bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of auditory neocortex ablation on pitch perception in the cat
Authors: Cranford J. L. , Igarashi M. , Stramler J. H.
Published: December 2017

Cats which received one- or two-stage bilateral ablations of auditory cortex were compared to unoperated cats on a test involving the discrimination of increases (1.2 kHz) from decreases (0.8 kHZ) in the frequency of ongoing 1.0-kHz tone pulses. Whereas two-stage cats exhibited more evidence of postoperative retention for the original task than did one-stage cats, both groups relearned the discrimination in approximately the same number of trials as normal cats. Individual differences in difficulty of relearning apparently reflected the degree of undercutting of the polysensory association areas of the suprasylvian and lateral gyri. Following retraining, all cats received two discrimination transfer tests. The first test was identical to the original dis crimination problem in all respects except that different frequency values were substituted for the original set (i.e., 1.6-kHz tones alternating with either 2.0- or 1.2-kHz signals). Whereas both unoperated and two-stage cats had difficulty discriminating the new positive from negative trials, the one-stage cats exhibited a significant tendency to continue responding to changes invoving 1.2-kHz tones in the same manner as in the original discrimination task. In the second test the cats were asked to discriminate the original 1.2- and 0.8-kHz tones against a silent background. Both operated and unoperated cats performed significantly above chance on this test. These results suggest that the cats solved the original discrimination on the basis of absolute frequency cues rather than the directionality of frequency changes. The significance of these findings are discussed in relation to current concepts of the functional capacity of auditory decorticate animals.
Mossy fiber neck and second-order labyrinthine projections to cat flocculus
Authors: Wilson V. J. , Maeda M. , Franck J. I. , Shimazu H.
Published: December 2017

In five decerebrate cats and in two under N2O-O2 anesthesia, a bipolar electrode array was inserted into a granular layer in the rostral flocculus. At this location MF field potentials were evoked by stimulation of the ipsilateral vestibular nerve and of the C2 dorsal root ganglion. Stimulation through the array was used to fire brain stem neurons antidromically. The activity of these neurons was recorded extracellularly with glass microelectrodes. Stimulation of the C2 dorsal root ganglion evoked in the caudal lateral brain stem a field potential caused by the arrival of impulses in primary afferent fibers. Cells projecting to the flocculus also responded to the stimulus, usually monosynaptically. These neurons were fired by stimulation of the area of the atlantoaxial joint. They did not respond to stimulation of the contralateral C2 dorsal root ganglion, and responded only rarely to stimulation of the dorsal rami of the C2 and C3 spinal nerves. Stimulation of the vestibular nerve was ineffective. Another group of cells projecting to the flocculus was fired at short latency by stimulation of the ipsilateral vestibular nerve. These neurons were usually inhibited by stimulation of the contralateral vestibular nerve. They were not affected by stimulation of any neck afferents. The location of many recording locations was identified by means of fast green dye marks. Most neurons relaying neck activity were in group x of Brodal and Pompeiano (4), a few were in the external cuneate nucleus, and one was in the descending vestibular nucleus. Neurons relaying labyrinthine activity were in the descending vestibular nucleus; one was found in the medial nucleus, in which tracks were made only rarely. There are two parallel pathways relaying neck and labyrinthine activity to the flocculus. While they are separate at the level of the brain stem, they converge in the same rostral areas of the flocculus. The neck afferent information may be required for proper performance of the flocculus in eye-movement control.
Effect of pulvinar lesions on visual pattern discrimination in monkeys
Authors: Chalupa L. M. , Coyle R. S. , Lindsley D. B.
Published: December 2017

This study compares the performance (percent correct responses and reaction times) of three unoperated control monkeys with the postoperative performance of eight monkeys with pulvinar lesions, either inferior pulvinar or medial and lateral pulvinar, on a tachistoscopically presented visual pattern-discrimination task highly demanding of attention. To further emphasize and assess the attentional factor in visual pattern discrimination, all monkeys who attained criterion performance (90% correct response on three consecutive sessions of 100 trials each) were tested for the effects of visually distracting interference stimuli added to the original discriminative stimuli. In addition, retention of postoperatively learned discriminations was tested after a 6-wk interval withou training and compared with the performance of control monkeys. Four monkeys with only inferior pulvinar lesions and one monkey with inferior pulvinar plus medial and lateral pulvinar lesions were markedly impaired in the postoperative learning of a visual pattern discrimination. Three of these monkeys failed to acquire criterion perfromance in 9,000 or more training trials, while two learned to ceiterion level only after prolonged training (7,400 and 6,900 trials). In contrast, monkeys with medial and lateral pulvinar lesions showed no deficit in learning ability compared to unoperated control monkeys. Furthermore, the performance of the two monkeys with inferior pulvinar lesions, who attained the criterion level of learning only with difficulty, was further impaired by the addition of distracting interference stimuli, where the performance of monkeys with medial and lateral pulvinar lesions as well as the control monkeys was only temporarily disrupted by this procedure. None of the monkeys with pulvinar lesions, who were tested for retention of the postoperatively learned discrimination, showed appreciable deficits in comparison to control monkeys. All monkeys, including controls and those uith pulvinar lesions who were able to learn the visual pattern discrimination, showed a common pattern of reaction time (RT) change during the course of the learning; that is, RT was low during change-level performance, increased during learning, and decreased once criterion performance was achieved. Reaction times of monkeys with inferior pulvinar lesions tended to be longer than for controls or for those with medial and lateral pulvinar lesions. These results provide the first behavior evidence that the inferior pulvinar of monkeys is involved in visual pattern discrimination and add further support to the concept of a second visual system in which the inferior pulvinar plays a role. The attentional aspects of the visual pattern-discrimination task employed in this study and the additional effects obtained with distracting stimuli suggest that the impairments arising from inferior pulvinar lesions may be dependent in part on visual attentional factors.
Intracellular responses from granule cell layer in slices of rat hippocampus: perforant path synapse
Authors: Dudek F. E. , Deadwyler S. A. , Cotman C. W. , Lynch G.
Published: December 2017

