The effects of auditory spatial attention across the hierarchy of early visual areas in human occipital cortex
Poster Presentation

Vivian Ciaramitaro
The Salk Institute

*Geoffrey Boynton
The Salk Institute

     Abstract ID Number: 155
     Full text: Not available
     Last modified: March 21, 2005

Abstract
We examined how auditory spatial attention influences responses in visual areas by measuring fMRI responses to unattended visual information when attention was directed to auditory information on the same or the opposite side of space.

Subjects simultaneously observed four stimuli: a drifting grating to the left and right of central fixation, and an auditory tone to the left and right ear. Auditory stimuli presented to the left ear were perceived on the left side of space, and vice versa. All stimuli were presented in two successive intervals at threshold. A central cue directed subjects to attend the left versus right ear, where they performed an auditory frequency discrimination task.

All early visual areas showed larger fMRI responses to unattended visual stimuli when auditory attention was directed to the same, compared to the opposite side of space. These results are consistent with previous ERP data (example, Eimer et al 2004) suggesting a crossmodal mechanism of spatial attention where attending a stimulus in one spatial region yields a processing advantage for other stimuli in the same spatial region, regardless of modality. Furthermore, our design allowed quantification of the separate contributions of visuo-spatial, audio-spatial and crossmodal attention across areas V1 to MT+.