bluuebunny/crossref_metadata_2025 huggingface dataset:
Corticopontine cells in area 18 of the cat
Authors: Gibson A. , Baker J. , Mower G. , Glickstein M.
Published: December 2017

1. Area 18 projects to the rostral pontine nuclei. The visual response properties of rostral pontine cells differ greatly from those that have been reported for area 18 cells. We identified and studied corticopontine cells in area 18 and compared their receptive-field properties to those of other area 18 cells and to pontine visual cells. 2. We first located the visual area in the rostral pons by microelectrode recording and placed stimulating electrodes at the same site. Anti-dromically invaded cells were then recorded in area 18. The antidromic invasion of each cell was verified by orthodromic-antidromic spike collision. 3. Fifty-seven well-isolated corticopontine cells were studied in detail. We also recorded 466 unitary antidromic potentials with a mean invasion latency of 3.5 ms and recorded from 40 additional area 18 units to serve as a comparison group for the corticopontine cells. The comparison group cells were located in the same area in the visual field as the corticopontine cells. 4. The average receptive-field area for corticopontine cells (485 deg2) was much larger than the comparison cells (59 deg2). Forty percent of the corticopontine cells responded preferentially to multiple-spot target. Properly oriented gratings, slits, or edges were the most effective stimuli for the comparison cells. Eighty-two percent of the corticopontine cells showed clear directional preferences to moving-spot stimuli, and downward movements were most commonly preferred. Fifty-five percent of the area 18 comparison cells showed some directional preference, but no particular direction was preferred. The optimal stimulus speeds for corticopontine cells were higher than those for the comparison cells. 5. The response properties of the area 18 corticopontine cells are similar to the response properties of rostral pontine visual cells, except for a somewhat higher selectivity for orientation in the corticopontine cells. 6. We conclude that most response properties of rostral pontine visual cells are already present in a subset of area 18 cortical cells which project to the pons. The corticopontine cells are sensitive to multiple-spot targets moving in particular directions over large portions of the visual field, such properties are consistent with a visuomotor function for the corticopontocerebellar pathway.
Evidence for nonsynaptic neuronal interaction
Authors: Alkon D. L. , Grossman Y.
Published: December 2017

1. Evidence is presented that synaptic interactions within and between the statocyst and visual pathways of Hermissenda are eliminated after 0.5-4 min exposure to 20-40 mM Co2+. 2. Synaptic blockade was also produced by perfusion with low Ca2+ (5mM) plus 10-20 mM Co2+. 3. Depolarization of hair cells by impulses of type A photoreceptors remains after the same exposure to Co2+, or low Ca2+ plus Co2+. 4. The increased resistance previously observed during this depolarization of hair cells cannot be observed after exposure to Co2+. 5. The depolarization which remains after exposure to Co2+ did not change with different levels of membrane potential from -20 mV below to +10 mV above the resting level. 6. The time course of potassium accumulation, monitored by the amplitude of the type A impulse afterpotential, closely followed the time course of hair cell depolarization and also of changes in the amplitude of the hair cell afterpotential. 7. The depolarization of hair cells by type A impulses decreased with increased extracellular potassium, but was only slightly reduced by lowered extracellular potassium. 8. The amount of potassium accumulation following a type A impulse train could be estimated from the effects of changes in extracellular potassium in the perfusate on the type A impulse afterpotential. From this extimated increase of extracellular potassium it was possible to predict with some accuracy, the observed hair cell depolarization. 9. Although type A cells are not electrically coupled to ipsilateral hair cells, firing of these hair cells slightly depolarized the type A photoreceptor which excites them. 10. Strophanthidin (10-4 M) did not block the depolarization of hair cells by type A impulses. 11. The data are evidence for nonsynaptic excitation of hair cells by type A photoreceptor impulses. The data are also consistent with the interpretation that the excitation arises from potassium accumulation around the type A and hair cell axonal membranes.
Synaptic transmission without action potentials: input-output properties of a nonspiking presynaptic neuron
Authors: Graubard K.
Published: December 2017

1. Input-output properties of the inhibitory synaptic connection between non-spiking neurons (EX1) and gastric mill (GM) neurons were examined in the stomatogastric ganglion of the spiny lobster, Panulirus interruptus. Current was injected into and the voltage was recorded during current injection, two independent microelectrodes were used. 2. The EX1-GM synaptic connection is a conductance-increase inhibitory type, with an input-output curve that resembles the curve for the squid giant synapse. There is a threshold level of depolarization for transmitter release from the presynaptic cell. Beyond that threshold, increasing presynaptic depolarization causes increasing postsynaptic hyperpolarization (and inhibition). 3. A long presynaptic current step always causes a postsynaptic response with an initial peak of hyperpolarization followed by a decay to a less hyperpolarized plateau level. The plateau level is maintained, in most cells, for the duration of the presynaptic depolarization even over long periods (30 s). 4. The peak, but not the plateau, part of the postsynaptic response is sensitive to the past history of the synaptic connection. If a large conditioning pulse is applied to the presynaptic cell causing a large postsynaptic hyperpolarization, then the postsynaptic response to a later presynaptic test depolarization will have a reduced peak, leaving the plateau component unchanged.
Specificity of afferent and efferent regeneration in the cockroach: establishment of a reflex pathway between contralaterally homologous target cells
Authors: Fourtner C. R. , Drewes C. D. , Holzmann T. W.
Published: December 2017

