Cortical activations associated with spatial remapping of finger touch using HR-EEG

The spatial coding of tactile information is functionally essential for touch-based shape perception and motor control. However, the spatiotemporal dynamics of how tactile information is remapped from the somatotopic reference frame in the primary somatosensory cortex to the spatiotopic reference frame remains unclear. This study investigated how hand position in space or posture influences cortical somatosensory processing. Twenty-two healthy subjects received electrical stimulation to the right thumb (D1) or little finger (D5) in three position conditions: palm down on right side of the body (baseline), hand crossing the body midline (position effect), and palm up (posture effect). Somatosensory evoked potentials (SEPs) were recorded using high-resolution electroencephalography (HR-EEG). One early-, two mid- and two late-latency neurophysiological components were identified for both fingers, showing different cortical activation patterns: P50, P1, N125, P200, N250. Compared to baseline, the crossing condition showed significant clustering at P1 for D1 and at N125 for D5, and the change in posture showed a significant cluster at N125 for D5. Clusters predominated at parietal electrodes. We did not find any modulation of functional connectivity related to position or posture. The results suggest that tactile remapping of fingers after electrical stimulation occurs around 100-125 ms in the parietal cortex.