Brain damage and the overlearning reversal effect

Abstract

Rats were either trained to criterion or given 100% overtraining on a tactile discrimination before receiving sham operations or frontal, somatic, or occipital cortex lesions. With preoperative training to criterion, the rats with frontal and somatic cortex lesions showed marked postoperative impairments when tested for reversal learning with the same tactile stimuli previously encountered, whereas animals with occipital cortex ablations did not differ significantly from sham-operated subjects. Preoperative overtraining failed to improve postoperative reversal learning among the sham-operated animals, and it did not attenuate the ablation effects displayed by rats with frontal or somatic cortex lesions. These data show that the overlearning reversal effect (ORE), which has been reported with visual and spatial stimuli, may be more difficult to demonstrate with tactile discriminanda. The findings further suggest that early reports of preoperative overtraining lessening postoperative lesion effects may have less generality than previously recognized.