1. In 132 cockroaches the main leg nerve on one side (right), of the metathoracic segment was crossed to the opposite (left) side and allowed to regenerate. In 3-8 wk, 59% of the animals displayed reflex activity in the left leg (behaviorally demonstrated by leg withdrawal following tarsal stimulation). 2. EMGs from the femoral extensor revealed potentials characteristic of normal activity in the extensor, which is innervated by an identified motor neuron, Ds. 3. Intracellular recordings from processes within the right hemiganglion of the metathoracic ganglion (CNS) demonstrated 1:1 activity between a unit in the CNS recording and the EMG of the left extensor. Subsequent intracellular staining revealed that the unit was on the right side of the CNS and was identified as motor neuron Ds by the location of its soma and dendrites. This finding indicated that specific, contralateral, efferent reinnervation occurs in the cockroach. 4. In normal cockroaches a monosynaptic reflex exists between hair plate afferents and Ds. A temporal analysis (stimulus-interval histogram) indicated that the reflex is also established in the crossed-regenerated animals. These data suggested that specific contralateral afferent reinnervation also occurs in the cockroach and that the monosynaptic nature of the normal reflex was reestablished. 5. Therefore, cell-to-cell specificity in neuron-to-neuron or neuron-to-muscle interactions not only occurs in normally developing or regenerating animals but also occurs between contralaterally homologous target cells, given the proper experimental conditions. It is also suggested that this experimental procedure of redesigning pathways may be a useful tool for further studies of behavior.
Effects of monocular lid closure on development of receptive-field characteristics of neurons in rabbit superior colliculus
Authors: Fox P. C. , Chow K. L. , Kelly A. S.
Published: December 2017

1. The receptive-field characteristics of superior colliculus neurons were studied in rabbit pups that had one eyelid sutured prior to eye opening. Units recorded from the superior colliculus (SC) receiving input from the unsutured eye provided normal developmental data, and those from the colliculus receiving input from the sutured eye were used to study the effect of visual deprivation. 2. A total of 1,054 cells recorded from 89 animals ranging in age from 7 to 35 days were obtained, 514 cells in the normal colliculus and 540 cells in the deprived colliculus. During normal development, three nonoriented cell types (concentric, uniform, motion) showed a progressive increase in relative frequency of occurrence, starting at about 7 days and reaching the adult level at about 15 days. Directionally selective cells developed slightly later, reaching an adult level at 3 wk. Oriented directional cells were the slowest to mature, requiring about 4 wk to reach the final level. 3. Eyelid suturing significantly affected the oriented directional cell development; these cells developed at a normal rate for about 3 wk, then rather abruptly began to decrease in number; a stable relative frequency of about one-fourth the normal value was reached at about 4 wk. A corresponding increase in the relative number of indefinite cells to above the normal level also occurred. In contrast, the development of nonoriented cells and directionally selective cells was not affected by the deprivation. 4. The development of rabbit superior colliculus receptive fields was found to be, in general, similar to development of kitten SC receptive fields. It also correlates well with developmental changes seen in rabbit ganglion cell receptive fields and with anatomical changes in developing rabbit SC. Indirect support is given for the hypothesis that changes seen in SC with deprivation are secondary to changes in the visual cortex.
Analysis of vestibulocollic reflexes by sinusoidal polarization of vestibular afferent fibers
Authors: Wilson V. J. , Peterson B. W. , Fukushima K. , Hirai N. , Uchino Y.
Published: December 2017

1. Canal vestibular-neck (vestibulocollic) reflexes have been studied in decerebrate cats by applying modulated polarizing current to individual ampullary nerves, usually the horizontal nerve. 2. Computer-generated stimuli sometimes consisted of sine or square waves at frequencies of 0.01--5 Hz. More often we used a compound wave form of nine superimposed sinusoids within an available frequency range of 0.009--6.11 Hz. The frequencies used were odd, relatively prime multiples of a base frequency selected to minimize distortion or interaction of responses. The response to each of the nine stimulating frequencies could be obtained in subsequent data analysis. 3. Responses to these stimuli were studied by recording the EMG of contralateral neck muscles and extracellular activity of second-order neurons. These neurons were identified by their monosynaptic responses to single-shock stimulation of ampullary nerves. 4. EMG was modulated sinusoidally. Below 0.1 Hz the response was variable, most likely due to differences in the preparations. In the frequency range of 0.1--0.4 Hz there was usually a phase lag, which decreased with incresing frequency and often reversed to a lead at 3 and 6 Hz. Gain decreased from the lowest frequencies, occasionally with an upturn at 3 or 6 Hz. 5. Second-order neuron firing was approximately in phase with the stimulus at the lowest frequencies. Phase advanced with increasing frequency to a lead of 30--50 degrees at 6 Hz. Gain generally increased with frequency. 6. By recording simultaneously from muscle and from second-order neurons, or by comparing the mean behavior of the two, it was possible to determine the central phase lag and gain of the vestibulocollic reflex. The lag was variable at low frequencies, had an average of 50 degrees at 0.18 Hz, and decreased to 20 degrees at 6 Hz. These results are comparable to those obtained by others using natural stimulation at frequencies of 1.0 Hz and below, and provide new information about the behavior of the central processer at higher frequencies. 7. The medial vestibulospinal tract (MVST), which contains the axons of crossed second-order vestibular neurons, was transected in six experiments. In agreement with previous workers there was no effect on phase at frequencies up to 0.4 Hz. There was also no selective effect of phase or gain at the higher frequencies. This shows that the disynaptic pathways in the MVST do not play any role that cannot be taken over by parallel pathways.
Response properties and synaptic connections of mechanoafferent neurons in cerebral ganglion of Aplysia
Authors: Rosen S. C. , Weiss K. R. , Kupfermann I.
Published: December 2017

