The role of the left hemisphere in motor control of touch: a functional magnetic resonance imaging analysis

Previous research using a simple finger-touching task has shown greater blood oxygenation level dependent (BOLD) activation volume in the motor cortex of the right hemisphere for contralateral finger touching compared to ipsilateral finger touching, but no significant contralateral advantage for the left hemisphere. Such equal involvement of the left hemisphere for both contralateral and ipsilateral finger touching suggests a special role of the left hemisphere for finger touching. In contrast, we found a contralateral advantage in the motor cortex of both hemispheres in a majority of participants (14/16) when consistently activated BOLD volumes were examined. However, participants who did not show a clear contralateral advantage for the left hemisphere did show activation in the left inferior frontal gyrus (IFG; Broca's Area) and in the left insular cortex, which suggests that verbally mediated sequencing of finger movements can account for our less frequent result.