HUMAN AUDITORY CORTICAL MECHANISMS OF SOUND LATERALIZATION .2. INTERAURAL TIME DIFFERENCES AT SOUND ONSET

Neuromagnetic responses were recorded over the right temporal cortex u sing a 24-channel gradiometer. Stimuli were binaural click trains, pre sented with six separate interaural time differences (ITDs). N100m to sound onset was larger and earlier for stimuli presented with left- th an with right-leading ITDs. With stimulus lateralization taken into ac count, monaural and binaural stimuli evoked responses of roughly equal amplitude. In selective adaptation and oddball experiments, stimuli p resented with different ITDs excited overlapping neuronal populations, but the amount of overlap decreased as the ITD between the stimuli in creased. There were no systematic differences in the cortical source l ocations of the N100m as a function of ITD, however. Thus it appears t hat ITD-sensitive neurons in the human auditory cortex are not organiz ed into a large-scale, orderly representation, which could be resolved by MEG.