title: Spatiotemporal analysis of the cortical sources of the steady-state visual evoked potential.
abstract: This study aimed to characterize the neural generators of the steady-state visual evoked potential (SSVEP) to repetitive, 6 Hz pattern-reversal stimulation. Multichannel scalp recordings of SSVEPs and dipole modeling techniques were combined with functional magnetic resonance imaging (fMRI) and retinotopic mapping in order to estimate the locations of the cortical sources giving rise to the SSVEP elicited by pattern reversal. The time-varying SSVEP scalp topography indicated contributions from two major cortical sources, which were localized in the medial occipital and mid-temporal regions of the contralateral hemisphere. Colocalization of dipole locations with fMRI activation sites indicated that these two major sources of the SSVEP were located in primary visual cortex (V1) and in the motion sensitive (MT/V5) areas, respectively. Minor contributions from mid-occipital (V3A) and ventral occipital (V4/V8) areas were also considered. Comparison of SSVEP phase information with timing information collected in a previous transient VEP study (Di Russo et al. [2005] Neuroimage 24:874-886) suggested that the sequence of cortical activation is similar for steady-state and transient stimulation. These results provide a detailed spatiotemporal profile of the cortical origins of the SSVEP, which should enhance its use as an efficient clinical tool for evaluating visual-cortical dysfunction as well as an investigative probe of the cortical mechanisms of visual-perceptual processing.
authors.affiliation: Department of Education in Sports and Human Movement, University of Motor Sciences (IUSM), Rome, Italy. fdirusso@iusm.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Russo
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pitzalis
authors.forename: Teresa
authors.initials: T
authors.lastname: Aprile
authors.forename: Grazia
authors.initials: G
authors.lastname: Spitoni
authors.forename: Fabiana
authors.initials: F
authors.lastname: Patria
authors.forename: Alessandra
authors.initials: A
authors.lastname: Stella
authors.forename: Donatella
authors.initials: D
authors.lastname: Spinelli
authors.forename: Steven A
authors.initials: SA
authors.lastname: Hillyard
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*