Impact of repetitive transcranial magnetic stimulation on the directed connectivity of autism EEG signals: a pilot study

To compare the differences in directed connectivity between typically developing (TD) and autism spectrum disorder (ASD) children and identify the potential effects of repetitive transcranial magnetic stimulation (rTMS) on brain connectivity and behavior of children with ASD; 26 TD children (18 males/8 females; the average age was 6.34 ± 0.45) and 30 ASD children (21 males/9 females; the average age was 6.42 ± 0.17) participated in the experiment. ASD children were divided randomly into an experimental group and a control group. The experimental group received 18 rTMS sessions (twice a week for nine weeks), whereas the control group received the same procedures with sham stimulation. Directed transfer function (DTF) was used to calculate the effective connectivity as a way of investigating differences between ASD and TD children while simultaneously evaluating the effectiveness of rTMS for ASD. The results illustrate that the DTF of TD children in the frontal lobe (Fp1, Fp2, F7, F8) and temporal lobe (T7, T8) is higher than that of ASD children in all frequency bands; however, the DTF of ASD children is higher than TD in the midline (Fz, Cz), central lobe (C3, C4), and parietal lobe (P3, P4). In the experimental group of ASD children, the effective connectivity decreased from O1 to T7 and from P7 to Fp1 in the alpha band and from Pz to T8 in the gamma band after stimulation. Significant changes in Autism Behavior Checklist (ABC) scores were also found in social behaviors. Effective connectivity derived from DTF distinguishes ASD from TD children. rTMS provides changes in connectivity and behavior, suggesting its potential use as a viable treatment option for ASD individuals.