Relationships between bilateral tapping skills and brain gray matter volumes: a voxel-based morphometry study

Brain activity associated with bilateral hand movements has been reported to involve multiple regions. However, the association between gray matter (GM) volume in these regions and bilateral hand movement remains unclear. Therefore, this study aimed to elucidate the association between tapping skills using both hands and GM volume. This study included 61 healthy adults. Each participant's Magnetic Resonance Imaging scans and bilateral motor task performance were evaluated. The motor task was a finger-tapping task, and the movement conditions were set as in-phase and antiphase. The participants were instructed to open and close their thumb and index finger as quickly and widely as possible, either simultaneously (in-phase condition) or alternately (antiphase condition) on both sides. Using voxel-based morphometry, we measured brain GM volume associated with the performance in the bilateral finger-tapping task. The results indicated a significant negative correlation between the similarity index of bilateral movement under the antiphase condition and GM volume around the left cingulate motor cortex. This result suggests that participants who were able to smoothly move both hands under the antiphase condition had greater GM volume in the left cingulate motor cortex. This GM volume may serve as a neurophysiological indicator of bilateral hand movement.