The Auditory Contralateral Occipital Positivity Within Unimodal Versus Bimodal Stimulation
Daniel Roberts1, Steven Chong1, Craig McDonald1, Baldwin Carryl1; 1George Mason University
A recently reported event-related potential component, the auditory-evoked contralateral occipital positivity (ACOP), has been suggested to reflect the influence of involuntary orienting to the position of a sound on subsequent visual processing. However, the ACOP has not been investigated in the context of concurrent bimodal stimulation. The present study investigated the ACOP in the context of concurrent bimodal stimulation, as well as how the component relates to objective vs. subjective estimates of spatial position. Participants completed a spatialization task, in which they were asked to estimate the spatial location of auditory and / or visual stimuli. On each trial, auditory and visual stimuli were independently presented from one of three spatial locations, or were absent. The four possibilities for each modality generated a grid of sixteen equiprobable stimulus combinations. These sixteen combinations included unimodal presentation for each modality at each position. Behaviorally, the presence of stimuli in one modality influenced their perception of the spatial position of the stimulus in the alternate modality, with visual stimuli influencing auditory spatial responses to a greater extent than auditory stimuli influencing visual spatial responses. Within unimodal auditory trials, the position of the auditory stimulus generated the previously reported ACOP. The ACOP was absent from unimodal visual trials. Additionally, within bimodal trials, the ACOP was not present. As the ACOP was still present within the sum of unimodal trial combinations, the ACOP appears to be sub-additive within concurrent bimodal stimulation.
Topic Area: ATTENTION: Multisensory