[Paradoxical transitory facilitation of performance in the Hebb-Williams labyrinth after lesion of the cingulate...

The effects of lesions of the anterior (Ant) or posterior (Post) regions of the cingulate cortex were tested using the closed-field maze tests of Hebb-Williams. Subjects were male BALB/c mice which had received restricted bilateral electrolytic lesions of the Ant or Post cingulate cortex. Their performances in acquisition or retention were compared to those of sham operated mice at different time intervals after the lesion. In a first series of experiments, naive animals were lesioned. The effects of lesions on acquisition were then tested at different time intervals (up to 45 days) after surgery. In a second series of experiments, the animals were lesioned only after prior complete acquisition of the maze tests and tested in a retention paradigm. The results show a differential effect of Ant versus Post cingulate lesions. Ant lesions had no significant effects whereas Post lesions induced a facilitation of performance at time intervals between 19 and 33 days (acquisition paradigm) or 11 and 25 days (retention paradigm). Conversely a reversal (impairment) of the effect was observed when Post animals were tested 28 days (acquisition) or 48 days (retention) after surgery. Taking into consideration the changing nature of the behavioral paradigm used, we suggest that the paradoxical and transitory facilitatory effects of the Post cingulate lesions may indicate that lesioned mice exhibited a greater degree of adaptability in each new learning situation. However, we can also postulate that these facilitatory effects resulted from a difficulty of lesioned mice in addressing long-term memory stores. This would therefore paradoxically protect them from interference generated by the high degree of familiarity in the behavioural testing apparatus.(ABSTRACT TRUNCATED AT 250 WORDS)