Supplementary motor area contributes to carrying previous movement information over to current movement.

ABSTRACT

The purpose of the present study was to determine the cortical areas contributing to the influence of the previous movement on the current movement. Right-handed healthy human participants abducted and then adducted the left index finger in response to a start cue. Twenty consecutive trials with 10 s intertrial intervals were performed in each trial block. An odd-numbered trial was considered to be the previous trial, and a trial immediately after the previous trial (even-numbered trial) was the current trial. In each trial block, transcranial magnetic stimulation (TMS) was given over one of the seven TMS sites with the start cue in the previous trial. The TMS site was over the supplementary motor area (SMA), right dorsolateral prefrontal cortex, right dorsal premotor cortex, right or left posterior parietal cortex or right primary sensory cortex. Sham TMS, producing magnetic stimulation with the coil tilting 90 degrees off the scalp, was delivered over the Cz. In the current trial, TMS was not delivered. The correlation coefficient of the reaction time between the previous and current trials was positive and significant in the sham TMS trial block. This indicates that the current movement is partially dependent on the previous movement. The correlation coefficient of the reaction time between the previous and current movements in the SMA trial block was significantly different from that in the sham TMS trial block, indicating that the SMA contributes to the influence of the previous movement on the current movement. The SMA contributes to carrying the responsiveness level in the previous movement over to the current movement.