R. A. Patton

Eye and hand preference in rhesus monkeys (Macaca mulatta)

The extent of eye and hand preference and their correlation was tested, first in 19 naive, immature Ss and then in seven experienced adolescent-to mature animals. There was no significant correlation between the two functions in either group. Hand preference, but not eye preference, was significantly greater in the older than in the younger monkeys.

Scopolamine effects on conditioned suppression: Influence of diurnal cycle and transitions between normal and drugged states

SummaryRats were exposed to either a drug-induced state (1.0 mg/kg scopolamine) or an undrugged state (saline) at each stage of a three-stage procedure. They were first trained to lick a tube, then were exposed to classical fear conditioning in the absence of the tube, and finally were tested for conditioned suppression of licking. Animals tested at the midst of the dark period of the daily light/dark cycle displayed a failure of conditioned suppression if conditioning had occurred under the novel state; suppression was less consistently impaired in animals tested at the midst of the photoperiod. All animals exposed to a consistent drugged (or undrugged) state displayed conditioned suppression. Results suggest that experimental procedures frequently employed in studying drug manipulations of learning and memory may be biased against the transfer of training to the test situation. Scopolamine effects, often attributed to changes in learning or memory, may often represent a weakening in stimulus control of behavior resulting from transitions between drugged and undrugged states. Several factors are suggested as contributing to the diurnal difference in drug effects.

Diurnal variation in performance of free-operant avoidance behavior of rats.

Possible daily periodicity in experiments involving conditioned behaviors has not usually been investigated or controlled. The present experiment argues for such studies in that variation in the performance of a free-operant avoidance task by 30 rats was detected as a function of when during the 24-hr. day behavioral testing occurred. In terms of shocks avoided, performance was best in the middle of the dark phase of the day and worst late in the light phase. The absence of a similar rhythm in the operant response rate suggests the 24-hr. periodic change in efficacy of avoidance was not related to diurnal variation in general activity levels. Implications of daily periodicity are discussed in terms of experimental procedures and controls.

Scopolamine effects on a one-trial test of fear conditioning

Conditioned suppression was demonstrated in rats trained under nondrug conditions and tested under either drug or nondrug conditions. When training occurred under drug conditions, suppression occurred only when testing was also under the drug. Results are interpreted in terms of dissociation between drug and nondrug states rather than as effects on mechanisms of learning and memory.

Hand and eye preference in unilaterally brain ablated monkeys.

Abstract Monkeys were observed for hand and eye preferences before and after having different amounts of unilateral brain ablation. Hemicerebrectomized monkeys were limited to using the hand ipsilateral to the ablation and consistently preferred the ipsilateral eye although each eye contributed to the remaining visual field. Animals with a similar visual field defect, as a result of occipital lobectomy, also preferred the ipsilateral hand and eye. Measurements taken 23–29 months later indicated a tendency for eye preference in the occipital group to return to preoperative levels, whereas eye preference decreased only sightly, if at all, for hemicerebrectomized animals. Results for normal monkeys and those with prestriate decortication showed no specific pattern of change from measurement to measurement. The results were discussed with regard to (a) locating or identifying modes of visual processing, (b) the directness of intrahemispheric connections as compared to interhemispheric pathways, and (c) related human data. The possibility of functional differences between the nasal and temporal retina in relationships with ipsilateral and contralateral motor control of the hand was suggested by these data.

Delayed alternation in hemicerebrectomized monkeys.

Monkeys subjected to extensive unilateral brain extirpation learned a delayed alternation task, although their rates of learning were significantly lower than those of a control group of normal animals. Visual field defects did not seem to account for the deficit.

Visual discrimination in hemicerebrectomized monkeys

Abstract Monkeys having different amounts of unilateral brain ablation were studied on 20 discrimination tasks involving visual-spatial stimuli. Retests and reversals of some tasks were included among the total series of tasks. Brain damaged animals were poorer than normal subjects on only five comparisons among the 60 that were possible. The group of primary interest, the hemicerebrectomized monkeys, were significantly poorer than normal animals on only a thickness discrimination, and a reversal of the thickness discrimination which followed a retest on it. The results of all groups are discussed in relation to other observations made during these experiments. The role of homonymous hemianopia is suggested to be of special importance to the results. Lastly, a comparison is made of these findings with those of similar experiments by others.

Eye preference in hemicerebrectomized monkeys

Following the surgical removal of either a left or a right cerebral hemisphere, eight monkeys were tested for eye preference. Although both eyes project fibers to the remaining hemisphere, each S showed a preference for use of the eye homolateral to the ablation.

Position response preference following unilateral brain ablation in monkeys

Monkeys with surgical removal of the right hemisphere showed an ipsilateral position response preference greater than normal animals or animals with partial, right, prestriate-temporal decortications. While other factors may contribute to this bias, a visual field defect of homonymous hemianopsia appears to be primarily related to the performance reported.

Amino-oxyacetic acid: Effects on multiple fixed ratio-fixed interval performance in the rat

Disruptions in multiple FI-FR operant performance as a function of administration of amino-oxyacetic acid, a drug which increases brain levels of gamma-aminobutryic acid, were studied. The drug caused profound disruptions in response rate and temporal patterning, but these effects were not temporally correlated with the time-course of neurochemical effects reported by other investigators.