bluuebunny/crossref_metadata_2025 huggingface dataset:
Antidromic activity in visual radiation during evoked cortical responses
Authors: Rosen A. D. , Vastola E. F.
Published: December 2017

1. Antidromic stimulation of the visual radiation of cats has been used to investigate the possibility that some of the activity in principal geniculate cells following an optic tract stimulus is antidromic. Single spikes were selected from two classes of poststimulus activity to condition the antidromic test spike--the undoubted orthodromic postsynaptic spike and the later spikes, occurring up to 100 ms after the optic tract stimulus. 2. In 15 of 39 cells the minimum antidromic activation times and the minimum spike-spike intervals were found to be shorter and latencies for antidromic stimulation were longer when the conditioning spikes belonged the class of late poststimulus activity. The differences are in accord with the assumption that some of the conditioning spikes were antidromic. 3. Test spikes were frequently found to have long and variable latency when the conditioning spike occurred more than 45 ms after the optic tract stimulus. Possible reasons are briefly discussed. 4. It is suggested that antidromic activity may occur in conditions of the cortex that are more physiological than those associated with a penicillin-induced seizure focus. Some possible mechanisms and functional significance are briefly discussed.
Homosynaptic depression and transmitter turnover in spinal monosynaptic pathway
Authors: Capek R. , Esplin B.
Published: December 2017

1. The transmission in the spinal monosynaptic pathway was studied during repetitive stimulation of a motor nerve by 10 stimuli at 2, 5, or 10 Hz in spinal cats. Initially, the amplitudes of the monosynaptic responses rapidly declined, reaching a plateau after a few stimuli. The level of the plateau was inversely related to the frequency of stimulation. 2. This depression of monosynaptic response was seen only when the same pathway was stimulated; the response elicited from the lateral gastrocnemius was not depressed when preceded by stimulation of the medial gastrocnemius nerve and vice versa. Pretreatment with semicarbazide left the homosynaptic depression unchanged while suppressing the dorsal root reflex. The participation of a depolarization of primary afferents in the described depression is, therefore, unlikely. 3. The decrease of transmitter release by successive volleys, which is the cause of the observed depression, could conceivably be related to the depletion of transmitter stores. 4. A procedure is described, based on this assumption, which allows the calculation of transmitter turnover. The input-output relation in the spinal monosynaptic pathway is used to convert the amplitudes of monosynaptic responses to the amounts of transmitter, both relative to the maximum response. The changes of transmitter release are analyzed under the assumption that each volley releases instantaneously a constant fraction of the transmitter store available for release and that this store is replenished at a constant fraction of the depleted part per second. 5. The values of fractional release per volley were about 0.4, irrespective of frequency of stimulation. 6. The values of fractional replenishment per second ranged from about 1 to 5 on the average, depending directly on the frequency of stimulation. 7. It is suggested that the described procedure might be useful in analyzing drug effects on synaptic transmission.
Physiological and kinetic properties of cholinergic receptors activated by multiaction interneurons in buccal ganglia of Aplysia
Authors: Gardner D. , Kandel E. R.
Published: December 2017

1. Neurons of Aplysia buccal ganglia contain three types of acetylcholine (ACh) receptors, each of which has been characterized by its sensitivity to inhibitors and kinetics of desensitization and by the properties of the conductance change it controls, including reversal potential, major ion, and functional consequence. The receptors are classified as depolarizing, slowly decrementing hyperpolarizing, and rapidly decrementing hyperpolarizing. Identified neurons are innervated by identified cholinergic multiaction interneurons; the form of the postsynaptic potential produced depends on the number and class of receptor found on each cell. 2. Interneuronal action potentials produce monosynaptic IPSPs by activating slowly decrementing hyperpolarizing receptors on seven cells in each ganglion. The IPSP reversal potential of 75 mV is shifted 42 mV in a depolarizing direction in Cl = free seawater. The ACh response has a reversal potential identical to that of the PSP; the PSP is blocked by 10(-4) g/ml curare but unaffected by hexamethonium. Interneuronal action potentials also produce monosynaptic EPSPs with a -14 mV extrapolated reversal potential by activating depolarizing receptors on one cell in each ganglion. This PSP is blocked by 10(-4) g/ml hexamethonium and mimicked by a Na-dependent ACh response. 3. Each interneuronal action potential also produces a diphasic depolarizing-hyperpolarizing synaptic potential in one cell in each ganglion as a result of released ACh acting on two classes of postsynaptic receptor on the same cell. One of these receptors is depolarizing; the other is a rapidly decrementing hyperpolarizing receptor. The two differ in their sensitivity to inhibitors, and the conductance changes they produce differ in their reversal potential, duration, and functional consequences. Both components can be mimicked by iontophoretic application of ACh. 4. Although the hyperpolarizing receptors on the inhibitory and diphasic follower cells have similar sensitivity to inhibitors and control similar conductance changes, they differ in their kinetics of desensitization. The hyperpolarizing receptor on the diphasic cell shows marked decrement to repeated presynaptic action potentials and to repeated iontophoretic application of ACh. This decrement is greater than that seen in either the hyperpolarizing receptor on the inhibitory follower cell or the depolarizing receptor on the dual follower cell. The shape of the PSP in the diphasic follower and its effect on firing of the cell are thus functions of both membrane potential and the degree of desensitization of the receptor. 5. Rate of desensitization is, therefore, an additional criterion for characterizing otherwise similar receptors for neurotransmitters.
Inking in Aplysia californica. III. Two different synaptic conductance mechanisms for triggering central program for inking
Authors: Carew T. J. , Kandel E. R.
Published: December 2017

