Serial ablations of the telencephalon and avoidance learning by goldfish (Carassius auratus)

Simultaneous bilateral ablation of the teleost telencephalon was confirmed to dramatically impair the retention, extinction, and "reversal learning" of a preoperatively learned instrumental avoidance response in a shuttle box. The focus of the experiment was on whether two-stage serial unilateral ablations of the teleost telencephalon would ameliorate the effects seen following one-stage bilateral ablation and whether such amelioration would be a function of the fish's experiences between the staged ablations. The degree of retention, relearning, and extinction of the avoidance response was not modulated by the serial ablation procedure whether or not there was interoperation retraining experience. However, reversal learning, in which the previous warning signal became the safety signal and the previous safety signal became the new warning signal, was less impaired following serial ablations than following single-stage bilateral ablation. These results are contrasted with those from experiments with mammalian subjects.