Neuromagnetic responses to frequency-tagged sounds: a new method to follow inputs from each ear to the human auditory cortex during binaural hearing.
Binaural cortical responses are mixtures of inputs from both ears. We introduce here a novel method that allows, for the first time, to selectively follow these inputs in humans up to the cortex during binaural hearing. We recorded neuromagnetic cortical responses to amplitude-modulated continuous tones, with different modulation frequencies at each ear. During binaural hearing, the left- and right-ear inputs competed strongly in both auditory cortices: the right-hemisphere responses were symmetrically suppressed, compared with monaural stimulation, for sounds of both ears, whereas the left-hemisphere responses were suppressed significantly more for ipsilateral than contralateral sounds, thereby intensifying the right-ear dominance of the left auditory cortex. This type of hemisphere- and ear-selective information on cortical binaural interaction could have important applications in human auditory neuroscience.
Fujiki
Nobuya
N
Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, FIN-02015 HUT, Espoo, Finland. fujiki@hs.m.kyoto-u.ac.jp
Jousmaki
Veikko
V
Hari
Riitta
R
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D004292:Dominance, Cerebral / Q000502:physiology; D004423:Ear / Q000502:physiology; D005260:Female; D005583:Fourier Analysis; D006309:Hearing / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D010898:Pitch Perception / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted