EFFECTS OF IBOTENIC ACID-INDUCED LOSS OF NEURONS IN THE MEDIAL PREFRONTAL CORTEX OF RATS ON BEHAVIORAL VIGILANCE - EVIDENCE FOR EXECUTIVE DYSFUNCTION

Rats were trained in a previously validated task for the assessment of sustained attention, or vigilance. This task required the animals to discriminate between signals of variable lengths and non-signal events by making an appropriate lever press. The performance of sham-lesione d animals in this task was characterized by a signal-length dependent number of hits. Also, approximately 70 percent of the non-signals were correctly rejected. Ibotenic acid-induced lesions of the medial prefr ontal cortex decreased the relative number of hits and correct rejecti ons and, in essence, resulted in random lever selection. The lesion di d not affect the number of omissions or side bias. Furthermore, the pe rformance of lesioned animals was insensitive to the detrimental effec ts of distracters. The effects of the lesions do not support an interp retation in terms of sustained attention. Rather, the pattern of the l esioned animals' performance is speculated to reveal a fundamental dis ruption of decisional processes, reminiscent of the executive dysfunct ions observed in patients with damage to ventromedial prefrontal areas or with schizophrenia.