We next confirmed these findings in recordings of 83 well-isolated single units from the BLA. 18 (21%) of these units exhibited significant phase-locking to the fast gamma oscillation (p < .05, Rayleigh test). One such unit is shown in Figure 5A, exhibiting firing phase-locked to the trough of fast gamma oscillations. Likewise, all fast gamma phase-locked single units were coupled close to the trough of the oscillation (Figure 5B). The firing rates of phase-locked units were directly correlated with simultaneously recorded LFP fast gamma power (Figure 5C), suggesting they are involved in generating these oscillations. A signature of this population was that they tended to fire in doublets with interspike intervals < 40 ms (Pape et al., 1998; Figure S6), consistent with models for achieving synchronous gamma frequency activity (Buzsáki and Wang, 2012).
