title: Dermatomal Organization of SI Leg Representation in Humans: Revising the Somatosensory Homunculus.
abstract: Penfield and Rasmussen's homunculus is the valid map of the neural body representation of nearly each textbook of biology, physiology, and neuroscience. The somatosensory homunculus places the foot representation on the mesial surface of the postcentral gyrus followed by the representations of the lower leg and the thigh in superio-lateral direction. However, this strong homuncular organization contradicts the "dermatomal" organization of spinal nerves. We used somatosensory-evoked magnetic fields and source analysis to study the leg's neural representation in the primary somatosensory cortex (SI). We show that the representation of the back of the thigh is located inferior to the foot's representation in SI whereas the front of the thigh is located laterally to the foot's representation. This observation indicates that the localization of the leg in SI rather follows the dermatomal organization of spinal nerves than the typical map of neighboring body parts as depicted in Penfield and Rasmussen's illustration of the somatosensory homunculus.
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Dietrich
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Kathrin R
authors.initials: KR
authors.lastname: Blume
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Franz
authors.affiliation: Department of Neurology, Biomagnetic Center, University Hospital Jena, Jena, D-07747,Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Huonker
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Carl
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Preißler
authors.affiliation: Berufsgenossenschaftliche Kliniken Bergmannstrost Halle, Halle/Saale, D-06112, Germany.|Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Jena, D-07747, Germany.
authors.forename: Gunther O
authors.initials: GO
authors.lastname: Hofmann
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Wolfgang H R
authors.initials: WHR
authors.lastname: Miltner
authors.affiliation: Department of Biological and Clinical Psychology, Friedrich Schiller UniversityJena, D-07743, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Weiss
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D010812:Physical Stimulation / Q000379:methods; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
keywords: MEG; SEF; dermatomes; somatosensory cortex; somatosensory-evoked fields