The effects of anteromedial cortex lesions on pattern discrimination learning in rat.

The visual angular difference threshold of rats with unilateral anteromedial cortex lesions was measured. The stereotyped running pattern and preoperatively preferred side of approach in a two-choice visual discrimination apparatus was recorded for each animal. Lesions in the hemisphere ipsilateral to the preferred approach side did not affect either the running pattern or the angular difference threshold. However, there was a general reduction in the detection of the positive stimulus throughout the scale. Lesions in the contralateral hemisphere produced a transient reversal of the side preference with an overall loss of S + detection in the field contralateral to the side approached.