1. The cells of two clusters of small neurons on the ventrocaudal surface of each hemicerebral ganglion of Aplysia were found to exhibit action potentials following tactile stimuli applied to the skin of the head. These neurons appear to be mechanosensory afferents since they possess axons in the nerves innervating the skin and tactile stimulation evokes spikes with no prepotentials, even when the cell bodies are sufficiently hyperpolarized to block some spikes. The mechanosensory afferents may be primary afferents since the sensory response persists after chemical synaptic transmission is blocked by bathing the ganglion and peripheral structures in seawater with a high-Mg2+ and low-Ca2+ content. 2. The mechanosensory afferents are normally silent and are insensitive to photic, thermal, and chemical stimuli. A punctate tactile stimulus applied to a circumscribed region of skin can evoke a burst of spikes. If the stimulus is maintained at a constant forces, the mechanosensory response slowly adapts over a period of seconds. Repeated brief stimuli have little or no effect on spike frequency within a burst. 3. Approximately 81% of the mechanoafferent neurons have a single ipsilateral receptive field. The fields are located on the lips, the anterior tentacles, the dorsal portion of the head, the neck, or the perioral zone. Because many cells have collateral axons in the cerebral connectives, receptive fields elsewhere on the body are a possibility. The highest receptive-field density was associated with the lips. Within each area, receptive fields vary in size and shape. Adjacent fields overlap and larger fields frequently encompass several smaller ones. The features of some fields appear invariant from one animal to the next. A loose form of topographic organization of the mechanoafferent cells was observed. For example, cells located in the medial cluster have lip receptive fields, and most cells in the posterolateral portion of the lateral clusters have tentacle receptive fields. 4. Intracellular stimulation of individual mechanoafferents evokes short and constant-latency EPSPs in putative motor neurons comprising the identified B-cell clusters of the cerebral ganglion. On the basis of several criteria, these EPSPs appear to be several criteria, these EPSPs appear to be chemically mediated and are monosynaptic. 5. Repetitive intracellular stimulation of individual mechanoafferent neurons at low rates results in a gradual decrement in the amplitude of the EPSPs evoked in B cluster neurons. EPSP amplitude can be restored following brief periods of rest, but subsequent stimulation leads to further diminution of the response. 6. A decremented response cannot be restored by strong mechanical stimulation outside the receptive field of the mechanoafferent or by electrical stimulation of the cerebral nerves or connectives...
Excitation of primate spinothalamic neurons by cutaneous C-fiber volleys
Authors: Chung J. M. , Kenshalo D. R. , Gerhart K. D. , Willis W. D.
Published: December 2017

1. The responses of spinothalamic tract cells in the lumbosacral spinal cords of anesthetized monkeys were examined following electrical stimulation of the sural nerve or the application of noxious thermal and mechanical stimuli to the skin on the lateral aspect of the foot. 2. The spinothalamic tract neurons were classified as wide dynamic range (WDR), high-threshold (HT), or low-threshold (LT) cells on the basis of their responses to mechanical stimuli. 3. All of the WDR and HT spinothalamic tract cells tested responded to volleys in A- and C-fibers. However, strong C-fiber responses were more common in HT than in WDR cells. 4. The responses atributed to C-fibers were graded with the size of the C-fiber volley. The latencies of the responses attributed to C-fibers indicated that the fastest afferents involved had a mean conduction velocity of 0.9 m/s. The responses remained after anodal blockade of conduction in A-fibers. 5. Temporal summation of the responses of spinothalamic tract cells was demonstrated both to brief trains of stimuli at 33 Hz and to single stimuli repeated at 1- to 2-s intervals. The latter phenomenon is often called "windup." 6. The responses of several spinothalamic tract cells to noxious heat pulses could still be elicited during anodal blockade of conduction in A-fibers. Similarly, it was possible to demonstrate an excitatory action of noxious mechanical stimuli despite interference with conduction in A-fibers by anodal current. 7. The cells investigated were located either in the marginal zone or in the layers of the dorsal horn equivalent to Rexed's laminae IV-VI in the cat. The cells were generally activated antidromically from the caudal part of the ventral posterior lateral nucleus of the thalamus.
Representation of sound frequency and laterality by units in central nucleus of cat inferior colliculus
Authors: Semple M. N. , Aitkin L. M.
Published: December 2017

