Cortical motor areas in plantar response: an event-related functional magnetic resonance imaging study in normal subjects.

The role of the cerebral cortices in normal plantar response was investigated with event-related functional magnetic resonance imaging (fMRI) at 3 Tesla in 12 right-handed normal subjects. During fMRI acquisition, the lateral (LS) and medial (MS) side of the left sole was mechanically stimulated every 16 s to evoke the plantar response under monitoring of the surface electromyogram. LS activated the contralateral supplementary motor area (SMA) more intensively than MS. In contrast, no difference was found in the commonly activated areas including the contralateral primary sensorimotor area, bilateral secondary sensory areas and the thalamus. The results support the hypothesis that the normal plantar response is influenced by the cerebral cortices, and that the SMA likely participates in the regulation of the plantar reflex arc at the spinal level.