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Biomedical subjects

C M Butter

Publications and source records attributed to C M Butter.

At least 37 records · Page 2Linked to original sources
PubMed1984

Effects of kainic acid and radiofrequency lesions of the pulvinar on visual discrimination in the monkey.

Monkeys with thermocoagulation or kainic acid lesions of the pulvinar and unoperated control monkeys were tested in two tasks: pattern discrimination retention and color discrimination learning in which the stimuli were located at the response sites or were separated spatially from them (S-R separation). The monkeys with kainic acid pulvinar lesions were mildly impaired in retention of the pattern discrimination, but were unimpaired in the color discrimination tasks with or without the S-R separation. The monkeys with thermocoagulation lesions, like monkeys with superior colliculus lesions in a prior study, were severely impaired in performing one of the color discrimination tasks with S-R separation. These findings suggest that: (a) the inferior pulvinar, unlike the superior colliculus, does not contribute to the performance of discriminations involving S-R separation; and (b) corticotectal projections traversing the pulvinar and destroyed by the thermocoagulation lesions are crucial to the performance of discriminations involving S-R separation. The results of an earlier experiment also suggested that interruption of corticotectal fibers passing through the pulvinar impairs performance in another task sensitive to superior colliculus lesions--spatial localization of light flashes. Thus, corticotectal projections may be crucial for the contribution of the colliculus to performance in a variety of visual tasks.

Animals↗
PubMed1984

Effects of damage to superior colliculi and pre-tectum on movement discrimination in rhesus monkeys.

Eight rhesus monkeys (Macaca mulatta) were trained to detect an instantaneous lateral displacement of a small spot of light. The smallest movement for 79% correct performance was then determined. Severing the splenium of the corpus callosum, which has to be done to reveal the superior colliculi, had no effect on the movement threshold. But when the superior colliculi were damaged in addition, there was an initial substantial impairment in the detection of movement and a smaller but permanent elevation in the threshold. Only if the rostral superior colliculi and pretectum were spared, was there no change in threshold, and there was evidence that the pretectal rather than collicular damage may be more important in relation to movement discrimination. Tests with human observers performing the same task showed that the threshold can be elevated by imprecise fixation and accomodation, suggesting that the consequences of mid-brain damage on movement detection may be wholly or in large part attributed to oculomotor disorders.

Accommodation, Ocular↗
PubMed1984

Monocular pattern discrimination performance in rabbits with unilateral interruption of the middle cerebral artery.

Rabbits were tested binocularly and with each eye separately, in pattern discriminations sensitive to the removal of the visual cortex opposite the exposed eye before and after the middle cerebral artery was unilaterally coagulated. Following surgery, the rabbits were not impaired in performing the discriminations with either eye; nor were any pathological changes found in the hemisphere in which surgery was performed. These findings imply that deficits in performing tasks dependent on the integrity of the visual cortical areas in rabbits may require interruption of the posterior and middle cerebral arteries, both of which supply the visual cortical areas.

Animals↗
PubMed1984

Effects of inferior temporal lesions on visual discrimination performance in monkeys with complete and incomplete striate cortex ablations.

In order to determine whether inferior temporal cortex participates in the relearning of visual discriminations following striatectomy, monkeys were retrained to perform two preoperatively acquired discriminations (brightness-flux and brightness-area) after receiving bilateral striate cortex lesions and then retested in the same tasks after bilateral inferior temporal surgery. After inferior temporal surgery, the monkeys with histologically verified total ablation of striate cortex showed little or no impairment in relearning the discriminations, whereas the monkeys with remnants of intact striate cortex were severely impaired. These findings suggest that inferior temporal cortex is, at most, of minor importance in relearning brightness-flux and brightness-area discriminations in the absence of striate cortex. This interpretation is consistent with the view that the contribution of inferior temporal cortex to visual discrimination performance depends on input from striate cortex.

Animals↗
PubMed1982

Localization and detection of visual stimuli in monkeys with pulvinar lesions.

Since the pulvinar receives a major ascending projection of the superior colliculus, pulvinar lesions might produce behavioral impairments resembling those that follow colliculus lesions. To test this possibility, we examined the effect of pulvinar lesions in monkeys on the localization and detection of brief light flashes, a task in which monkeys with colliculus lesions are severely impaired. Some of the pulvinar-lesioned monkeys showed localization impairments similar to those in monkeys with colliculus lesions. However, histological analyses of the lesions suggested that these deficits were related not to the pulvinar damage per se, but rather to interruption of corticotectal fibers that pass through the pulvinar. We conclude that the pulvinar is not critical for the ability to locate and detect brief visual stimuli.

Animals↗
PubMed1982

The role of frontal cortex-reticular interactions in performance and extinction of the classically conditioned nictitating membrane response in the rabbit.

In order to investigate the behavioral role of interactions between frontal cortex and reticular nuclei, we examined the effects of single and combined lesions of these structures on the classically conditioned nictitating membrane response (NMR) of rabbits. Lesions of frontal cortex decreased latencies of the conditioned NMRs in reacquisition and retarded extinction of the conditioned response. Lesions of nucleus reticularis pontis oralis (NRPO) produced similar effects. In contrast, lesions of nucleus reticularis tegmenti (NRT) increased NMR latencies during reacquisition. The opposite effects of frontal cortex and NRT lesions were abolished when the two lesions were combined, indicating that the two lesion effects summed. In contrast, the deficits due to frontal and NRPO lesions did not sum; combined frontal-NRPO lesions produced deficits very similar in magnitude and time course to those of the NRPO lesions alone. These findings suggest that frontal cortex may exert its inhibitory effects on behavior not by directly interacting with NRT, but by facilitating NRPO, which in turn may inhibit the nucleus of the VIth nerve, the final common pathway to the NMR. NRT may facilitate the motor pathway by modulating the inhibitory effect of NRPO on the VIth nerve nucleus.

