Thalamocortical Dysrhythmia: A Theoretical Update in Tinnitus.

Summary

Tinnitus has been attributed to bottom-up deafferentation and/or a top-down noise-cancelling deficit; both alter auditory thalamocortical signal transmission, producing thalamocortical dysrhythmia (TCD). In deafferentation, TCD appears as a slowing of resting alpha to theta with increased surrounding gamma, giving persistent theta, gamma cross-frequency coupling. Theta burst-firing raises network synchrony and recruitment, enabling long-range synchrony that can carry focal auditory gamma activity into a consciousness-enabling ('global workspace') network. With limited deafferentation the missing information is retrieved from neighbouring auditory cortex; when it is broader, from theta-mediated parahippocampal auditory memory. In Bayesian terms, tinnitus is the prediction error between predicted and sensed auditory input.

Key findings

• TCD: resting alpha slows to theta with increased surrounding gamma, giving persistent theta, gamma coupling.
• Theta bursts increase synchrony and recruitment, enabling focal auditory activity to reach a consciousness-enabling network.
• Narrow deafferentation draws missing information from neighbouring cortex; broad deafferentation from parahippocampal auditory memory.
• Bayesian reading: tinnitus is a prediction error, with reduced sensory updating (less alpha) and theta/beta, gamma coupling.