Tinnitus and hyperacusis: Central noise, gain and variance

Area of Science:

• Auditory Neuroscience
• Neuroscience of Sensory Perception
• Oto-neurology

Background:

• Tinnitus is a phantom auditory perception without external stimuli.
• Hyperacusis involves atypical sound sensitivity, perceiving sounds as painfully loud.
• Both conditions may arise from the brain's compensatory mechanisms for reduced auditory input.

Purpose of the Study:

• To differentiate between two proposed models of central auditory compensation.
• To explain the neural mechanisms potentially underlying tinnitus and hyperacusis.
• To propose a variance-based model for these auditory disorders.

Main Methods:

• Theoretical modeling differentiating additive central noise and multiplicative central gain.
• Analysis of how these models predict central representations of sound variance.
• Linking model predictions to existing literature on central gain and auditory processing.

Main Results:

• Additive central noise model is proposed to generate tinnitus.
• Multiplicative central gain model is proposed to generate hyperacusis.
• Both models predict increased variance in central sound representations, with multiplicative gain causing a nonlinear increase.

Conclusions:

• Increased central variance, predicted by both models, can limit compensation and reduce temporal synchrony.
• This variance increase may explain previously reported insufficient central gain in tinnitus and hyperacusis.
• Future research should gather trial-by-trial neural firing variance data to test this variance-based model.