Hemispheric asymmetries in auditory temporal integration: a study of event-related potentials

According to the asymmetric sampling in time hypothesis, the left auditory cortex processes stimuli using a short temporal integration window (~25-50 ms), whereas the right auditory cortex processes stimuli using a long temporal integration window (~200 ms). We examined N1 and T-complex responses to the second tone of tone-pairs presented with inter-stimulus intervals (ISIs) of 50 and 200 ms. Twenty-seven undergraduate students were presented with stimuli binaurally whilst the EEG was recorded. N1 and Ta responses were symmetric between hemispheres, with responses elicited by the second tone of the 50 ms ISI tone-pairs. Tb responses to the second tones were significantly attenuated over the right hemisphere when compared to the left hemisphere for the 50 ms ISI tone-pairs, but returned to similar amplitudes in the 200 ms condition. Our results suggest that temporal integration windows of the left and right primary auditory areas are symmetric whereas those of the left and right secondary auditory areas are asymmetric. These findings are consistent with the asymmetric sampling in time hypothesis and provide justification for further investigation of the involvement of temporal integration in higher order auditory processes.