| Abstract: | When presented with alternating low and high tones, listeners are more likely to perceive 2 separate streams of tones (“streaming”) than a single coherent stream when the frequency separation (Δ?) between tones is greater and the number of tone presentations is greater (“buildup”). However, the same large-Δ? sequence reduces streaming for subsequent patterns presented after a gap of up to several seconds. Buildup occurs at a level of neural representation with sharp frequency tuning. The authors used adaptation to demonstrate that the contextual effect of prior Δ? arose from a representation with broad frequency tuning, unlike buildup. Separate adaptation did not occur in a representation of Δ? independent of frequency range, suggesting that any frequency-shift detectors undergoing adaptation are also frequency specific. A separate effect of prior perception was observed, dissociating stimulus-related (i.e., Δ?) and perception-related (i.e., 1 stream vs. 2 streams) adaptation. Viewing a visual analogue to auditory streaming had no effect on subsequent perception of streaming, suggesting adaptation in auditory-specific brain circuits. These results, along with previous findings on buildup, suggest that processing in at least 3 levels of auditory neural representation underlies segregation and formation of auditory streams. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