1. In the previous two papers we described the motor elements which mediate all-or-none inking behavior in Aplysia (4) and the contribution of specific membrane properties of the ink-gland motor cells to the central program for inking (5). In the present paper we show that the central program for inking (a characteristic accelerating burst of action potentials in the motor cells) can be triggered in two different ways: 1) by means of a suprathreshold stimulus delivered to a single site on the animal; and 2) by means of two subthreshold stimuli closely spaced in time, delivered either to the same or to different sites on the animal. 2. The single suprathreshold stimulus triggers the central program primarily by means of a complex increased-conductance EPSP. The two subthreshold stimuli trigger the program by means of a complex decreased-conductance EPSP which is capable of augmenting subsequent afferent synaptic input. 3. The synaptic augmentation produced by the decreased-conductance EPSP is attributable to two properties of the EPSP: 1) it increases the input resistance of the ink-gland motor cells so that the synaptic current from afferent input onto the cells produces larger, more effective EPSP's; and 2) it increases the electrotonic coupling among the motor cells, thereby producing increased positive feedback among them. Thus, the decreased-conductance EPSP provides a novel mechanism for spatial and temporal summation.
Reversed visuomotor behavior mediated by induced ipsilateral retinal projections in goldfish
Authors: Easter S. S. , Schmidt J. T.
Published: December 2017

1. When one optic lobe of a goldfish is removed and the optic nerve from the contralateral eye is deflected ipsilaterally, the nerve innervates the intact, previously foreign side. When the control eye is left intact, the animal shows normal swimming and coordination of head and eyes. In some cases, however, optokinetic nystagmus evoked through the experimental eye is reversed, indicating a functional ipsilateral projection which was apparently outweighed by the normal projection during swimming. 2. When the same surgical procedure is accompanied by partial or complete destruction of the control eye, the animals show overt reversal of visuomotor behavior soon after the ipsilateral projection is established. They make a spontaneous nystagmus and circle continuously. The nystagmus and the circling persist in total darkness for days before they are extinguished. They resume as soon as the animal returns to light. 3. The vestibuloocular reflex is biased differently from normal, but the sign of the gain is normal. 4. We conclude that the neurological reversal of vision triggered the nystagmus and the circling, and that the many months with reversed vision resulted in some longer lasting change in the nervous system such that the behaviors persisted even in the absence of moment-to-moment visual stimulation.
Organization of peripheral nerves and spinal roots of the Atlantic stingray, Dasyatis sabina
Authors: Coggeshall R. E. , Leonard R. B. , Applebaum M. L. , Willis W. D.
Published: December 2017

1. The sizes and numbers of axons in peripheral nerves and spinal roots were investigated in the stingray, Dasyatis sabina. 2. The axons of the dorsal and ventral roots do not mingle in peripheral nerves of this animal as they do in higher vertebrates. Thus, it was usually possible to split the peripheral nerve into two portions, one containing only dorsal root axons, the other containing only ventral root axons. This feature was useful for the analysis of certain aspects of spinal cord organization. 3. The fact that dorsal and ventral root axons were segregated in peripheral nerves enabled us to demonstrate, without experimental surgery, that the central processes of the dorsal root ganglion cells and the proximal ventral root axons were 10-20% narrower, on the average, than the distal processes of the same dorsal root ganglion cells or the distal parts of the same ventral root axons. 4. The stingray is remarkable in having very few unmyelinated axons in the dorsal roots, ventral roots, or peripheral nerves. This paucity of unmyelinated axons distinguishes the Atlantic stingrays from all other vertebrates whose roots and nerves have been examined for unmyelinated fibers. 5. Similar findings were obtained for one spotted eagle ray (Aetobatus narinari) and two cow-nose rays (Rhinoptera bonasus).
Indirect, across-the-midline retinotectal projections and representation of ipsilateral visual field in superior colliculus of the cat
Authors: Antonini A. , Berlucchi G. , Sprague J. M.
Published: December 2017

