Deciding between conflicting motivations: what mice make of their prefrontal cortex.

We investigated the contribution of the mouse prefrontal cortex and, more specifically, the prelimbic area, to a learning task that highlights a choice between two conflicting motivations, the one for food seeking and the one for novelty exploration. We used a learning paradigm in a cross maze task that targets first motivation conflict and second flexible rule adaptation following environmental changes. We show that mice with prelimbic lesions, which showed normal spatial learning, exhibit impairment in switching from one type of reward - food retrieval - to another type - novelty exploration - and sustained difficulties in adapting their behaviour when the rule is changing repeatedly. Mice, like other mammals, possess a prefrontal cortex that participates in the control of the flexible switch between concurrent natural motivations and in the rapid and flexible adaptation to external changes. These results open a way to study in mice models motivation conflict and cognitive adaptation, brain functions known to be compromised in several psychiatric conditions in humans in which the prefrontal cortex functioning is altered.