Intracellular responses were recorded in vitro from the denate granule cell layer of hippocampal slices prepared from adult rats. Spontaneous activity of granule cells in vitro consisted of action potentials and small, graded depolarizations, presumably of synaptic origin. Granule cells could be activated by injection of depolarizing current or release of hyperpolarizing current. Individual granule cells spatially summed input from the perforant path and fired multiple action potentials in vitro following strong presynaptic volleys. Depolarization decreased and hyperpolarization increased the EPSP amplitude, which is consistent with a conductance-increase mechanism. Although we could demonstrate postexcitatory inhibition in some cells, granule cells in vitro appeared to receive less inhibitory feedback than in vivo, EPSP amplitude and spike output of granule cells showed frequency potentiation and posttetanic potentiation to perforant path stimulation. These intracellular responses in vitro complement some of the findings from field-potential analyses of the dentate gyrus in intact animals.
Role of centrifugal pathways to cochlear nucleus in determination of critical bandwidth
Authors: Pickles J. O.
Published: December 2017

Atropine sulfate was applied locally to the cochlear nucleus of three unanesthetized cats in order to block the cholinergic centrifugal innervation of the nucleus. The critical bandwidth was measured behaviorally from the masked thresholds of 1-kHz tone pips in different bandwidths of masking noise. Atropine increased the critical bandwidth markedly. This suggests that normally the centrifugal pathways influence the critical bandwidth. Saline solutions alone had no effect, and if the cannula was not accurately implanted over the cochlear nucleus, atropine had no effect either.
Changes in responses of medial pontomedullary reticular neurons during repetitive cutaneous, vestibular, cortical, and tectal stimulation
Authors: Peterson B. W. , Franck J. I. , Daunton N. G.
Published: December 2017

1. In cats anesthetized with chloralose, responses of medial pontomedullary reticular neurons to stimulation of the body surface, vestibular nerves, superior colliculi, pericruciate cortices, cerebral peduncles, and spinal cord were studied at different stimulus rates. Raising the rate from 1/10 s to between 1/4 s and 2/s caused a significant decrement or increment in the response of most neurons tested. Response decrement typically began near the beginning of the higher frequency stimulus sequence and increased throughout the sequence. Response increment usually began somewhat later, rose to a peak, and then declined. Recovery from response decrement or increment usually occurred within 30-60 s at a 1/10 s stimulus rate.2. Measurements of response latency and of changes occurring in the initial and longer latency portions of responses indicated that all components of a response typically decreased or increased in parallel. Background spontaneous activity did not change during response decrements, but sometimes increased during response increment.3. Where changes could be detected, response decrement usually developed more rapidly when a sequence of repetitive stimulation was repeated.4. Response decrement was most pronounced at the highest stimulation rates and lowest stimulus intensities. Response increment was usually maximal at a stimulus rate of 1/s: at lower rates less increment occurred; at higher rates responses began to exhibit decrement.5. Response changes varied with the type of stimulus applied. Response decrements predominated when the body surface, vestibular nerves, or ipsilateral superior colliculus were stimulated. Approximately equal amounts of response increment and decrement were produced by repetitive stimulation of the cerebral peduncles and contralateral superior colliculus. Stimulation of the surface of the pericruciate cortex or of the spinal cord usually produced a long-lasting response increment.6. Generalization of response decrement and increment was observed in cases where trains of stimuli at a rate of 2/s applied to one point produced changes in the response to stimulation of another point which was tested once per 10 s and where single-shock stimulation of the first point was without effect on the test response. Generalization of response decrement occurred most often when two nearby points were stimulated. Generalization of response increment appeared to spread widely between distant cutaneous points and stimuli of different kinds.7. The response decrement and increment observed in medial pontomedullary reticular neurons displayed most of the parametric features of behavioral habituation and sensitization (8, 33) and therefore appear to represent neural analogs of these latter phenomena. The properties of response decrement suggest that it may occur to a large extent within afferent pathways leading to medial reticular neurons...
Measurements of stiffness of extraocular muscles of the rabbit
Authors: Barmack N. H.
Published: December 2017

