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C K Peck

Publications and source records attributed to C K Peck.

At least 19 recordsLinked to original sources
PubMed1998

Spatial disparity affects visual-auditory interactions in human sensorimotor processing.

Information from the auditory and visual systems converges in the nervous system with physiological and behavioral consequences. Most of our knowledge about the rules governing such convergence has been obtained in experiments where the strength or the timing of the individual auditory and visual stimuli has been varied. Relatively little attention has been paid to the spatial relationship between different modalities of stimuli in multisensory experiments. We studied saccadic reaction times of human subjects to bimodal auditory and visual stimulus presentations under two conditions: first, with the targets spatially coincident and, second, with various degrees of spatial separation or disparity. In the first experiment, we found that the saccadic reaction times were consistently shorter than would be predicted by independent processing of information about the visual and auditory targets. These results suggest convergence of multimodal information at one or more loci within the nervous system. In the second experiment, we found that saccadic latency gradually increased as spatial distance between the auditory and visual targets increased. Evidence for neural summation was found over a wide range of spatial disparities. These results suggest that multisensory information can be integrated and have significant influences on behavior over a surprisingly large range of spatial disparity.

Eye Movements↗
PubMed1997

Discharge patterns of neurons in the rostral superior colliculus of cat: activity related to fixation of visual and auditory targets.

Neurons in the rostral superior colliculus (SC) of alert cats exhibit quasi-sustained discharge patterns related to the fixation of visual targets. Because some SC neurons also respond to auditory stimuli, we investigated whether there is a population of neurons in the rostral SC which is active in relation to fixation of both auditory and visual targets. We identified cells which were active with visual fixation and which continued to discharge if the fixation stimulus was briefly extinguished. The population of neurons exhibited similar discharge characteristics when the fixation stimulus was auditory. Few neurons were significantly more active during fixation of visual targets than during fixation of auditory targets. Most fixation neurons showed a diminished discharge rate during spontaneous (self-generated) saccadic eye movements away from a visual fixation stimulus, regardless of the direction of the saccade. This diminished discharge rate (or pause) typically began, on average, 12.2 ms before saccade onset and the duration of the pause was longer than the duration of the saccade. These observations are consistent with the hypothesis that increased discharge of these neurons is related to active fixation and that reductions in their activity are important for the generation of saccades. However, the lack of a precise relationship between pause duration and saccade duration implies that these neurons would be unlikely to project directly to the saccadic burst generator. The mean interval from the beginning of the pauses of fixation neurons to the beginning of the saccades away from fixation targets is also shorter than has been found in brainstem omnipause neurons. By analogy with the concept of a receptive field, a gaze position error field depicts the range of gaze position error for which a cell is active. Although fixation neurons appear to encode the magnitude and direction of the error between visual targets and the visual axis, visual error fields at the end of fixating eye movements were significantly larger than those at stimulus onset. For auditory stimuli, this difference was not significant. These observations are compatible with a number of recent experiments indicating that neural signals of eye position are damped or delayed with respect to current eye position.

Acoustic Stimulation↗
PubMed1997

Saccadic eye movements to visual and auditory targets.

Recent neurophysiological studies of the saccadic ocular motor system have lent support to the hypothesis that this system uses a motor error signal in retinotopic coordinates to direct saccades to both visual and auditory targets. With visual targets, the coordinates of the sensory and motor error signals will be identical unless the eyes move between the time of target presentation and the time of saccade onset. However, targets from other modalities must undergo different sensory-motor transformations to access the same motor error map. Because auditory targets are initially localized in head-centered coordinates, analyzing the metrics of saccades from different starting positions allows a determination of whether the coordinates of the motor signals are those of the sensory system. We studied six human subjects who made saccades to visual or auditory targets from a central fixation point or from one at 10 degrees to the right or left of the midline of the head. Although the latencies of saccades to visual targets increased as stimulus eccentricity increased, the latencies of saccades to auditory targets decreased as stimulus eccentricity increased. The longest auditory latencies were for the smallest values of motor error (the difference between target position and fixation eye position) or desired saccade size, regardless of the position of the auditory target relative to the head or the amplitude of the executed saccade. Similarly, differences in initial eye position did not affect the accuracy of saccades of the same desired size. When saccadic error was plotted as a function of motor error, the curves obtained at the different fixation positions overlapped completely. Thus, saccadic programs in the central nervous system compensated for eye position regardless of the modality of the saccade target, supporting the hypothesis that the saccadic ocular motor system uses motor error signals to direct saccades to auditory targets.

