Modulation of motor cortical excitability by continuous theta-burst stimulation in adults with autism spectrum disorder: The roles of BDNF and APOE polymorphisms

Objective: To assess the utility of the modulation of motor cortex (M1) excitability by continuous theta-burst stimulation (cTBS) as a physiologic biomarker for adults with autism spectrum disorder (ASD), and to evaluate the influences of brain-derived neurotrophic factor (BDNF) and apolipoprotein E (APOE) polymorphisms on cTBS aftereffects. Methods. 44 neurotypical individuals (NT; age 21-65, 34 males) and 19 age-matched adults with high-functioning ASD (age 21-58, 17 males) underwent M1 cTBS. Cortico-motor reactivity was assessed before cTBS and thereafter every 5-10 minutes for 60 minutes (T5-T60). Results. Logistic regressions found cTBS-induced change in amplitude of motor evoked potentials (ΔMEP) at T15 was a significant predictor of ASD diagnosis (p=0.04). ΔMEP at T15 remained a significant predictor of diagnosis among BDNF Met+ subjects and APOEε4- subjects (p-values < 0.05) but not BDNF Met- subjects. ΔMEP at T30 was the best predictor of diagnosis among APOEε4+ subjects (p = 0.08). Conclusions. We confirm previous findings on the utility of cTBS measures of plasticity for adults with ASD, and we find the diagnostic utility of cTBS is modulated by BDNF and APOE SNPs. Significance. It is important to control for BDNF and APOE polymorphisms when comparing TBS aftereffects in ASD and NT individuals.