Electrophysiological studies of auditory spatial attention

Abstract

Recordings of event-related potentials (ERPs) from the scalp can track the processing of auditory signals through the afferent pathways from brainstem to cortex. ERP components elicited in auditory cortex during the time range 50–200 ms are highly sensitive to selective attention, with attended sounds eliciting greater amplitudes than unattended sounds. Using combined ERP and behavioral measures, the allocation of auditory attention was studied in a free-field array of seven or eight speakers. Brief noise bursts were presented in a random, fast-paced sequence from all the speakers, and subjects were required to attend to the sounds at one location while ignoring the others. Both behavioral detection responses and ERP amplitudes were highest for stimuli at the attended location, with a progressive falloff for responses to increasingly distant sound sources. These data revealed the shape of spatial tuning curves for auditory attention in free-field and support gradient models of attentional allocation. An analysis of ERP waveforms indicated that spatial selectivity is established by consecutive stages of progressive fine-tuning over the time range 50–350 ms poststimulus. [Work supported by Grants from NIMH and ONR.]