1. The discharges of 632 units were isolated extracellularly during 42 penetrations of the central nucleus of the inferior colliculus (ICC) in 21 adult cats lightly anesthetized with pentobarbital and ketamine. Microelectrode penetrations were directed from caudal to rostral through ICC, parallel to the Horsley-Clarke (H-C) horizontal and sagittal planes. 2. The threshold best frequency (BF) and binaural response properties were examined for each unit, with the aim of elucidating the organization of these discharge characteristics within ICC. 3. Binaural unit classes consisted of monaural (contralateral) (EO), binaurally phase-sensitive (delay), contralateral excitatory/ipsilateral inhibitory (EI), binaurally excitatory (EE), and other more heterogeneous interaction patterns (other). 4. Detailed histological reconstruction of electrode tracks allowed the recording site for each unit to be related to the three dimensions of ICC. This structure was divided into three lateromedial and three rostrocaudal blocks such that each block contained a similar number of units, enabling meaningful statistical comparisons. Low (3.2 kHz greater than BF) and high (3.2 kHz less than BF) best-frequency classes provided a correlate of dorsoventral location. 5. The arrangements of BFs within ICC were found to be compatible with a model of this structure in which units having similar BFs are organized into layers lying in the H-C horizontal plane medially and gradually tilting in both a ventrolateral and ventrorostral direction. Low frequencies are concentrated dorsally and laterally; high frequencies, ventrally and medially. A rostrocaudal BF difference arises only in lateral aspects of the ICC, where lower frequencies are encountered rostrally. 6. Binaural response classes were distributed differentially throughout ICC. Thus, EO units were concentrated caudally, ventrally, and laterally, while delay units were in greatest numbers rostrally, dorsally, and laterally--almost totally segregated from EO and EI units. The latter populations overlapped ventrally and laterally, but EI units were in greatest density rostrally. The EE class occurred throughout the nucleus, but was most common medially. 7. It is suggested that the differential distributions of binaural responses reflect a partial segregation of the afferents, arising in the superior olive and cochlear nucleus, which terminate in ICC. The central nucleus of the inferior colliculus thus may be composed of several functionally segregated subregions contained within a common tonotopic organization.
Triggering of locust jump by multimodal inhibitory interneurons
Authors: Pearson K. G. , Heitler W. J. , Steeves J. D.
Published: December 2017

1. The locust jump is triggered by a sudden inhibition of activity in hindleg flexor tibiae motoneurons following cocontraction of the hindleg flexor and extensor tibiae muscles. The main result of this investigation was the identification of two interneurons (one for each hindleg) that monosynaptically inhibit flexor tibiae motoneurons and whose properties are all consistent with them being the trigger interneurons for initiating a jump. 2. These interneurons receive strong excitatory input from many sensory modalities (visual, auditory, tactile, and proprioceptive). Because of their multimodal response characteristics, we designated them M-neurons. A particularly strong excitatory input to each M-neuron is from both descending contralateral movement detector (DCMD) interneurons. 3. The threshold for spike initiation in the M-neurons is high (approximately 14 mV). As a consequence, input from any one sensory modality alone rarely initiates action potentials. 4. Each M-neuron is depolarized by sensory input from leg proprioceptors. We propose that proprioceptive feedback during the cocontraction phase depolarizes the M-neurons to decrease their threshold, thus enabling extrinsic sensory stimuli to generate action potentials in both M-neurons and in so doing trigger a jump. The function of the proprioceptive gating of inhibitory transmission from the various sensory systems to the flexor motoneurons (via the M-neurons) is to ensure the development of a strong isometric contraction of the extensor tibiae muscle, and thus a powerful jump in response to external stimuli. 5. Insofar as the initiation of the locust jump depends on sensory convergence onto large identified interneurons, this behavior is similar to ballistic movements in some other animals such as the crayfish tail flip and the startle response in fish. The unique feature of the locust jump is that the trigger interneurons initiate the jump only after a preceding phase (cocontraction) has been accomplished.
A calcium-activated hyperpolarization follows repetitive firing in hippocampal neurons
Authors: Hotson J. R. , Prince D. A.
Published: December 2017

