Researchers at Kanazawa University announced on June 12 that they have identified a previously unrecognized mechanism by which structural changes in the cerebellum influence social behavior. The study demonstrates that disruption of specialized extracellular structures surrounding cerebellar neurons alters neuronal activity across brain circuits involved in social behavior. The findings provide new insight into the neural mechanisms associated with autism spectrum disorder.
Autism spectrum disorder is a neurodevelopmental condition characterized primarily by difficulties in social interaction and communication. Increasing evidence suggests that autism arises not from dysfunction in a single brain region, but from alterations in the function of distributed neural circuits across the brain.
The cerebellum, traditionally known for its role in motor coordination, has more recently been recognized as an important regulator of higher-order brain functions, including cognition, emotion, and social behavior. However, the molecular and cellular mechanisms through which cerebellar abnormalities contribute to autism-related social deficits have remained largely unclear.
In this study, researchers investigated how changes in cerebellar neural circuits may influence social behavior associated with autism. The team analyzed multiple mouse models representing both environmental and genetic risk factors: a prenatal valproic acid exposure model and mice carrying a mutation in the Chd8 gene. The analysis revealed that neurons in the deep cerebellar nuclei exhibited a marked reduction in perineuronal nets (PNNs), specialized extracellular matrix structures known to stabilize neuronal excitability and support circuit maturation.
To examine functional significance, researchers selectively degraded PNNs using an enzymatic approach. Mice with disrupted PNNs showed impairments in social behavior, including reduced interaction and decreased interest in unfamiliar mice. Further experiments indicated that these structural changes resulted in diminished activation of neurons within key brain regions during exposure to social stimuli.
The study also found increased expression of transcription factor ARNT2 among neurons lacking PNNs; suppressing ARNT2 restored both neuronal activity and normal social behaviors. Researchers said these findings reveal a previously unknown mechanism linking reduced PNNs to altered neuronal activity and disrupted broader brain circuits affecting social behavior.
