Long-interval intracortical inhibition in individuals with autism spectrum disorders: A TMS-EEG study with source estimation analyses.

Researchers used brain stimulation and recording techniques to study how well the brain can 'put the brakes on' neural activity in people with autism compared to typical individuals. While they could successfully measure this braking effect in both groups, they found no significant differences between autistic people and controls. This suggests that this particular method may not be sensitive enough to detect the brain chemical differences that are thought to exist in autism.

This TMS-EEG study investigated Long-interval Intracortical Inhibition (LICI) in the dorsolateral prefrontal cortex of 32 individuals with ASD and 34 controls. The study used advanced source estimation techniques to examine brain inhibition patterns that may reflect GABA receptor function. Results showed that LICI successfully suppressed cortical activity 165-234ms post-stimulation in both groups, with additional suppressive effects in theta-alpha frequency bands (30-300ms). However, no significant differences were found between ASD and control groups in these inhibitory responses.

This represents the first application of source-estimation methods in TMS-EEG LICI studies in autism, though the technique alone may be insufficient to detect GABA receptor dysfunction in ASD.

Results suggest that TMS-EEG LICI may not be suitable as a standalone biomarker for autism-related brain differences. The technique successfully measures inhibitory brain function but doesn't distinguish autistic individuals from controls. Future research may need to combine multiple neurophysiological measures or refine methodology to detect subtle GABA-related differences in autism.

Single study design with relatively small sample sizes. Authors acknowledge that TMS-EEG LICI alone may be insufficient to detect GABA receptor dysfunction in ASD. No information provided about participant characteristics, medication status, or potential confounding variables.

This study aimed to evaluate Long-interval Intracortical Inhibition (LICI) in the Dorsolateral Prefrontal Cortex (DLPFC) of individuals with Autism Spectrum Disorder (ASD) using transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) with source-based estimation analyses. We applied the LICI paradigm to the left DLPFC of 32 individuals with ASD and 34 healthy controls. First, sensor-level Local Mean Field Power (LMFP) was calculated from TMS-evoked potentials for all participants to detect the LICI effect. Subsequently, source-based analyses were performed using dynamic statistical parametric mapping to minimize the influence of volume conduction.

Finally, time-frequency (TF) analyses at the source level were conducted to further characterize the LICI effects. LMFP analysis revealed that cortical activity in the interval of 165-234 ms post-stimulation was suppressed by LICI (p = 0.024). Source-based analyses confirmed inhibitory effects within the same time range. Additionally, TF analyses indicated suppressive effects within 30-300 ms in the theta to alpha bands.

However, no significant group differences in the LICI effects were detected. TMS-EEG combined with LICI alone may be insufficient to detect GABA(B) receptor dysfunction in ASD. This is the first TMS-EEG study to elucidate the LICI effect by applying source-estimation methods in ASD.