1. The stiffness of the eye and the extraocular muscles of the conscious rabbit was measured and compared with similar measurements made on human subjects. 2. The extraocular muscles of the rabbit developed less than 0.5 g at optimal isometric length when the contralateral eye was in "primary position". Deviations of the eye of the rabbit from primary position were accomplished by an increase in force of the agonist muscle with only a nominal decrease in force in the antagonist. 3. With all muscles attached to the globe, the stiffness of the eye for displacements of up to 35 degrees from primary position was 0.11 +/- 0.03 g/deg. 4. The stiffness of the human eye to lateral rotations was 1.09 +/- 0.24 g/deg. Hence, identical disturbances in force would cause deviations in the position of the eye of the rabbit which are nearly an order of magnitude greater than those of man. 5. The stiffness of the extraocular muscles of the rabbit was sensitive to levels of muscle activation produced either by indirect electrical stimulation or by the vestibuloocular reflex. 6. The implications of these findings for the development of eye position control in animals with good binocular vision are discussed.
Physiology of peripheral neurons innervating otolith organs of the squirrel monkey. III. Response dynamics
Authors: Fernandez C. , Goldberg J. M.
Published: December 2017

1. The discharge of peripheral otolith neurons in response to sinusoidal force variations was investigated in the barbiturate-anesthetized squirrel monkey (Saimiri sciureus). The sine waves were superimposed on a background force which biased the end organ so as to excite or inhibit the unit's firing. Both regularly and irregularly discharging neurons were studied. 2. The response amplitude, measured as a peak-to-peak changes in firing rate, reached near-maximal values during the first sine-wave cycle and, for most units, remained constant as sinusoidal stimulation was prolonged. 3. In regular units, introduction of an excitatory bias increased the sensitivity to sinusoidal stimulation in a manner consistent with the static asymmetries observed in the response to constant forces. Bias effects in irregular units were usually small and, in some cases, excitatory biases resulted in a decrease in sensitivity. 4. Variation in sine-wave amplitude had no effect on the sinusoidal gains or phases of regular units. For irregular units, there was some evidence of a small gain increase as stimulus amplitude decreased. 5. Nonlinear distortion was usually 10-20% and was mainly of an asymmetric type. In regular units, the distortion could be partially related to static asymmetries. 6. The response of regular units is predominantly tonic, that of irregular units more phasic. For regular units there was usually no more than a twofold gain enhancement as frequency was increased in the spectrum from DC to 2.0 Hz; typically, small phase leads at low frequencies were replaced by similar phase lags at higher frequencies. Irregular units were characterized by a 20-fold frequency-dependent gain enhancement over the same spectrum; phase leads of 20-40% were seen. 7. Bodeplots were fit by a family of transfer functions, each consisting of three terms. The first is a velocity-sensitive operator with a fractional exponent. The second is a low-frequency adaptation operator. Only the lag operator can be related to the dynamics of otoligh motion. Most of the variations among units, including those seen between regular and irregular units, can be accounted for by suitable variations in the velocity-sensitive and adaptation operators. 8. The transfer functions, when integrated and inverted, led to reasonable approximations of the response to force trapezoids. It is concluded that the transfer functions provide an adequate representation of the dynamic behavior of most units. The only exceptions are the few neurons showing delayed adaptation.
Response of unmyelinated (C) polymodal nociceptors to thermal stimuli applied to monkey's face
Authors: Beitel R. E. , Dubner R.
Published: December 2017

