Binaural cortical responses are mixtures of inputs from both ears.We introduce here "dichotic listening test" that speech sound used to selectively follow these inputs in humans up to the cortex during binaural hearing.We recorded neuromagnetic cortical responses with magnetoencephalogram (MEG) to amplitude-modulated speech sound, with different modulation frequencies at each ear.During binaural hearing, the left- and the right- ear inputs compered strongly in both auditory cortices: The right-hemisphere responses were symmetrically suppressed, whereas the left-hemisphere responses were suppressed significantly more for ipsilateral than contralateral sound, 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 new auditory check.
