bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanoreceptors in rat glabrous skin: redevelopment of function after nerve crush
Authors: Sanders K. H. , Zimmermann M.
Published: December 2017

In the glabrous skin of the rat's hindfoot the same triple set of low-threshold mechanoreceptors is present as has been found in other mammals: slowly adapting (SA), rapidly adapting (RA), and very rapidly adapting Pacinian corpuscle-like (PC) receptors. Their functional characteristics were examined in normal rats and compared with those of sensitive mechanoreceptors found in the glabrous skin of the foot 2-24 wk after crush of the plantar nerves, resulting in regeneration of the transected nerve fibers. After 2 wk of nerve regeneration, low-threshold RA and SA cutaneous mechanoreceptors reappeared in the foot skin. Responses of PC receptors were recorded again after 3 wk, at which time the proportion of fibers that could be identified as low-threshold cutaneous mechanoreceptors had regained control level. Discharge patterns of regenerated cutaneous mechanosensitive receptors were very similar to those of normal skin mechanoreceptors. Their sensitivity to controlled mechanical stimulation was, however, still reduced 4 wk after the lesion. After 8 wk RA and SA receptors had regained their normal dynamic sensitivity, i.e., the responsiveness to the velocity of skin indentation. The static sensitivity of SA receptors, i.e., responsiveness to maintained skin indentation, was not consistently reestablished within 24 wk. No shift in sensitivity could be deduced from tuning curves of PC receptors examined 3-24 wk after nerve crush. In addition to the low-threshold mechanoreceptors, high-threshold (HT) mechanoreceptive fibers were found in controls and in animals with regenerating nerves. This type of fiber was most frequently found 1 wk after the nerve crush, when reinnervation of the foot started. They probably represent fibers not connected to specific mechanoreceptor end organs. Thus, functional restitution of the highly specific cutaneous mechanoreceptors occurs fairly soon after invasion of the original territory by the regenerating nerve. It is assumed that the underlying mechanism is the rapid reconnection of fibers with the end organs that have either survived during the period of denervation or regenerated subsequent to reinnervation of the skin.
Central input to primary afferent neurons in crayfish, Pacifastacus leniusculus, is correlated with rhythmic motor output of thoracic ganglia
Authors: Sillar K. T. , Skorupski P.
Published: December 2017

A preparation is described in which the thoracic ganglia of the crayfish are isolated together with the thoracocoxal muscle receptor organ (TCMRO) of the fourth leg. This preparation allows intracellular analysis of both centrally generated and reflex activity in leg motor neurons (MNs). The isolated thoracic ganglia can spontaneously generate a rhythmic motor pattern resembling that used during forward walking (Fig. 4). This involves the reciprocal activity of promotor and remotor MNs, with levator MNs firing in phase with promotor bursts. Stretch of the TCMRO in quiescent preparations evokes a resistance reflex in promotor MNs (Fig. 6). In more active preparations the response is variable and often becomes an assistance reflex, with excitation of remotor MNs on stretch (Fig. 7). When rhythmic motor patterns occur, the neuropilar processes of the S and T fibers receive central inputs that are strongly correlated with the oscillatory drive to the MNs and probably have the same origin (Figs. 8 and 9). Central inputs to the S and T fibers occur in opposite phases within a cycle of rhythmic motor output. The S fiber is depolarized in phase with promotor MNs and the T fiber in phase with remotor activity. The input to the T fiber is shown to be a chemical synaptic drive that has a reversal potential approximately 14 mV more depolarized than the fiber's resting membrane potential. This input substantially modulates the amplitude and waveform of passively propagated receptor potentials generated by TCMRO stretch (Fig. 11). It is argued that the central inputs to the TCMRO afferents will modulate proprioceptive feedback resulting from voluntary movements.
Motoneuron electrophysiological and muscle contractile properties of superior oblique motor units in cat
Authors: Nelson J. S. , Goldberg S. J. , McClung J. R.
Published: December 2017

Intracellular techniques were used to study single motor units of the trochlear nucleus and superior oblique muscle in the cat. Motoneuron electrophysiological properties were correlated with muscle-unit contractile characteristics assessed under isometric conditions. Two distinct motor-unit types were identified and designated as twitch and nontwitch. Nontwitch units made up 5% of the total population studied. They responded only to tetanic stimulation with graded force that increased as stimulus frequency was increased up to 300-400 Hz. These units made up a homogeneous population in that they were innervated by slowly conducting axons, produced weak tetanic tensions, and were extremely fatigue resistant. Twitch units made up the majority (95%) of units studied. These units responded to single pulse stimulation with typical twitch contractions. The contraction speed and tension ranges for these units were comparable with those obtained from other extraocular muscle single units. Superior oblique twitch units, mechanically comparable with multiply innervated conducting units, identified in the cat inferior oblique muscle (31) were not observed. The twitch-unit population was heterogeneous in terms of neuromuscular fatigue resistance. Unit fatigability was inversely related to maximal tetanic tension. Motoneuron conduction velocity was related to muscle-unit contractile properties in a way similar to that seen in extremity motor units. The slowest twitch units were weak, fatigue resistant, and innervated by slow conducting axons. The fastest units were, in general, innervated by faster conducting axons, produced greater tetanic tensions, and were more susceptible to fatigue. Correlations among input resistance, rheobase, and conduction velocity were also observed. At present, subdivisions of the twitch-unit population on the basis of any one or combination of unit properties does not seem appropriate.
Voltage-clamp analysis of synaptic inhibition during long-term potentiation in hippocampus
Authors: Griffith W. H. , Brown T. H. , Johnston D.
Published: December 2017

