Lateral Cerebellar Theta Burst Stimulation Can Modulate Default Mode Network Connectivity in Autistic Adults

Developing effective neuromodulation strategies for core autistic symptoms remains a critical need. The lateral cerebellum, implicated in socio-cognitive functions often affected in autism, represents a promising target for repetitive transcranial magnetic stimulation (rTMS), which has not yet been tested in this population. Here, we report a pilot investigation of the safety, feasibility, and network-level effects of one-session intermittent theta burst stimulation (iTBS, a variant of rTMS; 1200 pulses delivered at 80% active motor threshold with a 15-minute inter-train interval) targeting the right lateral cerebellum (Crus I/II) in 10 autistic adults (7 assigned male, 3 assigned female at birth, aged 19-30 years). All participants tolerated the protocol well, with no severe adverse events and a 100% retention rate. Resting-state functional MRI indicated a significant post-iTBS decrease in functional connectivity within the default-mode network and somatosensory motor network, while other networks remained unchanged. Moreover, idiosyncrasy in functional connectivity within the ventral attention, frontoparietal, default-mode and visual networks significantly decreased after iTBS. These findings suggest that cerebellar iTBS is safe and feasible for autistic adults and may acutely modulate multiple large-scale functional networks in their brain. Future multi-session, sham-controlled trials are warranted to validate these results and investigate whether repeated cerebellar stimulation yields sustained neurobiological or clinical benefits in autism.