Figure 3

Intracortical stimulation mapping of the ipsilesional motor cortex. Somatotopic map in the motor cortex on the left (ipsilesional) hemisphere in the region of the hand area, before (left column) and after (right column) the cervical lesion for Mk1, Mk2 and Mk3 (from top to bottom). The data are presented on a surface view of the cerebral cortex, the portion accessible via the chronic recording chamber. The pre-lesion maps were established by daily ICMS sessions conducted during the 3 months preceding the lesion. The post-lesion maps were derived from daily ICMS sessions starting 2, 4.5 and 5 months after the lesion in Mk1, Mk2 and Mk3, respectively and lasting about 2 months each. Each symbol represents the location on the cortical surface of the penetration with an electrode for ICMS. The ICMS data given for each symbol is representative for the site of stimulation where the effect was observed at the lowest current intensity along the considered electrode track. The letter next to each symbol indicates the body territory activated at threshold for each track (see letter codes in the bottom right). The size of the symbols indicates the current intensity at threshold (in μA; see bottom left). Hand area(s), outlined by a solid line, was defined as a cortical region pre-lesion where ICMS at lowest threshold elicits movements of the fingers (electrode tracks represented by diamonds). Symbol X means that ICMS did not elicit any visible movement of muscles. The pointed lines outline the hand area, as defined post-lesion. Symbols in grey are for sites belonging to the hand area before lesion, which became part of other territories post-lesion. The grid in the background indicates steps of 1 mm. Syringes point to sites where muscimol was infused in order to inactivate M1 (see text). In order to make sure that the entire "post-lesion" hand representation was reversibly inactivated, the sites of infusion of muscimol were selected based on the "pre-lesion" map, exhibiting a larger hand representation than post-lesion. On the pre-lesion maps (left column), the approximate positions of the central (CE) and arcuate (AR) sulci are indicated by dashed lines.