bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodic simple cells in cat area 17
Authors: Mullikin W. H. , Jones J. P. , Palmer L. A.
Published: December 2017

Quantitative, high-resolution static receptive-field plots (response planes) in cat area 17 revealed simple cells whose receptive fields were composed of four to six excitatory regions alternating in space with up to seven inhibitory regions. The size, shape, and spacing of the excitatory regions within these receptive fields were highly regular, giving the receptive field a periodic appearance in space. We call these periodic simple cells. A periodic simple cell's response to moving stimuli could, in general, be anticipated from the detailed spatiotemporal map of excitatory and inhibitory regions provided by response planes. This observation suggests that periodic simple cells, like the more common simple cells composed of one to three excitatory regions, sum spatially distributed inputs in a roughly linear manner. Based on a quantitative assessment of the spatial distribution and time course of response of single excitatory regions within periodic receptive fields, as described in the previous paper, we characterized periodic simple cells as either X-like or Y-like. Furthermore, we found that periodic simple cells classified as X-like gave a more sustained response to standing contrast and had significantly smaller excitatory regions than those cells classified as Y-like. Periodic simple cells were found in layer III and at the border between layers III and IVab. It is suggested that these cells, which reside outside the primary zone of geniculate termination and include both X-like and Y-like types, may be constructed hierarchically from the convergence of lower order simple cells. In the spatial-frequency domain, periodic simple receptive fields were predicted to have bandwidths at half-maximum ranging from 0.80 to 1.4 octaves. By comparison, the predicted bandwidths of cells composed of two or three excitatory regions ranged from 1.6 to 4.3 octaves. Thus as additional excitatory regions are added to the receptive fields of simple cells, their bandwidth narrows in the spatial-frequency domain.
Rat hippocampal neurons in culture: voltage-clamp analysis of inhibitory synaptic connections
Authors: Segal M. , Barker J. L.
Published: December 2017

Inhibitory postsynaptic potentials (IPSPs) recorded at room temperature in cultured rat hippocampal neurons had the same reversal potential as Cl--dependent voltage responses to gamma-aminobutyric acid (GABA). The IPSPs had a relatively short latency and long duration and could be evoked for hours without change in their properties. They were consistently depressed by picrotoxin applied near cell bodies of the neurons under study. Postsynaptic cells exhibiting IPSPs were voltage clamped with two electrodes for the purpose of studying the properties of evoked inhibitory postsynaptic currents (IPSCs). The IPSCs shared the same reversal potential and sensitivity to [Cl-]i as was observed with membrane current responses to GABA. They were both depressed by picrotoxin, with little if any change in the kinetics of ion channel activity either estimated from fluctuation analysis of drug-depressed current responses to GABA or calculated from semilogarithmic plots of IPSC decay. The decay of the IPSC was well fitted by a single exponential with a time constant of about 20 ms, which corresponded closely to the estimated average duration of an ion channel activated by GABA. IPSC decay was sensitive to the potential at which the cell was held, increasing by up to 50% in some cells clamped at positive potentials relative to values obtained at the level of the resting potential. IPSCs were enhanced in amplitude by diazepam, which also prolonged their time constant of decay. Diazepam potentiated membrane current responses to GABA and fluctuation analysis of potentiated responses indicated that the drug effects could be accounted for by an increase both in estimated channel duration and channel frequency. IPSCs were also altered by pentobarbital, which markedly prolonged their time constant of decay with little if any change in their amplitude. Pentobarbital enhanced current responses to GABA, an effect that could be accounted for primarily in terms of a pronounced increase in estimated channel lifetime. None of the drugs used in the present study affected the elementary conductance estimated from fluctuation analysis of GABA-evoked current response. The results suggest that IPSPs and IPSCs evoked in these cultured hippocampal cells are mediated by GABA, about 1,700 Cl- ion channels are activated at the peak of the synaptic conductance, and clinically important drugs act postsynaptically on the kinetics of the channels so as to change the amplitude and/or time course of the synaptic conductance.
Nonlinear viscosity of human wrist
Authors: Gielen C. C. , Houk J. C.
Published: December 2017

