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Biomedical subjects

K H Pribram

Publications and source records attributed to K H Pribram.

At least 37 records · Page 2Linked to original sources
PubMed1980

A decisional analysis of the effects of inferotemporal lesions in the rhesus monkey.

Modified signal detection procedures were used to analyze the effects of inferotemporal cortical resections. The results demonstrated (a) a severe difficulty in responding to differences in luminance; (b) a severe difficulty in responding to differences in luminance; (b) a small but consistent change in sensitivity (d'), which is attributed to an increased sensitivity to noise or a deficiency in the suppression of irrelevant aspects of the environment; and (c) an enhanced bias to respond to a nonrewarded stimulus (a lowering of criterion). This altered bias contrasts with the results obtained from limbic resections in a previous experiment which produced a marked increase in bias to a rewarded contingency without influencing discrimination or detection.

Animals↗
PubMed1979

Role of the inferotemporal cortex in visual selective attention.

Electrocortical recordings were made from monkeys performing in a multidimensional visual task. Wave forms dependent on the stimulus presented (irrespective of task required) were recorded immediately following the stimulus primarily from electrodes implanted in the striate and prestriate cortex. Wave forms dependent on the panel pressed (irrespective of the stimulus or of the task) were recorded especially from motor and post-central cortex, and to a lesser extent in anterior frontal cortex, always just prior to or following the time of the response. Wave forms dependent on the task as determined by the reinforcing contingencies (but independent of the particular stimulus presented or the particular panel pressed) were recorded primarily from the inferior temporal cortex, and rarely from prestriate and anterior frontal cortex. While task-related wave forms began to appear shortly after stimulus presentation, they became especially apparent around the time of the response. This response-linking increased in prominence as the subject achieved 90% proficiency in each task, only to drop off with overtraining. Further, the task-related wave form does not change as rapidly as does overt behavior when the reinforcement contingency is shifted from one stimulus dimension to another. The relevance of these results to an understanding of the process of selective attention is discussed.

Animals↗
PubMed1978

The role of frontal and parietal cortex in cognitive processing: tests of spatial and sequence functions.

Normal monkeys and monkeys with resection of anterior frontal or posterior parietal cortex were trained to press a panel next to a green panel as a test of extrapersonal spatial orientation and to press a panel next to their own prior press as a test of personal spatial orientation. All monkeys also learned two sets of sequence problems in which the solutions were made independent of spatial location by randomly shifting the locations of the stimuli after each response within a trial. The Parietal Group was significantly impaired on the extrapersonal 'next-to' task but not the more difficult personal 'next-to' task. The Frontal Group was impaired on both the personal and the extrapersonal 'next-to' tasks but only when the relevant cues shifted spatial locations from trial to trial. The performance of the Parietal Group completely overlapped that of the Normal Group on the sequence problems regardless of the level of testing sophistication the monkeys had attained. In contrast, the Frontal Group demonstrated a significant impairment in learning sequences but only when the monkeys were naive. Once they became sophisticated they learned each sequence at a normal rate. Their poor performance was attributed to the lack of stability in the spatial location of the stimuli. The data support the view that a distinction between personal and extrapersonal spatial orientation is relevant to posterior parietal function but indicate that neither sequencing per se nor personal spatial orientation or spatial memory per se is dependent on intact frontal functioning. Rather, the frontal cortex is involved with a higher-order control essential to allow the monkey to perceive the reliable aspects of stimuli contained in a stimulus context full of unreliable noise and to further allow for flexible response pattern appropriate to the demands of a variable context.

Animals↗
PubMed1977

Size constancy in rhesus monkeys: effects of pulvinar, prestriate, and inferotemporal lesions.

The present study tested the theory that inferotemporal cortex integrates 1) distance information transmitted via superior colliculus-pulvinar afferents, with 2) form information transmitted via striate-prestriate cortex afferents (Gross, 1973a, 1973b). Monkeys were trained to choose the larger of two objects, independent of distance, to obtain a reward. Based on the integration theory, the following predictions concerning this size constancy discrimination were made: 1) monkeys with pulvinar lesions, unable to code distance, should be impaired and adopt strategies based on retinal image size; and 2) monkeys with prestriate lesions, unable to code retinal image size, should be impaired and adopt strategies based on distance. Contrary to these predictions, pulvinar lesions produced no deficit; and although prestriate lesions did produce an impairment, it was due to a failure to code distance in assessing the true size of the object. Thus, monkeys with prestriate lesions consistently responded to retinal image size instead of object size. Replicating an earlier report (Humphrey and Weiskrantz, 1969), inferotemporal lesions also produced an impairment; however, errors made by monkeys with inferotemporal lesions were random and could not be attributed to any consistent strategy. All monkeys reacquired the discrimmination postoperatively, indicating that there are multiple mechanisms available to the brain-damaged animal for the perception of size constancy.

Animals↗