The lateral nucleus of the amygdala (LA) is a crucial part of the neural circuit underlying auditory fear conditioning where a tone conditioned stimulus (CS) is paired with a shock unconditioned stimulus (US). The medial prefrontal cortex (mPFC) has also been implicated in fear conditioning, especially in the regulation of amygdala activity. CS-evoked response during fear learning in LA is positively and in mPFC is inversely correlated to freezing behavior. To further investigate the role of LA and mPFC in control of fear behavior, we designed a task where rats received an auditory CS (12KHz tone pips, 80 dB, 20 sec) paired with a weak para-orbital shock US. The CS-US pairing occurs with a 20% probability, and training continues for multiple days to establish a well-learned CS-US association. The rats had free access to Koolaid during the task, and the degree of CS-suppressed licking was the measure of conditioned fear. During the task, single unit activity was recorded in the LA and mPFC via implanted electrodes. CS-evoked responses of single neurons were compared when rats were licking vs. when licking was suppressed by the CS. Preliminary data suggest that neurons in LA and mPFC are correlated with behavior. The CS-evoked response in LA and mPFC is respectively larger and smaller when the rat is suppressing to the tone (thus expressing fear) than when the rat is licking during the tone (not expressing fear). These data suggest that cells in the LA and mPFC encode a representation of the CS-US relationship that depends on the motivational state and behavior of the animal.
Supported by: MH3877; J.C.E is an HHMI Pre-Doctoral Fellow