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T C Yin

Publications and source records attributed to T C Yin.

54 records · Page 3Linked to original sources
PubMed1983

Binaural interaction in low-frequency neurons in inferior colliculus of the cat. III. Effects of changing frequency.

The effects of changing stimulus frequency on the interaural phase sensitivity of neurons in the inferior colliculus (IC) were studied in barbiturate-anesthetized cats in order to reexamine the issue of characteristic delay (CD). Since the results obtained with the interaural delay and binaural beat stimuli are similar, we used the averaged interaural delay curves and binaural beat period histograms as comparable expressions of a neuron's interaural phase sensitivity. When the averaged interaural delay curves at different frequencies are plotted on a common time axis, for some cells the resulting superimposed delay curves show peaks or troughs that coincide at some CD. For most cells, though, this method of detecting a CD by visual inspection yields ambiguous and uncertain results. Composite curves, computed from the average of all the normalized superimposed delay curves, are also not helpful for showing CD. In order to provide a more objective means of analyzing the data, we plotted the mean interaural phase versus the stimulating frequency and computed the linear regression line, using the mean square error as a measure of linearity. The slope of the regression line is the CD for the neuron, and the phase intercept is referred to as the characteristic phase (CP). Cells that display a CD at the peak discharge have a CP = 0.0 cycles, while those that show a CD at the minimum discharge have a CP = 0.5. Cells that exhibit a CP at any value other than 0.0, 0.5, or 1.0 will have a CD at some relative amplitude other than the peak or trough. For cells that exhibit a CD at the peak or trough, results of the analysis procedure using the phase-frequency plot correspond to those obtained from visual inspection. For cells that do not show a common peak or trough, the analysis procedure not only specifies the location of the CD but also provides a statistical criterion of the linearity. From this analysis about 60% of the runs were identified as satisfying the criteria for CD at the P less than 0.005 level and 71% of these CDs are between +/- 300 micros. Most CD cells do not have the CD at the peak or trough of the response. Our results differ from those found in previous studies but they are in essential agreement with the original concept put forth by Rose et al. (31). Some cels exhibit little change in the CD or CP with variations in intensity, while others display marked systematic shifts in both CD and CP. In general, the peaks and troughs of the composite curves show less variability with intensity than the CD.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1983

Binaural interaction in low-frequency neurons in inferior colliculus of the cat. I. Effects of long interaural delays, intensity, and repetition rate on interaural delay function.

Detailed, quantitative studies were made of the interaural phase sensitivity of 197 neurons with low best frequency in the inferior colliculus (IC) of the barbiturate-anesthetized cat. We analyzed the responses of single cells to interaural delays in which tone bursts were delivered to the two ears via sealed earphones and the onset of the tone to one ear with respect to the other was varied. For most (80%) cells the discharge rate is a cyclic function of interaural delay at a period corresponding to that of the stimulating frequency. The cyclic nature of the interaural delay curve indicates that these cells are sensitive to the interaural phase difference. These cells are distributed throughout the low-frequency zone of the IC, but they are less numerous in the medial and caudal zones. Cells with a wide variety of response patterns will exhibit interaural phase sensitivities at stimulating frequencies up to 3,100 Hz, although above 2,500 Hz the number of such cells decrease markedly. Using dichotic stimuli we could study the cell's sensitivity to the onset delay and interaural phase independently. The large majority of IC cells respond only to changes in interaural phase, with no sensitivity to the onset delay. However, a small number (7%) of cells exhibit a sensitivity to the onset delay as well as to the interaural phase disparity, and most of these cells show an onset response. The effects of changing the stimulus intensity equally to both ears or of changing the interaural intensity difference on the mean interaural phase were studied. While some neurons are not affected by level changes, others exhibit systematic phase shifts for both average and interaural intensity variations, and there is a continuous distribution of sensitivities between these extremes. A few cells also showed systematic changes in the shape of the interaural delay curves as a function of interaural intensity difference, especially at very long delays. These shifts can be interpreted as a form of time-intensity trading. A few cells demonstrated orderly changes in the interaural delay curve as the repetition rate of the stimulus was varied. Some of these changes are consonant with an inhibitory effect that occurs at stimulus offset. The responses of the neurons show a strong bias for stimuli that would originate from he contralateral sound field; 77% of the responses display mean interaural phase angles that are less than 0.5 of a cycle, which are delays to the ipsilateral tone.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1983

Visual-evoked responses from strabismic cats. A comparison of esotropes with exotropes.

We examined cortical responses evoked by 8-Hz, phase-shifted sine wave gratings at a range of contrasts and spatial frequencies in normal cats and in cats raised with artificial esotropia or exotropia. There were no significant differences between the amplitudes of the responses evoked through the two eyes of the normal cats, but for some esotropes and exotropes the responses evoked through the unoperated eye were larger than those evoked through the operated eye. Interocular response differences were comparable in all affected cats and were most pronounced at high contrasts. These results indicate that rearing with artificial strabismus can produce amblyopia in both esotropes and exotropes, and that the amblyopia is similar in the two cases.