Nonlinear viscous properties of stretch and unloading reflexes in the human wrist were examined using constant-velocity ramp stretches and releases in the range between 5 and 500 mm/s. Subjects were asked to oppose an initial flexor preload and were instructed not to intervene voluntarily when the changes in position were applied. Electromyographic (EMG) activity and net force exerted by the wrist were measured. Although subjects were instructed not to intervene to the applied stretches, even well-practiced subjects sometimes showed unintended triggered reactions, which character could be assisting or resisting. A trial comparison method was used to detect and eliminate responses contaminated by unintended reactions. Ramp stretches further loaded the preloaded flexor muscles. Responses of EMG and force increased steeply initially but after about 1-cm displacement, the slope of these responses decreased to a lower value and remained constant during the remainder of the 5-cm ramp. For higher stretch velocities, the magnitudes and slopes of the responses of EMG and force increased but less than proportionally with ramp velocity. Except for the initial transient, EMG in the loaded flexor muscles and force responses could be described by a product relationship between a linear position-related term and a low fractional power of velocity, after a correction was made for delays in the reflex arc. Mean value of the exponent in the power function of velocity was 0.3 for EMG and 0.17 for force. For higher preloads, incremental responses of force to constant-velocity stretches, plotted as a function of wrist position, shifted to higher values and the slope of increase of force with position became somewhat steeper. This upward shift of the force trace reflects a change of apparent threshold of the stretch reflex. Ramp releases shortened and unloaded the preloaded flexor muscles and stretched the initially inactive extensor muscles. Flexor EMG activity declined progressively with a time course that was independent of velocity. Extensor EMG response depended on preload. At high preloads, there was no activity except for some bursting at the highest velocities. At low preloads, EMG activity was initially absent but started part way through the ramp. The increase of activity was somewhat greater for higher ramp velocities. Force responses to shortening ramps depended on preload. At high preloads, force responses superimposed at all of the low velocities but fell to slightly lower forces at the higher velocities. At low preloads, force traces again superimposed for low velocities and at high velocities only during the initial part of the response.(ABSTRACT TRUNCATED AT 400 WORDS)
Electrophysiological characteristics of lumbar spinal cord neurons backfired from lateral reticular nucleus in the rat
Authors: Menetrey D. , de Pommery J. , Besson J. M.
Published: December 2017

Spinal neurons antidromically activated from either the lateral reticular nucleus (LRN) or immediately adjacent areas were identified in the rat lumbar spinal cord. In agreement with previous anatomical work (60), these neurons were widely distributed in both the dorsal and ventral horns of the spinal cord and could be subdivided into three main groups according to their location: a) deep ventromedial (DVM) cells, which project more substantially to the LRN than to other supraspinal targets; b) cells of the median portion of the neck of the dorsal horn (mNDH), which project exclusively to the LRN; c) cells lying in other parts of the dorsal horn (superficial layers, nucleus proprius, reticular extension of the neck), by their location, they are indistinguishable from cells projecting to other supraspinal targets. The probability is high that the DVM and mNDH cells contribute exclusively, or at least preferentially, to the lateral component of the spinoreticular tract (lSRT), defined as the direct spinal pathway to the LRN. Although electrophysiological properties of cells were clearly related to their spinal location, several subpopulations could be recognized in each of the three main groups. The majority of DVM neurons were in lamina VII, with some in laminae VI, VIII, and X. With the exception of a few lamina X cells, the DVM neurons had high conduction velocities. Four subpopulations of these neurons were recognized. a) Innocuous proprioceptive cells responded to small changes in joint position, some showing convergence of nonnoxious cutaneous inputs. b) High-threshold cells (approximately 50% of DVM cells). Seventy-five percent of these cells were excited from bilateral receptive fields (mostly symmetric) with noxious cutaneous pinching that extended to subcutaneous tissues. Their evoked responses had long-lasting postdischarges that continued up to several minutes after cessation of the stimulus. c) Inhibited cells had no demonstrable excitatory receptive fields and a high ongoing activity that was tonically depressed by pressure or pinch; poststimulus effects of long duration were observed. d) Cells with no resting discharge and demonstrable excitatory peripheral receptive fields. mNDH cells had recording sites at the medial border of the internal portion of the reticular area of the neck of the dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of cat primary auditory cortex for sound-localization behavior
Authors: Jenkins W. M. , Merzenich M. M.
Published: December 2017

Small lesions designed to completely destroy the cortical zone of representation of a restricted band of frequency were introduced within the primary auditory cortex (AI) in adult cats. Physiological mapping was used to guide placement of lesions. Sound-localization performance was evaluated prior to and after induction of these lesions in a seven-choice free-sound-field apparatus. All tested cats had profound contralateral hemifield deficits for the localization of brief tones at frequencies roughly corresponding to those whose representations were destroyed by the lesion. Sound-localization performance was normal at all other test frequencies. In a single adult cat, a massive lesion destroyed nearly all auditory cortex unilaterally, with only the representation of a narrow band of frequency within AI spared by the lesion. This cat had normal abilities for azimuthal sound localization across that frequency band but a profound contralateral deficit for the azimuthal localization of brief sounds at all other frequencies. Recorded sound-localization deficits were permanent. Localization of long-duration tones was not affected by a unilateral AI lesion. These studies indicate that, at least in cats, AI is necessary for normal binaural sound-localization behavior; among auditory cortical fields, AI is sufficient for normal binaural sound-localization behavior; sound-location representation is organized by frequency channel in the auditory forebrain; and AI in each hemisphere contributes to only contralateral free-sound-field location representation.
Analysis of rhythmical jaw movements produced by electrical stimulation of motor-sensory cortex of rabbits
Authors: Lund J. P. , Sasamoto K. , Murakami T. , Olsson K. A.
Published: December 2017