1. A long-lasting afterhyperpolarization (AHP) follows current-induced repetitive firing in hippocampal CA1 neurons studied in vitro. A 10-25% increase in membrane slope conductance occurs during the AHP, suggesting that it may be mediated by an increased conductance to either K+ or Cl-. 2. Intracellular Cl- iontophoresis does not alter the AHP but does attenuate the IPSP. In contrast Ba2+, a cation that can decrease K+ conductance, eliminates the AHP but not the IPSP. These findings suggest the AHP is produced by a long-lasting increased conductance to K+, and is distinct from the IPSP. 3. Mn2+, a Ca2+-channel blocker, eliminates the AHP. In comparison, the AHP persists in the presence of the Na+-channel blocker, tetrodotoxin (TTX), and appears to be temporally associated with TTX-resistant "Ca2+ spikes." It is concluded that AHP is probably activated by Ca2+ influx. 4. These observations indicate that the AHP may be produced by a Ca2+ activated K+ current. A balance between cellular depolarization produced by Ca2+ entry and repolarization generated by a Ca2+-activated K+ current appears to operate to control excitability in some mammalian cortical neurons as it does in molluscan neurons. Disruption of this balance by Ba2+ produces spontaneous membrane-potential oscillations and recurrent burst firing in hippocampal neurons. Increases in the magnitude and duration of Ca2+ depolarization and/or decreases in the Ca2+-activated, K+-mediated repolarization may be mechanisms that lead to spontaneous, epileptiform bursting in mammalian cortical neurons.
Neuronal sites of action of a neurosecretory peptide, egg-laying hormone, in Aplysia californica
Authors: Stuart D. K. , Strumwasser F.
Published: December 2017

1. Egg-laying hormone (ELH) is a polypeptide of about 4,500 mol wt synthesized in the bag cell neurons of the abdominal ganglion of Aplysia. We studied the effects of ELH on the neuronal activity of the attached head ganglia (buccal, cerebral, pleural, and pedal), on the isolated buccal ganglia, as well as on feeding in intact Aplysia. 2. Starved animals (n = 7) injected with crude extract containing ELH stopped eating algae at 17 +/- 4 min and their eggs first appeared at 29 +/- 4 min after injection at 20 degrees C. This cessation of eating is significant when compared to the seven controls (P less than 0.01). These data clearly indicate that a suppression of feeding activity occurs before the appearance of eggs. 3. ELH applied to the paired buccal ganglia in vitro activates a pair of neurons into a tonic pacemaker mode (approximately 1 spike/s). This activation also occurs in a high-magnesium, zero calcium solution that blocks chemical synapses. The time for the full appearance of this activity in vitro correlates well with the time for suppression of feeding in vivo. Each of these neurons has an ipsilateral axon in buccal nerve 3. The neuron has been identified by intracellular recording. 4. ELH increases the rate of firing of a second pair of buccal neurons, each with an ipsilateral axon in the cerebrobuccal connective. 5. ELH, when applied to the attached head ganglia, causes large bursts of neuronal activity in pedal nerves to the foot and increased activity in the nerve to the penis; the relevant neurons remain to be identified. 6. These in vitro effects were produced by ELH partially purified from bag cell cluster homogenates using ammonium sulfate precipitation followed by anion exchange and gel filtration chromatography or by ELH released from activated bag cells in isolated abdominal ganglia and then purified by gel filtration. The isolated buccal ganglia effects have been confirmed with fully purified ELH. 7. The ELH effects on the in vitro nervous system support the hypothesis that ELH in vivo acts directly on the nervous system to suppress feeding activity, controlled by the buccal and cerebral ganglia. ELH may also produce characteristic movements of the head during egg laying, controlled probably by the pedal and cerebral ganglia.
Effects of neonatal enucleation on receptive-field properties of visual neurons in superior colliculus of the golden hamster
Authors: Rhoades R. W. , Chalupa L. M.
Published: December 2017

1. Monocular enucleation in infant hamsters results in a marked expansion of the normally very limited ipsilateral retinotectal projection (13). In 34 hamsters subjected to removal of one eye within 12 h of birth, the receptive-field characteristics of superior collicular neurons ipsilateral and contralateral to the remaining eye were investigated quantitatively and compared to those of normal animals. In six additional neonatal enucleates, the density of the expanded retinotectal projection was studied with the autoradiographic method and an attempt was made to relate the anatomical reorganization with the electrophysiological findings, 2. The response characteristics of visual cells in the colliculus contralateral to the remaining eye were not significantly different from those observed in normal animals. In the ipsilateral tectum, however, numerous changes were observed. Visual receptive fields were abnormally large. The incidence of directional selectivity was markedly reduced, as were the magnitudes of the discharges elicited by either flashed or moving stimuli. Fewer cells were activated by small flashed spots and most of the units that were responsive to such stimulation failed to exhibit the surround suppression typical for the majority of tectal neurons in normal hamsters. Most cells in the ipsilateral colliculus responded only to relatively low (less than 50 degrees/s) stimulus velocities and response decrements resulting from repeated stimulation also occurred much more readily for the neurons tested on this side. 3. The results of additional experiments in neonatal enucleates (n = 8), which were also subjected to acute bilateral removal of the visual cortex, demonstrated that such damage resulted in a marked reduction in the incidence of directional selectivity in the colliculus contralateral to the remaining eye but had no effect on the responses of cells innervated by the aberrant ipsilateral pathway. 4. A correlation between the relative density of the ipsilateral retinal projection at different points in the colliculus, as demonstrated by the autroradiography and the nature of the visual responses obtained in different portions of the structure, indicated that receptive-field size was negatively correlated with the density of the aberrant retinotectal projection and that absolute responsivity (number of impulses elicited by an optimal stimulus) was positively correlated with autoradiographic grain density. 5. These findings demonstrate that while the aberrant retinocollicular projection can, along with the other visual inputs to the tectum, result in the organization of normal response properties for a small number of tectal neurons, the majority of the visual cells innervated by this pathway have responses that are appreciably different from normal.
Experimental strabismus in the kitten
Authors: Van Sluyters R. C. , Levitt F. B.
Published: December 2017

