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Re: Technique can pinpoint tinnitus

Dear John,

we are far from knowing the fine mechanisms of tinnitus but there is a consensus in the field (I think) stating that tinnitus is caused by some central mechanisms (i.e. release from central inhibition) after a decrease in sensory inputs (caused by hearing loss). Noise trauma, which is known to decrease spontaneous activity at cochlear nerve level, and which is a strong and common "tinnitus inducer", corroborate the view of a central tinnitus (a decrease in neural activity is likely not related to a perception). Interestingly, the percept of tinnitus corresponds strictly to the frequency range of hearing loss (Norena et al., 2002). Moreover, it is worth mentioning that cochlear implant subjects often present a tinnitus and that a section of the cochlear nerve does not always abolish tinnitus. Finally, some papers have shown neural changes (both in term of firing rate and synchrony) after noise trauma in AI of (anesthetized) cats circumscribed to neurons with characteristic frequency corresponding to the frequency range of hearing loss (for instance: Norena and Eggermont, 2003 - sorry for the self-promotion :-) ).

This model suggests that the decrease in afferent inputs should be compensated to prevent/reverse the central changes causing tinnitus. Hearing aids could be a way for stimulating/reeducating the auditory system (as long as the cochlea transmits sensory inputs, i.e. absence of "dead regions"). However, the immediate release from tinnitus caused by hearing aids is likely caused by the partial masking of tinnitus by the amplified background.
arnaud norena

2009/10/6 Beerends, J.G. (John) <john.beerends@xxxxxx>
Dear All,

In this paper there is no mentioning of any relation between tinnitus and hearing loss.
The spontaneous neural activity may just be the result of unused neural capacity that was stimulated before getting damaged. Are there any experts that know if this relation exists? And if so, is this relation is linked to damage of both the outer and inner hair cells, or to either one of them?

I know experts who say that tinnitus often gets less when a subject with hearing loss (and tinnitus) starts wearing a correctly fitted hearing aid. This would support the idea of hearing loss induced spontaneous neural activity.

John Beerends
The Netherlands

-----Original Message-----
From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Kevin Austin
Sent: dinsdag 6 oktober 2009 1:15
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Technique can pinpoint tinnitus

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Arnaud Norena
Université de Provence
Centre St Charles, Pôle 3C - Case B
3, Place Victor Hugo
F - 13331 Marseille Cedex 03