The excitatory synaptic response evoked by stimulating the mossy fiber synaptic input to hippocampal CA3 neurons in normally accompanied by concomitant feedforward or recurrent inhibition. The purpose of the present study was to determine whether a decrease in the inhibitory conductance of this mixed synaptic response contributes to the enhanced synaptic efficacy observed during long-term potentiation (LTP). Intracellular recordings were made from CA3 neurons of rat hippocampal brain slices. Current- and voltage-clamp measurements of the mixed excitatory/inhibitory evoked synaptic response were made, using a single-electrode clamp system. Outward and inward rectification were reduced, respectively, by intracellular injection and bath application of Cs+. Biophysical analysis of the evoked synaptic conductance sequence was performed before and 15 min to 1 h after inducing LTP. As expected, measurements made in the early part of the conductance sequence, which represents primarily the monosynaptic excitatory input, demonstrated an increase in the slope conductance during LTP. Measurements made later in the conductance sequence, when the excitatory component appeared to have declined to a negligible value, revealed no decrease in the slope conductance of the inhibitory component of the mixed response. We conclude that a decrease in the conductance associated with the inhibitory component of the mixed synaptic response plays little or no role in the increase in synaptic efficacy observed during LTP of this synaptic system.
Disparity-induced and blur-induced convergence eye movement and accommodation in the monkey
Authors: Cumming B. G. , Judge S. J.
Published: December 2017

The dynamics of vergence eye movement and of ocular accommodation were studied in two monkeys trained to track a haploscopically presented target that appeared to move in depth. The target was presented under four conditions: monocular viewing, normal binocular viewing, accommodation-open-loop binocular viewing, and "conflict" viewing, in which the accommodation and vergence stimuli did not correspond to those produced by any real target in three-dimensional space. The first and third conditions were chosen because in each case only one of the two primary cues that guide accommodation and vergence was operative: blur in the first case and disparity in the third. We usually studied responses to apparent target movement directly toward or away from the right eye, in which accommodation was measured. The latencies of the accommodation responses to steps toward the monkey were approximately 180 and 240 ms in the two monkeys, while in both monkeys the latencies of convergence were approximately 160 ms. Neither the vergence latencies nor the accommodation latencies were greatly different in monocular and binocular viewing. Responses to a sinusoidally moving target (frequencies 0.1-1.2 Hz; peak-to-peak amplitude 0.5-4 diopters or meter-angles) were studied in the first three of the above viewing conditions. In binocular viewing, even with accommodation open-loop, vergence and accommodation showed much smaller phase lags than in monocular viewing. Furthermore, in response to step changes, both vergence and accommodation velocities were higher in binocular viewing than in monocular viewing. Thus the dynamic control of both vergence and accommodation relies predominantly on disparity signals. At low frequencies (0.2 or 0.3 Hz) the monkeys showed only a modest ability to separate their accommodation and vergence responses when presented with conflicting blur and disparity cues. A simple linear calculation based on the data above was used to predict the responses in such situations. The predicted and observed responses were in reasonable agreement.
Role of central interneurons in habituation of swimming activity in the medicinal leech
Authors: Debski E. A. , Friesen W. O.
Published: December 2017

Swimming activity evoked by light tactile stimulation of a body wall flap in dissected leech preparations undergoes habituation (5). In this study, we examine the activity of several interneurons (cell 204, cell 205, the S cell, and cell 208) during habituation trials to study further the neuronal mechanisms that mediate this decline in responsiveness. Light tactile stimulation of the leech body wall evoked initially a marked excitatory response in cell 204 homologs (segmental swim-initiating neurons) that preceded the initiation of swimming activity. This response decreased over the course of repeated stimulus trials; however, no marked decline in cell 204 activity accompanied the cessation of swim initiation. A similar activity pattern was observed in cell 205. Thus the habituation of swimming activity to stroking of the body wall is not due solely to reduced input to cell 204 and cell 205. The early activity of cell 204 was not correlated to the duration of subsequent swim episodes. However, the impulse frequency of cell 204 during swim episodes was negatively correlated to the period of swim cycles. This correlation between cell 204 activity and cycle period occurred both within individual episodes as well as between trials in a habituation series. Direct stimulation of cell 204 with current pulses evoked swimming activity reliably for an average of 72 trials. Therefore, habituation that results from stroking the body wall (which occurs after approximately 6 trials) is not mediated by plasticity in the connections between cell 204 and the swim oscillator. The S cell fired repeatedly in response to light tactile stimulation. This response declined with repeated trials. Intense intracellular stimulation of the S cell was sufficient to initiate swimming activity in some preparations. The magnitude and duration of the excitation required to initiate swimming by this means were far greater, however, than that which occurred during stroking the body wall. The response of cell 208 (a swim oscillator cell) to body wall stimulation during habituation trials was variable; usually an initial hyperpolarization was followed by some depolarization. No aspect of this response correlated with the onset of habituation. Our results are consistent with the idea that cell 204 and cell 205 are part of the pathway that mediates swimming activity in response to light tactile stimulation of the leech body wall, and that habituation occurs, in part, as the result of reduced sensory input to this cell.(ABSTRACT TRUNCATED AT 400 WORDS)
Velocity sensitivity and direction selectivity of neurons in areas V1 and V2 of the monkey: influence of eccentricity
Authors: Orban G. A. , Kennedy H. , Bullier J.
Published: December 2017