The anterolateral regions of the cerebral cortex of rabbits anesthetized with urethan were stimulated with either short trains of electrical pulses at high-frequency (3 pulses, 500 Hz) or 10-s trains of shocks at 50 Hz. The movements of the mandible and the electromyographic (EMG) activity from the muscles of mastication were recorded on magnetic tape and later analyzed by computer. Two basic types of responses are reported: twitches of the digastric muscles that followed the stimulus at short-latency (4-6.7 ms) and rhythmical masticatory movements that could only be evoked by prolonged stimulation. The cortical representations of the short-latency twitch contractions and mastication overlap. Different masticatory patterns are represented in separate areas of the cortex. The movements represented in the anteromedial half of the masticatory area are made mainly in the vertical plane, whereas stimulation of the posterolateral part produces movements in which the jaw swings to the contralateral side during closure. Increases in stimulus intensity usually increase the frequency of the movements, but other changes in the pattern depend on the site of stimulation. The rhythmical bursts of EMG activity often contain stimulus-bound short-latency responses but, since these are not always present, we conclude that they are not essential components of the masticatory pattern. We suggest that the basic patterns of mastication are elaborated by brain stem circuits that are themselves controlled by specific regions of the motor-sensory cortex.
Eye-head coordination in cats
Authors: Guitton D. , Douglas R. M. , Volle M.
Published: December 2017

Gaze is the position of the visual axis in space and is the sum of the eye movement relative to the head plus head movement relative to space. In monkeys, a gaze shift is programmed with a single saccade that will, by itself, take the eye to a target, irrespective of whether the head moves. If the head turns simultaneously, the saccade is correctly reduced in size (to prevent gaze overshoot) by the vestibuloocular reflex (VOR). Cats have an oculomotor range (OMR) of only about +/- 25 degrees, but their field of view extends to about +/- 70 degrees. The use of the monkey's motor strategy to acquire targets lying beyond +/- 25 degrees requires the programming of saccades that cannot be physically made. We have studied, in cats, rapid horizontal gaze shifts to visual targets within and beyond the OMR. Heads were either totally unrestrained or attached to an apparatus that permitted short unexpected perturbations of the head trajectory. Qualitatively, similar rapid gaze shifts of all sizes up to at least 70 degrees could be accomplished with the classic single-eye saccade and a saccade-like head movement. For gaze shifts greater than 30 degrees, this classic pattern frequently was not observed, and gaze shifts were accomplished with a series of rapid eye movements whose time separation decreased, frequently until they blended into each other, as head velocity increased. Between discrete rapid eye movements, gaze continued in constant velocity ramps, controlled by signals added to the VOR-induced compensatory phase that followed a saccade. When the head was braked just prior to its onset in a 10 degrees gaze shift, the eye attained the target. This motor strategy is the same as that reported for monkeys. However, for larger target eccentricities (e.g., 50 degrees), the gaze shift was interrupted by the brake and the average saccade amplitude was 12-15 degrees, well short of the target and the OMR. Gaze shifts were completed by vestibularly driven eye movements when the head was released. Braking the head during either quick phases driven by passive head displacements or visually triggered saccades resulted in an acceleration of the eye, thereby implying interaction between the VOR and these rapid-eye-movement signals. Head movements possessed a characteristic but task-dependent relationship between maximum velocity and amplitude. Head movements terminated with the head on target. The eye saccade usually lagged the head displacement.(ABSTRACT TRUNCATED AT 400 WORDS)
Direction and orientation selectivity of neurons in visual area MT of the macaque
Authors: Albright T. D.
Published: December 2017

