Abstract
Humans rapidly adjust their movements in response to disturbances, a process thought to involve a feedback controller tuned to task goals and constraints. Supporting this, numerous studies have shown that electromyographic (EMG) responses to mechanical perturbations are modulated by task constraints as early as 60ms post-perturbation. It is assumed that selection of a feedback controller occurs during motor planning. In electroencephalography (EEG), motor planning is commonly associated with beta (13–30Hz) event-related desynchronization (ERD). For instance, stronger ERD is observed for movements involving more elaborate planning. However, the EEG markers of feedback controller selection during motor planning remain unknown, leaving a gap in our understanding of how feedback gains are tuned. To investigate this, we recorded EEG and EMG from 28 healthy adults as they performed a delayed reaching task toward either a wide (80cm) or narrow (2cm) target. On a subset of trials, ±12N mechanical perturbations were applied to assess feedback responses. We hypothesized that the narrow target condition would be associated with greater EMG responses and stronger beta ERD during planning. As expected, the narrow target led to significantly larger long-latency EMG responses, in the pectoralis for the +12N perturbation (p<0.001), and posterior deltoid for the −12N perturbation (p=0.002). Most importantly, the narrow target was also associated with significantly greater beta ERD over bilateral parieto-frontal regions during planning (p=0.002). These findings replicate known effects of task constraints on feedback responses and provide new evidence linking enhanced beta ERD during planning to the upregulation of feedback gains.
