The initiation and expression of fear states involve synchronized activity in the basolateral amygdala (BLA), medial prefrontal cortex (mPFC), and hippocampus (HPC). Synchronous theta frequency (4-12 Hz) oscillations recorded in the local field potentials (LFPs) of these brain regions reflect synchronized neural firing, believed to facilitate communication between regions in response to aversive stimuli (Adhikari et al., 2010b; Lesting et al., 2011; Paz et al., 2008; Popa et al., 2010; Seidenbecher et al., 2003). Further, dynamic shifts in BLA-mPFC-HPC theta synchrony have functional relevance to successful consolidation of conditioned fear during paradoxical sleep (Popa et al., 2010), extinction of conditioned fear (Lesting et al., 2013), and discrimination between aversive and safe cues (Likhtik et al., 2014). Thus, synchronous activity in this circuit is highly relevant to the signaling of both fear and safety.
