Figure 3.

Amid power asymmetry, partial spike-LFP coherence reveals selective cross-cortical interactions. A, A neural simulation (I-F neurons) of a brain-wide common driver, driving PRR LFPs at greater amplitude than PMd LFPs, generates significant Granger causality, even if all signals are completely synchronous and at the same phase (Δ = difference between GC in either direction, GC(LFP_PRR,LFP_PMd) − GC(LFP_PMd,LFP_PRR)). Therefore, Granger causality does not distinguish an asymmetric common drive from a case in which PRR's spikes have a selective interaction directly with PMd (right column); displayed here as an interaction shared between a subset of PRR cells and PMd, with an antisynchronous phase; * indicates significant Granger causality, p value arbitrarily small as number of simulations increase. B, The same is true for simple spike-LFP coherence (* indicates significant simple spike-LFP coherence). However, partial spike-LFP coherence (C) between PRR spikes and PMd, with respect to PRR LFPs, can indicate whether PRR spikes interact with PMd selectively and independently of the common drive (* indicates significant partial spike-LFP coherence).