Fast spiking and regular spiking neural correlates of fear conditioning inthe medial prefrontal cortex of the rat

In order to investigate whether and how medial prefrontal cortex (mPFC) of the rat is involved in processing of information related to fear conditioni ng, we recorded from single units in the prelimbic and infralimbic cortex o f fear-conditioned rats in response to an explicit conditional stimulus (CS : an auditory tone) or contextual cues (conditioning box). The majority of units changed their activities significantly in response to the CS in a del ay or trace conditioning paradigm. Both transient and tonic activity change s, including delay cell activity, were observed as in other behavioral task s. When exposed to the context without GS delivery, most units changed thei r activities as well. These results show that both tone and contextual info rmation are processed in the rat mPFC in expectation of the delivery of an aversive stimulus (electric foot shock). Interestingly, fast spiking cells (putative inhibitory interneurons) and regular spiking cells (putative proj ection neurons) showed different patterns of responses. Fast spiking cells tended to show transient responses and increased their firing rates followi ng CS presentation, whereas a complementary pattern was observed in the reg ular spiking cells. Our results enhance our understanding of the neural mec hanisms underlying prediction of an aversive stimulus in the mPFC.