PERCEPTUAL CONTEXT AND THE SELECTIVE ATTENTION EFFECT ON AUDITORY EVENT-RELATED BRAIN POTENTIALS

Two experiments examined the effect of the perceptual context establis hed through tonal grouping on neuroelectric responses during selective listening. Subjects monitored one of the extreme pitches in four-pitc h tone sequences and detected rare longer tones of the designated pitc h. In the first study, tonal grouping was manipulated by changing the tonal separation between the extreme pitches and their nearest neighbo r, keeping the extreme pitches constant. Grouping increased the negati vity of the attended-unattended difference potential. A second study e xamined the effect of grouping on the attention-related negativity whe n it opposed the effect of physical similarity. The proximity of extre me pitches varied, keeping the middle pitches constant. The effect of grouping on event-related potentials (ERPs) for the middle pitches was varied according to the tone being attended. ERPs for the middle tone adjacent to the attended tone became more negative with grouping, whe reas ERPs for the distant middle tone became less negative with groupi ng. These effects suggest that the attention-related negativity is sen sitive to contextual information.