To examine gamma frequency activity elicited during fear, mice with chronically implanted stereotrodes in the BLA (Figure S1A-B) as well as microelectrodes in the mPFC, vHPC, and dHPC, were conditioned in a discriminative fear paradigm, as described previously (Likhtik et al., 2014). The mice were exposed to two different auditory stimuli (each presented as one 50 ms pip per second for 30 seconds). One stimulus (CS+) was paired with a mild (0.4 mA) foot shock, while the other (CS−) was explicitly unpaired. On three consecutive training days, animals were presented with five CS+ and five CS− stimuli daily, in a pseudo-random order. On day four, the same stimuli were presented in a new environment without the accompanying shocks, while neural activity was recorded (Figure 1A). Freezing behavior to the CS+ was only weakly attenuated during this fear recall session, with a decrease in mean freezing of 6.4 +/− 4.5% from trial 1 to trial 5 (Figure S1C; F30,1 = 3.74, p = .0554, repeated measures ANOVA); for this reason, data from all five CS+ trials were collectively analyzed.
