Deafferentation-based pathophysiological differences in phantom sound: Tinnitus with and without hearing loss

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Clinical Neurology

Background:

• Tinnitus is often perceived as an auditory phantom percept.
• A theoretical multiphase compensation mechanism at the cortical level links auditory deafferentation to tinnitus.
• A Bayesian brain model predicts two distinct tinnitus types based on hearing loss severity.

Purpose of the Study:

• To investigate the validity of the Bayesian brain model for tinnitus.
• To differentiate tinnitus mechanisms based on the degree of hearing loss.
• To explore the relationship between hearing loss and brain activity in tinnitus.

Main Methods:

• Resting-state electroencephalography (EEG) recordings were analyzed in 129 tinnitus patients.
• Source analysis of EEG data was performed.
• EEG findings were correlated with mean hearing loss, hearing loss range, and hearing loss at the tinnitus frequency.

Main Results:

• Tinnitus is associated with two distinct underlying mechanisms.
• In patients with minimal or no hearing loss, tinnitus relates to auditory cortex activity, not hippocampal activity.
• In patients with significant hearing loss, tinnitus is linked to hippocampal mechanisms, with the auditory cortex playing a lesser role.
• Hearing loss appears to modulate functional and effective connectivity between the auditory cortex and the parahippocampus.

Conclusions:

• The study supports the existence of two different tinnitus mechanisms.
• The severity of hearing loss is a critical factor in determining the neural basis of tinnitus.
• Hearing loss influences inter-regional brain communication, specifically between the auditory cortex and parahippocampus, in tinnitus.