We recorded from single neurons in the middle temporal visual area (MT) of the macaque monkey and studied their direction and orientation selectivity. We also recorded from single striate cortex (V1) neurons in order to make direct comparisons with our observations in area MT. All animals were immobilized and anesthetized with nitrous oxide. Direction selectivity of 110 MT neurons was studied with three types of moving stimuli: slits, single spots, and random-dot fields. All of the MT neurons were found to be directionally selective using one or more of these stimuli. MT neurons exhibited a broad range of direction-tuning bandwidths to all stimuli (minimum = 32 degrees, maximum = 186 degrees, mean = 95 degrees). On average, responses were strongly unidirectional and of similar magnitude for all three stimulus types. Orientation selectivity of 89 MT neurons was studied with stationary flashed slits. Eighty-three percent were found to be orientation selective. Overall, orientation-tuning bandwidths were significantly narrower (mean = 64 degrees) than direction-tuning bandwidths for moving stimuli. Moreover, responses to stationary-oriented stimuli were generally smaller than those to moving stimuli. Direction selectivity of 55 V1 neurons was studied with moving slits; orientation selectivity of 52 V1 neurons was studied with stationary flashed slits. In V1, compared with MT, direction-tuning bandwidths were narrower (mean = 68 degrees). Moreover, V1 responses to moving stimuli were weaker, and bidirectional tuning was more common. The mean orientation-tuning bandwidth in V1 was also significantly narrower than that in MT (mean = 52 degrees), but the responses to stationary-oriented stimuli were of similar magnitude in the two areas. We examined the relationship between optimal direction and optimal orientation for MT neurons and found that 61% had an orientation preference nearly perpendicular to the preferred direction of motion, as is the case for all V1 neurons. However, another 29% of MT neurons had an orientation preference roughly parallel to the preferred direction. These observations, when considered together with recent reports claiming sensitivity of some MT neurons to moving visual patterns (39), suggest specific neural mechanisms underlying pattern-motion sensitivity in area MT. These results support the notion that area MT represents a further specialization over area V1 for stimulus motion processing. Furthermore, the marked similarities between direction and orientation tuning in area MT in macaque and owl monkey support the suggestion that these areas are homologues.
Signals used to compute errors in monkey vestibuloocular reflex: possible role of flocculus
Authors: Lisberger S. G. , Miles F. A. , Zee D. S.
Published: December 2017

Adaptive changes were induced in the vestibuloocular reflex (VOR) of monkeys by oscillating them while they viewed the visual scene through optical devices (“spectacles”) that required changes in the amplitude of eye movement during head turns. The “gain” of the VOR (eye velocity divided by head velocity) during sinusoidal oscillation in darkness underwent gradual changes that were appropriate to reduce the motion of images on the retina during the adapting procedures. Bilateral ablation of the flocculus and ventral paraflocculus caused a complete and enduring loss of the ability to undergo adaptive changes in the VOR. Partial lesions caused a substantial but incomplete loss of the adaptive capability. We conclude that the flocculus is necessary for adaptive changes in the monkey's VOR. Further experiments in normal animals determined the types of stimuli that were necessary and/or sufficient to cause changes in VOR gain. Full-field visual stimulation was not necessary to induce adaptive changes in the VOR. Monkeys tracked a small spot in conditions that elicited the same combination of eye and head movements seen during passive oscillation with spectacles. The gain of the VOR showed changes 50-70% as large as those produced by the same duration of oscillation with spectacles. Since the effective tracking conditions cause a consistent correlation of floccular output with vestibular inputs, these data are compatible with our previous suggestion that the flocculus may provide signals used by the central nervous system to compute errors in the gain of the VOR. Prolonged sinusoidal optokinetic stimulation with the head stationary caused only a slight increase in VOR gain. Left-right reversal of vision and eye movement during sinusoidal vestibular oscillation caused decreases in VOR gain. In rabbits, both of these stimulus conditions produced large increases in the gain of the VOR, which implied that eye velocity signals were used instead of vestibular inputs to compute errors in the VOR. Our different results argue that vestibular signals are necessary for computing errors in VOR gain in the monkey. The species difference may reflect the additional role that smooth pursuit eye movements play in stabilizing gaze during head turns in monkeys.
Contrasting neuronal activity in supplementary and precentral motor cortex of monkeys. I. Responses to instructions determining motor responses to forthcoming signals of different modalities
Authors: Tanji J. , Kurata K.
Published: December 2017

The present report contrasts neuronal activity in two motor cortical fields after instructions that determine which of two sensory signals will trigger a movement and which will not. The goal of the study was to determine possible differential roles of the two cortical fields in the process of preparing to move in response to one external cue and to ignore another. Single-cell recordings were made from the supplementary motor area (SMA) and the precentral motor area (PCM) of monkeys trained to perform key-press movements in two different modes. In the auditory mode, an instruction signal warned the animal to prepare to start the movement promptly in response to a forthcoming 1,000-Hz tone burst (trigger signal), but to remain motionless if the signal was vibrotactile (nontrigger signal). In the tactile mode, the trigger and nontrigger signals were reversed: a different instruction signal warned the animal to prepare to perform the key-press movement in response to the vibrotactile cue, but to withhold it in response to the 1,000-Hz tone. The instruction signals were auditory tones of 300 Hz for the auditory mode and 100 Hz for the tactile mode. Out of 259 task-related SMA neurons, 128 (49%) responded to instructions. Three types of instruction responses were observed: 1) 95 neurons showed continuous instruction-induced activity changes lasting until the occurrence of the movement-triggering signal, regardless of whether an intervening nontrigger signal occurred. 2) 24 neurons showed increased activity until the occurrence of the nontriggering signal, after which the activity subsided. When there was no nontrigger signal, the activity increased during a period when the nontrigger signal might have been given. 3) Nine neurons responded with a transient, short-latency discharge after the instruction. The responses of SMA neurons to two instructions were often different. Forty-four SMA neurons exhibited a selective response to only one of the two instructions. In 43 neurons the response was differential, with the magnitude of activity increase or decrease being at least three times greater after one instruction than the other. In the remaining 41 neurons the response was nondifferential. Out of 112 task-related PCM neurons, 25 (22%) responded to the instructions. In the majority of them (21 neurons), the instruction response was nondifferential.(ABSTRACT TRUNCATED AT 400 WORDS)
Modification of saccadic eye movements by GABA-related substances. II. Effects of muscimol in monkey substantia nigra pars reticulata
Authors: Hikosaka O. , Wurtz R. H.
Published: December 2017

