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Ayelet Landau, Lynn Robertson; Spatial attention accelerates inter-hemispheric transfer time. Journal of Vision 2008;8(6):1092. doi: 10.1167/8.6.1092.
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The present study was designed to examine perceptual responses under different spatial attention conditions to lateralized stimuli. EEG was recorded from scalp electrodes while participants were either attending or ignoring faces presented to the right or left of fixation. Event Related Potentials (ERPs) to interspersed faces were measured for two attention conditions (attend-face/ignore-face). Each display contained a symbol at the center of fixation and a lateralized presentation of a face. Faces either appeared to the left of fixation or to the right of fixation (in separate blocks). In the attend-face condition, participants were monitoring the peripheral faces covertly for an inverted face. In the ignore-face condition participants were instructed to monitor the symbols for an ‘x’ and pay no attention to the subsequently presented face while maintaining fixation. ERPs to attended and ignored faces were compared in a group of 16 neurologically healthy participants. General perceptual markers (P1) and indices of face processing (N170) were modulated by spatial attention. The nature of this modulation for faces was different for right visual field (RVF) and left visual field (LVF). Most importantly, analysis of peak latencies for both P1 and N170 revealed a robust acceleration in the interhemispheric transfer with spatial attention. When the face was attended the time difference between ipsilateral and contralateral response over extrastriate channels was smaller compared to when the faces were ignored. The acceleration in transfer time between the hemispheres was symmetric and equal for LVF and RVF presented faces. These findings suggest that the speed of hemispheric cross-talk in addition to amplitude modulations is influenced by spatial attention in the visual modality.
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