Adaptation reveals multiple levels of representation in auditory stream segregation.
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 (Deltaf) between tones is greater and the number of tone presentations is greater ("buildup"). However, the same large-Deltaf 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 Deltaf arose from a representation with broad frequency tuning, unlike buildup. Separate adaptation did not occur in a representation of Deltaf 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., Deltaf) 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.
Snyder
Joel S
JS
Department of Psychology, University of Nevada, 4505 South Maryland Parkway, Box 455030, Las Vegas, NV 89154-5030, USA.
Carter
Olivia L
OL
Hannon
Erin E
EE
Alain
Claude
C
D000222:Adaptation, Physiological; D000328:Adult; D001306:Auditory Pathways / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011571:Psychoacoustics; D014796:Visual Perception / Q000502:physiology