Atypical Cerebellar Responses are Associated with Altered Neural Habituation during Sensory Stimulation in Autism

Sensory processing atypicalities are highly prevalent in autistic youth; yet, the neural mechanisms underlying these differences are not well understood. While the cerebellum plays a key role in sensorimotor coordination and is structurally and functionally atypical in the autistic brain, it has been overlooked in research investigating sensory challenges in autism. Previous evidence has linked sensory over-responsivity in autism to altered neural habituation in sensory and limbic regions, but the role of the cerebellum in atypical habituation is as yet unknown. In the current study, we investigated sensory-evoked cerebellar responses in autistic and typically-developing (TD) youth, and how these responses related to sensory-limbic habituation. Fifty-two autistic and 41 TD participants aged 8-18 years underwent fMRI during mildly aversive auditory and tactile stimulation. We found increased activity in the contralateral (to the tactile stimulation) cerebellum in ASD compared to TD. Greater cerebellar activity was associated with more habituation in sensory-limbic regions for TD youth. In contrast, stronger activity in lobule VII (including crus I and II) was associated with less amygdala habituation in ASD. There were no diagnostic group differences in the relationship between cerebellar activation and habituation in sensory cortices. Results inform understanding of the role of the cerebellum in processing aversive sensory information and, taken together, findings of hyper-active cerebellar responses as well as an atypical relationship between cerebellar function and amygdala habituation suggest cerebellar involvement in sensory alterations in autism.