The Somatosensory Mismatch Negativity.

Mismatch negativity (MMN) is a well-established neural signature of automatic change detection in the auditory modality. Growing evidence suggests that analogous responses exist in other sensory domains, including somatosensation. This review provides an initial overview of the somatosensory MMN (sMMN), summarizing findings from both human and animal research concerning its underlying neural mechanisms and functional significance as a predictive error signal. We discuss electrophysiological and neuroimaging evidence identifying primary and secondary somatosensory cortices (S1 and S2) as key generators of the sMMN, highlighting the roles of sensory and stimulus-specific adaptation, as well as true deviance detection or surprise. Computational studies further support a hierarchical inference process, where somatosensory mismatch responses encode probabilistic structures based on transition probabilities of sequential input. We also address the clinical relevance of the sMMN in neurodevelopmental, psychiatric, and neurological disorders, as well as its role in aging and body representation. Understanding the neuronal mechanisms underlying the sMMN not only advances our knowledge of somatosensory predictive processing but also contributes to the broader study of perception and learning in the brain.