Abstract
Neuroimaging studies have identified several motion-sensitive visual areas in the human brain, but the time course of their activation cannot be measured with these techniques. In the present study, we combined electrophysiological and neuroimaging methods (including retinotopic brain mapping) to determine the spatio-temporal profile of motion-onset visual evoked potentials for slow and fast motion stimuli and to localize its neural generators. We found that cortical activity initiates in the primary visual area (V1) for slow stimuli, peaking 100 ms after the onset of motion. Subsequently, activity in the mid-temporal motion-sensitive areas, MT+, peaked at 120 ms, followed by peaks in activity in the more dorsal area, V3A, at 160 ms and the lateral occipital complex at 180 ms. Approximately 250 ms after stimulus onset, activity fast motion stimuli was predominant in area V6 along the parieto-occipital sulcus. Finally, at 350 ms (100 ms after the motion offset) brain activity was visible again in area V1. For fast motion stimuli, the spatio-temporal brain pattern was similar, except that the first activity was detected at 70 ms in area MT+. Comparing functional magnetic resonance data for slow vs. fast motion, we found signs of slow-fast motion stimulus topography along the posterior brain in at least three cortical regions (MT+, V3A and LOR).
Highlights
Visual-evoked potentials (VEPs), have been used extensively to study motion processing and integrity of the visual system
Following the analysis described by Di Russo and colleagues [4,11], regions of interest were selected by clustering the fMRI spots, and resulting coordinates (Table 1) were compared to the locations of unseeded models (Table 2) to create a final model based on the closest fMRI spot, with the source orientations optimized to the new locations
This study localized the main sources of the motion-onset VEPs for high and low speed stimuli by combining high-resolution EEG recordings with neuroimaging data
Summary
Visual-evoked potentials (VEPs), have been used extensively to study motion processing and integrity of the visual system. Motion-onset VEPs have three main components called P1, N2 and P2 (reviewed in [1]). This spatiotemporal structure appears simpler when compared to other VEP stimulation modalities, such as pattern-onset, which are described by at least six components. The reason for this apparent simplicity may be due to the size and position of the stimulus in the visual field. Some studies have localized the P1 component in striate and extrastriate visual areas This lack of agreement among previous studies may be due to methodological differences
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