One hundred and forty two neurons in V1 and V2 were quantitatively tested using a multihistogram technique in paralyzed and anesthetized macaque monkeys. V1 neurons with receptive fields within 2 degrees from the fixation point (central V1 sample) and V1 neurons with eccentric receptive fields (15-25 degrees eccentricity, peripheral V1 sample) were compared to assess changes in velocity sensitivity and direction selectivity with eccentricity. The central V1 sample was compared with V2 neurons with receptive fields in the same part of the visual field (central V2 sample) to compare the involvement of both areas in the analysis of motion. Velocity sensitivity of V1 neurons shifts to faster velocities with increasing eccentricity. V1 and V2 neurons subserving central vision have similar preference for slow movements. All neurons could be classified into three categories according to their velocity-response curves: velocity low pass, velocity broad band, and velocity tuned. Most cells in parts of V1 and V2 subserving central vision are velocity low pass. As eccentricity increases in V1, velocity low-pass cells give way to velocity broad-band cells. There is a significant correlation between velocity upper cutoff and receptive field width among V1 neurons. The change in upper cutoff velocity with eccentricity depends both on temporal and spatial factors. Direction selectivity depends on stimulus velocity in most V1 cells. Neurons in the central V1 sample retain their direction selectivity at lower speeds than do neurons in the peripheral V1 sample. The proportion of direction-selective cells is low in both V1 and V2. In V1, direction selectivity decreases with eccentricity. In V1, both velocity upper cutoff and direction selectivity correlate more with laminar position than with receptive field type. The similarity between V1 of the monkey and area 17 of the cat, and the dissimilarity between V2 of the monkey and area 18 of the cat, are discussed.
Postnatal development of receptive field surround inhibition in kitten dorsal lateral geniculate nucleus
Authors: Tootle J. S. , Friedlander M. J.
Published: December 2017

We recorded the responses to visual stimulation of single neurons in the A-layers of the dorsal lateral geniculate nucleus (LGNd) of 4- to 5-wk-old kittens and adult cats. Visual stimuli were generated on a cathode-ray tube (CRT) display and consisted of circular spots and annuli whose contrast was twice the threshold for each neuron and was modulated about a background luminance of 28 cd/m2 at 0.5 Hz. Neural responses were collected as interspike intervals and displayed as instantaneous firing rates for individual trials. From the responses to a series of sizes of spot stimuli, area-response functions were constructed and used to derive a quantitative measure of the strength of the receptive field (RF) surround inhibition of each neuron, the spatial density minimum ([SDmin[). To separate neural from optical factors that affect measurements of surround inhibition, published values for the posterior nodal distances of the kitten and adult eye were used to scale stimuli in terms of the retinal area subtended. Of 153 kitten and 95 adult LGNd neurons studied, the responses to a complete series of spot stimuli of different sizes (areas) were obtained for 52 kitten neurons [44 with linear spatial summation (L) and 8 with nonlinear spatial summation (NL)] and 45 adult (24 X-and 21 Y-) neurons. In addition, intracellular recordings were made from 30 of the kitten neurons that were filled iontophoretically with horseradish peroxidase (HRP) and were evaluated structurally. In the adult, neurons were classified as X-or Y-cells on the basis of a battery of physiological properties, including linearity of spatial summation, latency to electrical stimulation of the optic chiasm, and ability to respond reliably to rapidly moving stimuli. Kitten neuronal responses allowed them to be clearly identified as exhibiting linear or nonlinear spatial summation, but application of additional criteria produced ambiguous results for classification into X-or Y-categories. Kitten L or NL neurons showed differences typical of adult X-and Y-cells on some [e.g., RF center size (P less than 0.01)] but not other [e.g., latency to stimulation of optic chiasm (P greater than 0.40)] properties. In addition, by direct comparison of morphological features with these physiological responses, some kitten cells with adult X-cell physiological properties on these tests were found to have typical adult Y-cell somadendritic structure.(ABSTRACT TRUNCATED AT 400 WORDS)
Objective classification of motion- and direction-sensitive neurons in primary somatosensory cortex of awake monkeys
Authors: Warren S. , Hamalainen H. A. , Gardner E. P.
Published: December 2017

