The right hand knows what the left hand is feeling

The mislocalization profile, describing incorrect localization of faint tactile stimuli to different regions of the body, has been shown to provide insight into the processing of tactile stimuli. Interhemispheric somatosensory processing was examined in 15 subjects by studying the interference of left-hand stimulation on right-hand perception. In different conditions supra-threshold interference stimuli were applied to the left thumb or little finger either 200 or 500 ms prior to the application of a test stimulus on the right hand. Data show that interference stimuli applied to the left hand massively altered localization responses for stimuli applied to the right side. Stimulating the left thumb yielded an increased number of mislocalizations to the right thumb. Similarly, stimulating the left little finger caused a shift in localization responses towards the right ring finger. Results support the hypothesis that interaction of somatosensory information originating from different sides of the body follows a somatotopic organization.