1. In agreement with previous work, we have found that the ipsilateral visual field is represented in an extensive rostral portion--from one-third to one-half--of the superior colliculus (SC) of the cat. This representation is binocular. The SC representation of the ipsilateral visual field can be mediated both directly, by crossed retinotectal connections originating from temporal hemiretina, and indirectly, by across-the-midline connections relaying visual information from one-half of the brain to contralateral SC. 2. In order to study the indirect, across-the-midline visual input to the SC, we have recorded responses of SC neurons to visual stimuli presented to either the ipsilateral or the contralateral eye of cats with a midsagittal splitting of the optic chiasm. Units driven by the ipsilateral eye, presumably through the direct retinotectal input and/or corticotectal connections from ipsilateral visual cortex, were found throughout the SC, except at its caudal pole, which normally receives fibers from the extreme periphery of the contralateral nasal hemiretina. Units driven by the contralateral eye, undoubtedly through an indirect across-the-midline connection, were found only in the anterior portion of the SC, in which is normally represented the ipsilateral visual field. Receptive fields in both ipsilateral and contralateral eye had properties typical of SC receptive fields in cats with intact optic pathways. 3. All units having a receptive field in the contralateral eye had also a receptive field in the ipsilateral eye; for each of these units, the receptive fields in both eyes invariably abutted the vertical meridian of the visual field. The receptive field in one eye had about the same elevation relative to the horizontal meridian and the same vertical extension as the receptive field in the other eye; the two receptive fields of each binocular unit matched each other at the vertical meridian and formed a combined receptive field straddling the vertical midline of the horopter...
An intracellular analysis of some intrinsic factors controlling neural output from inferior mesenteric ganglion of guinea pigs
Authors: Weems W. A. , Szurszewski J. H.
Published: December 2017

1. In vitro studies were conducted on neurons within the inferior mesenteric ganglion (IMG) of guinea pigs to investigate how intrinsic features of the spike-generating process interact with preganglionic inputs to produce the output firing patterns of these neurons. Intracellular-electrode techniques were used to monitor and control electrical activity of IMG neurons. Preganglionic inputs were activated either synchronously by stimulating an attached nerve trunk or asynchronously by leaving the ganglion attached to a segment of terminal colon and activating the colonic-IMG mechanosensory system. 2. Ninety-seven percent of the neurons studied demonstrated an afterspike hyperpolarization (ASH). The ASH process was activated only by the occurrence of a spike and did not have a synaptically induced component. Further activation of this process was produced by two or more spikes having interspike intervals less than the duration of an ASH following a single spike. An aftertrain hyperpolarization (ATH) resulted from this progressive activation. The amplitude of both the ASH and the ATH decreased when the resting membrane potential was hyperpolarized by current injection or by increasing the external potassium ion concentration. 3. Neuronal excitability was reduced during the ASH. From this observation it was concluded that when IMG neurons operate in the occasional-firing mode, the ASH process prevents output frequency from greatly exceeding the reciprocal of the ASH duration produced by a single spike. 4. Two types of synaptically induced slow depolarizations were observed: a slow, long-latency depolarization and a short-latency depolarization (SLD). These depolarizations differed in their latency, onset, and duration. Both were capable of converting synchronous, preganglionic input from subthreshold (non-spike-activating) to threshold (spike-activating) activity. 5. Neurons having resting potentials more positive than -60 mV were capable of firing in the rhythmic-firing mode; 40% of these neurons demonstrated tonic- and 60% phasic-firing behavior. Frequency-current relations for tonic-discharging neurons were linear from the rhythmic-firing threshold to current levels approximately 2.5 times the threshold value. Minimal frequency for tonic firing and the slope of the linear portion of the frequency-current relation were indirectly related to the duration of the ASH. 6. This study suggests that sympathetic, noradrenergic neurons of the IMG can operate in either the occasional- or rhythmic-firing mode. In the physiologic state in vivo, most IMG neurons probably do not produce action potentials in excess of 10-15 Hz because of their intrinsic properties which regulate firing in both modes of operation.
Sustained depolarizing potentials in reticulospinal axons during evoked seizure activity in lamprey spinal cord
Authors: Matthews G. , Wickelgren W. O.
Published: December 2017

1. Intracellular recordings were made from lamprey reticulospinal axons (Muller axons) during seizures evoked by electrical stimulation of the isolated spinal cord in saline containing either 0 Cl or 1 mM picrotoxin. The seizures had tonic and clonic-phases similar to ictal seizures in mammalian brain. 2. During seizures Muller axons were depolarized by 10-15 mV. These seizure-depolarizations were not due to any direct effect of the evoking stimulus on the Muller axons themselves nor were they initiated by an accumulation or extracellular potassium. 3. A decrease in axonal input resistance occurred during a seizure-depolarization. Also, the amplitude of a seizure-depolarization was decreased by depolarizing the axon 5-15 mV with injected current. Further, hyperpolarizing the axon increased the amplitude of the seizure-depolarization, but the growth flattened out beyond 30-40 mV of hyperpolarization. The decrease in input resistance during the seizure-depolarization and the dependence of the response amplitude on axonal membrane potential suggested that the seizure-depolarization was an excitatory synaptic potential. However, the failure of the seizure-depolarization amplitude to continue to grow at membrane potentials greater than 30 mV negative to the resting potential was not consistent with this interpretation. 4. A synaptic conductance change as the cause of the seizure-depolarization was ruled out by setting the axonal membrane potential at different levels with injected current and monitoring the input resistance of the axon before and during seizure-depolarizations. It was found that no change in input resistance occurred during the seizure-depolarization when the axon was hyperpolarized more than approximately 30 mV, the same potential at which the growth in the response amplitude ceased. From analysis of these data and the passive current-voltage properties of Muller axons it is concluded that the seizure-depolarization is not a chemical synaptic potential, but rather the result of the passive injection of depolarizing current into the axons. 5. The source of the depolarizing current which flows into Muller axons during seizures is probably paroxysmal action-potential activity in spinal motoneurons and interneurons, many of which are electrically coupled to Muller axons.
Frequency-response analysis of vestibular-induced neck reflex in cat. II. Functional significance of cervical afferents and polysynaptic descending pathways
Authors: Ezure K. , Sasaki S. , Uchino Y. , Wilson V. J.
Published: December 2017