In order to classify movement-sensitive neurons in SI cortex, and to estimate their relative distribution, we have developed a new simple method for controlled motion of textured surfaces across the skin, as well as a set of objective criteria for determining direction selectivity. Moving stimuli were generated using 5 mm thick precision gear wheels, whose teeth formed a grafting. They were mounted on the shafts of low-torque potentiometers (to measure the speed and direction of movement) and rolled manually across the skin using the potentiometer shaft as an axle. As the grafting wheel was advanced, its ridges sequentially contacted a specific set of points on the skin, leaving gaps of defined spacing that were unstimulated. This stimulus was reproducible from trial to trial and produced little distention of the skin. Three objective criteria were used to categorize responses: the ratio of responses to motion in the most and least preferred directions [direction index (DI)], the difference between mean firing rates in the two directions divided by the average standard deviation [index of discriminability (delta'e)], and statistical tests. Neurons were classified as direction sensitive if DI greater than 35, delta's greater than or equal to 1.35 (equivalent to 75% correct discrimination by an unbiased observer), and firing rates in most- and least-preferred directions were significantly different (P less than 0.05). Good agreement was found between the three classification schemes. Recordings were made from 1,020 cortical neurons in the hand and forearm regions of primary somatosensory cortex (areas 3b, 1 and 2) of five macaque monkeys. Tangential motion across the skin was found to be an extremely effective stimulus for SI cortical neurons. Two hundred eighty six of 757 tactile neurons (38%) responded more vigorously to moving stimuli than to pressure or tapping the skin. One hundred twenty-one cells were tested with moving gratings and were classified according to their ability to differentiate movement in longitudinal and transverse directions. Responses to the moving gratings resembled those observed when stroking the skin with brushed, edges, or blunt probes. Three major types of firing patterns were found: motion sensitive, direction sensitive, and orientation sensitive. Motion-sensitive neurons (37%) responded to movement in both longitudinal and transverse directions with only slight difference in firing rates and interval distributions. Responses throughout the field were fairly uniform, and no clear point of maximum sensitivity was apparent. Direction-sensitive neurons (60%) displayed clear preferences for movement in one or more directions.4
Calcium currents and transmitter output in cultured spinal cord and dorsal root ganglion neurons
Authors: Jia M. , Nelson P. G.
Published: December 2017

The effects of repetitive activation upon voltage-dependent calcium currents (ICa) and transmitter release were studied in dissociated cell cultures of fetal mouse spinal cord and dorsal root ganglion. Sodium and potassium currents were suppressed with tetrodotoxin (TTX) and tetraethylammonium (TEA) ions, 4-aminopyridine (4-AP), and cesium sulfate. Calcium currents were compared under voltage clamp before and after a series of depolarizing clamp pulses in spinal cord (SC) and dorsal root ganglion (DRG) neurons. Repetitive activation resulted in an exponential decline in ICa, with the decrease in ICa being much more marked in DRG compared with SC neurons. Both voltage-dependent inactivation and inactivation related to the intracellular movement of Ca2+ appeared to be involved in the decrement in ICa with repetitive activation. A decrease in transmitter output occurred with repetitive activation in DRG neurons but not in SC neurons (either excitatory or inhibitory). DRG neuron synaptic boutons had fewer mitochondria than did the boutons of either excitatory or inhibitory of SC neurons. The decrement in both ICa and synaptic transmitter output in DRG neurons could last for prolonged periods (at least minutes) following repetitive activation. We hypothesize that this vulnerability of DRG neurons to repetitive activation may be related, at least in part, to a relative incapacity to maintain a low intracellular calcium ion concentration [Ca]i during periods of increased calcium ingress associated with excitation. Such an incapacity to buffer [Ca]i may be one mechanism leading to the inactive synapses seen in some studies in vitro and in vivo of synaptic transmission.
Neural mechanisms of tone-on-tone masking: patterns of discharge rate and discharge synchrony related to rates of spontaneous discharge in the chinchilla auditory nerve
Authors: Sinex D. G. , Havey D. C.
Published: December 2017

