The fast detection of rare auditory feature conjunctions in the human brain as revealed by cortical gamma-band electroencephalogram.
Natural environments typically contain temporal scatters of sounds emitted from multiple sources. The sounds may often physically stand out from one another in their conjoined rather than simple features. This poses a particular challenge for the brain to detect which of these sounds are rare and, therefore, potentially important for survival. We recorded gamma-band (32-40 Hz) electroencephalographic (EEG) oscillations from the scalp of adult humans who passively listened to a repeated tone carrying frequent and rare conjunctions of its frequency and intensity. EEG oscillations that this tone induced, rather than evoked, differed in amplitude between the two conjunction types within the 56-ms analysis window from tone onset. Our finding suggests that, perhaps with the support of its non-phase-locked synchrony in the gamma band, the human brain is able to detect rare sounds as feature conjunctions very rapidly.
Ruusuvirta
T
T
Cognitive Brain Research Unit, Department of Psychology, Siltavuorenpenger 20 C, P.O. Box 9, University of Helsinki, 00014 Helsinki, Finland. timo.ruusuvirta@cbru.helsinki.fi
Huotilainen
M
M
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011930:Reaction Time; D012815:Signal Processing, Computer-Assisted