1. We have examined the relative roles of visual and nonvisual input to striate cortex cells in causing the breakdown of binocularity produced by brief periods of visual-axis misalignment in kittens. 2. In the first study, the binocularity of single neurons recorded from the striate cortex was assessed in kittens reared with either surgical or optical strabismus. Surgical strabismus was induced by performing a unilateral medial rectus tenotomy, and optical strabismus by means of goggles that held prisms of equal power before the two eyes with their bases oriented in opposite directions. The loss of functional binocular connections was of comparable severity in these two groups of kittens. Control kittens, reared wearing goggles containing prisms whose bases were oriented in the same direction, showed normal levels of binocularity. 3. In the second experiment, normal kittens were given a surgical strabismus at around 1 mo of age and kept in total darkness for 2 days, 2 wk, or 4 wk. Cortical binocularity was normal in these kittens. 4. Finally, a group of kittens was reared in the illuminated colony with a symmetric surgical strabismus (bilateral medial rectus tenotomy). These kittens suffered a severe loss in cortical binocularity that was comparable to that seen in control kittens reared with asymmetric (unilateral) strabismus. 5. We conclude that altered visual input caused by misregister of the images falling in the two eyes is necessary and almost certainly sufficient to cause breakdown of cortical binocularity in kittens exposed to brief periods of divergent strabismus and that, when strabismus is induced surgically, this loss of binocularity is not dependent on the symmetry of the surgical manipulation; we thus find no evidence for a special role of afferents from the extraocular muscles in producing this effect.
Reappraisal of somatotopic tactile representation within trigeminal subnucleus caudalis
Authors: Yokota T. , Nishikawa N.
Published: December 2017

1. The medulla oblongata caudal to the obex was explored with glass capillary microelectrodes filled with fast green dye in urethan-chloralose-anesthetized cats. Concurrently, the trigeminal integument was mechanically stimulated. Two classes of units, which were activated by innocuous mechanical stimulation of the ipsilateral trigeminal integument, were identified. Both of them showed a somatotopic organization. 2. Units maximally activated by tactile stimulation of a small receptive field in the ipsilateral trigeminal integument were located in pars magnocellularis of the trigeminal subnucleus caudalis. Receptive field falling within, the mandibular distribution were found in the dorsomedial part of pars magnocellularis, maxillary fields occurred next, and ophthalmic fields were represented ventrolaterally. The rostrum (the mouth and nose) was represented just behind the obex, and the receptive field represented gradually shifted to the periphery of the face along the rostrocaudal axis, finally proceeding to dermatomes of cervical segments. At each transverse plane, tactile sensation of the most rostral segment of the represented integument projected onto the marginal zone of pars magnocellularis immediately adjacent to substantia gelatinosa, while the most peripheral segment projected onto the core of quasi-semicircular pars magnocellularis. The result is in contrast with the scheme proposed by previous investigators. 3. Within the lateral part of subnucleus reticularis dorsalis medullae oblongatae, which is ventromedially contiguous with pars magnocellularis, trigeminal units homologous with lamina V units in the spinal dorsal horn were identified. Typically, these units had a graded response in the center of the receptive field, but responded only to strong mechanical stimuli applied to the periphery of the receptive field. In the center of the receptive field, tactile stimulation of a small restricted area was effective, and the tactile receptive field showed a somatotopic organization. The mandibular distribution was represented dorsomedially, the maxillary distribution next to that, and the ophthalmic distribution laterally. Furthermore, a rostrocaudal differentiation similar to that observed with tactile units in pars magnocellularis was found. Hence, a double somatotopic representation of tactile sensation within the caudal medulla oblongata was indicated.
Localization and morphology of cat retractor bulbi motoneurons
Authors: Spencer R. F. , Baker R. , McCrea R. A.
Published: December 2017

