficiale and in the stratum griseum intermediate, there were smaller proportions of direction-selective visual units in the decorticated animals than in normal ones. 3. In the upper stratum griseum superficiale, a larger proportion of units responded to stroboscopic illumination in the decorticated animals than in normal ones. Also, in the decorticated animals, there was a larger proportion of units whose responses to a small moving stimulus were inhibited by the simultaneous presentation of stroboscopic illumination. 4. In both the upper and lower parts of the stratum griseum superficiale, a larger proportion of visual units responded well to stationary stimuli and a smaller proportion of visual units showed habituation in decorticated animals compared to normal ones. 5. In the lower stratum griseum superficiale, the receptive fields of units were larger and were more elongated in the anterior-posterior dimension in the decorticated animals than in normal ones. 6. In the two preparations, units did not differ in responsiveness or spontaneous activity; and visual units did not differ in the sustained or transient nature of their responses, the selectivity for light or dark stimuli, the selectivity for onset or offset of the stimuli, or the selectivity for stimulus velocity. 7. This study provides evidence for the importance of the visual corticotectal projection in the elaboration of the visual receptive-field properties of units in the superior colliculus of the rabbit. In addition, this study shows that the subdivisions of the superior colliculus are differentially affected by the loss of the visual corticotectal projection.
Identification of interneurons with contralateral, caudal axons in the lamprey spinal cord: synaptic interactions and morphology
Authors: Buchanan J. T.
Published: December 2017

1. As part of a continuing investigation of the organization of the spinal cord of the lamprey, propriospinal interneurons with axons projecting contralaterally and caudally (CC interneurons) were surveyed with intracellular recordings. 2. CC interneurons were identified by recording their axon spikes extracellularly in the spinal cord during intracellular stimulation of the cell body. The axon projections of Cc interneurons were confirmed after intracellular injection and development of horseradish peroxidase. 3. Intracellular stimulation of CC interneurons produced synaptic potentials in myotomal motoneurons, lateral interneurons and other CC interneurons that lay caudally on the opposite side of the spinal cord. Most CC interneurons were inhibitory, but some were excitatory. 4. CC interneurons were divided into three classes on the basis of reticulospinal Muller cell inputs. CC1 interneurons were excited by the ipsilateral Muller cell B1 and the contralateral Mauthner cell. CC1 interneurons were inhibitory. They were excited polysynaptically by ipsilateral sensory dorsal cells and were inhibited by contralateral dorsal cells. They were distinguished morphologically by having no rostral axon branch and no contralateral dendrites. CC1 interneurons were phasically active during fictive swimming with their peak depolarizations preceding those of myotomal motoneurons by about 0.15 cycle. 5. CC2 interneurons were also inhibitory, but they were distinguished from CC1 interneurons by their excitation from the ipsilateral Muller cells B2-4 nd by their thin rostral and thicker caudal axonal branches on the contralateral side of the spinal cord. 6. CC3 interneurons were excitatory, and they were inhibited by the ipsilateral Muller cell I1. CC3 interneurons could have contralateral dendrites and bifurcating axons, and they had lower average axonal conduction velocities than CC1 and CC2 interneurons. 7. Inhibitory CC interneurons may be important for motor coordination in the lamprey. Movements of the lamprey body during reflexes and swimming consist of contraction and relaxation of myotomal muscles on opposite sides of the body. By being coactive with ipsilateral myotomal motoneurons, inhibitory CC interneurons could contribute to the inhibition of contralateral motoneurons during these movements.
Analysis of synaptic depression contributing to habituation of gill-withdrawal reflex in Aplysia californica
Authors: Byrne J. H.
Published: December 2017

1. Repeated stimulation of the siphon skin results in short-term habituation of the reflex contractions of the gill (38). The habituation, in turn, is correlated with a depression of the excitatory postsynaptic potentials (EPSPs) in motor neurons from mechanoreceptor sensory neurons (SN) (7, 16). The present study was undertaken to examine the parametric features of the synaptic depression and gain insights into the mechanisms underlying the reduced transmitter release. 2. Single sensory neuron action potentials were repeatedly elicited with depolarizing current pulses while the amplitude of the resultant EPSPs in the motor neuron was monitored. Synaptic depression varies as a complex function of interstimulus interval (ISI). At an ISI of 1 s, depression is rapid and reaches a plateau at 36% of control. In contrast, the depression at an ISI of 100 s is less pronounced, showing a gradual decay to 65% of control with the 10th EPSP. Surprisingly, there are no significant differences in time course or magnitude of depression across a broad range of intermediate ISIs (3, 10, and 30 s), although depression at these ISIs is intermediate between the 1 and 100 s ISIs. 3. There is also a complex relationship between spike interval and the depression of the second of two EPSPs. Thus, depression of the second of two EPSPs or depression of a train of EPSPs is not a monotonic function of spike interval. Indeed, the data suggest that there may be a slight underlying facilitatory process with short spike intervals. 4. The results also indicate that the recovery of synaptic depression following a train of 10 stimuli is not constant. Shorter spike intervals produce more rapid recovery. 5. These data are inconsistent with a classical depletion model (33) for synaptic depression and indicate that either a single complex function of time and ISI or multiple functions underlie synaptic depression and its recovery at the sensory neuron synapse.
Retinotopic organization of lateral eye input to Limulus brain
Authors: Chamberlain S. C. , Barlow R. B.
Published: December 2017

