Foreground-background discrimination indicated by event-related brain potentials in a new auditory multistability paradigm.

For studying multistable auditory perception, we propose a paradigm that evokes integrated or segregated perception of a sound sequence, and permits decomposition of the segregated grouping into foreground and background sounds. The paradigm combines 3-tone pitch patterns with alternating timbres, resulting in a repeating 6-tone structure that can be perceived as rising based on temporal proximity, or as falling based on timbre similarity. Listeners continuously report their percept while EEG is recorded. Results show an ERP modulation starting at ∼70 ms after sound onset that can be explained by whether a sound belongs to perceived foreground or background, with no additional effect of integrated versus segregated grouping. Auditory grouping as indexed by the mismatch negativity did not correspond with reported sound grouping. The paradigm offers a new possibility for investigating effects of conscious perceptual organization on sound processing.