1. Three major inputs to cervical motoneurons were analyzed with frequency-response methods in decerebrate and unanesthetized cats: the afferent system including the gamma-loop, the vestibulospinal tract, and some polysynaptic tract that transmits vestibular influences in the vestibulocollic reflex. 2. The dorsal roots C1-C4 were cut in order to open the feedback loop through the gamma-fiber spindle-afferent system. No effects were observed on the gain and the phase lag of motor-unit response. However, the DC components of the response were consistently decreased by deafferentation both in motor-unit and compound EMG responses. Firing of muscle spindle afferents was modulated during oscillation of the turntable. The majority of responses of spindle afferents was in phase with the simultaneously recorded extrafusal motor activity. These results indicate the existence of alpha-gamma coactivation in the vestibulocollic reflex. 3. Intracellular recording from cervical motoneurons showed that monosynaptic EPSP's were induced by dorsal root stimulation. By far the larger EPSP's, however, were observed with latencies of 10-15 ms, showing the existence of more powerful polysynaptic routes. It is postulated that the cervical afferent system controls the gain of the reflex by changing the number of motor units participating in the vestibulocollic reflex through some polysynaptic pathways, and that the afferent system scarcely changes, the gain or phase lag of individual motor units through a short stretch reflex loop. 4. The medial vestibulospinal tract in the MLF was interrupted, but no effects were detected on the dynamic characteristics of the frequency response. This shows the existence of other effective descending pathways which function as an integrator. 5. Remarkable phase advances were induced by intravenous infusion of Nembutal. This suggests that the Nembutal decreased the activity of the polysynaptic pathways and that the neural integrator, composed of polysynaptic networks, was prevented from fulfilling its ordinary function.
Correlation of neural discharge with pattern and force of muscular activity, joint position, and direction of intended next movement in motor cortex and cerebellum
Authors: Thach W. T.
Published: December 2017

1. Monkeys were trained to grasp a rod movable in a horizontal arc (Fig. 1), and to hold the rod by angulation of the wrist in each of three positions (A,B, C). A maintained load was placed on the rod alternately to oppose flexion and extension. At a light signal, the monkey had to move to the next position in a prescribed sequence (ABCBABCBA, ETC.). The task was designed to dissociate, while holding in position, the following variables: 1) pattern of muscular activity in the forearm required to hold the wrist in position, determined by the direction of the load (flexor or extensor muscles); 2) position of the rod, and thus angulation of the wrist joint (A, B, and C); and 3) set for the direction of the intended next movement (flexor or extensor). These variables are subsequently referred to as MPAT, JPOS, and DSET, respectively. 2. After training, recordings were made of the EMG activity of muscles used in the task and of the discharge of single neurons in the motor cortex of the cerebrum and the interposed and dentate nuclei of the cerebellum. 3. While holding the wrist in position, EMG and interpositus behaved uniformly, with higher discharge frequency under load in one direction and lower discharge frequency under load in the opposite direction. This relation was relatively independent of the position held and of the direction of the intended next movement. Thus, interpositus and EMG both seemed best related to the MPAT variable, as opposed to JPOS and DSET variables. By contrast, neurons in motor cortex and in dentate fell into three categories: one category discharged in relation to the pattern of muscular activity (MPAT), a second to the position of the wrist (JPOS), and a third to the direction of the intended next movement (DSET). While MPAT neurons formed a distinct dissociated group, neurons that were best related to JPOS were often related to DSET, and vice versa. 4. A few of the MPAT neurons in interpositus and motor cortex were further studied by varying the magnitude (as well as the direction) of the loads. Both interpositus and motor cortex MPAT neurons changed firing frequency in relation to the magnitude of load, and though few neurons were thus studied, the relation seemed clearer for interpositus than for motor cortex. 5. Anatomically, the three types of neurons thus classified by firing pattern during the hold periods were intermixed in the arm area of motor cortex. In dentate and interpositus, those neurons thus related to the performance were localized to a narrow strip across the posterior part of both nuclei. Neurons apparently related to eye and drinking movements were located more posteriorly still, suggesting somatotopic representation.
Postnatal development of visually evoked activity within motor cortex of cat
Authors: Glass J. D. , Fromm G. H. , Chattha A. S. , Bloom R. D.
Published: December 2017