Acoustic Stimulation↗
PubMed1996

Visual-auditory integration in cat superior colliculus: implications for neuronal control of the orienting response.

Previous physiological studies have demonstrated that inputs from different sensory modalities converge on individual neurons in the superior colliculus. Moreover, in anesthetized, paralyzed animals, those tectal neurons which are most directly connected to brain stem circuits mediating orienting eye and head movements are highly likely to exhibit significant integration of sensory inputs from multiple modalities. The purpose of the present study was to examine the responses of tectal neurons in the alert cat when visual and auditory stimuli were presented as targets for ocular fixation and orienting responses. For comparison to previous work in anesthetized, paralyzed animals, we also examined the responses of tectal neurons to the presentation of these stimuli during periods when the cats voluntarily maintained their eyes near primary position in the absence of a fixation target. Under these conditions, there were significant differences between the strength of the response to the simultaneous presentation of visual and auditory targets and the strength of response to the most effective unimodal stimulus in about 40% of the cells tested. Many tectal neurons also responded tonically during fixation of visual, auditory and bimodal targets, and some of these also exhibited significant bimodal interactions. However, among individual neurons which responded phasically to stimulus onset or offset and tonically during fixation, there was only a weak correlation between the extent of bimodal interaction under the two conditions. Finally, among saccade-related neurons, the magnitude of saccade-related activity was only slightly affected when a biomodal target was used to elicit a saccade, and the extent of bimodal interactions was generally less than was found for the onset and offset of sensory targets. Such multisensory interactions can be significant for behavior. Indeed, simply using a multisensory target has been shown to influence the probability and latency of overt orienting responses, although the extent of such effects will probably vary across both tasks and stimulus conditions. Strong multi-sensory interactions are most likely to occur when low intensity stimuli are used. Our use of moderately intense sensory stimuli probably accounts for our finding of a relatively small percentage of cells in which bimodal responses were greater than the sum of their unimodal responses.

Animals↗
PubMed1995

Express saccades in cat: effects of task and target modality.

Saccadic eye movements to visual, auditory, and bimodal targets were measured in four adult cats. Bimodal targets were visual and auditory stimuli presented simultaneously at the same location. Three behavioral tasks were used: a fixation task and two saccadic tracking tasks (gap and overlap task). In the fixation task, a sensory stimulus was presented at a randomly selected location, and the saccade to fixate that stimulus was measured. In the gap and overlap tasks, a second target (hereafter called the saccade target) was presented after the cat had fixated the first target. In the gap task, the fixation target was switched off before the saccade target was turned on; in the overlap task, the saccade target was presented before the fixation target was switched off. All tasks required the cats to redirect their gaze toward the target (within a specified degree of accuracy) within 500 ms of target onset, and in all tasks target positions were varied randomly over five possible locations along the horizontal meridian within the cat's oculomotor range. In the gap task, a significantly greater proportion of saccadic reaction times (SRTs) were less than 125 ms, and mean SRTs were significantly shorter than in the fixation task. With visual targets, saccade latencies were significantly shorter in the gap task than in the overlap task, while, with bimodal targets, saccade latencies were similar in the gap and overlap tasks. On the fixation task, SRTs to auditory targets were longer than those to either visual or bimodal targets, but on the gap task, SRTs to auditory targets were shorter than those to visual or bimodal targets. Thus, SRTs reflected an interaction between target modality and task. Because target locations were unpredictable, these results demonstrate that cats, as well as primates, can produce very short latency goal-directed saccades.

Acoustic Stimulation↗
PubMed1995

Effects of eye position on saccadic eye movements and on the neuronal responses to auditory and visual stimuli in cat superior colliculus.