Amblyopia↗
PubMed1981

Homotopic and heterotopic callosal afferents of caudal inferior parietal lobule in Macaca mulatta.

We have examined callosal-axon neurons giving rise to homotopic and heterotopic callosal projections to caudal inferior parietal lobule (area PG) in Macaca mulatta, identifying these neurons by means of retrograde axonal transport of horseradish peroxidase. The labeled neurons in the homotopic region occur predominantly in layers IIIB and V.A moderate number are also seen in layer VI, a smaller number of layer IV, and rare cells occur in layer II. These neurons occupy a region very similar in outline to the injection area, and though variable in density in the horizontal plane, are continuously distributed in this plane. The heterotopic neurons are seen in the contralateral cingulate gyrus, continuing caudally into medial parietal cortex, in the cortex of the superior temporal and occipitotemporal sulci, in the caudal superior temporal gyrus, and in the caudal inferior parietal lobule, behind the homotopic area. These same regions on the ipsilateral side contain labeled neurons of origin of ipsilateral association projections to area PG. For other ipsilateral labeling was found. A review of the literature on heterotopic callosal connections of a particular generalization of this conclusion: The callosal heterotopic connections of a particular cortical area are made with regions which on the ipsilateral side have associated connections with that area, though usually not with all of such regions.

Animals↗
PubMed1979

Response of cat inferior colliculus neurons to binaural beat stimuli: possible mechanisms for sound localization.

The interaural phase sensitivity of neurons was studied through the use of binaural beat stimuli. The response of most cells was phase-locked to the beat frequency, which provides a possible neural correlate to the human sensation of binaural beats. In addition, this stimulus allowed the direction and rate of interaural phase change to be varied. Some neurons in our sample responded selectively to manipulations of these two variables, which suggests a sensitivity to direction or speed of movement.

Animals↗
PubMed1978

Convergence of cerebral inputs onto dentate neurons in monkey.

The patterns of convergence of inputs from different areas of the cerebral cortex and the peripheral nerves onto single dentate neurons was studied in cebus monkeys. Dentate neurons receive their strongest and most numerous inputs from the premotor and supplementary motor regions of area 6. The sensorimotor and frontal cortices have weaker projections to the dentate nucleus, while peripheral nerves and many other association cortical areas were found to be effective in influencing cells of the lateral cerebellum. Dentate cells that respond to stimulation of hindlimb regions of the sensorimotor cortex tend to receive their principal input from the supplementary motor area and medial premotor regions, while neurons responding to forelimb sensorimotor cortex tend to receive lateral premotor inputs. In addition there is a topographical organization within the ventral pole of dentate with the hindlimb represented in the anterior regions and the forelimb in the posterior regions. These results are compared with those of similar studies of interpositus and dentate neurons in cat and monkey. The differences between the afferent inputs to dentate and interpositus are consistent with the suggestion that the lateral cerebellum is involved in programming movement parameters before movement initiation while the intermediate zone is involved in up-dating the evolving movement.

Animals↗
PubMed1978

Mechanisms of neural integration in the parietal lobe for visual attention.

The impulse discharges of neurons in the inferior parietal association cortex (area 7) were studied in the alert, behaving rhesus monkey, trained to fixate and follow visual targets. Four classes of cells related to visual or visuomotor function were found. Cells of one of these are sensitive to visual stimuli and have large, contralateral receptive fields with maximal sensitivity in the far temporal quadrants. Cells of the other three classes are related to visuomotor functions: visual fixation, tracking, and saccades. They are neither sensory nor motor in the usual sense for they are activated only by interested fixation of gaze or tracking, or before visually evoked saccadic eye movements. They are not activated during the spontaneous saccades and fixations that the monkey makes while casually exploring his environment. It is hypothesized that the light-sensitive neurons provide the visual input to the visuomotor cells that, in turn, produce a command signal for the direction of visual attention and for shifting the focus of attention from one target to another.

Animals↗
PubMed1977

Visual input to the visuomotor mechanisms of the monkey's parietal lobe.

A newly identified class of neurons of the parietal cortex, studied in waking monkeys (Macaca mulatta), is activated by visual stimuli, perhaps via the retino-collicular visual pathway. This afferent input is thought to provide the visual cues activating the visuomotor mechanisms of the parietal lobe for the direction of visual attention.

Action Potentials↗
PubMed1977

Integration of cerebral and peripheral inputs by interpositus neurons in monkey.

The patterns of convergence of cerebral and peripheral nerve inputs onto interpositus neurons were studied in cebus monkeys. The strongest inputs to interpositus neurons are from motor and somatosensory cortex, with weaker inputs from peripheral nerves and cerebral area 6. The neurons in the anterior portion of interpositus receive cerebral and peripheral inputs primarily representing the hindlimb, while inputs to neurons in the posterior division represent forelimb or mixed forelimb and hindlimb. The hindlimb neurons integrate signals principally from motor cortex, somatosensory cortex, nerves, supplementary motor and medial pre-motor areas, while forelimb neurons receive inputs from motor, somatosensory, lateral premotor cortical areas and nerves. The results from this study are compared with those from studies of interpositus and dentate neurons in cat and monkey in order to determine the role of n. interpositus in movement. It is suggested that the inputs integrated by interpositus neurons are consistent with a role in up-dating skilled movements.

