STUDYING THE MISMATCH NEGATIVITY AS AN OBJECTIVE MEASURE OF AUDITORY SENSORY MEMORY IN PATIENTS WITH TINNITUS

Tinnitus is a phantom sound perceived in one or both ears without an external sound source.(1) It affects approximately 11-30 % of the population.(2) Evidences of altered central neural activity in tinnitus patients exist.(3,4) It was suggested that tinnitus persistence could be linked to the impaired sensory memory processing.(5, 6) Moreover, it was concluded that there is a mixed behavioural support that tinnitus impairs working memory.(7,8) More objective electrophysiological approaches are also available for evaluation of sensory memory duration, namely the mismatch negativity (MMN) response.(6, 9) The MMN is elicited by the brain ability to detect occasional deviation of sound changes within a presented sound sequence.(10) It reflects early sensory processing of auditory input and its encoding into a memory trace making it a powerful objective approach for evaluation of neural correlates of auditory sensory memory processes.(6, 9) MMN was found to be more representative of auditory sensory memory status when measured with long inter-stimulus interval (ISI ≥ 2 seconds) rather than short one.(9) Based on these findings, the main aim of the current study was to find out if there are any differences in auditory sensory memory duration in tinnitus subjects compared to normal hearing matched controls.