1. The development of visually evoked activity within motor cortex was studied in chloralose-anesthetized kittens of 3, 4, and 5 mo of age and adult cats. 2. The slow-wave response from motor cortex of the adult cat is a triphasic negative-positive-negative wave. In 3-mo-old kittens the response is only a long-duration negative wave, while at 4 mo the positive and late negative waves emerge, and at 5 mo of age the adult form of the response is present. 3. Single neurons in the adult respond to the light during the positive component of the slow-wave response. When only the negative wave is present in kittens of 3 and 4 mo of age, neurons do not respond to the photic stimulus. At 5 mo of age the correlation between unit activity and the positive component of the response is identical to the adult. 4. The laminar analysis of the positive component of the response suggests that it originates relatively superficially in cortex and migrates down toward the deeper layers. Its correlation with unit activity indicates that the positive component represents excitatory postsynaptic potentials. 5. These results are consistent with an excitatory drive on neurons within motor cortex undergoing development change until the 5th mo of life.
External nucleus of inferior colliculus: auditory and spinal somatosensory afferents and their interactions
Authors: Aitkin L. M. , Dickhaus H. , Schult W. , Zimmermann M.
Published: December 2017

1. The discharges of 129 units were studied in the external nucleus of the inferior colliculus of 11 anesthetised and paralyzed cats. This region is known to receive fibers from auditory nuclei and the dorsal column nuclei. 2. Stimuli used were pure tone bursts, monaural or binaural, tactile stimulation of the body surface, and electrical stimulation of the dorsal columns (DC) at a low cervical level and of the contralateral and ipsilateral tibial nerves. 3. Forty-six percent of units were only influenced by one type of stimulation (26% auditory, 20% DC). Of the remaining bimodally influenced units, the majority was excited by pure tone stimuli and inhibited by DC stimulation. 4. A small proportion of the total population (18%) was excited by both DC and auditory input, and units sensitive to both tones and tactile stimulation of the skin were rare (4%). 5. Auditory tuning curves were generally very broad compared with those of units in the central nucleus of the inferior colliculus. Similarly, somatic receptive fields were large and usually extended over a whole limb. 6. The majority of tone-responsive units were influenced binaurally (70%); most somatic receptive fields were located on the contralateral fore- or hindlimb (16/18). 7. The results indicate that both auditory and somatosensory information is contained in the discharges of units in the external nucleus of the inferior colliculus. 8. Speculations are made about the role of this nucleus in descending auditory input to the spinal cord and in the comparison of auditory and cutaneous information during sound-evoked coordinated body movements.
Eye alignment in kittens
Authors: Olson C. R. , Freeman R. D.
Published: December 2017

1. The alignment of the pupillary axes and of the visual axes has been measured in 23 normally reared cats ranging in age from 14 days to adulthood. 2. In agreement with a previous report, we find that pupillary divergence, as measured from photographs, tends to decrease during the first 2 mo of life. 3. The angle between the visual axes of cats of various ages was determined during paralysis by plotting the receptive fields of neurons in cortical area 17, and extrapolation to the angle of alignment of the freely moving animal was accomplished by comparing pupillary photographs taken before and after immobilization. Results obtained by this method reveal that in cats of all ages the visual axes are convergent, and that the average angle of convergence is approximately the same at all ages. 4. We conclude that young kittens may be capable of coordinated binocular vision. Further study will be required to determine whether animals as young as 2 wk are able to align their eyes accurately so as to bring the two retinal images of object space into register. 5. Pupillary divergence decreases during development as a result of changes in the geometry of the eye characterized by a reduction of the angle between the pupillary axis and the visual axis in each eye. This angle changes from around 25 degrees at 14 days to around 16 degrees in adulthood. 6. The role of visual experience in the maintenance of normal eye alignment was investigated by rearing five cats in darkness until the age of 4-7 mo. In three animals, visual axis alignment was within the normal range. The two remaining cats were slightly exotropic. 7. A change occurs during development in the apparent cyclotorsional alignment of the eyes, as determined by measuring the intorsional angle formed by the two slit pupils. This angle increases during the 1st and 2nd mo, assuming a mean value of 14 degrees. In dark-reared cats the increase continues through the 3rd mo, culminating in an abnormally large angle of pupillary intorsion (mean of 24 degrees). The possibility that these changes reflect true shifts in cyclotorsional alignment of the eyes is discussed.
Development of single-neuron responses in kitten's lateral geniculate nucleus
Authors: Daniels J. D. , Pettigrew J. D. , Norman J. L.
Published: December 2017

1. In the lateral geniculate nucleus (LGN) of 18 kittens whose ages ranged from 6 to 40 days, 445 cells were studied. 2. LGN cells of kittens younger than 21 days are characterized by very low maintained rates, long latencies to full-field flash, response fatigue, large receptive field, absence of surround responses and surround inhibition, poor responses to fast-moving stimuli, and low-amplitude responses to flashing spots. 3. Cells were characterized as sustained or transient, and on, off, or on-off by their responses to flashing spots of light, and as X-like of Y-like by their responses to contrast reversal. Prior to 21 days, cells are hard to classify as X or Y. 4. A large proportion of cells in kitten LGN have both on- and off-responses to small and center-sized spots of light. This proportion decreases with development. 5. A small number of cells develop mature receptive-field properties very early (14--20 days). These are cells with X-type responses (linear summation) to contrast reversal and tend to have sustained responses to flashing spots. 6. Y-like cells, with nonlinear summation, develop mature receptive-field properties later than 34 days of age and later than all X-cells. 7. We conclude that there are different developmental patterns for cells of the kitten LGN. These different patterns may be important in determining the visual responses of cortical cells and their degree of susceptibility to environmental modification.
Receptor potential and spike initiation in two varieties of snake muscle spindles
Authors: Fukami Y.
Published: December 2017