1. The response of C polymodal nociceptors to thermal and mechanical stimuli applied to the monkey's face was recorded extracellulary in the trigeminal ganglion in rhesus monkeys anesthetized with sodium pentobarbital. Conduction velocities, determined from electrical stimulation of receptive fields (RFs), were in the range for unmyelinated C fibers (mean=0.82 m/s, n=20; SD=+/-0.17). With two exceptions cutaneous RFs were single spots (median=2 mm2; n=37) and usually were identical for thermal and mechanical stimuli. The median force threshold for the sample of units was 1.2 g (von Frey technique; n = 39; range = 0.07-8.5 g). 2. Discharges to thermal stimuli were investigated with a feedback-controlled contact thermode which permitted temperature changes less than or equal 12.0 degrees C/s. Thermal thresholds ranged from 38 degree to 49 degree C (median=46 degrees C; n=37), and maximum discharge frequencies were obtained in the noxious heat range (45-55 degrees C). For a graded series of 5 s duration stimuli from an adapting temperature of 35 degrees C, the number of impulses increased as a monotonic function of stimulus intensity over the range from threshold temperature to 50-53 degrees C. Many stimulus-response functions were positively accelerated, and linear regression analyses showed that most units examined were best fit by nonlinear functions. 3. The typical pattern of activity to 5 s duration temperature shifts into the noxious heat range was a short accelerating burst of impulses followed by deceleration to a lower rate of discharge prior to termination of the stimulus. The temporal profile of the discharge of impulses was virtually identical at different adapting temperatures. In units tested with 30 s duration stimuli at 2-6 degrees C above threshold, the mean frequency of discharge during the final 25 s was 1.46 impulses/s (n=6; SD=+/-0.89). 4. Application of noxious heat stimuli a few degrees above threshold temperature typically sensitized or enhanced the response of the unit to subsequent application of heat stimuli. The signs of sensitization consisted of a decrease in threshold temperature, increased frequency of discharge, decreased latency to the first impulse, and afterdischarges. Units failed to respond throughout the duration of 30 s stimuli if the final temperature exceeded 50 degrees C. Depressed responses were sometimes produced by application of intense (greater than or equal 55 degrees C) stimuli, presumably as a result of partial inactivation of the receptor. 5. In a correlative analysis, the latency and pattern of discharge in a sample of units were compared with escape responses in two monkeys to temperature shifts into the noxious heat range (49 and 51 degrees C). The analysis revealed that the discharge of C polymodal nociceptors alone cannot account for fast escape responses, but the discharge may contribute to escape responses which occur more than 3.5 s after the onset of stimulation.
Simple striate neurons in the cat. I. Comparison of responses to moving and stationary stimuli
Authors: Emerson R. C. , Gerstein G. L.
Published: December 2017

1. Peristimulus time (PST) histograms of simple striate responses to static presentations of narrow bright and dark bars in an array of receptive-field (RF) positions have demonstrated one to four response regions with distinct response properties. 2. There is a high degree of correlation of these responses with PST histograms of responses to the same stimuli moving smoothly ("dynamic" stimuli) in a direction perpendicular to the long axis of the RF. 3. Trailing responses to smoothly moving bar stimuli usually occur as the stimulus leaves an apparently inhibitory (for that stimulus) RF region. 4. Spatially leading responses to smoothly moving stimuli occur just as a bar stimulus enters an excitatory RF region, and may be based on certain gradient-detecting properties of neurons. 5. Close agreement in peak firing rates and in positions of responses for statically and dynamically elicited responses in units that are not strongly directionally selective suggests the possibility that in most respects smooth movement responses may be the sequential linear superposition of static responses. A quantitative superposition of static responses from two units supports this conclusion. 6. The dependence on a steady background for sustained responses to static presentation of dark bars illustrates the significance of steady illumination in the RF and raises questions about the efficacy of using edge stimuli as elemental visual probes.
Functional organization of catfish retina
Authors: Naka K.
Published: December 2017

1. The basic organization of the biphasic (or concentric) receptive field is established in the bipolar cells as the result of an interaction between two signals, one local representing the activity of a small number of receptors, and the other integrating (19, 20) or global (28) coming from the S space or a lamina formed by the horizontal cells (8, 14, 22, 29). 2. Bipolar-ganglion cell pairs are segregated into two types; A (on center) and B (off center) pairs. A depolarization of a bipolar cell produces spike discharges from ganglion cells of the same type and a hyperpolarization depresses their discharges. I haven't detected any cross talk between the types A and B pairs. Bipolar and ganglion cells must be interfaced by the classical chemical synapses, the only such kind in the catfish retina. 3. Horizontal and type N neurons form two lateral transmission systems, one distal and the other proximal (19, 20). Signals in the lateral systems are shared by the two receptive-field types and are not excitatory or inhibitory in themselves; it is incumbent upon the postsynaptic neurons to decide the polarity of the synaptic transmission. The horizontal cell participates directly in the formation of biphasic receptive fields of bipolar cells by providing their surrounding, whereas type N neuron seems to modify the receptive-field organization established in the bipolar cells. 4. Type N neurons are amacrine cells because they do not produce spike discharges (2, 18, 21) and because they influence the activity of both A and B receptive fields. 5. The function of the type C neuron is as unique as its structure (21) and is not fully clear as yet. It is not a conventional amacrine cell as the type N appears to be, nor is it a classical ganglion cell which forms either a type A or B receptive field (2). 6. Type Y neurons are a class of ganglion cells which forms either a type A or B receptive field.
Saccular and utricular input to cat neck motoneurons
Authors: Wilson V. J. , Gacek R. R. , Maeda M. , Uchino Y.
Published: December 2017