Action Potentials↗
PubMed1977

Parietal lobe mechanisms for directed visual attention.

1. Experiments were made on the cortex of the inferior parietal lobule in 10 hemispheres of six alert, behaving monkeys. The electrical signs of the impulse discharges of single cortical cells were recorded as the monkeys executed tasks requiring them to fixate stationary visual targets, track those which moved slowly, and to make saccadic movements to foveate those which suddenly jumped from one locus to another within the field of view. A total of 907 neurons of area 7 were identified in terms of their physiological properties, particularly the correlation of their activity with the oculomotor components of these behavioral acts of directed visual attention; 480 of these were located by cytoarchitectural layer. Most identifiable cells of area 7 are visuomotor neurons, in a special and conditional sense. Their discharge frequencies increase before and during those steady fixations and movements of the eyes which secure and maintain foveation of objects, but only if the visual targets engaged are linked by a strong motivational drive; in our experiments, one between thirst and the light whose dimming the animal has learned to detect for liquid reward. We have identified and studied three major classes of neurons in area 7. 2. The visual fixation neurons (57%) accelerate discharge synchronously with fixation of a visual object the animal desires. The incremented discharge continues until reward, but then declines abruptly even when there is no immediate shift of the line of gaze. Fixation neurons are relatively inactive during those casual fixations by which the animal insepcts the surrounding environment. Mist fixation neurons subtend gaze fields limited to one quadrant or half of the total gaze field. The sum of the gaze fields of the fixation neurons in one hemisphere is weighted moderately toward the contralateral side. Fixation cells also discharge during slow pursuit movements in any direction so long as the movement stays within the gaze field of the neuron under study. About 40% of fixation cells are suppressed before and during saccadic movements of the eyes to a new target within the gaze field of the fixation cell. Those suppressed are located preferentially in layer V of the cortex. Suppression is maximal for saccades directed contralaterally to the hemisphere under study. 3. Visual tracking neurons are active during oculomotor pursuit of slowly moving visual objects, not during steady fixations. They show a marked directional but no laterality relation, and are suppressed before and during a visually evoked saccade superimposed on the smooth pursuit movement. The rate of discharge is a flat function of tracking speed so that these cells do not appear to emit signals which specify the speed of smooth pursuit movements. 4. The saccade neurons are active before and during visually evoked saccadic movements of the eyes but not before spontaneous saccades, no matter whether made in light or near darkness. The discharge of saccade neurons leads the eye movement by as much as 150 ms (mean, 73 ms)...

Action Potentials↗
PubMed1976

Dynamic response and transfer characteristics of joint neurons in somatosensory thalamus of the cat.

1. The dynamic response of neurons sensitive to knee joint rotation in the cat somatosensory thalamus was studied during sinusoidal variation of joint angle. The input sine waves were applied with a precise voltage-controlled, electromechanical actuator. The average rate of discharge of a single cell was considered as the output parameter. Describing functions of the sensory system were extracted by correlation and spectral analysis techniques. The effects of anesthetic, bias angle, and excursion angle were investigated. Discrete and swept sinusoidal waveforms between 0.1 and 7.0 Hz were used as inputs.2. The majority of joint cells in the thalamus were rapidly adapting and had frequency-response curves that were characterized as highpass filters. Although the major features of the response curves for individual cells were very similar, they could not all be fit with a single transfer function. The describing function of all the rapidly adapting cells averaged together was well fit by a transfer function that could be termed velocity sensitive in the bandwidth between 0.1 and 6.5 Hz. Most of these phasic cells showed a phase-locking tendency, particularly at high frequencies.3. The dynamics of the response for the rapidly adapting cells was relatively independent of anesthetic, bias angle, and excursion angle. Threshold and saturation effects were exhibited by some cells for very small (less than 1 degree) and large (greater than 10 degrees) input amplitudes, respectively. In addition a few (17%) showed a bidirectional response, i.e., responded at both flexion and extension of the limb. The anesthetic had a strong effect in depressing the spontaneous discharge of the cells and seemed to change the character of the tonic response by introducing a bursting component.4. The transfer characteristic of the thalamic cells was found to be a single-pole low-pass filter plus a time delay. The optimized value for the filter was found to have a corner frequency of 6.0 Hz with a time delay of 6 ms.5. Of the knee joint sensitive cells, 17% were slowly adapting or tonic, and more tonic cells were found in the unanesthetized animals. Only one tonic cell was studied in detail, and its dynamic characteristics were similar to that of the slowly adapting joint receptors at low frequencies. In this respect the rapidly adapting and slowly adapting joint cells in the thalamus have strikingly different frequency-response curves, the former curves have a much steeper slope in the magnitude.6. The functional implications of these results and of other recent findings in relation to the probable role of joint receptors in mediating proprioception are discussed.

Animals↗