Evidence for a motor gamma-band network governing response interference.

The gamma-band response is thought to represent a key neural signature of information processing in the human brain. These brain signals have been associated with a variety of sensory modalities (vision, sensation, and audition) and also following basic motor responses, yet the functional significance of the motor gamma-band response remains unclear. We used the Multi-Source Interference Task (MSIT) to assess the sensitivity of these cortical motor gamma-band rhythms to stimuli producing response interference. We recorded MEG from adult participants (N=24) during MSIT task performance and compared motor gamma-band activity on Control and Interference trials. Reaction time on MSIT Interference trials was significantly longer (~0.2 s) for all subjects. Response interference produced a significant increase in motor gamma-band activity including ~0.5 s sustained increase in gamma-band activity from contralateral primary motor area directly preceding the response. In addition, activation of increased right Inferior Frontal Gyrus (R-IFG) was observed at gamma-band frequencies ~0.2 s prior to the button press response. Post-hoc analysis of R-IFG gamma-band activity was observed to correlate with reaction time increases to response interference. Our study is the first to record MEG during MSIT task performance. We observed novel activity of the motor gamma-band on interference trials which was sustained prior to the response and in novel locations including contralateral (BA6), and R-IFG. Our results support the idea that R-IFG is specialized structure for response control that also functions at gamma-band frequencies. Together, these data provide evidence for a motor gamma-band network for response selection and maintenance of planned behavior.