Spatial Selective Attention Affects Early Extrastriate But Not Striate Components of the Visual Evoked Potential

TLDR

The study examined how spatial selective attention modulates sensory processing in visual cortex using visual evoked potentials and source localization. Patterned stimuli were rapidly presented to left and right visual fields while subjects fixated centrally and attended one field, and spatiotemporal dipole modeling of the early VEP sources was performed relative to MRI‑defined cortical anatomy. Attention enhanced the P1 and N1 VEP components but not C1 or P2; the C1 source was localized to V1, whereas the P1 source was in extrastriate area 19, indicating that spatial attention selectively amplifies extrastriate but not primary visual cortical activity.

Abstract

Abstract The effects of spatial selective attention on sensory processing in visual cortical areas were investigated by means of visual evoked potential (VEP) recordings and source localization techniques. Patterned stimuli were rapidly presented in random order to the left and right visual fields while subjects maintained central fixation and attended to one visual field at a time. Attended stimuli evoked enhanced P1 (100-130 msec) and N1 (120-200 msec) components of the VEP, whereas no effects of attention were observed on the C1 (50-100 msec) or P2 (200-240 msec) components. Spatiotemporal dipole modeling of the early VEP sources was carried out in relation to MRI-defined cortical anatomy. The dipolar generator of the C1 component was found to lie in calcarine cortex, the human homologue of area V1, whereas the attention-sensitive P1 generator was localized to ventral-lateral occipital cortex, within extrastriate area 19. These results support the hypothesis that spatial attention does not affect the initial activity evoked in area V1 but rather produces an enhancement within extrastriate visual areas of sensory signals arising from stimuli at attended locations.