Responses of chinchilla auditory nerve fibers to brief probe tones in the presence of a fixed tonal masker were obtained. The stimulus conditions were analogous to those that have been used in many psychophysical experiments. The relation between previously described response properties of auditory nerve fibers and features of psychophysical tone-on-tone masking was examined. In psychophysical studies, a fixed narrowband masker produces a characteristic pattern of masked thresholds, which becomes broad and asymmetrical at high masker levels. In the present experiment 1, a 5,000-Hz masker was presented at 30, 50, and 70 dB SPL. Masked thresholds based on the average rate of response to probe tones were estimated for single auditory nerve fibers. The lowest of these masked thresholds formed a pattern similar to the psychophysical masking pattern, becoming broader and more asymmetrical as the masker was increased to 70 dB SPL. The masked thresholds of fibers with low and medium rates of spontaneous discharge (SR) were as low as or lower than the masked thresholds of fibers with high SRs. In certain frequency regions, masked thresholds based on responses to cochlear distortion products were lower than the masked thresholds of any fiber responding to the probe tone; this result is also similar to previous psychophysical observations. In experiment 2, responses of chinchilla auditory nerve fibers to probe tones in the presence of a masker at 1,000 Hz and 50 dB SPL were studied. Probe tone thresholds in the presence of this masker have been measured psychophysically in chinchillas. Thus the relation between behavioral and neural masked thresholds in the same species could be examined. Masked thresholds were estimated from average discharge rate responses and also from discharge synchrony. Good quantitative agreement was observed between the probe tone levels at which changes in average discharge rate were observed and the chinchilla's behavioral masked thresholds. For fibers matched for characteristic frequency, the masked thresholds based on average discharge rate of high-SR fibers tended to be elevated compared with the thresholds of medium-SR fibers. Changes in discharge rate synchronized to the probe tone occurred at levels lower than the chinchilla's behavioral masked thresholds. If discharge synchrony can be used for detection, the code would appear to be based on the relative synchrony to the probe tone and to the masking tone. Low synchrony masked thresholds were obtained from fibers with all SRs.(ABSTRACT TRUNCATED AT 400 WORDS)
Epileptiform burst activity induced by potassium in the hippocampus and its regulation by GABA-mediated inhibition
Authors: Korn S. J. , Giacchino J. L. , Chamberlin N. L. , Dingledine R.
Published: December 2017

Intracellular and extracellular recordings were made from pyramidal neurons in hippocampal slices in order to study spontaneous paroxysmal bursting induced by raising the extracellular potassium concentration from 3.5 to 8.5 mM. Extracellular recordings from all hippocampal subfields indicated that spontaneous bursts appeared to originate in region CA3c or CA3b as judged by burst onset. Burst intensity was also greatest in regions CA3b and CA3c and became progressively less toward region CA2. Intracellular recordings indicated that in 8.5 mM potassium, large spontaneous excitatory postsynaptic potentials (EPSPs), large burst afterhyperpolarizations, and rhythmic hyperpolarizing-depolarizing waves of membrane potential were invariably present in CA3c neurons. High potassium (8.5 mM) induced a positive shift (+9 mV) in the reversal potential of GABAergic inhibitory postsynaptic potentials (IPSPs) in CA3c neurons without changing input resistance or resting potential. This resulted in a drastic reduction in amplitude of the IPSP. Reduction of IPSP amplitude occurred before the onset of spontaneous bursting and was reversible upon return to normal potassium. A new technique to quantify the relative intensity of interictal-like burst discharges is described. Pentobarbital, diazepam, and GABA uptake inhibitors, which enhance GABA-mediated synaptic inhibition, reduced the intensity of potassium-induced bursts, whereas the GABA antagonist bicuculline increased burst intensity. Diphenylhydantoin and phenobarbital, anticonvulsants that have little effect on GABAergic inhibition, were without effect on spontaneous bursts. Burst frequency was reduced by bicuculline and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol but was unaffected by other drugs. Reduction of slice temperature from 35 to 19 degrees C dramatically reduced burst intensity but did not markedly affect burst frequency. We hypothesize that high potassium induces a rise in intracellular chloride concentration, possibly by activating an inward KCl pump or by a passive Donnan effect, which results in a decreased IPSP amplitude. With inhibition suppressed, the large spontaneous EPSPs that appear in high potassium cause individual CA3c neurons to fire. A combination of synaptic and electrical interactions among CA3c cells then synchronizes discharges into interictal spike bursts.
Climbing fiber afferent modulation during treadmill locomotion in the cat
Authors: Kim J. H. , Wang J. J. , Ebner T. J.
Published: December 2017

The relationship of the climbing fiber afferent discharge to the unperturbed and perturbed step cycle was evaluated in the cat. Following a precollicular-premamillary decerebration, cats walked spontaneously on a motorized treadmill. Purkinje cells were recorded extracellularly and simple and complex spikes were discriminated. Right forelimb displacement, biceps and triceps EMG activity, as well as treadmill velocity, were also monitored. In some animals pressure measurements of the contact of the footpad with the treadmill were obtained. Cells were studied during both “normal” and perturbed locomotion. The perturbation consisted of a braking of the treadmill at different phases in the step cycle. Histograms of the simple and complex spike activity, and averages of the right forelimb displacement, biceps, and triceps EMG activity and treadmill velocity were constructed. The complex spike activity of 163 Purkinje cells was averaged through a minimum of 50 sweeps in either normal and/or perturbed locomotion. Statistical analysis revealed that the probability of the climbing fiber afferent discharge in 54% of the cells (36/67) studied during normal locomotion was significantly modulated with the step cycle. For most Purkinje cells the onset of the increase in climbing fiber afferent discharge was coupled to triceps activity and the onset of stance phase. A group of cells exhibited complex spike discharge in association with biceps onset and swing. These observations suggest that complex spike discharge occurs preferentially at the phase transition periods in the step cycle when the trajectory of the forelimb changes from swing to stance or stance to swing. During treadmill braking 51% of the cells exhibited complex spike modulation (70/137). A number of different patterns of climbing fiber afferent modulation occurred. The most common pattern was an increase in complex spike discharge with the resumption of the treadmill movement and locomotion. Analysis of the time of these periods of increased climbing fiber activity suggests that, although in some cells the response is coupled to the treadmill onset, in other cells the modulation occurs at longer latencies. Subsequent analysis aligning the EMG, displacement, and treadmill velocity signals with the times of the climbing fiber afferent discharge suggested some responses were coupled to the reinitiation of the locomotor cycle. The second most common pattern was an increase in climbing fiber afferent discharge at the onset of the perturbation. Also, in some cells, complex spike discharge decreased during the period in which the step cycle was arrested.(ABSTRACT TRUNCATED AT 400 WORDS)
Corticogeniculate neurons, corticotectal neurons, and suspected interneurons in visual cortex of awake rabbits: receptive-field properties, axonal properties, and effects of EEG arousal
Authors: Swadlow H. A. , Weyand T. G.
Published: December 2017

