STAGES OF AUDITORY FEATURE CONJUNCTION - AN EVENT-RELATED BRAIN POTENTIAL STUDY

Auditory event-related brain potentials (ERPs) were recorded to tones of different frequencies and locations in a dichotic selective attenti on task in which Ss responded to occasional deviant tones of a prespec ified location and frequency. Attention effects were isolated as negat ive difference (Nd) waves by subtracting ERPs to tones with no attende d features from ERPs to the same tones when they shared target frequen cy, location, or both cues. The N1/P90 (latency 80-100 ms), originatin g in a tonotopically organized generator, was enhanced for all tones i n the attended ear. Nd waves, beginning at 80 ms and lasting up to 700 ms, were seen to tones with either attended feature. Nd waves to freq uency and location features had different scalp distributions consiste nt with generation in different cortical fields. Conjunction-specific Nds began 30-50 ms after Nds to individual features. The relative timi ng suggests that feature conjunction began before the analysis of indi vidual features was complete.