Reversal Learning Impairments in the Maternal Immune Activation Rat Model of Schizophrenia

One of the cognitive symptoms observed in schizophrenia is decreased flexibility in several tasks, including reversal learning. Reversal learning has previously been tested in rats following maternal immune activation (MIA), a risk factor for schizophrenia, with varying results. Whereas some previous studies have shown that MIA rats are slower to learn a reversal, others have reported more rapid learning compared with controls. Several of these latter studies have, however, used a T-maze task with aversive, negative reinforcement as a motivating factor. Because most human studies use positive reinforcement in reversal tasks, here we tested whether reinforcement valence might be a critical factor. We ran male MIA and control rats in a T-maze reversal procedure that was very similar to previous studies except that positive, appetitive reinforcement was used for motivation. The results showed that MIA animals performed similarly to controls during training, but in contrast to the previous, aversively motivated T-maze studies, slower reversal learning was observed. These results show that MIA animals are impaired in reversal learning under conditions of positive reinforcement, consistent with the effects observed in individuals with schizophrenia.