Cross-frequency coupling during auditory perception in human cortex.

Cross-frequency coupling plays an important role in coordinating neuronal computations underlying human perception, learning and memory. Here we compared four methods for measuring phase/amplitude coupling (PAC) of theta (4-7 Hz) and high-gamma (70-150 Hz) in intracranial electrocorticographic (ECoG) recordings. Time-frequency spectral and time-domain evoked responses were derived for comparison. All four methods showed significant increases in theta/high-gamma PAC in auditory cortex at sites where significant event-related increases in high-gamma power were also observed. Similarly, all PAC methods revealed stimulus effects (type, probability). However, the patterns of PAC increases differed across methods. Results suggest that PAC measures may be differentially sensitive to the underlying neural activity, including high-gamma amplitude, phase locking, and response timing.