Are observed effects of movement simulated during motor imagery performance?

Motor learning relies on adjusting the performance of movements via error detection and correction. How motor learning proceeds via motor imagery, the imagination of movement, is not understood. Motor imagery-based learning is thought to rely on comparing the predicted effect of movement, resulting from the forward model, against its intended effect. Whether motor imagery-based learning uses the observed effect of movement, simulated in motor imagery, to make comparisons to the intended effect to permit error detection and correction, is an open question. To address this, transcranial magnetic stimulation was used to inhibit the left inferior parietal lobe (L_IPL) after each trial of a task requiring participants to reproduce complex trajectories via motor imagery. From past work, we speculated the L_IPL was a candidate for integrating simulated feedback about task performance (simulated observed effects), hypothesizing inhibition of the L_IPL would impair learning, suggesting simulated observed effects of movement are used in motor imagery-based learning. Participants received stimulation to the L_IPL or over the vertex of the head after each trial. Learning was defined as reduced error on a repeated trajectory in comparison to randomly generated trajectories. Regardless of group participants learned, a finding countering our hypothesis, suggesting (a) observed effects of movement are not simulated in motor imagery; (b) the L_IPL is not involved in integrating simulated observed effects of movement; or (c) the timing of the stimulation did not align with the speculated role of the L_IPL. Results encourage further research probing simulated feedback in motor imagery and its neural correlates. (PsycInfo Database Record (c) 2022 APA, all rights reserved).