The relationship between the implicit visuomotor control and the motor planning accuracy

It has been well established that an implicit motor response can be elicited by a target perturbation or a visual background motion during a reaching movement. Computational studies have suggested that the mechanism of this response is based on the error signal between the efference copy and the actual sensory feedback. If the implicit motor response is based on the efference copy, the motor command accuracy would affect the amount of the modulation of the motor response. Therefore, the purpose of the current study was to investigate the relationship between the implicit motor response and the motor planning accuracy. We used a memory-guided reaching task and a manual following response (MFR) which is induced by visual grating motion. Participants performed reaching movements toward a memorized-target location with a beep cue which was presented 0 or 3 s after the target disappeared (0-s delay and 3-s delay conditions). Leftward or rightward visual grating motion was applied 400 ms after the cue. In addition, an event-related potential (ERP) was recorded during the reaching task, which reflects the motor command accuracy. Our results showed that the N170 ERP amplitude in the parietal electrodes and the MFR amplitude were significantly larger for the 3-s delay condition than the 0-s delay condition. These results suggest that the motor planning accuracy affects the amount of the implicit visuomotor response. Furthermore, there was a significant within-subjects correlation between the MFR and the N170 amplitude, which could corroborate the relationship between the implicit motor response and the motor planning accuracy.