1. In two series of cats all vestibular afferents except those innervating the saccular or utricular macula were transected and allowed to degenerate. Subsequent anatomical and physiological verification showed that the saccular nerve had been selectively spared in six cats. The utricular nerve was wholly or partly spared in five cats, but there was some possibility of contamination from other vestibular afferents. 2. The connections of the remaining nerve with dorsal neck motoneurons were studied 27-179 days after the initial surgery in preparations anesthetized with chloralose. 3. Stimulation of the saccular nerve usually evoked IPSPs in contralateral, EPSPs in ipsilateral neck motoneurons. Some of the potentials were disynaptic, many were later and probably trisynaptic. 4. The effects of utricular nerve stimulation were more complex, perhaps because of contamination by other vestibular, particularly canal, afferents. The predominant pattern consisted of ipsilateral inhibition and contralateral excitation, opposite to the effects of saccular nerve stimulation. Many potentials were disynaptic. 5. Various factors that may complicate interpretation of the results, including plastic changes following denervation, are considered. It is concluded that they are not a significant factor. 6. Our main result is a demonstration that the sacculus can contribute to vestibulospinal reflexes acting on the head.
Time course and magnitude of effects of changes in tonicity on acetylcholine release at frog neuromuscular junction
Authors: Kita H. , van der Kloot W.
Published: December 2017

1. The time course for the changes in miniature end-plate potential (min epp) frequency and in epp amplitude produced by alterations in the tonicity of the Ringer at the frog neuromuscular junction was studied. The relations between the tonicity and min epp frequency as well as epp amplitude were also investigated. 2. The change in min epp frequency occurred within 1 min after the start of the change in the tonicity of the extracellular solution. Following a shift to a hypertonic solution, the min epp frequencies were often maintained at a relatively steady, elevated level, even with large (+100 mosM) changes in tonicity. In other instances the elevation was transitory like the reported data for the rat neuromuscular junction. Essentially the same results were obtained in very low Ca2+-Ringer. Unlike the rat neuromuscular junction, the final level after hours of the increased min epp frequency caused by raising the osmolarity by more than 75 mosM was well above the control level. Following the return from a hypertonic to an initial solution there was a prompt decrease in min epp frequency to about the initial level; there was no indication of the transitory depression in min epp frequency following the return from hypertonic solution that has been reported in mammals. 3. Until the osmolarity of the Ringer reached about 420 mosM, the frequency of min epp continued to rise along a line relating log (min epp frequency) to (osmolarity)0.5. When the osmolarity exceeded 460 mosM, the relation started to level off. 4. The hypothesis that the min epp frequency in a Ringer with a given increased tonicity is a fixed multiple of the frequency in normal Ringer is not in accord with the data. 5. The decrease in epp amplitude caused by markedly hypertonic solutions also came about within 1 or 2 min after the start of the change in the tonicity of the solution surrounding the nerve terminal. 6. Hypertonic solutions did not appear to affect facilitation. 7. Below 360 mosM increasing the tonicity of the Ringer had little effect on the amplitude of epp. Above this level the amplitude decreased as the tonicity increased. At a given junction an increase in tonicity in a range above 360 mosM can cause an increase in min epp frequency and a decrease in epp amplitude. 8. The results are discussed in terms of the theories proposed to account for the effects of osmolarity on synaptic function. Two theories--the water flow hypothesis (11) and the barrier of water hypothesis (2)--do not fit with the results. The two other theories--calcium elevation (1) and screening of surface charges (3, 13, 21)--fail to account for important aspects of the results and therfore cannot be accepted without substantial modifications. None of the theories devised to account for the increase in min epp frequency predicts the falloff in frequency and in evoked quantal release that occurs in highly hypertonic solutions.
Relationship between Muller cell responses, a local transretinal potential, and potassium flux
Authors: Karowski C. J. , Proenza L. M.
Published: December 2017

1. In the Necturus retina, light-evoked field potentials, Muller (glial) cell responses, and extracellular potassium ion concentration ([K+]0) were recorded and found to exhibit the three-way correlation characteristic of these variables elsewhere in the nervous system. 2. Muller cell responses to a flashed spot or annulus consist primarily of slow depolarizations at both light onset and offset. The responses are maximum to 0.5-mm-diameter spots and decrease with larger diameters. Responses to stimulus intensity and flicker were also used to characterize Muller cell behavior. 3. In response to long-duration stimuli, the initial Muller cell depolarization is followed by a very slow hyperpolarization, which is likely the origin of slow PIII. 4. A new extracellular potential is described, the M-wave, the basic properties of which suggest that it is generated by Muller cells. Moreover, the M-wave and Muller cells show remarkably similar behavior to a wide variety of stimulus parameters. 5. In the proximal retina, [K+]0 increases at both light onset and offset with a time course similar to that of Muller cell depolarizing responses. This K+ increase also behaves similarly to the Muller cell depolarization in response to changes in stimulus parameters. 6. It is concluded that light stimulation leads to an increase in [K+]0 in the proximal retina and that this increase depolarizes Muller cells whose associated currents, in turn, generate the M-wave.
Swimming movements elicited by electrical stimulation of turtle spinal cord. I. Low-spinal and intact preparations
Authors: Lennard P. R. , Stein P. S.
Published: December 2017

