Human cortical activity during streaming without spectral cues suggests a general neural substrate for auditory stream segregation.
The brain continuously disentangles competing sounds, such as two people speaking, and assigns them to distinct streams. Neural mechanisms have been proposed for streaming based on gross spectral differences between sounds, but not for streaming based on other nonspectral features. Here, human listeners were presented with sequences of harmonic complex tones that had identical spectral envelopes, and unresolved spectral fine structure, but one of two fundamental frequencies (f0) and pitches. As the f0 difference between tones increased, listeners perceived the tones as being segregated into two streams (one stream for each f0) and cortical activity measured with functional magnetic resonance imaging and magnetoencephalography increased. This trend was seen in primary cortex of Heschl's gyrus and in surrounding nonprimary areas. The results strongly resemble those for pure tones. Both the present and pure tone results may reflect neuronal forward suppression that diminishes as one or more features of successive sounds become increasingly different. We hypothesize that feature-specific forward suppression subserves streaming based on diverse perceptual cues and results in explicit neural representations for auditory streams within auditory cortex.
Gutschalk
Alexander
A
Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA. Alexander_Gutschalk@med.uni-heidelberg.de
Oxenham
Andrew J
AJ
Micheyl
Christophe
C
Wilson
E Courtenay
EC
Melcher
Jennifer R
JR
D000161:Acoustic Stimulation / Q000379:methods; D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001303:Auditory Cortex / Q000098:blood supply / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D003463:Cues; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D015225:Magnetoencephalography; D008297:Male; D010100:Oxygen / Q000097:blood; D011571:Psychoacoustics; D013057:Spectrum Analysis
D010100:Oxygen