Investigating the effect of manipulating effector load on corticospinal excitability during motor imagery

Abstract

Motor imagery drives motor skill improvement and acquisition, however recent research suggests the theories proposed to explain how this occurs may not fully account for the patterns of brain activation observed during imagery. This study probed the validity of imagery theories by comparing how corticospinal excitability scales during imagined and overtly executed performance of a grip task at varying forces. Participants completed 160 trials at 10-80% of their maximum voluntary contraction. Half the trials were performed via imagery, half via overt execution. Participants were pseudorandomized into high and low fidelity groups. A single pulse of TMS measured corticospinal excitability in each trial. Results showed that while corticospinal excitability increased across forces in imagery and overt execution, the trend was significantly different between modalities. There was no effect of image fidelity on corticospinal excitability. Results indicate that none of the current theories can fully explain the mechanisms involved in motor imagery.