The Reduced Cochlear Output and the Failure to Adapt the Central Auditory Response Causes Tinnitus

[erik]

Tinnitus is proposed to be caused by decreased central input from the cochlea, followed by increased spontaneous and evoked subcortical activity that is interpreted as compensation for increased responsiveness of central auditory circuits. We compared equally noise exposed rats separated into groups with and without tinnitus for differences in brain responsiveness relative to the degree of deafferentation in the periphery. We analyzed (1) the number of CtBP2/RIBEYE-positive particles in ribbon synapses of the inner hair cell (IHC) as a measure for deafferentation; (2) the fine structure of the amplitudes of auditory brainstem responses (ABR) reflecting differences in sound responses following decreased auditory nerve activity and (3) the expression of the activity-regulated gene Arc in the auditory cortex (AC) to identify long-lasting central activity following sensory deprivation. Following moderate trauma, 30% of animals exhibited tinnitus, similar to the tinnitus prevalence among hearing impaired humans. Although bothtinnitus and no-tinnitus animals exhibited a reduced ABR wave I amplitude (generated by primary auditory nerve fibers), IHCs ribbon loss and high-frequency hearing impairment was more severe in tinnitus animals, associated with significantly reduced amplitudes of the more centrally generated wave IV and V and less intense staining of Arc mRNA and protein in the AC. The observed severe IHCs ribbon loss, the minimal restoration of ABR wave size, and reduced cortical Arc expression suggest that tinnitus is linked to a failure to adapt central circuits to reduced cochlear input.

 

[Hudson]

You gotta include links to these buddy! haha

 

[erik]

Sorry that was the whole thing, no other data at this time

 

[Markku]

Here is the full article: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057247

 

[joejunior]

I think its basically saying that tinnitus is a result of related brain areas being unable to compensate for loss of cochlear input. It adds that 'increased neuronal activity in the auditory periphery is a compensation of peripheral input – avoiding tinnitus – rather than a correlate or even the origin of tinnitus.; Not really surely what that means.
It appears to be a well conducted study.

I hope we get to the stage soon where there is a unified and agreed understanding of tinnitus. So that all effort is directed to developing therapies