1. Electrical stimulation applied within the dorsolateral funiculus of the spinal cord of an intact, unanesthetized turtle can elicit rhythmic limb movements similar to those observed during swimming. 2. A spontaneous display of hindlimb swimming movements is not observed in adult turtles whose spinal cord is transected at D2. Such swimming movements are observed in these "low-spinal" turtles in response to electrical stimulation applied within the dorsolateral funiculus caudad to the transection. 3. The repetition rate of these swimming movements can be altered by changing stimulus parameters, such as the frequency of electrical pulses. 4. The present results indicate that, in the turtle, a neural pattern generator contributing to the production of hindlimb movements during swimming is located mainly in structures caudad to the cervical enlargement of the spinal cord. These data support the hypothesis that a pattern generator for locomotion is largely resident within the spinal cord.
Neuronal organization of crayfish escape behavior: inhibition of giant motoneuron via a disynaptic pathway from other motoneurons
Authors: Wine J. J.
Published: December 2017

1. A circuit that produces a 70-100 ms IPSP in the crayfish giant motoneuron is described. The IPSP is produced by a disynaptic pathway from the nongiant fast flexor motoneurons to the motor giant. 2. An inhibitory interneuron in the pathway has been identified. Its axon runs at least the entire length of the abdominal nervous system. The inhibitory interneuron is excited bilaterally in all abdominal ganglia except the last and bilaterally inhibits the motor giants thoughout the abdominal CNS. 3. Evidence for a monosynaptic connection between the interneuron and the motor giant includes short latency, stability during repetitive stimulation, gradual decrement in high-Mg2+ solutions, and persistence in high-Ca2+ solutions. Similar but less complete evidence suggests a monosynaptic connection from the fast flexor motoneurons to the inhibitory interneuron. 4. A single impulse in the inhibitor can produce a prolonged IPSP in the motor giant. The inhibitor did not display trains of impulses and was not spontaneously active. 5. The inhibitory interneuron appears to be highly specific; no other outputs were observed. 6. Direct stimulation of axons in the connectives suggests that four pairs of inhibitory interneurons converge on the motor giants; at least two pairs are activated by the fast flexor motoneurons. 7. This circuit limits the burst duration of the motor giant and may function to protect the motor giant's depression-prone neuromuscular junction.
Contribution of individual mechanoreceptor sensory neurons to defensive gill-withdrawal reflex in Aplysia
Authors: Byrne J. H. , Castellucci V. F. , Kandel E. R.
Published: December 2017

1. To evaluate the contribution which mechanoreceptor sensory neurons make to the defensive gill-withdrawal reflex we developed an isolated reflex preparation. We then reduced this isolated reflex to a microcircuit (consisting of a single sensory cell and single motor cell) so as to causally relate the contribution of individual cells to the expression and plastic properties of the behavior. 2. Mechanoreceptor neurons make significant contributions to the amplitude and duration of the complex PSP in the motor neurons. A single spike in a sensory neuron produces an EPSP in the motor neuron which accounts for 7-36% of the complex EPSP produced by weak tactile stimulation of the skin. 3. More than 50% of the synaptic input to the gill motor neurons appears to be monosynaptic. Perfusing the ganglion with solutions of high divalent cations reduced the motor neurons' complex PSP by only 40%. 4. The population response of the mechanoreceptors to a point stimulus can be simulated by repetitively firing a single sensory neuron. Firing a single sensory cell discharges the motor neuron and produces a gill contraction similar to that produced by a natural stimulus. 5. Mechanoreceptors make monosynaptic connections onto gill motor neurons which decrement with repeated stimulation paralleling the decrement of the complex PSP to punctate tactile stimulation of the skin. 6. The results indicate that the known neural elements may quantitatively account for most of the expression of the behavior and its short-term habituation.
Effect of load disturbances during centrally initiated movements
Authors: Bizzi E. , Dev P. , Morasso P. , Polit A.
Published: December 2017

1. We have investigated the relative contributions of mechanical and reflex mechanisms in generating the forces produced by the neck muscles when loads were unexpectedly applied during centrally programmed head movements in monkeys. These movements, subserved by muscles well endowed with muscle spindles, are part of the coordinated eye-head response to the appearance of a stimulus in the animal's visual field. Our preparation was a chronically vestibulectomized monkey trained to make a visual discrimination. 2. Two procedures were used to evaluate the torque generated by the neck musculature when an unexpected load disturbance was applied: first, by surgically interrupting the afferent loop subserving the reflex action (section of cervical dorsal roots) and second, by building a mathematical model of the head-neck system and carrying out a process of simulation. 3. Our results indicated that the compensatory torque of reflex origin stimulated by the application of an opposing force was less than 10--30% of that required for perfect compensation, and the larger fraction of the observed compensation was due to the mechanical properties (inertial, viscous, and elastic) of the neck musculature. The combined action of reflex and mechanical processes never completely compensated for the disturbance.
Color vision mechanisms in monkey striate cortex: dual-opponent cells with concentric receptive fields
Authors: Michael C. R.
Published: December 2017