Many neurons in the deeper layers of the superior colliculus (SC) respond to multiple sensory inputs--visual, auditory, and somatic--as well as provide signals essential for saccadic eye movements to targets in different modalities. When the eyes and pinnae are in primary position, the neural map of auditory space is in rough topographic alignment with the map of visual space, and if the auditory map is based solely on headpinna coordinates, any changes in eye position in the orbit will cause misalignment of the maps. We investigated the effects of eye position on the response of sound-sensitive neurons in the SC of cats because previous work on cats and on monkeys had suggested the possibility of species differences in the representation of auditory signals in the SC. We also investigated the effects of eye position on the accuracy of saccades to auditory, visual, and bimodal stimuli. All studies were conducted in alert, trained cats with the head restrained in a fixed position. Neuronal and behavioral responses were studied during periods when the eyes were steadily directed to different positions relative to the position of the sound. Cats showed partial compensation for eye position in making saccades, regardless of the modality of the target, and they showed similar patterns of error in saccades to auditory and visual targets. These behavioral data are consistent with coding the location of visual and auditory targets in the same coordinate system. In the vast majority of intermediate-layer neurons, eye position significantly affected the number of spikes evoked by sound stimuli. For most of these neurons, changes in eye position produced significant shifts in the speaker location producing maximal response. In some neurons, eye position significantly facilitated the magnitude of neuronal response evoked by sounds from a variety of speaker locations. Because few pinna movements could be detected, in is unlikely that these changes in neuronal response could be due to changes in the position of the pinnae. Our results indicate that the deep layers of the SC contain an eye-centered representation of sound location. Because eye position did not affect the percentage of neurons exhibiting multimodal integration, visual and auditory maps appear to remain integrated in the SC even when the eyes are directed eccentrically.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1990

Neuronal activity related to head and eye movements in cat superior colliculus.

1. Movement-related discharges were recorded from single cells in the superior colliculus of alert cats while they made eye saccades (with head fixed) or gaze saccades (with head free). 2. Visual and auditory stimuli were used as saccade targets. In addition, saccades were made to the remembered location of targets and spontaneously, in the absence of targets, during intertrial intervals. 3. When the head was still and the cat performed either spontaneous saccades or saccades to remembered targets, only one class of tectal neurone, the saccade-related burst neurone, inevitably discharged prior to all saccades of appropriate amplitude and direction. 4. Neurones with longer lead times and less intense presaccadic discharges were obligately linked only to visually elicited saccades. The discharge of some of these long-lead neurones was also influenced by the spatial position of the visual target (that is, by craniotopic motor error), while that of the saccade-related burst neurones was a function of retinocentric motor error. 5. Most neurones which discharged before head movements also discharged before eye movements and had large, contralateral movement fields.

Action Potentials↗
PubMed1989

Visual responses of neurones in cat superior colliculus in relation to fixation of targets.

1. Visually elicited discharges were recorded from single cells in the intermediate and deep layers of the superior colliculus of alert, trained cats. With the behavioural protocols used, vigorous and consistent visual responses to the onset and offset of small, stationary targets were encountered in all layers of the colliculus. In addition, the responses of many cells depended on the behavioural context in which the response occurred. Specifically, thirty-nine cells were encountered in which discharge was contingent upon prolonged fixation of the visual stimulus. Thirty of these were located in the intermediate and deep layers and comprised 22% of the 134 isolated cells which were not related to saccadic eye movement. 2. Fixation-related cells showed sustained increases or decreases in firing during fixation of a visual target. Responses to presentation of a visual target at the same retinal location, without active fixation by the animal, were either absent, much weaker, or had extremely variable latencies. 3. Changes in activity were well established by the end of the fixation saccade. The neuronal response was sustained if fixation was sustained. Moreover, the neuronal response began to decrease before the onset of the saccade which broke fixation even though the receptive field location of the target had not yet changed. 4. In these neurones, the discharge rate was not a function of the position of the eye in the orbit. 5. Neurones in which the discharge rate was suppressed during fixation had larger receptive fields than cells in which the discharge rate was enhanced during fixation. There were fewer fixation-suppressed cells (n = 7, 5%) than fixation-activated cells (n = 23, 17%).