The preceding study (21) showed that a gamma-aminobutyric acid (GABA) agonist or antagonist injected into the superior colliculus (SC) disrupted saccadic eye movements. The purpose of the present experiments was to determine whether this result was due to altering the inhibitory input to the SC from the substantia nigra pars reticulata (SNr). SNr cells are themselves inhibited by GABA. Injection of muscimol, a GABA agonist, into the SNr should increase the inhibition acting on SNr cells and should reduce the inhibition acting on the SC. If the effects of GABA inhibition in the SC results from terminals originating in the SNr, muscimol in the SNr should act like bicuculline in the SC. Muscimol in the SNr has the same general effect as bicuculline in the SC. The monkey made irrepressible saccades toward the contralateral visual field where cells in the SNr at the injection site had their visual or movement field. During visual fixation saccadic jerks occurred, interspersed with spontaneous saccades, instead of saccades to visual targets or to remembered targets. Saccades to remembered targets were more vulnerable to these saccadic intrusions than were saccades to visual targets. Since muscimol in the SNr acts like bicuculline in the SC, we conclude that a substantial fraction of GABA-mediated inhibitory inputs in the SC originates from the SNr. These experiments, in conjunction with previous experiments, show that the SNr exerts a tonic inhibition on saccade-related cells in SC and that this inhibition is mediated by GABA. The role of the SNr in initiation of saccades to remembered targets is particularly important since these saccades are more severely disrupted by muscimol in the SNr as well as in the SC. We suggest that both of these conclusions about eye movement might apply to skeletal movements as well. First, the basal ganglia contribute to the initiation of movement by a release of the target structure from tonic inhibition. Second, this mechanism is particularly critical of the movements based on stored or remembered signals that are not currently available as incoming sensory inputs.
Sensory processing in a thermal afferent pathway
Authors: Davies S. N. , Goldsmith G. E. , Hellon R. F. , Mitchell D.
Published: December 2017

Extracellular recordings were made from cold-receptive afferent fibers in the trigeminal ganglion of rats anesthetized with halothane. By applying a standardized series of steady or changing temperatures to the receptive fields, we recorded the static and dynamic responses of the afferents. Comparable recordings were made from neurons in the marginal layer of the caudal trigeminal nucleus onto which the cold fibers synapse. The static and dynamic responses of the afferent fibers were reproduced faithfully by the second-order neurons, but at a much higher level of activity. Ganglionectomy silenced the second-order cells. Their continuous high level of activity appears to depend on the tonic input from the afferent fibers and not on any intrinsic circuits in the medulla.
Sensitivity to amplitude modulated sounds in the anuran auditory nervous system
Authors: Rose G. J. , Capranica R. R.
Published: December 2017

Auditory responses were recorded from single units in the eighth nerve and in the midbrain torus semicircularis of the leopard frog (Rana pipiens). Acoustic stimuli included sinusoidally amplitude-modulated (AM) tones and noise, as well as pure tones. Mean spike rates were measured at various rates of AM, and the degree to which a unit's spikes were restricted to a particular phase of the modulation cycle was described by a synchronization coefficient. The firing rate of eighth-nerve fibers was largely independent of the rate of AM over the modulation range 10 to 150 Hz. Further, the general shape of the spike rate vs. AM-rate function was invariant with either depth of modulation or sound-pressure level (SPL). Although virtually all eighth-nerve fibers exhibited significant synchronization to the envelope of AM, the shape of the synchronization function depended on the unit's best-excitatory frequency (BEF). Fibers with highest BEF's, presumed to innervate the basilar papilla, generally showed greater synchronization as the AM rate was increased (up to 100-150 Hz). Fibers tuned to the low-and midfrequency region, which innervate the amphibian papilla, exhibited low-pass synchronization characteristics. As the depth of modulation was reduced, the degree of synchronization of eighth-nerve fibers decreased. For a given depth of modulation an increase in sound level tended to decrease the degree of synchronization, but significant synchronization could still be observed at stimulus intensities at least 65 dB above threshold. On the basis of the spike rate vs. AM-rate functions, the temporal selectivity of single cells in the torus could be characterized by five response types: AM nonselective (spike rate was largely independent of the AM rate); AM high-pass (activity increased as the AM rate was increased); AM low-pass (response was greatest for slow AM rates and decreased at high rates); AM band-suppression (these neurons responded well to low and high AM rates, but responded weakly to intermediate rates); and AM-tuned (spike rate was greatest over a narrow range of modulation rates). In these measurements the depth of modulation was held constant at 100%. The five response categories are not discrete, but rather reflect representative examples along a continuum with regard to temporal selectivity. The temporal selectivity exhibited by toral units in their firing rates was not evident in their AM-synchronization functions.(ABSTRACT TRUNCATED AT 400 WORDS)
Primate globus pallidus and subthalamic nucleus: functional organization
Authors: DeLong M. R. , Crutcher M. D. , Georgopoulos A. P.
Published: December 2017

