Active avoidance is permanently abolished after lesions of the nucleus interpeduncularis in rat

Active avoidance learning, retention and relearning were investigated before and after lesions of the interpeduncular nucleus (IP) of rat in a Y-maze and a jump test box. Preoperatively learnt active avoidance was abolished after the lesions and rats were not able to relearn it. Unconditioned escape responses remained unchanged in the Y-maze. Postoperative avoidance learning was impossible. Brightness discrimination in a goal alternation paradigm was learned or relearned, respectively, after IP lesions. The IP rats were hypoactive and showed diminished exploratory activity but had unchanged escape speed. The IP is evidently enclosed in a network controlling avoidance behaviour.