Animals↗
PubMed1982

Further analysis S-R separation effects on visual discrimination performance of normal rhesus monkeys and monkeys with superior colliculus lesions.

Rhesus monkeys discriminated between two color-differentiated stimuli presented on a screen only when they fixated the center of the screen. The stimuli were presented 8 degrees, 20 degrees, or 32 degrees from the screen's center, for 2 sec or 100 msec, a duration too brief to permit their fixation. Performance declined when the response sites, located either centrally (8 degrees eccentricity) or peripherally (32 degrees eccentricity), were separated from the stimuli, whether they were presented for 2 sec or 100 msec. These findings suggest that the stimulus-response separation effect is due to selective attention to the response sites and not to fixating them during stimulus presentation. Following superior colliculus lesions, the monkeys were impaired in discriminating between peripheral stimuli, but only when they responded centrally. This deficit was not due to (a) a failure to fixate the stimuli, for it occurred when the stimuli were 100 msec or 2 sec or (b) reduced sensory capacities, for it disappeared when the subjects responded peripherally. This deficit may reflect deficient attentional shifts from the response sites to the stimuli.

Animals↗
PubMed1980

Impairments in visual discrimination performance and gaze shifts in monkeys with superior colliculus lesions.

Eye movements of monkeys were recorded while they performed a visual discrimination task before and after superior colliculus (SC) lesions or control surgery. The monkeys with SC lesions were impaired in orienting their eyes toward the visual stimuli when they were presented eccentrically 15 degrees to 32 degrees from the center of the display screen, toward which their heads were directed. This impairment in shifting the gaze to eccentric stimuli may account for the concomitant deficit in discriminating between these eccentric stimuli. The eye movement deficit appears to depend on destruction of the deep as well as more superficial layers of the SC and may reflect a disturbance in visual-oculomotor coordination.

Animals↗
PubMed1979

Contrasting effects of lateral striate and superior colliculus lesions on visual discrimination performance in rhesus monkeys.

Rhesus monkeys with lesions of lateral striate cortex, monkeys with superior colliculus lesions, and unoperated monkeys were tested for retention of a preoperatively acquired pattern discrimination. The three groups of monkeys were then tested in two-choice, color, color discrimination tests, one involving varying degrees of stimulus-response (S-R) separation and the other, administered several months later, involving various directions of S-R separations. The monkeys were also tested in a series of two-choice pattern discriminations, following each of which they were tested for relearning when the patterns were masked with bars or circles. The monkeys with lateral striate lesions were moderately retarded in retention of the pattern discrimination, whereas those with superior colliculus lesions were not. The monkeys with colliculus lesions, but not those with lateral striate lesions, were impaired in both S-R separation tests, which demonstrates that their deficit was not transient or solely due to a difficulty in shifting the gaze in one direction. The lateral striate monkeys, unlike those with colliculus lesions, were dificient in relearning discriminations between masked patterns. These findings suggest that superior colliculus and striate cortex may be involved in two different aspects of attention: respectively, shifting attention (and orientation) from one spatial locus to another and maintaining attention on fixated stimuli. Alternative interpretations of the effects of the lesions, based on their retinotopic loci, are discussed.

Animals↗
PubMed1978

Localization and detection of visual stimuli following superior colliculus lesions in rhesus monkeys.

Rhesus monkeys were trained to fixate a central stimulus and to detect and localize a 50 msec light flash presented 6-80 degrees on either side of the central stimulus. Following large lesions of the superior colliculus, they showed persistent deficits in localizing flashes presented 43-80 degrees from the fixation stimulus. However, they were not consistently impaired when the flashes were presented more centrally, and their performance with peripheral stimuli improved when the stimulus duration was 1 sec. Thus, the superior colliculus appears to be necessary for the localization of brief visual stimuli in the far periphery.

Animals↗
PubMed1972

Alterations in aversive and aggressive behaviors following orbital frontal lesions in rhesus monkeys.

We utilized the methods of comparative psychology and of ethology to assess the effects of frontal lesions on species-specific aversive and aggressive behaviors in rhesus monkeys. Removal of orbital frontal (OF) cortex enhanced aversive reactions and reduced aggressive reactions in several threatening situations, including a social colony. The deficit in aggresion was not due to enhanced aversion or to locomotor hyperactivity. Nor did the OF monkeys lose the capacity to execute aggressive reactions. Rather, their degree of deficit seemed to vary with the degree of threat in the test situation. Moreover, these emotional alterations are produced by lesions restricted to the posteromedial portion of OF cortex, which is closely associated with limbic structures, as well as by lesions of the dorsomedial nucleus, with which this portion of OF cortex is interconnected. While lesioning either of these structures reduced aggression and enhanced aversion, amygdalectomy reduced both aggression and aversion. The view that monkeys with OF lesions are overaroused by threatening situations was not supported by analysis of autonomic responses following OF lesions. The emotional alterations produced by OF lesions may be due to the disturbance of stress mechanisms which prepare the organism for reacting appropriately to highly threatening situations.

Aggression↗