Interaural interaction in the human auditory cortex.

We studied the effect of binaural, contralateral and ipsilateral stimulation on middle- and long-latency auditory-evoked magnetic fields using trains of 40-Hz clicks. The stimuli evoked both a transient response (N100m) and a 40-Hz response, which presumably reflects coalescence of middle-latency responses. Binaural stimuli elicited significantly larger 40-Hz responses and sustained fields than contralateral stimuli. N100m amplitudes did not differ between binaural and contralateral stimulation; the dipole moments were even smaller to binaural than contralateral stimuli. Responses to the ipsilateral stimuli were always the smallest.