A Unified Theory for the Development of Tinnitus Perception and Hyperacusis Based on Associative Plasticity in the Dorsal Cochlear Nucleus.

Summary

Hyperacusis is associated with tinnitus far more often than tinnitus is associated with hyperacusis, a striking asymmetry suggesting a shared origin. This theoretical model proposes that both arise from associative (Hebbian-like) synaptic plasticity within the dorsal cochlear nucleus, but at different synapses onto the same fusiform neurons: strengthening of cochlear (sound) input is proposed to produce hyperacusis, while strengthening of somatosensory input produces chronic tinnitus. The model predicts that hearing loss alone tends to produce tinnitus, while noise exposure (which can also strengthen cochlear input before it causes hearing loss) tends to produce hyperacusis, offering a mechanistic reason for the observed asymmetry.

Key findings

• Proposes tinnitus and hyperacusis arise from distinct, associative-plasticity-strengthened synapses onto the same DCN fusiform neurons.
• Somatosensory-input strengthening is proposed to underlie chronic tinnitus; cochlear-input strengthening to underlie hyperacusis.
• Offers a mechanistic explanation for why hyperacusis so often co-occurs with tinnitus, but tinnitus less often occurs with hyperacusis.
• Explicitly framed as a theoretical model intended to stimulate future experimental testing, not a proven account.