Abnormal functional asymmetry and its behavioural correlates in adults with ADHD: A TMS-EEG study

• DOI: 10.1371/journal.pone.0285086
• Publication Date: 2023-05-25T17:39:38Z
• Authors: Amir Avnit; Samuel Zibman; Uri Alyagon; Abraham Zangen
• Keywords: Adult; Brain Mapping; ADHD; EEG; frontal asymmetry; response inhibition; TMS; Attention Deficit Disorder with Hyperactivity; Science; Q; R; Medicine; Humans; Brain; Electroencephalography; Evoked Potentials; Research Article

Objectives Abnormal functional brain asymmetry and deficient response inhibition are two core symptoms of attention deficit hyperactivity disorder (ADHD). We investigated whether these symptoms are inter-related and whether they are underlined by altered frontal excitability and by compromised interhemispheric connectivity.

Methods We studied these issues in 52 ADHD and 43 non-clinical adults by comparing: (1) stop-signal reaction time (SSRT); (2) frontal asymmetry of the N200 event-related potential component, which is evoked during response inhibition and is lateralised to the right hemisphere; (3) TMS-evoked potential (TEP) in the right frontal hemisphere, which is indicative of local cortical excitability; and (4) frontal right-to-left interhemispheric TMS signal propagation (ISP), which is reversely indicative of interhemispheric connectivity.

Results Compared to controls, the ADHD group demonstrated elongated SSRT, reduced N200 right-frontal-asymmetry, weaker TEP, and stronger ISP. Moreover, in the ADHD group, N200 right-frontal-asymmetry correlated with SSRT, with TEP, and with symptoms severity. Conversely, no relationship was observed between ISP and N200 right-frontal-asymmetry, and both TEP and ISP were found to be unrelated to SSRT.

Conclusions Our results indicate that abnormal frontal asymmetry is related to a key cognitive symptom in ADHD and suggest that it is underlined by reduced right-frontal excitability.