The intrinsic stability of the rabbit eye was exploited to enable receptive-field analysis of antidromically identified corticotectal (CT) neurons (n = 101) and corticogeniculate (CG) neurons (n = 124) in visual area I of awake rabbits. Eye position was monitored to within 1/5 degrees. We also studied the receptive-field properties of neurons synaptically activated via electrical stimulation of the dorsal lateral geniculate nucleus (LGNd). Whereas most CT neurons had either complex (59%) or motion/uniform (15%) receptive fields, we also found CT neurons with simple (9%) and concentric (4%) receptive fields. Most complex CT cells were broadly tuned to both stimulus orientation and velocity, but only 41% of these cells were directionally selective. We could elicit no visual responses from 6% of CT cells, and these cells had significantly lower conduction velocities than visually responsive CT cells. The median spontaneous firing rates for all classes of CT neurons were 4-8 spikes/s. CG neurons had primarily simple (60%) and concentric (9%) receptive fields, and none of these cells had complex receptive fields. CG simple cells were more narrowly tuned to both stimulus orientation and velocity than were complex CT cells, and most (85%) were directionally selective. Axonal conduction velocities of CG neurons (mean = 1.2 m/s) were much lower than those of CT neurons (mean = 6.4 m/s), and CG neurons that were visually unresponsive (23%) had lower axonal conduction velocities than did visually responsive CG neurons. Some visually unresponsive CG neurons (14%) responded with saccadic eye movements. The median spontaneous firing rates for all classes of CG neurons were less than 1 spike/s. All neurons synaptically activated via LGNd stimulation at latencies of less than 2.0 ms had receptive fields that were not orientation selective (89% motion/uniform, 11% concentric), whereas most cells with orientation-selective receptive fields had considerably longer synaptic latencies. Most short-latency motion/uniform neurons responded to electrical stimulation of the LGNd (and visual area II) with a high-frequency burst (500-900 Hz) of three or more spikes. Action potentials of these neurons were of short duration, thresholds of synaptic activation were low, and spontaneous firing rates were the highest seen in rabbit visual cortex. These properties are similar to those reported for interneurons in several regions in mammalian central nervous system. Nonvisual sensory stimuli that resulted in electroencephalographic arousal (hippocampal theta activity) had a profound effect on the visual responses of many visual cortical neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Suppressive rod-cone interaction in distal vertebrate retina: intracellular records from Xenopus and Necturus
Authors: Frumkes T. E. , Eysteinsson T.
Published: December 2017

The influence of dim diffuse adapting fields upon the sensitivity to focal photic stimulation was studied by means of intracellular recording in retinal neurons of the south african clawed frog, Xenopus and the mudpuppy, Necturus. In cones and in most horizontal and bipolar cells lacking color opponency, dim diffuse backgrounds have little influence upon the response to diffuse flicker of low (less than 2 Hz) temporal frequencies; however, with small diameter test probes of higher temporal frequencies, presentation of dim backgrounds enhance the peak-to-peak amplitude of responses to sinusoidal flicker by as much as 800%. This background enhancement effect adheres to the spectral sensitivity of the green-absorbing rod photopigment, and appears to be largely independent of the influence of the adapting field upon cone photopigment or ambient membrane potential in the recorded neuron. This effect cannot be obtained with rod-driven flicker responses. We designate this background influence on flicker, suppressive rod-cone interaction (SRCI) and attribute it to a tonic suppressive (probably inhibitory) influence of rods upon cone pathways that is removed by rod light adaptation. SRCI is also observed in the response of most sustained ON and OFF ganglion cells. However, no corresponding effect occurs in rods, color-opponent second-order neurons, ON-OFF amacrine cells, or most ON-OFF ganglion cells. The spatial and temporal limitations of SRCI observed by means of intracellular recording in amphibians are very similar to those documented by means of psychophysical or electroretinogram (ERG) procedures in a wide variety of species including humans (2, 4, 11, 22, 23, 29). SRCI most probably reflects a process that is mediated by horizontal cells. The specifics of the underlying mechanism remain unclear.
Control of abdominal and expiratory intercostal muscle activity during vomiting: role of ventral respiratory group expiratory neurons
Authors: Miller A. D. , Tan L. K. , Suzuki I.
Published: December 2017

