Phase locking of auditory steady state responses is modulated by a predictive sensory context and linked to degree of myelination in the cerebellum

Background 40 Hz auditory steady state responses (ASSR) can be evoked by brief auditory clicks delivered at 40 Hz. While the neuropharmacology behind the generation of ASSR is well examined, the link between ASSR and microstructural properties of the brain is unclear. Further, whether the 40 Hz ASSR can be manipulated through processes involving top-down control, such as prediction, is currently unknown. Methods We recorded EEG in 50 neurotypical participants while they engaged in a 40 Hz Auditory steady state paradigm. We manipulated the predictability of tones to test the modulatory effect of prediction on 40 Hz steady state responses. Further, we acquired T1w and T2w structural MRI and used the T1/T2 ratio as a proxy to determine myelination in grey matter. Results The phase locking of the 40 Hz ASSR was indeed modulated by prediction and this modulation extended to all frequency bands, suggesting prediction violation as a phase resetting mechanism. Interestingly, we found that the prediction violation of the phase locking at 40 Hz (gamma) was associated with the degree of grey matter myelination in the right cerebellum. Discussion We demonstrate that prediction violations evoke resetting of oscillatory activity and suggest that the efficiency of this process is promoted by greater cerebellar myelin. Our findings provide a structural-functional relationship for myelin and phase locking of auditory oscillatory activity. These results introduce a setting for looking at the interaction of predictive processes and ASSR in disorders where these processes are impaired such as in psychosis.