Poster B9, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Task instruction modulates alpha band event-related spectral perturbation to ambiguously located auditory stimuli
Daniel M. Roberts1, Craig G. McDonald1, Carryl L. Baldwin1; 1George Mason University
Recent work has suggested a biasing of visual spatial attention towards the location of an auditory stimulus, even if the task requires no visual detection or discrimination. This effect, termed the auditory-evoked contralateral occipital positivity (ACOP) is observable as a lateral occipital ERP component beginning at around 260 ms following auditory stimulus onset. Additionally, the same experimental conditions have been associated with event-related alpha suppression over lateral occipital electrode locations, with suppression of greater magnitude contralateral to the side of the presented auditory stimulus. However, the factors that influence the ACOP and lateralized alpha suppression are currently unclear. The current investigation sought to identify potential top-down influences on the ACOP and alpha suppression by manipulating participant beliefs about the spatial location of sounds via task instruction. Participants monitored centrally presented auditory noise stimuli for the presence of an embedded pure tone. In addition, lateralized tones were presented from locations that were ambiguous with respect to front or back direction. Between blocks, top-down beliefs of tone location (front vs. back presentation) were manipulated via task instruction. ACOP and event-related alpha band lateralization to left vs. right tones replicated past work. In addition, a main effect for alpha suppression was observed for task instruction, such that greater alpha power suppression was observed for front instruction blocks relative to back instruction blocks, to the same physical stimuli. It is suggested the suppression of alpha power over lateral occipital electrodes to auditory stimuli may be influenced in part by participant beliefs of sound location.
Topic Area: ATTENTION: Multisensory