iTBS Stimulation of the Bilateral IFG/IPL Alters the Oscillatory Pattern in ASD

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Clinical Neuroscience

Background:

• Autism Spectrum Disorder (ASD) is a neurodevelopmental condition linked to aberrant brain connectivity and neuronal oscillations.
• Mirror neuron system dysfunction in the inferior frontal gyrus (IFG) and inferior parietal lobule (IPL) is implicated in social cognition deficits in ASD.
• Repetitive transcranial magnetic stimulation (rTMS) shows modest behavioral benefits, but intermittent theta-burst stimulation (iTBS) effects on oscillations in ASD are unexplored.

Purpose of the Study:

• To investigate if iTBS targeting bilateral IFG and IPL modulates EEG-derived oscillatory activity in adolescents with ASD.
• To explore the relationship between oscillatory changes and social reciprocity.

Main Methods:

• Six adolescents with ASD (ages 13-18) received bilateral iTBS targeting IFG and IPL.
• Participants underwent a randomized waitlist-controlled crossover design (9 sham, 9 active sessions).
• EEG recordings and power spectral analyses were conducted, alongside Childhood Autism Rating Scale, Second Edition (CARS2) assessments.

Main Results:

• iTBS was well-tolerated; behavioral analysis showed significant CARS2 score reduction, indicating improved social reciprocity.
• EEG revealed a transient, immediate post-stimulation increase in gamma-band power during the first active session (EEG-1).
• Subsequent sessions (EEG-2) showed no consistent gamma enhancement, with attenuation of the initial response observed.

Conclusions:

• Bilateral iTBS targeting IFG and IPL induces transient gamma oscillation enhancement in ASD, attenuating with repeated stimulation.
• This suggests adaptive homeostatic plasticity within neural circuits, possibly involving GABAergic interneurons.
• EEG shows potential as a biomarker for neuromodulation in ASD, highlighting the need for network-level analysis and personalized strategies.