Official websites use. Share sensitive information only on official, secure websites. The classic understanding of the role of the primary somatosensory cortex SI is to be a first major unimodal area processing somatosensory input and reflecting the physical location of peripheral stimulation in the form of the famous homunculus. Whereas in the past this functional topography was believed to be fixed, recent studies challenge this view.
For example, in upper extremity amputees the cortical representation of the mouth was found to invade the region that formerly represented the amputated limb. Moreover, several studies demonstrated dynamic modulations of the body map in SI by tactile illusions. The present study aims to further explore the role of SI by creating an illusion of feeling a supernumerary artificial limb. Using an artificial hand and arm that were connected to their body, subjects were given the visual impression that they had a supernumerary third arm.
The topography in SI was examined with neuromagnetic source localization. Results revealed that the participants not only viewed the artificial arm but felt to have three arms.
Furthermore, during the illusion the cortical representation of the thumb shifted to a more medial and superior position. Because this modulation in SI could predict the strength of the feeling that the third arm was belonging to the own body, the results suggest that the somatosensory homunculus is reflecting the perceived shape of the body rather than physical aspects of peripheral stimulation even when feeling an artificial third arm.
Hum Brain Mapp Keywords: illusions, body image, multisensory, somatosensory cortex, touch, vision, magnetoencephalography. It is long established that SI represents our body in the form of the somatosensory homunculus [Penfield and Boldrey, ]. However, the traditional view of a fixed body map representation in SI is questioned by the results of recent studies. For instance, in upper extremity amputees the cortical representation of the mouth region was found to invade the region that formerly represented the amputated limb [Yang et al.