1. The retinotopic organization of retinal inputs from the lateral eye of Limulus to the optic ganglia of the brain was determined from microelectrode recordings of nerve impulses. 2. The central connections of the natural subunits of the lateral optic nerve were determined using cobalt impregnation of cut axons. 3. Complete retinal maps exist in both the lamina and medulla. The laminar map is a simple rotation and folding of the retinal array. The medullar map is more complex as a result of the combined effects of the chiasma and the basic subunit structure of the optic nerve, which is preserved in the lamina and medulla. 4. The chiasma between the lamina and medulla reverses the anterior-posterior axis of the retinal map. There is no corresponding reversal in the dorsal-ventral axis.
Electrophysiological properties of neocortical neurons in vitro
Authors: Connors B. W. , Gutnick M. J. , Prince D. A.
Published: December 2017

1. Intracellular recordings were obtained from neurons of the guinea pig sensorimotor cortical slice maintained in vitro. Under control recording conditions input resistances, time constants, and spiking characteristics of slice neurons were well within the ranges reported by other investigators for neocortical neurons in situ. However, resting potentials (mean of -75 mV) and spike amplitudes (mean of 93.5 mV) were 10-25 mV greater than has been observed in intact preparations. 2. Current-voltage relationships obtained under current clamp revealed a spectrum of membrane-rectifying properties at potentials that were subthreshold for spike generation. Ionic and pharmacologic analyses suggest that subthreshold membrane behavior is dominated by voltage-sensitive, very slowly inactivating conductances to K+ and Na+. 3. Action potentials were predominantly Na+ dependent under normal conditions but when outward K+ currents were reduced pharmacologically, it was possible, in most cells, to evoke a non-Na+-dependent, tetrodotoxin-(TTX) insensitive spike, which was followed by a prominent depolarizing after-potential. Both of these events were blocked by the Ca2+ current antagonists, Co2+ and Mn2+. 4. A small population of neurons generated intrinsic, all-or-none burst potentials when depolarized with current pulses or by synaptic activation. These cells were located at a narrow range of depths comprising layer IV and the more superficial parts of layer V. 5. Spontaneous excitatory synaptic potentials appeared in all neurons. Spontaneous inhibitory events were visible in only about 10% of the cells, and in those cases apparently reversed polarity at a level slightly positive to resting potential. Stimulation of the surface of the slice at low intensities evoked robust and usually concurrent excitatory and inhibitory synaptic potentials. Unitary inhibitory postsynaptic potentials (IPSPs) reversed at levels positive to rest. Stronger stimulation produced a labile, long-duration, hyperpolarizing IPSP with a reversal potential 15-20 mV negative to the resting level. 6. Neocortical neurons in vitro retain the basic membrane and synaptic properties ascribed to them in situ. However, the array of passive and active membrane behavior observed in the slice suggests that cortical neurons may be differentiated by specific functional properties as well as by their extensive morphological diversity.
Mechanisms underlying pattern generation in lobster stomatogastric ganglion as determined by selective inactivation of identified neurons. IV. Network properties of pyloric system
Authors: Miller J. P. , Selverston A. I.
Published: December 2017

1. In three preceding papers in this series (6, 33, 45), the functional roles, intrinsic cellular properties, and synaptic connections of identified neurons in the lobster stomatogastric ganglion were investigated using the dye-sensitized photoinactivation technique. In this paper, we investigate the network properties of the pyloric system. 2. The relative strengths of the synaptic interactions between all possible motor neuron pairs were measured from the neuronal cell bodies. 3. Experiments were performed to determine the minimal subset of the pyloric neurons that could generate rhythmic activity due to network interactions alone. With the endogenously bursting anterior burster (AB) cell excluded from consideration, the minimum number of elements was found to be two. These two elements behaved as a classical "half-center" oscillator when their overall activity levels were appropriately adjusted. 4. Two cells in the commissural ganglia supply the pyloric system with rhythmic excitatory input phase locked to ongoing pyloric activity. The rhythmicity of that input is shown to be functionally irrelevant. The inputs can exert their effects on pyloric system activity through tonic firing. 5. A qualitative explanation of three important aspects of the pyloric motor pattern is presented, based on the intrinsic properties of pyloric neurons and the systematic properties of the network they form. The existence of the pattern results from oscillatory membrane properties of the individual neurons in combination with the multiple reciprocally inhibitory interactions within the network. The phase relationships derive from the synaptic connectivity and depend on relative synaptic strengths, postinhibitory rebound, rebound delay, and the kinetics of the plateau and bursting pacemaker-potential generation mechanisms. The overall pattern frequency is determined by the AB interneuron via its intrinsic oscillatory behavior and strong synapses with the rest of the pyloric neurons.
Connections of midbrain periaqueductal gray in the monkey. I. Ascending efferent projections
Authors: Mantyh P. W.
Published: December 2017

1. To obtain a comprehensive map of the ascending projection of the midbrain periaqueductal gray, small amounts of [3H]leucine were injected into discrete regions of the periaqueductal gray (PAG) of the monkey. 2. Despite the fact that different regions of the PAG were injected in separate animals, the majority of the PAG's efferent projections to the forebrain remained constant. 3. The diencephalic projection areas include the nucleus reticularis thalami, the nucleus medialis dorsalis, the midline thalamic nuclei, the intralaminar thalamic nuclei, the preoptic area, and the anterior, dorsal, periventricular, ventromedial, periarcurate, lateral, and posterior hypothalamic nuclei. 4. More caudal areas receiving a projection from the PAG include the zona incerta and the mesencephalic reticular formation. 5. The main route for PAG-diencephalic projections is through the periventricular bundle. This implies that if a stimulating electrode was placed in this region, both the diencephalic leads to PAG and PAG leads to diencephalic pathways would be stimulated. This observation may explain the wide variety of side effects often encountered in stimulation-produced analgesia in humans. 6. These results support our hypothesis that the PAG functions as a visceral, nociceptive, and cognitive integrator.