1. Receptor potentials, in response to ramp-and-hold stretch, have been recorded from two varieties of snake muscle spindles. 2. The two types of spindles have a similar sensitivity of impulse discharge to amplitude of receptor potential during the static phase of stretch. 3. Receptor potentials from short-capsule spindles show a high dynamic sensitivity to velocity of stretch. Amplitude of dynamic receptor potentials is well related to frequency of dynamic discharge except beyond a certain velocity of stretch where the frequency deviates progressively more than expected from linearity. 4. Receptor potentials from long-capsule spindles show a low dynamic sensitivity to velocity of stretch and amplitude of dynamic receptor potentials is well correlated with dynamic firing frequency. 5. The threshold level of receptor potential for initiating spike discharge varies with the velocity of stretch, the relation being similar for the two types of spindles. 6. It is concluded that the basis for functional differentiation of snake spindles may lie in the mechanism by which deformation of sensory endings is transformed into receptor potential. 7. Late adaptation of impulse discharge, a characteristic feature of the response of the short-capsule spindle to maintained stretch, has been related to length changes of the sensory region measured directly with Nomarski optics. The linear relation found between the slow adaptive fall of impulse discharge and the simultaneous shortening of the sensory region strongly suggests a mechanical basis for the late adaptation.
Excitatory termination of abducens internuclear neurons on medial rectus motoneurons: relationship to syndrome of internuclear ophthalmoplegia
Authors: Highstein S. M. , Baker R.
Published: December 2017

1. Field potentials and intracellular records were obtained from the medial rectus subdivision of the IIIrd nucleus in anesthetized cats following electrical stimulation of the abducens nuclei, vestibular nerves, pontomedullary brain stem, and the medial longitudinal fasciculi (MLF). 2. Stimulation of the contralateral abducens nucleus produced unique field potentials in the medial rectus subdivision. They consisted of an early sharp transient volley followed by a slower postsynaptic negativity. 3. Monosynaptic EPSPs were evoked in medial rectus motoneurons following contralateral abducens nucleus stimulation. The EPSP amplitudes were graded when the stimulus intensity was increased from threshold to supramaximal. EPSPs produced by contralateral abducens nucleus stimulation were larger in amplitude than those produced by ipsilateral vestibular nerve stimulation. The current-voltage relationship and reversal potentials for Vi- and abducens-evoked EPSPs were similar and indicated an overlapping location of excitatory synaptic terminals on medial rectus motoneurons. 4. Secondary vestibular axons activated monosynaptically by ipsilateral vestibular nerve stimulation were not recruited by abducens nucleus stimulation. 5. Ipsilateral MLF stimulation produced EPSPs with similar profiles as those observed following abducens nucleus stimulation; however, stimulation of the contralateral MLF at comparable stimulus intensities did not produce any changes in transmembrane potential. 6. When higher intensity stimuli were applied to the contralateral MLF, the synaptic potentials recorded in the medial rectus were occluded by those produced by weaker stimulation applied to the ipsilateral MLF. This suggests that the potentials resulting from stronger contralateral stimulation were due to current spread to the ipsilateral MLF. 7. While recording in the medial rectus subdivision, various sites in the ponto-medullary brain stem were explored with a stimulating electrode. Analysis of evoked field potentials suggested that the ascending internuclear axons were contained only in the MLF ipsilateral to the medial rectus. Acute brain stem lesions confirmed this suggestion. 8. Chronic lesions were placed in the brain stem to isolate the abducens nucleus from either extrinsic fibers of passage or axon collaterals. Acute electrophysiological experiments in these chronic animals corroborated the suggestion that the medial rectus pathway originated from within the abducens nucleus. 9. We conclude that axons from the internuclear neurons of the abducens nucleus exit from the nucleus medially, cross the midline, ascend in the opposite MLF, and terminate monosynaptically on medial rectus motoneurons. 10. we believe that the syndrome of internuclear ophthalmoplegia associated clinically with lesions of the medial longitudinal fasciculus could be due to the absence of ascending physiological activity from internuclear neurons of the abducens nucleus.
Response properties and electrical constants of caudate nucleus neurons in the cat
Authors: Sugimori M. , Preston R. J. , Kitai S. T.
Published: December 2017

