Regulation of motor representation by phase-amplitude coupling in the sensorimotor cortex

Abstract

High-γamplitude (80-150 Hz) represents motor information, such as movement types, on the sensorimotor cortex. In several cortical areas, high-γamplitudes are coupled with low-frequency phases, e.g., α; and Θ(phase-amplitude coupling,PAC).However,suchcoupling has notbeenstudied in the sensorimotor cortex; thus, its potential functional role has yet to be explored. We investigated PAC of high -γamplitude in the sensorimotor cortex during waiting for and the execution of movements using electrocorticographic (ECoG) recordings in humans. ECoG signals were recorded from the sensorimotor cortices of 4 epilepsy patients while they performed three different hand movements. A subset of electrodes showed high-γactivity selective to movement type around the timing of motor execution, while the same electrodes showed nonselective high-γactivity during the waiting period (>2sbeforeexecution).Crossfrequencycouplinganalysisrevealedthatthehigh-γamplitude during waiting was strongly coupled with the α phase (10 -14 Hz) at the electrodes with movement-selective high-γamplitudes during execution. This coupling constituted the high-γamplitude peaking around the trough of the α oscillation, and its strength and phase were not predictive of movement type. As the coupling attenuated toward the timing of motor execution, the high-γamplitude appeared to be released from the α phase to build a motor representation with phase-independent activity. Our results suggest that PAC modulates motor representation in the sensorimotor cortex by holding and releasing high-γactivity in movement-selective cortical regions. ©2012 the authors.