Animals↗
PubMed1987

Visual-auditory interactions in cat superior colliculus: their role in the control of gaze.

Superior colliculus cells that respond to a given sensory input (visual or auditory) were influenced by the presence of a stimulus in the other modality. This is a form of sensory-sensory integration which has previously been thought to be involved in initiating the orientation of receptor organs in response to such cues. The present results demonstrate directly that some neurons in cat superior colliculus exhibit premotor discharges which are facilitated when evoked by combinations of visual and auditory stimuli. Other neurons showed sensory interactions which were more difficult to relate directly to orienting behavior; these cells might have a role in mediating attentional functions.

Acoustic Stimulation↗
PubMed1987

Saccade-related burst neurons in cat superior colliculus.

Single-unit activity was studied in the intermediate and deep layers of the superior colliculus in 4 trained cats. One class of neuron was isolated which resembles the saccade-related burst neurons (SRBNs) previously reported in monkey. These neurons produce a discrete burst of impulses preceding the onset of saccades of particular amplitudes and direction. Many of these neurons also paused during saccades in the opposite direction. Similar discharge patterns were seen when saccades were made to remember target locations as well as when a visual target was present. These findings are consistent with the idea that some neurons in the superior colliculus neurons play a role in the coding of voluntary or memory-contingent saccades as well as in the initiation of visually elicited saccades.

Action Potentials↗
PubMed1986

Eye position signals in cat superior colliculus.

Single unit activity was studied in the intermediate and deep layers of the superior colliculus in two trained cats. Eye movements were recorded with a magnetic search coil, the head being fixed. Discharge rates which varied as a function of eye position were consistently observed in 7 of 67 (about 10%) of the sample of eye movement-related units. These units showed similar changes in firing rate as a function of eye position in total darkness and during task related fixation of visual targets and thus appear to convey an "eye position" signal. Their activity may originate either from proprioception or from corollary discharge.

Animals↗
PubMed1984

'Corollary discharge' neurons in cat superior colliculus.

A new type of saccade-related neuron has been encountered in the superior colliculus of the alert cat. These cells discharge with and during, but rarely before, saccades of all directions and amplitudes. Their response properties suggest that they may be conveying a corollary discharge to the superior colliculus, thus providing a signal which allows visual neurons to distinguish real movement from self-induced movement.

Action Potentials↗
PubMed1984

Amblyopia results from chronic blurring of visual images during development.

Atropine was instilled daily into either one or both eyes of developing kittens from the time of eye opening until 3.5 months of age. Visual acuity was assessed after recovery from the acute effects of atropine. Both binocularly and monocularly treated kittens showed a loss of acuity in the treated eye(s), and an improvement in acuity when tested binocularly.

Amblyopia↗
PubMed1984

Blinking and associated eye movements in humans, guinea pigs, and rabbits.

Recordings of upper eyelid movements in humans, guinea pigs, and rabbits demonstrated that all three species displayed qualitatively similar patterns of eyelid movement. The relation between amplitude, duration, and maximum velocity in rabbits and humans was nearly identical. Guinea pig blinks were faster than those of rabbit and man. Electromyographic (EMG) recordings in humans demonstrated that the orbicularis oculis muscle participated in downward movement of the upper eyelid during blinks and eyelid closure but did not participate actively in the downward lid movement occurring with gaze changes. When looking straight ahead, the estimated stiffness and viscosity of the upper eyelid were 10 g/mm and 0.38 g X s X mm-1 for humans and 1.17 g/mm and 0.062 g X s X mm-1 for rabbits. Upward and abducting rotations of the eye accompanied blinks in rabbits and guinea pigs. Simultaneously, the eyeball retracted (translational movement) into the orbit. These translational and rotational eye movements resulted from contraction of the retractor bulbi muscle and cocontraction of antagonistic extraocular muscles. The data suggested that humans also retracted the eye during voluntary blinks. The retraction produced a rotation of the eye toward a "primary position" rather than a rotation in one specific direction. The relationship between the maximum velocity, duration, and amplitude of the down phase of a blink may be expressed as a single equation, maximum velocity = c X average velocity, where c is a constant. The same relationship, with a similar value for c, also describes saccadic eye movements and rapid skeletal movements. This implies that all three movements employ comparable neural mechanisms.