1. Response properties and passive electrical constants were assessed for caudate nucleus neurons in pentobarbital-anesthetized cats. The neurons studied were those which could be monosynaptically excited by substantia nigra and thalamic (centromedian-parafascicular) stimulation. 2. Input resistance and membrane time constant were estimated from the plateau value and time course, respectively, of the neuronal membrane response to intracellularly applied current pulses. The average values obtained were 16.5 Momega and 11.3 ms. Specific resistance and capacitance values were calculated. 3. Single or repetitive spikes were readily evoked by nigral or thalamic stimuli or by the application of direct depolarizing currents. Spike thresholds were higher for direct than for synaptic activation (7.2 vs. 5.6 mV). 4. Direct depolarizing stimuli with durations up to 600 ms elicited repetitive discharge with little adaptation of firing rate. The maximum discharge rates induced by direct stimuli were near 200 spikes per second. 5. The intracellular application of tetraethylammonium chloride (TEA) produced spike-prolongation effects in caudate neurons that were similar to the effects reported for other nerve membrane. 6. The probable identity of the recorded neurons as medium spiny neurons was discussed and, in addition, it was proposed that the characteristic silence of these cells is not likely due to intrinsic membrane specialization.
Comparison of receptive-field properties of X and Y ganglion cells with X and Y lateral geniculate cells in the cat
Authors: Bullier J. , Norton T. T.
Published: December 2017

1. To examine the transmission of visual information through the lateral geniculate nucleus, we have studied the receptive-field properties of 65 X and Y optic tract axons and compared them with the receptive-field properties of X and Y LGN cells in paralyzed cats anesthetized with N2O/O2 (70/30%). The same experimental conditions and quantitative methods have been used as in the preceding study of LGN cells (2). 2. The spatiotemporal organization of the receptive fields of X and Y retinal axons are similar to those of X and Y LGN cells. X ganglion cell receptive fields show a simple center-surround organization, whereas Y ganglion cell receptive fields show a more complex organization with three concentric regions: a central region of center-type response, a region of mixed center-type and surround-type responses, and a region of surround-type response. 3. The inhibitory strengh of the surrounding region was tested with a centrally located flashing light spot of successively increased diameter. As in the LGN, the inhibitory strenght of the surrounding region was stronger in retinal X-cells than in retinal Y-cells, and the strength of the inhibition decreased as the diameter of the receptive-field center increased. 4. The decrease of the inhibitory strength of the surrounding region with increasing distance from the receptive-field center was similar in the retina and in the LGN for cells belonging to the same class (X or Y) and having the same receptive-field center size. 5. The differences in properties in the LGN between small-field X-, large-field X-, and Y-cells are best explained by assuming that they are driven, respectively, by small-field X, large-field X, and Y retinal ganglion cells. There does not appear to be a significant mixing of properties either between cells having different receptive-field center sizes. 6. The principal transformation we found between retinal and LGN units is that X LGN cells have sharply lower spontaneous activities and driven activities, as compared with X ganglion cells. Y LGN units show only a small decrease in spontaneous activity in comparison with Y ganglion cells. 7. We conclude that there is a significant alteration in the LGN only in the properties of X-cells, possibly by way of a strong inhibitory pool converging on X LGN units. We further suggest that this inhibitory pool plays a role in the modulation of transmission of information through the LGN only in the X channel, while the Y channel appears to be relatively unaffected.
Adrenergic inhibition of serotonin release from neurons in guinea pig Auerback's plexus
Authors: Wood J. D. , Mayer C. J.
Published: December 2017

1. Norepinephrine reversibly blocked both the fast and slow stimulus-evoked EPSPs in myenteric ganglion cells. This action of norepinephrine was offset by the alpha-adrenergic blocking agent, phentolamine. 2. The putative neurotransmitter for the fast EPSP is acetylcholine, and serotonin (5-HT) is the suspected transmitter for the slow EPSP. 3. Norepinephrine did not block the excitatory effect of microiontophoresis of 5-HT onto the ganglion cells. 4. Norepinephrine decreased the input resistance and suppressed neuronal excitability. This effect was reversed by addition of 5-HT to the perfusion solution and was attributed to presynaptic blockade by norepinephrine of ongoing release of 5-HT. 5. Addition of norepinephrine after the slow EPSP had been evoked did not shorten the duration of the slow EPSP. 6. The results suggested that the mechanism of the blocking action of norepinephrine was inhibition of release of the excitatory neurotransmitters form presynaptic nerve terminals. This is probably one of the mechanisms that is involved in suppression of gastrointestinal motor function during activation of the sympathetic innervation of the bowel.
Chronic paw denervation causes an age-dependent appearance of novel responses from forearm in "paw cortex" of kittens and adult cats
Authors: Kalaska J. , Pomeranz B.
Published: December 2017

1. In normal kittens and cats, cells in a region of primary somatosensory cortex (SI) responded exclusively to input from the contralateral front paw; we called this area paw cortex (PC). A neighboring region of SI responded to input from the contralateral forearm above the wrist; we called this area forearm cortex (FC). The centers of PC and FC were about 4 mm apart. 2. In kittens several weeks after transection of the nerves to the front paw, the following changes were observed in PC: a) 52% of PC cells had receptive fields on the forearm; normally, PC cells responded to natural stimulation only of the front paw; b) many cells in PC (58%) responded to electrical stimulation of the medial cutaneous nerve from the forearm; normally, very few PC cells (9%) responded to this nerve; c) there was a 370% increase in the median amplitude of medial cutaneous-evoked potentials in PC; d) in contrast to these enhanced inputs, PC responses to ulnar nerve stimulation decreased significantly. 3. In adult cats, paw denervation initiated a similar process as in kittens, but with less marked somatotopic changes. 4. In both kittens and adults, FC was unaffected by the nerve injuries. 5. We conclude that a chronic peripheral nerve injury can produce extensive changes in SI cortex somatotopic organization; the nature of the effect is age dependent.
Stumbling corrective reaction: a phase-dependent compensatory reaction during locomotion
Authors: Forssberg H.
Published: December 2017

