Mismatch negativity linked with sound lateralization in elderly individuals

Abstract

Elderly individuals tend to experience a decline in auditory functions. One of these is poor lateralization ability. This study aimed to investigate the relationship between sound lateralization and mismatch negativity (MMN) in elderly individuals using a lateralization test and event-related potential (ERP) measuring test. In the lateralization test, participants were presented with sound stimuli with an interaural time difference (ITD) in the right or left ear and were required to indicate the sound direction. The ERP measuring test estimated unconscious brain activity during participants’ exposure to sound stimuli using an ITD in the right or left ear. Two ITDs (i.e., 0.4 ms and 0.8 ms) of a 1-kHz pure tone were measured in elderly and young participants. For sounds with phase reversal between the onset and ongoing parts, young individuals performed lateralization based on the onset part. In contrast, at an ITD of 0.8 ms, elderly participants unable to perceive the onset part tended to demonstrate less negative MMN. In conditions where the preceding ear in onset and ongoing parts was reversed, elderly participants exhibited ambiguous lateralization, and their cortical evoked potentials did not significantly differ from activity associated with standard stimuli without an ITD.