1. I have recorded with tungsten microelectrodes from single cells in the monkey's visual cortex and have specifically studied those neurons which were sensitive to the color of the stimulus. In the primate striate cortex there are four classes of color-coded cells. The cells described in this paper have concentric receptive fields with one red-green opponent-color system in the field center and the opposite organization in the surround. These dual-opponent cells were nost sensitive to the simultaneous presentation of two different colors, one covering the field center and the other illuminating the surround. They are probable involved in the perception of simultaneous color-contrast phenomena. 2. Spectral sensitivity curves revealed that both the field centers and the surrounds received opposite types of inputs from red-sensitive and green-sensitive cones. None of the cells tested had inputs from rods. 3. Area-sensitivity curves showed that peripheral suppression was present for both phases of the center opponent-color system. The boundary between the center and the surround was the same for both sets of opponent systems. Some cells had "silent" surrounds, which did not respond to annular stimuli. 4. Multiple-unit recordings from a concentric cell and one of its presumed afferents yielded information regarding its possible synaptic inputs. In some cases the cells appeared to receive contacts from red/green opponent-color geniculated fibers with circular receptive fields that lacked an antagonistic surround (similar to Wiesel and Hubel's (37) type II class). In other instances the afferents had on-center, off surround receptive fields or the reverse, but received inputs from only one cone type, either red or green (similar to Wiesel and Hubel's type III class). 5. Concentric cells were always driven by only one eye. 6. The laminar distribution of these cells was limited almost entirely to layer IV and its subdivisions. 7. The cumulative evidence presented in this paper indicates that the concentric cells probably received direct geniculate inputs and, therefore, they are the first cortical stage in the integration of color-contrast information.
Discharge properties of pontine reticulospinal neurons during sleep-waking cycle
Authors: Wyzinski P. W. , McCarley R. W. , Hobson J. A.
Published: December 2017

1. Reticulospinal neurons were identified by antidromic invasion from spinal cord electrodes chronically implanted at C4 in cats. 2. Most of the neuronal population studied lay within the medial portion of the giant cell field from the anterior pontine and to the anterior medullary reticular formation (FTG). A few cells were found in the tegmental reticular nucleus (TRC) which has not previously been known to project to the spinal cord. 3. Extracellular action potentials from the neuronal somata of the identified neurons were recorded continuously throughout naturally occurring sleep-waking cycles. 4. The identified reticulospinal neurons shared three properties, suggesting a generator function in desynchronized sleep (D) (with previously recorded but unidentified FTG neurons): selectivity (or concentration of discharge in D); tonic latency (or firing rate increases beginning several minutes prior to D); and phasic latency (or firing rate increases occurring prior to eye movements within D). 5. The location, discharge properties, and spinal projections of FTG neurons are, thus, all consistent with the hypothesis that they may directly mediate some of the descending excitatory and inhibitory influences on spinal reflex pathways in desynchronized sleep.
Generation of scratching. II. Nonregular regimes of generation
Authors: Berkinblit M. B. , Deliagina T. G. , Feldman A. G. , Gelfand I. M. , Orlovsky G. N.
Published: December 2017

1. The activity of muscle nerves and that of spinal interneurons from the L4 and L5 segments was recorded during fictitious scratching (5), which was evoked in decerebrate curarized cats by stimulation of the cervical spinal cord. In some experiments, rhythmical generation was disturbed by stimulation of the fifth lumbar dorsal root (DL5). 2. Excluding the very beginning of scratching, rhythmical generation was usually rather regular: fluctuations of the cycle duration were less than +/-5%. But changes in the stimulation strength, in the stimulating electrode position, and in the hindlimb position led to changes of the generation regime. In different regimes, the mean value of the cycle duration could differ by 20-30%. No correlation was found between mean durations of flexor and extensor phases for different regimes. 3. Rhythmical generation was possible only if the hindlimb was put to "scratch posture," i.e., deflected forward. Generation immediately stopped when the limb was deflected backward, and immediately started when it was returned to scratch posture. 4. In some experiments, stimulation of the cervical spinal cord first resulted in generation of slow oscillations with the temporal pattern typical of stepping (cycle duration about 500 ms, flexor and extensor phases being almost equal to each other). Then, during 5-20 cycles, gradual transition to a normal scratch cycle (about 250 ms) occurred mainly due to considerable shortening (5-10 times) of the extensor phase. In some experiments, considerable spontaneous variations of the flexor phase were observed, while the extensor phase was constant. 5. A single stimulus applied to DL5 considerably affected the cycle duration. Repetitive DL5 stimulation,with a rhythm close to that of scratching, resulted in synchronization of the spinal generator by the stimuli. 6. Spinal interneurons recorded during transition from slow oscillations to a normal scratch cycle only slightly changed phases of their activity in relation to the activity of motoneurons. 7. A hypothesis is advanced that generation of different kinds of limb movements is produced by one and the same central spinal mechanism which can operate in different regimes. The role of sensory input for operation of this mechanism is discussed.
Physiological consequences for the cat's visual cortex of effectively restricting early visual experience with oriented contours
Authors: Stryker M. P. , Sherk H. , Leventhal A. G. , Hirsch H. V.
Published: December 2017