Neuronal relations to active movements of individual body parts and neuronal responses to somatosensory stimulation were studied in the external (GPe) and internal (GPi) segments of the globus pallidus (GP) and the subthalamic nucleus (STN) of awake monkeys. In GPe (n = 249), GPi (n = 151), and STN (n = 153), 47, 29, and 28% of the cells, respectively, discharged in relation to active arm movements, 10, 11, and 15% to leg movements, and 22, 22, and 18% to orofacial movements. Of the neurons whose activity was related to arm movements, 26, 16, and 21% in GPe, GPi, and STN, respectively, discharged in relation to movements of distal parts of the limb. Of cells whose discharge was related to active limb movements, 37, 22, and 20% in GPe, GPi, and STN, respectively, also responded to passive joint rotation, which was usually specific in terms of joint and direction of movement. Only a small percentage of cells responded to muscle or joint palpation, tendon taps, or cutaneous stimulation. Short-latency, direction-specific neuronal responses to load perturbations confirmed the existence of proprioceptive driving. In both GPe and GPi, leg movement-related neurons were centrally located in the rostrocaudal and dorsoventral dimensions. In contrast, arm movement-related cells were found throughout the entire rostrocaudal extent of both segments, although in greater numbers caudally. In the central portions they were situated largely inferior and lateral to leg movement-related neurons. Neurons related to orofacial movements were largely confined to the caudal halves of both segments, where they were located largely ventral to arm movement-related cells. The STN cells whose activity was related to leg movements were observed largely in the central portions of the nucleus in the rostrocaudal and mediolateral dimensions. Cells whose activity was related to arm movements were found throughout the rostrocaudal extent of the nucleus, but were most numerous at the rostral and caudal poles. Neurons related to movements of the facial musculature and to licking and chewing movements were distributed over the entire rostrocaudal extent of the nucleus, where they generally occupied the ventrolateral regions. In all three nuclei, neurons with similar functional properties were sometimes clustered together. Within the arm and leg areas, however, there was no clear evidence for a simple organization of clusters related to different parts of the limb. These studies provide further evidence for a role of the basal ganglia in the control of limb movements.(ABSTRACT TRUNCATED AT 400 WORDS)
Roles of aspartate and glutamate in synaptic transmission in rabbit retina. I. Outer plexiform layer
Authors: Bloomfield S. A. , Dowling J. E.
Published: December 2017

Intracellular recordings were obtained from horizontal and bipolar cells of the superfused, isolated retina-eyecup of the rabbit. The putative neurotransmitters aspartate, glutamate, and several analogues were added to the superfusate while the membrane potential and light-responsiveness of the retinal neurons were monitored. Both L-aspartate and L-glutamate mimicked the actions of the endogenous photoreceptor transmitter on horizontal cells, on-bipolar cells, and off-bipolar cells. At applied concentrations of 2.5-20 mM, the actions of L-aspartate and L-glutamate were indistinguishable. D-aspartate potentiated the effects of both L-aspartate and L-glutamate on horizontal cells. This suggests that active uptake systems for these amino acids exist in the outer plexiform layer (OPL) of the rabbit retina. The glutamate analogue kainate produced effects similar to those of aspartate and glutamate on second-order neurons, but at concentrations lower by over two orders of magnitude. The glutamate analogue quisqualate had effects similar to kainate but with much less potency. The aspartate analogue n-methyl DL-aspartate (NMDLA) antagonized the effects of the photoreceptor transmitter on horizontal and off-bipolar cells. This action of NMDLA was only observed at low concentrations (50 microM). In addition, NMDLA could block the effects of exogenously applied kainate. The NMDLA had no clear effects on on-bipolar cells. The glutamate analogue 2-amino-4-phosphonobutyrate reversibly blocked the responses of on-bipolar cells but had no effect on either horizontal or off-bipolar cell responses. This suggests that on-bipolar cells possess a unique synaptic receptor. The aspartate analogue 2-amino-3-phosphonoproprionate did not show this selectivity, suggesting that this unique receptor is a glutamate-preferring receptor. The antagonists alpha-methyl glutamate, alpha-amino adipate, and glutamate diethyl ester all showed only a weak ability to antagonize the actions of the photoreceptor transmitter on second-order neurons. The results of this study indicate that glutamate or a glutamate-like substance is the likely transmitter of rods and cones in the rabbit retina. A comparison of the present findings with those previously obtained in lower vertebrate retinas suggests that the basic pharmacological design of the OPL of all vertebrate retinas is very similar.
Physiology of a bidirectional, excitatory, chemical synapse
Authors: Anderson P. A.
Published: December 2017

