Cortical processing of location changes in a "cocktail-party" situation: Spatial oddball effects on...

Neural mechanisms of selectively attending to a sound source of interest in a simulated "cocktail-party" situation, composed of multiple competing sources, were investigated using event-related potentials in combination with a spatial oddball design. Subjects either detected rare spatial deviants in a series of standard sounds or passively listened. Targets either appeared in isolation or in the presence of two distractor sound sources at different locations ("cocktail-party" condition). Deviant-minus-standard difference potentials revealed mismatch negativity, P3a, and P3b. However, mainly the P3b was modulated by spatial conditions of stimulation, with lower amplitude for "cocktail-party", than single, sounds. In the active condition, cortical source localization revealed two distinct foci of maximum differences in electrical activity for the contrast of single vs. "cocktail-party" sounds: the right inferior frontal junction and the right anterior superior parietal lobule. These areas may be specifically involved in processes associated with selective attention in a "cocktail-party" situation.