1. The early visual experience of nine cats was restricted to viewing horizontal or vertical lines inside opaque goggles. 2. When the kittens were 3-4 mo old, extracellular recordings were made in the primary visual cortex. To obtain a representative sample of cortical cells, units were studied at regularly spaced intervals along the course of electrode penetrations traveling oblique to the cortical surface. An automated assessment of preferred orientation using a computer-driven optical display was employed, and during the recording session the experimenters did not know which orientation(s) each animal had viewed in early life. 3. In the cats that viewed horizontal lines with one eye and vertical lines with the other during rearing, two major findings of previous workers (14) were confirmed. First, a majority of units were not selective for orientation. Second, units with preferred orientations near vertical tended to be activated exclusively by the eye that had viewed vertical, and likewise for horizontal. 4. In cats that viewed lines of the same orientation with both eyes during rearing, a substantially smaller proportion of units were selective for orientation; the preferred orientations of these units also tended to match the orientation to which the cats had been exposed. 5. Portions of some electrode penetrations showed an orderly arrangement of cells according to preferred orientation similar to that seen in normal cats, but with regions over which only nonselective cells were found. Many penetrations appeared less orderly. 6. The results are consistent with a role for early visual experience in maintaining the responsiveness and innate selectivity of cortical neurons, although they cannot entirely rule out the possibility that experience may alter or determine the preferred orientation of some cells.
Neuronal responses to electrosensory input in mormyrid valvula cerebelli
Authors: Russell C. J. , Bell C. C.
Published: December 2017

1. We have examined a large portion of the valvula cerebelli of the mormyrid fish Gnathonemus petersii for responses related to the three known classes of electroreceptors. Evoked potential and extracellular single-unit records from curarized and non-curarized preparations show that a separate area of the valvula is related to each of the different electrosensory modalities. 2. The area related to ampullary receptors is also strongly affected by mechanical stimulation to the skin. In the mormyromast and Knollenorgan regions, responses to sensory stimuli depend on when they are given in relation to the command to fire the electric organ. In the Knollenorgan region the interaction is quite simple. Responses are completely blocked if the stimulus is given during a brief period when the electric organ discharge occurs. A greater variety of interactions is seen in the mormyromast region. 3. Large areas of the valvula do not appear to be clearly and strongly retated to any of the three electrosensory modalities, suggesting the possibility that much of the structure is not devoted to electrosensory processing.
Tectopontine pathway in the cat: laminar distribution of cells of origin and visual properties of target cells in dorsolateral pontine nucleus
Authors: Mower G. , Gibson A. , Glickstein M.
Published: December 2017

1. The superior colliculus projects to the dorsolateral nucleus of the pons. Retrograde transport of horseradish peroxidase (HRP) revealed that cells in the superior colliculus, which send their axons to the pons, lie in both superficial (III) and deep (IV--VII) layers. Superficial cells outnumbered deep cells. The inferior colliculus also projects heavily to the dorsolateral pontine nucleus. 2. Dorsolateral pontine visual cells were activated only by visual stimulation. Cells responsive to somatic or auditory stimulation were also found in the dorsolateral nucleus, and they too responded to only one sense modality. 3. Of the dorsolateral pontine visual cells, 69% were directionally selective. 4. Dorsolateral pontine visual cells were responsive to moving targets over a wide range of stimulus velocities. Velocities between 25 and 100 degrees/s were the most effective. No cells responded to a stationary stimulus. 5. Single-spot targets were the most effective stimuli. Stimulus size was a more important parameter than stimulus configuration. Many cells had inhibitory regions outside of their excitatory fields. 6. The excitatory receptive fields of dorsolateral pontine cells were very large (median, 1,100 deg2). 7. Nearly all receptive fields were centered in the contralateral visual hemifield, and 91% of the dorsolateral visual cells were activated from either eye. 8. We conclude that the visual cells in the dorsolateral nucleus have receptive-field properties that are similar to those of cells in the superior colliculus. The preference of dorsolateral cells for single-spot targets contrasts strongly with the multiple-spot preference of medial pontine cells, which receive their input from visual cortex.