Impaired Predictive Coding in the Somatosensory Mismatch Detection Network in Essential Tremor: A Cerebello-Cortical Perspective.

BACKGROUND

According to predictive coding theory, mismatch detection relies on comparing sensory inputs with internal predictions. In the somatosensory domain, this process involves interactions between cerebellar lobule VIII (CL8) and the secondary somatosensory cortex (S2) within the cortical tactile mismatch detection network. Essential tremor (ET) is a cerebellar disorder that provides a model to explore how cerebellar dysfunction affects the tactile mismatch detection network.

OBJECTIVES

To test the hypothesis that cerebello-cortical interactions between CL8 and S2, involved in tactile predictions, are altered in ET.

METHODS

Twenty patients with ET and matched healthy individuals underwent two tactile oddball functional magnetic resonance imaging (fMRI) paradigms, manipulating the predictability of deviant stimuli. fMRI signal and functional connectivity were assessed across the cortical somatosensory mismatch detection network and the CL8. Psychophysiological interaction (PPI) analyses were used to evaluate cerebello-cortical functional connectivity changes related to tactile predictions between ET and healthy individuals.

RESULTS

In healthy individuals, the predictable condition elicited reduced fMRI signal compared with the unpredictable condition at S2 cortex and within the cortical mismatch detection network. PPI analysis showed that the predictable condition was characterized by a negative correlation of fMRI signals between S2 cortex and CL8 not observed in the unpredictable condition. ET showed no significant difference in the mismatch detection network according to the predictability of tactile stimuli and no functional connectivity change between CL8 and S2 cortex.

CONCLUSION

These results support a contribution of the cerebellum to impaired predictive coding within the cortical network responsible for detecting tactile mismatches in ET. © 2025 International Parkinson and Movement Disorder Society.