1. Tactile stimuli to the paw consisting of a stick making contact or an air puff aimed at the dorsum were used to study the phasic influence of locomotor activity on the reflex pattern elicited in extensor and flexor muscles and on the induced compensatory movements in intact cats. The resulting movements and reflex pattern are called "stumbling corrective reactions." 2. The basic reflex pattern and movements of the stumbling corrective reaction are: a) if the stimulus occurs during the swing phase, a short-latency activation of the flexor muscles, which induces an additional flexion of the limb lifting the paw over the obstacle; b) if the stimulus occurs during the support phase, an inhibition followed by an excitation of the extensor muscles, which neither increase nor decrease the extension. However, the stimulus evokes an increased flexor activity in the succeeding swing phase, which induces a brisker flexion. 3. Tactile stimuli to the proximal part of the limb or to the belly in front of the knee evoked the same type of phase-dependent compensatory reactions. Such reactions would presumably be beneficial for the animal to avoid high obstacles that impede movement. 4. A nonnoxious electrical stimulus (typically 2 mA; 1 ms) applied to the dorsum of the paw was used to study systematically the reflex pattern of the stumbling corrective reaction. Two pathways were defined to the knee flexor (semitendinosus). One early burst was evoked at about 10 ms and one later at about 25 ms after the stimulus. Short inhibitory pathways and longer excitatory pathways (20-50 ms) projected to the extensor nuclei. A short-latency (10 ms) excitatory pathway to the ankle extensor (lateral gastrocnemius) was also activated. 5. A painful electrical stimulus applied to the dorsum of the paw evoked large flexor responses during the whole step cycle. During the support phase the locomotion was disrupted as the supporting limb was withdrawn. 6. The results demonstrate that intact cats are able to compensate rapidly for unpredicted perturbations and that the reflex pattern and the induced corrective movements are adapted to the locomotor activity so that functionally meaningful movements are evoked in each phase of the step cycle. 7. The evoked reflexes and their modulation are consistent with those previously found in chronic spinal cats during walking and in paralyzed spinal cats performing "fictive locomotion." It is suggested that the same spinal pathways are used, and that they are controlled by the spinal "locomotor generator."
Neural correlates of nystagmus in abducens nerve
Authors: Honrubia V. , Reingold D. B. , Lau C. G. , Ward P. H.
Published: December 2017

1. The firing rates of action potentials of abducens nerve single fibers were recorded in the cat's orbit during a variety of vestibular and optokinetic stimulations. 2. Comparison was made of the neural firing rates associated with agonist and antagonist responses during slow and fast components of vestibular and optokinetic nystagmus. It was found that the relationship between the motoneuron firing rates and the eye motion was independent of the reflex with which they were associated--vestibular or optokinetic, or the type of response--agonist or antagonist. No neurons were observed that responded only during the fast or only during the slow nystagmus phase. Motoneuron firing rates were proportional to both velocity and position of the eye in a ratio of 1 (spikes/s)/(deg/s) to 7.2 (spikes/s)/deg. The behavior of the motoneurons was compatible with the hypothesis that thier firing rates are sufficient to overcome both elastic and viscous forces by which the muscles and ligaments hold the eye in the orbit. 3. For low-frequency head rotations, eye displacement and neural responses showed a small phase angle difference. At higher frequencies, however, while the eyes maintained a fixed relationship to the head rotation, the neural responses showed an increasing phase lead. One component of this phase lead compensated for the phase lag introduced by the orbital mechanics. The other was modeled as a constant delay of approximately 70 ms, which may be accounted for by neuromuscular transmission and transduction.
Effects of temperature and deuterium oxide on crustacean stretch receptor
Authors: Ono T. , Nakajima S.
Published: December 2017

1. The receptor potential was recorded intracellularly from the isolated stretch receptor neuron of crayfish. Total substitution of D2O for H2O in the bathing solution reversibly decreased the amplitude of the receptor potential to a level of 34% of the control. The input resistance of the neuron was slightly increased by the D2O treatment, while the resting potential and the input capacity were virtually unchanged. The viscoelastic property of the receptor muscle was not altered by the D2O substitution. Thus, D2O seems to inhibit directly the activation process of the receptor potential. 2. Temperature change over the range of 25-5 degrees C did not affect the amplitude of receptor potential. However, the input resistance of the neuron was increased about twofold by the lowering of temperature from 25 to 5 degrees C. 3. We conclude that when the temperature is lowered, the receptor current is diminished, but this decline is just about compensated for by the increase in membrane resistance, resulting in a near constancy of the receptor potential. This is the cellular basis for the relative constancy of the transduction process of the stretch receptor in the face of large temperature changes. On the other hand, in the case of D2O substitution the compensation mechanism of the resistance increase does not work, and the sensory transduction is inhibited substantially.