1. Motoneurons innervating the cat retractor bulbi muscle have been identified by retrograde axonal transport of horseradish peroxidase (HRP). Following injections of the four slips of the retractor bulbi muscle, labeled motoneurons were found in the abducens nucleus overlapping the distribution of lateral rectus motoneurons and in the oculomotor nucleus partially overlapping the distribution of medial rectus motoneurons. Retractor bulbi motoneurons also were found in the accessory abducens nucleus situated ventral and lateral to the abducens nucleus. 2. Retractor bulbi motoneurons varied considerably in shape and size, but in all instances contained similar cytoplasmic organelles. Quantitative analyses of mean soma diameter indicated that the average size of retractor bulbi motoneurons was larger than the average size of lateral rectus and medial rectus motoneurons. 3. Retractor bulbi motoneurons in the accessory abducens nucleus were identified electrophysically and stained by intracellular injection of HRP. Neuronal reconstructions demonstrated a dorsomedial axonal trajectory directed toward the abducens nucleus and elongated dendritic fields oriented in a dorsomedial-ventrolateral axis. Another major dendritic extension was directed toward the magnocellular division of the spinal trigeminal nucleus, a major source of excitatory input to these motoneurons. 4. Quantitative analyses of synaptic density indicated that the somata of retractor bulbi motoneurons were contacted by significantly fewer synaptic endings than the somata of motoneurons in the abducens nucleus. Retractor bulbi motoneurons in the abducens nucleus exhibited variations in synaptic density that were similar to the densities on lateral rectus motoneurons. 5. Given the morphological differences in location, size, and somadendritic extent between motoneurons in the accessory abducens, abducens and oculomotor nuclei, it is suggested that such features reflect functional differences between the motoneurons with respect to fiber composition of the muscles they innervate, and subsequently to the role each muscle plays in eye movement. 6. Since the morphological features of retractor bulbi motoneurons in the accessory abducens nucleus are quite different from those in either the abducens or oculomotor nuclei, it appears that each motoneuronal population may perform unique oculomotor functions.
Neurodynamic response analysis of anterior semicircular canal afferents in the pigeon
Authors: Landolt J. P. , Correia M. J.
Published: December 2017

1. The neurodynamic responses to sinusoidal and pulse angular accelerations were studied in anterior semicircular canal afferents in the barbiturate-anesthetized pigeon. 2. The resting discharge frequency, aS, varied from 7.4 to 149.0 impulses/s. For most units, aS remained fairly constant for long periods of time during the experiment. 3. The neural-response harmonic distortion, resulting from stimulation by sinusoidal angular accelerations, varied in different units. Percent distortions from as low as 3% to those as high as 57% were determined. 4. Intensity-function plots of peak first harmonic neural response as a function of the peak sinusoidal angular acceleration (with frequency, f, as a parameter) are of two types: one has a linear relationship between the variables; the other demonstrates pronounced nonlinearities ("saturation," particularly for low values of f). In saturation-type units, the data of which fit a power law function, the exponent of the function is frequency dependent, becoming closer and closer to unity with increasing f. 5. Data for all units fit the transfer function, G'(s) = Csk/(tauLS + 1), where G'(s) relates the unit response to angular acceleration, C is a gain constant, 0 < k < 1, and tauL is the so-called long time constant of the classical torsion pendulum model. tauL varied from 4.45 to 22.17 S (mean +/- SE = 10.24 +/- 1.20 S). This may be interpreted as an indication of a regional distribution of tauL'S within the neuroepithelium. Arguments are advanced to show that this is consistent with our present understanding of the ampullary end organ. 6. The degree of regularity of the spontaneous discharge (as determined by the coefficient of variation, CV) was significantly correlated with the parameter k in G'(S). The larger the CV, the larger is the corresponding k. Further work indicated that the larger the value of k, the more adaptation a unit exhibited (k varied from 0.017 to 0.66). 7. The time-domain response of G(S) = G'(S)/(tauSS + 1) to different durations of pulse angular acceleration stimuli agreed well with the neural response to these stimuli (tauS = 2.27 ms is the short time constant of the torsion pendulum model). 8. The term Sk was decomposed into an expression containing a series of polynomials in S in the numerator and denominator. The first term in this expansion K0tau1S/(tau1S + 1), has previously been shown to describe so-called adaptation properties in the dynamics of the semicircular canals. A mean (+/-SE) tau1 = 71.56 (+/-10.01) S was determined. Evidence is presented that Sk probably represents a relaxation phenomenon comprised of a time-varying intracellular Na+/K+-transport process, components of which are summed with the generator potential in the afferent terminal(S) of the receptor hair cell.
Correlations between task-related activity and responses to perturbation in primate sensorimotor cortex
Authors: Wolpaw J. R.
Published: December 2017

1. Monkeys were trained to maintain hand position against a range of constant forces. Short-latency responses to passive wrist extension or flexion, as well as short-latency responses to stretch of a single wrist muscle, were recorded from units in areas 4, 3, 1, and 2. These responses were compared to unit activity during active holding and during active movement. 2. Units related to active holding and to active movement were most common in areas 4 and 2. Three-quarters of these units displayed a specific correlation between their passive and active behaviors. Thus, a unit excited by passive extension was excited during active holding against extension force and excited during an active flexion movement. This behavior is similar to the expected concurrent behavior of muscle stretch receptors. By demonstrating that a significant number of task-related units give qualitatively similar responses to passive extension and passive flexion, the results appear to explain the disagreement among previous studies (5, 9, 36) in regard to area 4 behavior during active and passive movements. 3. Area 4 units responded similarly to passive wrist extension and electromagnetic stretch of a single flexor muscle occurring in the absence of wrist extension, indicating that muscle stretch was important in determining area 4 unit responses to passive movements. 4. The similarity of area 4 behavior to area 2 behavior in active and passive situations, along with the observation that area 2 responses to passive movements occurred several milliseconds earlier than those of area 4, emphasizes the importance of area 2 in motor performance and is consistent with significant area 2 mediation of area 4 responses. 5. Results support the hypothesis of an oligosynaptic transcortical pathway (22, 32, 34), beginning in large part with muscle stretch receptors. Furthermore, the correlation noted between short-latency responses to passive movement and task-related activity suggests that this transcortical pathway not only mediates responses to passive movement but may be responsible, to a significant degree, for task-related activity during undisturbed performance. Thus, active position maintenance and active movement were probably accomplished, at least in part, by increasing and decreasing the influence of this pathway on specific area 4 neurons and thereby producing the patterns of area 4 activity responsible for task performance.
Stochastic properties of gustatory impulse discharges in rat chorda tympani fibers
Authors: Nagai T. , Ueda K.
Published: December 2017

