Activation of the human posterior parietal and temporoparietal cortices during audiotactile interaction.

We recorded cortical-evoked responses with a whole-scalp neuromagnetometer to study human brain dynamics associated with audiotactile interaction. The subjects received unilateral auditory (A) or tactile (T) stimuli, or both stimuli simultaneously (AT), alternating to the left and right side. Responses to AT stimuli differed significantly from the algebraic sum of responses to A and T stimuli (A + T) at 75-85 and 105-130 ms and indicated suppressive audiotactile interaction. Source modeling revealed that the earlier interaction occurred in the contralateral posterior parietal cortex and the later interaction in the contralateral parietal opercula between the SII cortex and the auditory cortex. The interaction was significantly stronger in the left than the right hemisphere. In most subjects, AT responses were far more similar to T than to A responses, suggesting suppression of auditory processing during the spatially and temporally concordant audiotactile stimuli in which the tactile component was subjectively more salient.