Tonotopic map changes during tinnitus remediation

Background: Tinnitus has been associated with the abnormal organisation of the tonotopic map in the auditory cortex (Eggermont, 2006). However, it is currently not clear whether successful tinnitus remediation which shows improved subjective outcomes, can affect the reorganisation of the tonotopic map towards a non-disrupted state. Therefore the aims of the present study were: (i) to compare tonotopic maps acquired from magnetoencephalography (MEG) recordings in individuals with significant tinnitus with non-tinnitus participants to determine whether disruptions could be measured; (ii) to identify whether changes in the tonotopic map and evoked responses occurred during and after a tinnitus remediation program; and (iii) to identify whether these changes occurred in parallel with subjective changes of tinnitus impact. Method: Twelve tinnitus participants were recruited and completed audiometric evaluation, subjective measurement of tinnitus using the tinnitus reaction questionnaire (TRQ), measurement of psychoacoustic characteristics of tinnitus, and evaluation of depression and anxiety before during and after tinnitus remediation. Ten normal hearing non-tinnitus participants were recruited for comparison. Sound stimuli of 500Hz, 1kHz, 2kHz, 4kHz and 8kHz tones were presented to each ear individually and cortical activity was measured using MEG. All tinnitus participants completed a Neuromonics rehabilitation program over 25 weeks and MEG was measured at 5 or 10 week intervals. MEG data were analysed using Brain Electrical Source Analysis (BESA). Results & conclusions: MEG results indicated that the tinnitus subjects’ source locations were more anterior compared to that of the control group (for all presented frequencies). After undergoing remediation, the tinnitus subjects’ source strengths increased (for normal hearing frequencies) while source locations moved towards a more posterior location (towards that of non-tinnitus participants). These results suggests that tinnitus remediation using Neuromonics affects source strength and tonotopic map of the tinnitus participants.