hippocampus during exploratory behaviors (Bragin et al., 1995). Subsequent studies further elaborate the role of hippocampal theta-gamma PAC in learning and memory (Axmacher et al., 2010; Canolty et al., 2006; Lega et al., 2016; Wulff et al., 2009). PAC is not limited to hippocampus but involves several cortical regions. Cortical PAC has been found between cortical layer-specific neural networks oscillating at different frequencies, with gamma activity from cortical layers 4/5 being modulated by phase of alpha rhythms generated in layers 2/3 (Spaak et al., 2012).