Neurons of the motor nerve net of the jellyfish Cyanea are connected by chemical synapses that, from their ultrastructure, appear to be bidirectional chemical synapses. These synapses were examined physiologically, by recording intracellularly from synaptically connected cells, with the whole cell configuration of the patch-clamp recording technique. Subthreshold depolarizations produced neither small voltage responses indicative of electrical coupling, nor unitary depolarizations suggestive of excitatory postsynaptic potentials (EPSP). Synaptic transmission was affected only when the presynaptic cell was depolarized above spike threshold. The synaptic delay was slightly less than 1 ms at room temperature. The postsynaptic response was initially suprathreshold, resulting in an action potential, but with time this gave way to a large 60 mV amplitude EPSP that did not produce action potentials. The amplitude of the EPSP was directly related to the postsynaptic membrane potential and extrapolated to a reversal potential close to zero mV. Reversal of the EPSP was never observed, even in the presence of intracellular tetrathylammonium (TEA). The relationship between presynaptic depolarization and postsynaptic response was difficult to examine in normal conditions, but in the presence of extracellular lidocaine, which blocked the Na+ and K+ channels in these membranes, a distinct relationship was apparent. The synapse was physiologically nonpolarized and conducted equally well in either direction with a constant synaptic delay.
Tonotopic organization in lateral part of posterior group of thalamic nuclei in the cat
Authors: Imig T. J. , Morel A.
Published: December 2017

Responses of single units and clusters of units to tone-burst stimulation were recorded at 100-micron intervals along vertical electrode penetrations through the lateral part of the posterior group of thalamic nuclei (Po) in five barbiturate-anesthetized cats. Best frequencies and minimum response latencies to tone-burst stimulation were studied at each location along a penetration. Most of Po is located rostral to the medial geniculate body (MGB) and is contiguous with the ventral nucleus and medial division. Po is characterized physiologically by narrowly tuned, short-latency (less than 40 ms) responses. Considerable scatter of best frequencies occurs along electrode penetrations, although a clear tonotopic organization is apparent in the distribution of best frequencies obtained from several electrode penetrations located in the same frontal plane of an individual brain. A "single" frequency is represented as an irregularly shaped lamina. A three-dimensional "block" model of the tonotopic organization of Po is described in which the highest best frequencies are located caudally, and the lowest best frequencies are located rostrally within the nucleus. The high-frequency representation of Po is contiguous with the high-frequency representation of the ventral nucleus of the MGB. The low- and middle-frequency representations of the ventral nucleus and Po are discontinuous. The ventral nucleus and Po have similar physiological properties and together constitute the tonotopic division of the auditory thalamus in the cat. Neurons in the medial division adjacent to the medial border of Po are larger than neurons in Po, lack tonotopic organization, and respond at short latencies.
Similarity of dynamic range adjustment in auditory nerve and cochlear nuclei
Authors: Gibson D. J. , Young E. D. , Costalupes J. A.
Published: December 2017

Rate versus level functions were recorded for responses to best-frequency (BF) tones of 116 cochlear nucleus units and 53 auditory-nerve fibers in the presence of interrupted tone backgrounds and continuous noise backgrounds of various intensities. The backgrounds shifted the dynamic ranges of rate-level functions to higher test intensities, so in the presence of backgrounds, rate saturation occurred at higher intensities than in quiet. The shift in saturation intensity evoked by each background was measured by comparing the rate-level function recorded with the background to one recorded without. The relation between change in saturation intensity and background intensity could be approximated by the formula (formula: see text) delta Isat is the shift in saturation intensity, I is the background intensity, theta is the threshold for evoking shift, and A is the ratio of shift to background intensity re theta. In the appendix, it is shown that A is a measure of a unit's ability to avoid saturation by the background stimulus. The optimal value of A is unity, at which point a unit's operating range is infinite. The value of A depended on BF for interrupted tone backgrounds, but not for continuous noise backgrounds. For BF less than 10 kHz, the mean value of A for tone backgrounds was 0.33 in the auditory nerve, 0.37 in the ventral cochlear nuclei (VCN), and 0.47 in the dorsal cochlear nucleus (DCN). The difference between auditory nerve and VCN was not statistically significant. For BF greater than 10 kHz, the mean A was 0.16 in auditory nerve and 0.30 in VCN. The mean value of A for noise backgrounds was 0.79 in auditory nerve, 0.86 in VCN, 0.86 in DCN units of response types II and III, and 1.04 in DCN type IV units. Only the differences between DCN type IV and the non-DCN unit groups were statistically significant. The qualitative changes produced in rate-level functions by tone and noise backgrounds were similar in auditory nerve and cochlear nuclei except for DCN type IV units. The shifts in rate functions produced by interrupted tone backgrounds did not prevent saturation of the rate response at background intensities above the dynamic range of the unit as recorded in quiet. However, the rate response to test tones was preserved in the presence of all noise background levels used (up to a 30-dB spectrum level). The shift in rate function produced by the noise was almost sufficient to allow the unit to encode test intensity relative to noise background intensity.(ABSTRACT TRUNCATED AT 400 WORDS)
Localization of cortical areas activated by thinking
Authors: Roland P. E. , Friberg L.
Published: December 2017

