title: District-related frequency specificity in hand cortical representation: dynamics of regional activation and intra-regional synchronization.
abstract: The aim of this work was to study the degree of neuronal synchronization occurring within the portion of the somatosensory cortex devoted to hand control during an external sensory stimulation. In this way, we focused on the properties of the sensory cortical representation, rather than the more investigated motor one. To this aim, we collected magnetoencephalograhic data from healthy subjects during separate stimulation of their thumbs and little fingers and analyzed these data by means of a time-dependent 'synchronization index'. The properties of this index within the beta [16-32 Hz] and gamma [36-44 Hz] frequency bands suggest that the hand representation in the human primary cortex follows a frequency coding, in addition to the somatotopic one, for discriminating different districts. Our results showed that the gamma synchronization is higher following stimulation of the thumb than of the little finger and we suggest that the strength of gamma band synchronization works as a code for functional prevalence. In particular, our comparative analysis of the dynamic synchronization index and the signal amplitude suggests that a prevalent district (thumb) recruits a smaller number of higher-synchronic gamma band tuned neurons than a non-prevalent district (little finger).
authors.affiliation: Dip. Fisica ed SMC INFM, Univ. La Sapienza, Centro Fermi Rome, Italy. f.tecchio@istc.cnr.it
authors.forename: Franca
authors.initials: F
authors.lastname: Tecchio
authors.forename: Marzia
authors.initials: M
authors.lastname: De Lucia
authors.forename: Carlo
authors.initials: C
authors.lastname: Salustri
authors.forename: Marco
authors.initials: M
authors.lastname: Montuori
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bottaccio
authors.forename: Claudio
authors.initials: C
authors.lastname: Babiloni
authors.forename: Luciano
authors.initials: L
authors.lastname: Pietronero
authors.forename: Filippo
authors.initials: F
authors.lastname: Zappasodi
authors.forename: Paolo M
authors.initials: PM
authors.lastname: Rossini
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003344:Cortical Synchronization; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D012016:Reference Values; D013003:Somatosensory Cortex / Q000502:physiology*