Temporal integration on human auditory sensory memory revealed by mismatch negativity

Mismatch negativity (MMN), a component of event-related potentials (ERP), was recorded to investigate the properties of temporal integration in auditory sensory memory, which integrates the short-term history of presented auditory temporal sequences to the sensory memory using a time window. At first, the MMN elicited by the infrequent change in a pair of closely spaced tones was evaluated to determine the temporal capacity of sensory memory. Under ignore condition, it was shown that the amplitude of elicited MMN decreased when the total duration of the tone pair (stimulus duration) increased, and for three out of four subjects, there was no significant MMN observed when the stimulus duration was 400 ms. This result shows that the function of temporal integration existed in sensory memory and the maximum period of the time window was 300-400 ms. However, MMN was also elicited under attend condition when the stimulus duration was 500 ms, and a scalp topography of MMN showed additional activity in the frontal area. This might support the hypothesis of the contribution of higher-order processes to the sensory memory process. Secondly, the relationship between the temporal configuration of tone sequence and elicited MMN was evaluated under ignore condition. Temporal configuration was changed by inserting additional tones between the pair of tones. The MMN amplitude decreased when the number of inserted tones was increased, and the duration or temporal position of a single inserted tone affected the MMN amplitude. From the results of this experiment, it is believed that the capacity of the auditory sensory memory is influenced by the temporal configuration of the tone sequence to be stored, as well as its total duration. These results will help to approach the neuronal mechanism of auditory scene analysis.