The Journal of Neuroscience, 2002, 22:RC205:1-4
RAPID COMMUNICATION
Neuromagnetic Responses to Frequency-Tagged Sounds: A New Method
to Follow Inputs from Each Ear to the Human Auditory Cortex during
Binaural Hearing
Nobuya
Fujiki1, 2,
Veikko
Jousmäki1, and
Riitta
Hari1, 3
1 Brain Research Unit, Low Temperature Laboratory,
Helsinki University of Technology, FIN-02015 HUT, Espoo, Finland,
2 Department of Otolaryngology-Head and Neck Surgery,
Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto,
606-8507, Japan, and 3 Department of Clinical
Neurophysiology, Helsinki University Central Hospital, FIN-00290
Helsinki, Finland
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.
Key words:
magnetoencephalography; frequency tagging; binaural
hearing; amplitude-modulated tone; right-ear dominance; binaural
suppressive interaction; steady-state responses
Copyright © Society for Neuroscience 0270-6474//$05.00/0
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