title: Functional topography of the secondary somatosensory cortex for nonpainful and painful stimulation of median and tibial nerve: an fMRI study.
abstract: Functional magnetic resonance imaging (fMRI) was used to study the cortical activity of the bilateral secondary somatosensory cortex (SII) during nonpainful (motor threshold) and painful electrical stimulation of median and tibial nerves. fMRI recordings were performed in eight normal young adults. The aim was at evaluating the working hypothesis of a spatial segregation of nonpainful and painful populations not only in the "hand" representation of SII [Ferretti, A., Babiloni, C., Del Gratta, C., Caulo, M., Tartaro, A., Bonomo, L., Rossini, P.M., Romani, G.L., 2003. Functional topography of the secondary somatosensory cortex for nonpainful and painful stimuli: an fMRI study. NeuroImage 20, 1625-1638.] but also in its "foot" representation. Results showed that, in both "hand" and "foot" representations of bilateral SII, the activity elicited by the painful stimulation was localized more posteriorly with respect to that elicited by the nonpainful stimulation. A fine spatial analysis of the SII responses revealed a clear somatotopic organization in the bilateral SII subregion especially reactive to the nonpainful stimuli (i.e., segregation of the hand and foot representations). In contrast, it was not possible to disentangle the "hand" and "foot" representations of SII for painful stimuli. These results extended to the SII "foot" representation previous evidence of a spatial segregation in the SII "hand" representation of subregions for the painful and nonpainful stimuli. Furthermore, they suggest that noxious information is not somatotopically represented in human bilateral SII, at least as inferred from fMRI data at 1.5 T.
authors.affiliation: Department of Clinical Sciences and Bio-imaging, University of Chieti, Chieti, Italy. aferretti@itab.unich.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Ferretti
authors.forename: Cosimo
authors.initials: C
authors.lastname: Del Gratta
authors.forename: Claudio
authors.initials: C
authors.lastname: Babiloni
authors.forename: Massimo
authors.initials: M
authors.lastname: Caulo
authors.forename: Donatello
authors.initials: D
authors.lastname: Arienzo
authors.forename: Armando
authors.initials: A
authors.lastname: Tartaro
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Romani
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D008279:Magnetic Resonance Imaging; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010146:Pain / Q000503:physiopathology*; D013003:Somatosensory Cortex / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology*
chemical_list: D010100:Oxygen