The effects of transcranial random noise stimulation on excitation/inhibition balance in ADHD

Background Children with attention-deficit/hyperactivity disorder (ADHD) often show aberrant neural activity, including excitation/inhibition (E/I) imbalances, atypical event-related potentials (ERPs), and neural network dysfunction. Transcranial Random Noise Stimulation (tRNS) has shown promise in modulating neural activity in ADHD. Methods The current study examined differences in behavioral and EEG signals recorded during an inhibitory control task in children with (N = 23) and without (N = 33) ADHD. Changes in these signals were further assessed following a combined tRNS and cognitive training intervention targeting the right inferior frontal gyrus and left dorsolateral prefrontal cortex in a sham-controlled randomized trial within the ADHD group only (n = 11 and 12 for intervention and sham groups, respectively). Results At baseline, children with ADHD showed slower reaction times, and higher commission error rates compared to healthy controls. Neurally, they exhibited elevated EEG aperiodic exponents, indicating lower E/I balance. Following intervention, we found slower task speed but fewer omission errors in the active compared to the sham group. Regression model showed reduced aperiodic exponents (β = –1.13, t(21) = –2.45, p = 0.023), decreased late ERP-P3b amplitude, and diminished theta and alpha band activity at the cortical level. There was a weaker but still significant reduction in aperiodic exponent values at follow-up compared to immediately post-treatment (β = 0.485, t(63) = 2.182, p = 0.033). Conclusion Aperiodic exponent may serve as a useful indicator of treatment-related neural modulation and may provide complementary information to traditional ERP and event-related spectral perturbation (ERSP) measures, warranting further investigation in larger samples.