Potentiation of conditioned freezing following dorsomedial prefrontal cortex lesions does not interfere with fear reduction in mice.

In Experiment 1, an auditory conditioned stimulus (CS) was paired with footshock, except when it was preceded by another stimulus (a visual conditioned inhibitor [CI]). After conditioning, all mice displayed less CS-evoked freezing when the CI-CS compound was presented than when the CS was presented alone. However, lesions of the dorsomedial prefrontal cortex (dmPFC) potentiated CS-evoked freezing on each of the 2 sessions (i.e., CI CS and CS alone). In Experiment 2, mice were submitted to fear extinction (CS-alone presentation for 3 days). Lesioned mice exhibited a higher level of freezing behavior than controls on each of the 3 sessions. However, lesioned mice and controls displayed the same rate of reduction of freezing over the 3 days of extinction. These data in mice support previous studies in rats, which suggests that the dmPFC is not critical for either conditioned inhibition or extinction of acquired freezing behavior.