Impaired reversal learning in the Dlg2+/- rat model of genetic risk for psychiatric disorder: Important questions regarding the neuro-behavioral mechanisms of reversal learning.

In this issue, Griesius et al report that heterozygous Dlg2+/- rats showed a reversal learning impairment on a specific bowl-digging task, whereas other reversal tasks were unaffected. The study suggests that Dlg2 gene disruption, which has been linked to neuropsychiatric disorders, including schizophrenia, may cause relatively specific impairments in reversal learning, an important aspect of cognitive flexibility. The study draws attention to two important issues regarding the neuro-behavioral mechanisms of reversal learning, namely that hippocampal dysfunction, which is prominent in Dlg2+/- rats, may contribute to reversal learning impairments and that, depending on the task and previous experience, brain and behavioral mechanisms of reversal learning may differ.