title: Suppression of putative tinnitus-related activity by extra-cochlear electrical stimulation.
abstract: Studies on animals have shown that noise-induced hearing loss is followed by an increase of spontaneous firing at several stages of the central auditory system. This central hyperactivity has been suggested to underpin the perception of tinnitus. It was shown that decreasing cochlear activity can abolish the noise-induced central hyperactivity. This latter result further suggests that an approach consisting of reducing cochlear activity may provide a therapeutic avenue for tinnitus. In this context, extra-cochlear electric stimulation (ECES) may be a good candidate to modulate cochlear activity and suppress tinnitus. Indeed, it has been shown that a positive current applied at the round window reduces cochlear nerve activity and can suppress tinnitus reliably in tinnitus subjects. The present study investigates whether ECES with a positive current can abolish the noise-induced central hyperactivity, i.e., the putative tinnitus-related activity. Spontaneous and stimulus-evoked neural activity before, during and after ECES was assessed from single-unit recordings in the inferior colliculus of anesthetized guinea pigs. We found that ECES with positive current significantly decreases the spontaneous firing rate of neurons with high characteristic frequencies, whereas negative current produces the opposite effect. The effects of the ECES are absent or even reversed for neurons with low characteristic frequencies. Importantly, ECES with positive current had only a marginal effect on thresholds and tone-induced activity of collicular neurons, suggesting that the main action of positive current is to modulate the spontaneous firing. Overall, cochlear electrical stimulation may be a viable approach for suppressing some forms of (peripheral-dependent) tinnitus.
authors.affiliation: Laboratory of Adaptive and Integrative Neuroscience, CNRS, and Aix-Marseille Université, Fédération de Recherche 3C, Marseille, France; and arnaud.norena@univ-amu.fr.
authors.forename: A J
authors.initials: AJ
authors.lastname: Noreña
authors.affiliation: The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: W H A M
authors.initials: WH
authors.lastname: Mulders
authors.affiliation: The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: D
authors.initials: D
authors.lastname: Robertson
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects; D000200:Action Potentials; D000818:Animals; D004195:Disease Models, Animal; D004599:Electric Stimulation Therapy / Q000379:methods*; D006168:Guinea Pigs; D007245:Inferior Colliculi / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D009622:Noise / Q000009:adverse effects; D014012:Tinnitus / Q000503:physiopathology* / Q000628:therapy*
keywords: auditory perception; cochlear nerve; hearing loss; noise trauma; plasticity; spontaneous activity