1. The present study was intended to elucidate the role of temporal patterns of impulse discharges of the gustatory primary afferents in the coding of taste qualities by the use of simultaneous analyses of the across-neuron patterning (5) and the temporal patterning of impulses. 2. Impulse discharges of 43 rat chorda tympani fibers elicited by gustatory stimulation (0.1 M NaCl, 0.5 M sucrose, 0.01 N HCl, 0.02 M quinine hydrochloride, 0.3 M KCl, and 0.02 M saccharin sodium) were recorded. The temporal patterns of impulse discharges elicited by these stimuli were statistically analyzed both in an initial dynamic phase and a succeeding stationary phase of responses. In the dynamic phase, the time courses of firing frequency were studied; however, these were not clearly associated with the qualities of taste stimuli. In the stationary phase, the stochastic properties of impulse trains were studied regarding the impulse trains as a stochastic point process (30). In this study, interspike interval histograms (ISI histograms), joint interval histograms, serial correlograms, and autocorrelograms were computed. 3. In general, the distribution patterns of ISI histogram were not absolutely specific to the taste qualities. However, the gamma or the exponential distribution occurred most often with 0.1 M NaCl, and the bimodal or the skewed distribution was dominated with 0.5 M sucrose stimulation among the stimuli tested. The rhythmic discharges did not occur exclusively with the sweet taste stimulation, though they occurred more often with the sweet taste stimulation than with other taste stimulations. The joint interval histogram and the serial correlogram were used to examine the stochastic properties of impulse trains with particular reference to the time dependence in the impulse trains. Generally, the time dependence was not concerned with the taste qualities. 4. The chorda tympani fibers were classified into three types according to the magnitude of responses and the temporal patterns of impulse discharges. The neurons predominantly responsive to NaCl and unresponsive to sucrose were classified as type I neurons. The remaining neurons, which moderately responded to both NaCl and sucrose, were further categorized into type II neurons and type III neurons, depending on their temporal patterns of impulse discharge. The type II neurons tended to show the rhythmic or burstlike firing of impulses in response to more than one kind of taste stimuli. 5. The results showed that the taste quality was represented in the characteristic temporal patterning of impulses as well as in the across-neuron patterning of responses. The possible origin of the temporal discharge pattern and its significance in gustatory information processing were discussed on the basis of the neuron types described above.
Nonlinear properties of stretch reflex studied in the decerebrate cat
Authors: Aldridge J. W. , Stein R. B.
Published: December 2017

1. Pairs of brief stretches or a series of stretches at random intervals (Poisson process) were applied to a slow (soleus) and a fast (plantaris) muscle in decerebrate cats to analyze the nonlinear effects of one stretch on the reflex responses to subsequent stretches. Neural activity, electromyogram (EMG), and force were recorded. The reflex responses due to stretch were compared with reflexes as a result of electrical stimulation of nerves. Nonlinearities of muscle were also examined in the absence of reflexes. Short-latency neural activity produced by the stimuli at all intervals studied was quite constant, so changes in sensory activity cannot account for the nonlinearities. Three phases of nonlinear interactions were observed, and mechanisms for these nonlinearities are suggested. 2. For short intervals (less than 100 ms) following a stretch the force and EMG produced by a second stretch is depressed. This early depression could be due to the after hyperpolarization of the motoneuron cel body or to synaptic mechanisms, since the depression of EMG is seen with electrical stimulation of Ia sensory, but not alpha-motor axons. In addition, a second stretch can disrupt the reflex contraction produced by the first stretch if it occurs at a time when new actomyosin bonds are not readily formed. Because of this force suppression, the total reflex force produced in response to two stretches may be less than the response to a single stretch. 3. For intervals between 100 and 300 ms the force and EMG produced by a second stretch is enhanced. This potentiation is also seen with electrical stimulation of large sensory but not motor axons and could result from a synchronization of motoneuronal excitability cycles. It is more prominent in the homogeneous (soleus) muscle than the mixed (plantaris) muscle, probably because the motoneuron cell bodies will reach a period of high excitability at more nearly the same time in the homogeneous muscle. 4. For longer intervals the force produced by a second stretch is reduced even when the EMG is close to control values. This late depression is also observed with electrical stimulation of cut motor axons and therefore arises from the contractile properties of muscles. 5. With a random series of stretches, the same time course of nonlinear interactions is observed. However, as the mean rate of the random stretches is increased, the average response of the reflex decreases. Thus, the stretch reflex will be most effective in correcting for occasional perturbations to a movement, rather than for continuously varying disturbances.