OVERTRAINING DOES NOT MITIGATE CONTEXTUAL FEAR CONDITIONING DEFICITS PRODUCED BY NEUROTOXIC LESIONS OF THE BASOLATERAL AMYGDALA

The influence of overtraining on the magnitude of fear-conditioning de ficits produced by neurotoxic lesions of the basolateral amygdala (BLA ) was examined. Either 1 d before or 1 week after the administration o f neurotoxic BLA lesions, rats received either 1 or 25 conditioning tr ials consisting of the delivery of unsignaled foot shock in a novel ob servation chamber; freezing served as the measure of conditional fear. In this conditioning paradigm, asymptotic performance is reached in f ive conditioning trials, and 25 conditioning trials constitutes an ove rtraining procedure. The results revealed that overtraining does not a ffect the magnitude of the contextual freezing deficits produced by po st-training BLA lesions. Similarly, overtraining did not influence the level of reacquisition obtained by rats with post-training BLA lesion s after 10 reacquisition trials. A similar pattern of results was obse rved in rats with pretraining BLA lesions. Neurotoxic BLA lesions did not alter either motor activity or shock reactivity, These results ind icate that overtraining does not limit the important role of the BLA i n the acquisition and expression of contextual fear conditioning.