The role of ventral respiratory group (VRG) expiratory (E) neurons in the control of abdominal and internal intercostal (expiratory) muscle activity during vomiting was examined in decerebrate cats by recording from these neurons during fictive vomiting in paralyzed animals and comparing abdominal muscle activity during vomiting before and after sectioning the axons of these descending neurons. Fictive vomiting was defined by a series of bursts of coactivation of abdominal and phrenic nerves elicited by either subdiaphragmatic vagus nerve stimulation or emetic drugs. Such coordinated activity would be expected to produce vomiting if the animals were not paralyzed. Data were recorded from 27 VRG E neurons that were antidromically activated from the lower thoracic (T13) or lumbar spinal cord. During fictive vomiting, almost two-thirds of these neurons (17/27) were mainly active in between periods of abdominal and phrenic nerve coactivation, when the internal intercostal motoneurons are known to be active. This group of neurons was termed INT neurons. INT neurons were subdivided according to whether they were active between every burst of phrenic and abdominal nerve coactivation (INTa neurons, n = 10) or only between some bursts (INTb neurons, n = 7). Another one-third of the VRG E neurons had normal or increased levels of activity when the abdominal nerves were active during fictive vomiting (ABD neurons). The one remaining neuron was mainly silent throughout fictive vomiting. ABD neurons were indistinguishable from INT neurons on the basis of their location in the VRG, type of firing pattern (ramp versus step ramp), conduction velocity, or extent of projection in the lumbar cord. However, INTa neurons had a significantly higher discharge rate during respiration than either ABD or INTb neurons. Abdominal muscle EMG and nerve activity were recorded from six unparalyzed cats before and after cutting the axons of VRG E neurons as they cross the midline between C1 and the obex. The lesions abolished or almost eliminated expiratory modulation of abdominal muscle activity. In contrast, the abdominal muscles were always active during vomiting; however, the amplitude of postlesion abdominal activity varied from approximately 70-100% of prelesion values in three cats to 60-70% of normal in a fourth animal to only approximately 20% of prelesion values in two other cats.(ABSTRACT TRUNCATED AT 400 WORDS)
Effect of a spider toxin (JSTX) on excitatory postsynaptic current at neuromuscular synapse of spiny lobster
Authors: Miwa A. , Kawai N. , Saito M. , Pan-Hou H. , Yoshioka M.
Published: December 2017

1. We studied the blocking properties of a spider (Nephila clavata) toxin (JSTX) purified from venom on the spiny lobster neuromuscular junction. 2. When a small amount of JSTX was applied to the neuromuscular junction, the excitatory postsynaptic potential (EPSP) was partially suppressed. The amplitude of EPSPs remained at a steady level for several hours during the washing of the preparation, showing that the action of JSTX is irreversible. 3. We recorded the excitatory postsynaptic current (EPSC) from synaptic site using a macro-patch electrode. The amplitude of EPSC increased linearly with hyperpolarization of the membrane potential in the presence and absence of JSTX. 4. The decay phase time constant of EPSC and spontaneous EPSC was decreased by hyperpolarizing the membrane potential both in the absence and in the presence of JSTX. The relationship between the decay time constant and the membrane potential was not modified by JSTX. 5. It is suggested that JSTX irreversibly blocks EPSC by acting on the site that is apart from the ionic channel of the glutamate receptor molecule.
Implications of rotational kinematics for the oculomotor system in three dimensions
Authors: Tweed D. , Vilis T.
Published: December 2017

1. This paper develops three-dimensional models for the vestibuloocular reflex (VOR) and the internal feedback loop of the saccadic system. The models differ qualitatively from previous, one-dimensional versions, because the commutative algebra used in previous models does not apply to the three-dimensional rotations of the eye. 2. The hypothesis that eye position signals are generated by an eye velocity integrator in the indirect path of the VOR must be rejected because in three dimensions the integral of angular velocity does not specify angular position. Computer simulations using eye velocity integrators show large, cumulative gaze errors and post-VOR drift. We describe a simple velocity to position transformation that works in three dimensions. 3. In the feedback control of saccades, eye position error is not the vector difference between actual and desired eye positions. Subtractive feedback models must continuously adjust the axis of rotation throughout a saccade, and they generate meandering, dysmetric gaze saccades. We describe a multiplicative feedback system that solves these problems and generates fixed-axis saccades that accord with Listing's law. 4. We show that Listing's law requires that most saccades have their axes out of Listing's plane. A corollary is that if three pools of short-lead burst neurons code the eye velocity command during saccades, the three pools are not yoked, but function independently during visually triggered saccades. 5. In our three-dimensional models, we represent eye position using four-component rotational operators called quaternions. This is not the only algebraic system for describing rotations, but it is the one that best fits the needs of the oculomotor system, and it yields much simpler models than do rotation matrix or other representations. 6. Quaternion models predict that eye position is represented on four channels in the oculomotor system: three for the vector components of eye position and one inversely related to gaze eccentricity and torsion. 7. Many testable predictions made by quaternion models also turn up in models based on other mathematics. These predictions are therefore more fundamental than the specific models that generate them. Among these predictions are 1) to compute eye position in the indirect path of the VOR, eye or head velocity signals are multiplied by eye position feedback and then integrated; consequently 2) eye position signals and eye or head velocity signals converge on vestibular neurons, and their interaction is multiplicative.(ABSTRACT TRUNCATED AT 400 WORDS)
Properties of neuronal activity related to a visual reaction time task in the monkey prefrontal cortex
Authors: Sawaguchi T.
Published: December 2017

