Figure 2.

Grand average responses to digit stimulation. Stimulation of median and ulnar nerve-innervated digits evoked bilateral brain response with a characteristic temporal pattern. Responses are shown here on the average inflated surface (dark grey are sulci and light grey are gyri). (A) In healthy controls (HV), response first peaked in contralateral S1 cortex ∼26 ms. (B) Initial S1 response appeared slightly later in subjects with carpal tunnel syndrome at ∼31 ms post-stimulus. (C) By 113 ms post-stimulus, contralateral S2, ipsilateral S2 (iS2) and medial cortex including supplementary motor areas (SMAs) were active in both subject groups. In carpal tunnel syndrome, some response also localized within anterior cingulate areas (circle). (D) By 150 ms post-stimulus, all evoked responses had dissipated in both subject groups. PFC = prefrontal cortex.