Human electrophysiology of endogenous auditory spatial attention

Abstract

Whereas perceiving the location of a stimulus in space relies on unique bottom-up processing, focusing attention to that location requires the availability and use of separate higher-level processes. It is unclear from previous work how selective attention might mediate and possibly sharpen spatial tuning, as behavioral tasks often lack an unattended comparison, and electrophysiological tasks often lack an attended comparison. We measured evoked responses to changes in the location of continuous noise in the free field when young, normal-hearing listeners were either passively listening or explicitly attending to one speaker location. Stimuli were presented from 1 of 5 frontal loudspeaker locations in the horizontal plane for 1.6 s before switching to another loudspeaker without pause. To ensure active attention for certain blocks, listeners were directed to press a button at the onset of a sound presented from the target location. Results show evidence of both facilitation for attended locations and suppression for unattended locations when compared to passive listening, and hemispheric distribution of activity was hemifield specific. Together, the data provide electrophysiological measures of a listener’s left-right orientation and another step toward cortical models of auditory spatial attention.