The claustrum is a brain structure that is identified in most mammalian species but little experimental evidence supports its hypothetical functions, resulting from the difficulty to specifically manipulate claustral activities without affecting surrounding brain areas. The first study thus aimed to relate better the physiology of the network of claustral neurons to behavior, and investigate its functional role. We characterized a group of claustral neurons during several behaviors by microendoscope. Given the importance of the contribution of the claustrum to the cognitive task requiring attentional set shifting, the second study aimed to assess the ability of attentional set shifting in heterozygous Nr4a2 deletion mice which a genetic mouse model of schizophrenia, and to investigate the involvement of the claustrum in the pathology. Our findings propose that the claustrum-medial prefrontal cortex network controls attentional set shifting and suggest the potential role of the network in attention dysfunctions observed in schizophrenia.