1. Quantitative properties of neuronal activity related to a visual reaction time task were studied in the monkey prefrontal cortex. The task consisted of an initial waiting phase (3.0-s period), a warning phase (green lamp, a variable period of 1.5-3.5 s), a go phase (red lamp), and a reward phase. 2. A total of 189 task-related neurons showed 233 changes in discharge rates during the warning (n = 86), GO (n = 103), and reward (n = 44) phases of the task. Most of the task-related neurons (145/189, 77%) showed changes during only one of the task phases, and were designated W (warning phase)-type (n = 42), GO (go phase)-type (n = 59), and RE (reward phase)-type (n = 44) neurons. The remainder (n = 44, 23%) showed changes during both the warning and the go phases, and were designated WG (warning and go phase)-type neurons. In each phase, onset latencies, peak latencies, and decay times of each change were measured and compared. 3. The changes during the warning phase (n = 86) were separated into three groups based on decay time; that is, phasic changes (n = 31), phasic-tonic changes (n = 23), and tonic changes (n = 32). Onset latencies and peak latencies were homogeneously distributed, and there were no clear groupings, although phasic and phasic-tonic changes tended to show shorter latencies than tonic changes. 4. The changes during the go phase (n = 103) did not show distinct differences, either in terms of decay time or of latency. The changes during the go phase showed various degrees of coupling to both the visual go signal (GS) and lever-release hand movement. To quantitate the coupling, a value to indicate the degrees of coupling (coupling index) was calculated. The changes coupled more strongly to the GS (cue coupled), those coupled more closely to the lever release (movement coupled), and intermediate changes could be distinguished from each other. The cue-coupled changes showed shorter latencies from the time onset of the GS than the movement-coupled changes, and the intermediate changes showed intermediate latencies. The decay time and the duration of the intermediate changes were longer than those of the cue-coupled changes and the movement-coupled changes. 5. The properties of WG-type neurons were compared with those of W-type and GO-type neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Long-Term Potentiation of Synaptic Transmission in Kitten Visual Cortex
Authors: Komatsu Y. , Fujii K. , Maeda J. , Sakaguchi H. , Toyama K.
Published: December 2017

Y. Komatsu, K. Fujii, J. Maeda, H. Sakaguchi, and K. Toyama, “Long-Term Potentiation of Synaptic Transmission in Kitten Visual Cortex.” Page 140: the fifth and sixth lines of the left-hand column should be deleted.
The axon terminal of goldfish retinal horizontal cells: a low membrane conductance measured in solitary preparations and its implication to the signal conduction from the soma
Authors: Yagi T. , Kaneko A.
Published: December 2017

1. Mechanical dissociation of the enzyme-treated goldfish retina yielded somata and axon terminals of horizontal cells. The membrane properties of these solitary axon terminals were investigated using the whole-cell patch-clamp technique. 2. Axon terminals had a large input resistance, comparable to the seal resistance (approximately 30 G omega). Most axon terminals (greater than 80%) showed a nearly linear current-voltage relation between -60 and +10 mV, where the slope conductance was as small as 5 muS/cm2. Some axon terminals showed a shallow negative slope conductance in the same potential range. 3. The membrane current consisted of two components: transient and sustained. The transient component was carried by sodium ions, and the sustained component was a mixture of calcium and potassium currents. The sodium current (INa) was activated by depolarization of beyond -45 mV and was maximal (approximately 60 pA) at -10 mV. It was blocked by 5 microM tetrodotoxin and disappeared in Na+-free medium. The maximum amplitude of INa was less than 10% of INa of the soma. 4. A small calcium current (less than 6 pA) was isolated in a small proportion of cells, with an amplitude approximately 5% of the calcium current evoked in the soma under the identical recording conditions. 5. A small amount of potassium current through the anomalous rectifier was induced in the axon terminal when the membrane potential was below -60 mV. Its conductance was 15-20 muS/cm2, only 1/20 of the estimate in the soma. Other types of potassium currents were not detected. 6. It is concluded that the soma and the axon terminal have a similar set of membrane currents, but the specific membrane conductance of the axon terminal is extremely low. The signal conductivity from soma to axon terminal was assessed using a passive cable model together with numerical values obtained from the present experiments. Although the membrane conductance of the connecting axon was not measurable directly, the calculation strongly suggests that low conductance of the axon terminal membrane minimizes the leakage of signals arriving electrotonically through the thin connecting axon, even if the membrane conductance of the axon was overestimated as being identical to the soma membrane. 7. These results can explain why light-evoked responses recorded from the axon terminal are similar in amplitude as well as in waveform to those recorded from the soma, despite the lack of direct inputs from photoreceptors.