Evidence for a Transient State of Auditory Hypersensitivity During Initial Onset of Tinnitus, Evidenced by Intensity Dependence of the Auditory Evoked Potential (IDAEP)

Our understanding of tinnitus pathophysiology may be greatly advanced by understanding how the condition evolves from its initial onset or acute stage to its chronic manifestation. Such a transition likely reflects dynamic neurophysiological changes within central auditory and non-auditory networks. Our integrated model of tinnitus posits that sensory precision (sensory weighting) may be heightened during the acute stages of tinnitus to resolve degraded auditory input, but in chronic tinnitus, its role may diminish as plastic processes take over the percepts maintenance. Consequently, we hypothesize that bottom-up neural mechanisms linked to initiation of tinnitus, such as central gain and neural synchrony, are maximal around the time of tinnitus onset, but later subside by way of regression to the mean. We evaluated this hypothesis by measuring central auditory reactivity through the Intensity Dependence of Auditory Evoked Potential (IDAEP), a non-invasive index of higher-order inhibitory processing within the auditory system. A steeper IDAEP slope is associated with heightened sensory reactivity (higher sensitivity to changes in auditory stimuli), indicative of reduced central inhibition. Conversely, a shallower slope reflects greater inhibitory control. Studying a group with acute tinnitus (onset within six weeks), with a repeated assessment after six months from onset, we found an initially increased IDAEP slope in the acute stage, which had significantly reduced at follow-up, supporting our hypothesis that there is increased sensory reactivity during tinnitus onset, which need not persist in order for tinnitus to become chronic.