Distinct sources and behavioral correlates of macaque motor cortical low and high beta

SUMMARY HIGHLIGHTS The low beta rhythm is dominant in M1 and the high beta rhythm in PMd The beta rhythms correlate with task-instructed and uninstructed behavior Low beta reflects movement preparation and spontaneous postural dynamics High beta reflects temporal task prediction and dynamical visuospatial attention Low and high beta frequency rhythms were observed in the motor cortex, but their respective sources and behavioral correlates remain unknown. We studied local field potentials during pre-cued reaching behavior in macaques. They contained a low beta band (<20Hz) dominant in primary motor cortex and a high beta band (>20Hz) dominant in dorsal premotor cortex. Low beta correlated positively with reaction time from visual cue onset, and negatively with uninstructed hand postural micro-movements throughout the trial. High beta reflected temporal task prediction, with selective modulations before and during cues, which were enhanced in moments of increased focal attention when the gaze was on the work area. This double-dissociation in sources and behavioral correlates of motor cortical low and high beta, with respect to both task-instructed and spontaneous behavior, reconciles the largely disparate roles proposed for the beta rhythm, by suggesting band-specific roles in both movement control and spatio-temporal attention.