Abstract
This study aimed to characterize the neural generators of the steady-state visual evoked potential (SSVEP) to 6 Hz pattern-reversal gratings. Multichannel scalp recordings (64 channels)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 second harmonic of SSVEP. Dipole locations were seeded to visual cortical areas in which fMRI activations were elicited by the same stimuli.
The results provide strong evidence that the major contribution to the SSVEP arises from activity in the primary visual cortex (area V1) and in motion sensitive area (MT/V5). Further contribution could be accounted for by dipoles that were in close proximity to fMRI activations in the the transverse parietal sulcus, ventral occipital areas VP and V4v and dorsal occipital areas V3A/V7. The present results showed that is possible decompose the steady-state VEP waveforms in a series of cortical components on the basis of their phase.
Present results provide a detailed spatio-temporal profile of the cortical origins of the SSVEP, which should enhance its utility in both clinical and basic studies of visual-perceptual processing.