These experiments were undertaken to demonstrate that pure mental activity, thinking, increases the cerebral blood flow and that different types of thinking increase the regional cerebral blood flow (rCBF) in different cortical areas. As a first approach, thinking was defined as brain work in the form of operations on internal information, done by an awake subject. The rCBF was measured in 254 cortical regions in 11 subjects with the intracarotid 133Xe injection technique. In normal man, changes in the regional cortical metabolic rate of O2 leads to proportional changes in rCBF. One control study was taken with the subjects at rest. Then the rCBF was measured during three different simple algorithm tasks, each consisting of retrieval of a specific memory followed by a simple operation on the retrieved information. Once started, the information processing went on in the brain without any communication with the outside world. In 50-3 thinking, the subjects started with 50 and then, in their minds only, continuously subtracted 3 from the result. In jingle thinking the subjects internally jumped every second word in a nine-word circular jingle. In route-finding thinking the subjects imagined that they started at their front door and then walked alternatively to the left or the right each time they reached a corner. The rCBF increased only in homotypical cortical areas during thinking. The areas in the superior prefrontal cortex increased their rCBF equivalently during the three types of thinking. In the remaining parts of the prefrontal cortex there were multifocal increases of rCBF. The localizations and intensities of these rCBF increases depended on the type of internal operation occurring. The rCBF increased bilaterally in the angular cortex during 50-3 thinking. The rCBF increased in the right midtemporal cortex exclusively during jingle thinking. The intermediate and remote visual association areas, the superior occipital, posterior inferior temporal, and posterior superior parietal cortex, increased their rCBF exclusively during route-finding thinking. We observed no decreases in rCBF. All rCBF increases extended over a few square centimeters of the cortex. The activation of the superior prefrontal cortex was attributed to the organization of thinking. The activation of the angular cortex in 50-3 thinking was attributed to the retrieval of the numerical memory and memory for subtractions. The activation of the right midtemporal cortex was attributed to the retrieval of the nonverbal auditory memory.(ABSTRACT TRUNCATED AT 400 WORDS)
Gustatory responses of cortical neurons in rats. III. Neural and behavioral measures compared
Authors: Yamamoto T. , Yuyama N. , Kato T. , Kawamura Y.
Published: December 2017

The responses of 39 cortical neurons to 13 kinds of taste stimuli including the four putative basic taste solutions (sucrose, NaCl, HCl, and quinine HCl) applied to the anterior portion of the tongue were recorded extracellularly in lightly anesthetized rats. The neural responses were analyzed in terms of the four hypotheses of quality coding: across-neuron response pattern, labeled-line, matrix pattern, and across-region response pattern notions. Animals were given a conditioned taste aversion to one of the 11 stimuli by pairing it with a gastrointestinal illness caused by intraperitoneal injection of 0.15 M LiCl. Behavioral taste profiles were constructed for each stimulus from the suppression of rate of drinking, which indicates the extent of generalization of aversion to each of the four basic taste stimuli. Neural taste profiles of each taste stimulus, which indicate the relation of the taste of a stimulus to each taste of the four basic stimuli, differed more or less depending on the kind of quality-coding notions employed. Among the four analyses, across-region correlation coefficients that were derived from an across-region response-pattern theory showed the highest correlation with the behavioral suppression rates. Therefore we conclude that processing of taste information in the cortex involves differences in both response magnitude across neurons and the spatial localization of those neurons. Fluid intake per day of each of the 12 taste solutions was measured by the single-bottle preference method. When the amount of intake was described in terms of an hedonic index (HI), which indicates the hedonic aspect of the taste of each solution, HI's for sucrose, NaCl, HCl, and quinine were 1.17, 0.43, -0.49, and -0.89, respectively. These values represent the degree of deviation of solution intake above (i.e., preferable) or below (aversive) the standard water intake. Then, HI's were calculated for each of the 12 taste stimuli based on the neural taste profiles and actual HI's for each of the four basic taste stimuli. The correlations between the calculated and the actual (or behaviorally obtained) HI's were very high (ranging from 0.832 to 0.941). This result suggests that the hedonic dimension of taste can be matched well by any one of the four proposed hypotheses.