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

## TL;DR

Transcranial random noise stimulation (tRNS) combined with cognitive training improved neural activity and behavior in children with ADHD.

## Contribution

tRNS reduced aperiodic exponents more consistently than ERP or ERSP indices, suggesting a novel approach to modulating E/I balance in ADHD.

## Key findings

- Children with ADHD showed elevated EEG aperiodic exponents compared to healthy peers.
- tRNS with cognitive training improved neurobehavioral outcomes and reduced aperiodic exponents in ADHD children.
- The effects of tRNS on E/I balance were sustained at follow-up assessment.

## Abstract

•Children with ADHD show elevated EEG aperiodic exponents vs. healthy peers.•tRNS with cognitive training modulated neurobehavioral outcomes vs. sham in ADHD.•tRNS reduced aperiodic exponent more consistently than ERP or ERSP indices.•Effects of tRNS on E/I balance persisted at follow-up assessment.

Children with ADHD show elevated EEG aperiodic exponents vs. healthy peers.

tRNS with cognitive training modulated neurobehavioral outcomes vs. sham in ADHD.

tRNS reduced aperiodic exponent more consistently than ERP or ERSP indices.

Effects of tRNS on E/I balance persisted at follow-up assessment.

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.

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).

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).

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.