Posterior Cortical Lesions Research Articles

Shift and retention deficits in hippocampectomized and neodecorticate rats

A series of four experiments are reported in which the effect of hippocampal lesions on retention, and the ability to shift responses with changes in reward contingencies was investigated on a spatial discrimination reversal, DRL, and two-choice visual discrimination task. While animals with hippocampal lesions or posterior cortical lesions were deficient in the retention of spatial reversals, the type of error made by each group differed. Contrary to current theories of hippocampal function, animals with hippocampal lesions were not deficient in the abilities required to shift their responses and, in some situations, were actually more flexible than controls. The results are discussed in terms of an inhibition model of hippocampal function. It is suggested that the role of the hippocampus is to inhibit stimulus-response bonds.

Frontal cortex lesions and fixed-interval acquisition in the rat.

This research was designed to study the behavioral effects of frontal cortex lesions upon the performance of rats in a fixed-interval reinforcement situation. Prior to testing, 10 Ss were prepared with posterior frontal cortical lesions in areas 10 and 6. 10 control Ss received sham operations. Following post-operative recovery, the animals were placed on a 23-hr. food deprivation schedule and trained to press a bar for a pellet of food which would be delivered only if 1 min. had elapsed since the previous reward. Analysis of variance showed no significant difference between the 2 groups in the ability to learn the temporal discrimination. However, lesioned Ss yielded a significantly divergent distribution of responses within the interval and a much lower terminal rate of response than the controls.

Unilateral posterior cortical and unilateral collicular lesions and visually guided behavior in the rat.

Unilateral posterior cortical and unilateral collicular lesions and visually guided behavior in the rat.

Potentiation of behavioral arousal after cortical damage and subsequent recovery

The effect of ablating the frontal cortex on the rat's activity-response to amphetamine was tested across a wide range of dosages and following varying postoperative intervals. Removal of the frontal poles (but not posterior cortical lesions) greatly potentiated the normal increases in spontaneous activity caused by amphetamine, and this effect became significantly reduced with longer postoperative intervals. Frontal lesions by themselves did not produce any changes in daily activity. The results are interpreted as supporting the hypothesis that the frontal cortex normally serves to control changes in behavioral arousal, and showing that recovery of this brain function takes place following cortical destruction.

EFFECTS OF POSTERIOR CORTICAL LESIONS ON PERFORMANCE OF A BRIGHTNESS-DISCRIMINATION TASK.

EFFECTS OF POSTERIOR CORTICAL LESIONS ON PERFORMANCE OF A BRIGHTNESS-DISCRIMINATION TASK.