Animals↗
PubMed1984

Saccade-related neurons in cat superior colliculus: pandirectional movement cells with postsaccadic responses.

The superior colliculus is known to contain cells discharging before saccadic eye movements as well as cells responding to sensory stimuli. In this study extracellular single unit recordings were made in the alert trained cat with the head fixed. A novel type of eye movement-related response was found in 9% (32/344) of the cells recorded. These cells differ from previously reported eye movement-related neurons in the timing of their discharge, which accompanies but does not precede saccades. The timing of discharge varies across units from less than 10 ms after the onset of eye movement to as much as 80 ms. Comparable latencies were found regardless of whether saccades were directed contralateral or ipsilateral to the recording site. Most units have an abrupt onset of discharge, but some show a very gradual increase in discharge rate. Most cells (69% or 22/32) discharged with equal vigor for all saccades, regardless of direction. The remainder tended to show higher-frequency bursts when saccades were directed contralaterally, but even these units were not encoding saccade direction by their pattern of discharge. Thus the discharge pattern could be summarized as an omnidirectional burst. For the vast majority of cells (81% or 26/32) the duration of discharge did not correlate with the duration of eye movement. The same pattern of firing was seen with saccades in light and in complete darkness. Thus the saccade-related discharge was not due to changes in visual stimulation during saccades. A minority of the units (15% or 5 of 32) that discharged with but not before saccades also responded to visual stimuli in the absence of eye movements. Saccade-related activity was dependent on alertness of the cat, as measured by behavioral performance and EEG. The close temporal association between saccades and unit discharge disappeared during drowsiness. These units could be reflecting either proprioceptive or corollary discharge signals to the superior colliculus. However, their response properties differ somewhat from those found in previous studies of proprioceptive inputs to the colliculus. Such differences could be due to the effects of the anesthetics that were used in studies of proprioceptive responses. Alternatively, the cells reported here could be conveying a corollary discharge signal. These cells occurred in patches or clusters. This is consistent with a wealth of anatomic data indicating a modular organization of the colliculus.

Animals↗
PubMed1982

Behavioral consequences of early visual exposure to contours of a single orientation.

Kittens were reared with goggles which presented horizontal stripes to both eyes, vertical stripes to both eyes, or horizontal stripes to one eye (HE) and vertical to the other (VE). Acuity was lower than in normally-reared cats, and the axis of best acuity did not correspond to the orientation experienced during rearing. In contrast, there were consistent differences in discrimination between two lines differing in orientation which did reflect visual experience. VE was more accurate in detecting differences in the orientation of near-vertical contours and HE was more accurate in detecting differences of near-horizontal contours.

Aging↗
PubMed1981

A relationship between visual suppression and amblyopia in cats with cyclodeviations of the eyes.

Visual pattern and brightness discriminations were tested in cats which had undergone surgical cyclodeviations of one or both eyes. Half of the pattern discriminations were learned with both eyes open and performance was tested with each eye separately; the other half were learned monocularly with the normal eye (in cats with monocular rotations, MR) or with the less amblyopic eye (in cats with binocular rotations, BR) and then the rotated (or amblyopic) eye was tested alone. No deficits were found in brightness discriminations. With monocularly learned pattern discriminations all but one cat showed positive savings when tested with the rotated eye. However, on binocularly learned discriminations half of the animals performed poorly with the rotated eye and required extensive retraining; they showed negative savings when compared to original learning. These animals seem to be suppressing the strabismic eye during binocular vision. For MR cats, there was a positive relationship between visual acuity and percent savings after binocular learning. The relationship between amblyopia and suppression suggests a common cause.

Amblyopia↗