Effects of Non-Invasive Right Prefrontal Stimulation on Cognitive Performance of ADHD Patients

Author(s): Lihi Bokovza, Guy Baz, Hadar Shalev

Aims: Attention deficit hyperactivity disorder (ADHD) is a prevalent neuropsychiatric disorder. Recent study from our lab has shown lasting electrophysiological alterations and clinical improvement following 15 daily high-frequency (HF) deep transcranial magnetic stimulation (dTMS) sessions directed to the right prefrontal cortex (rPFC). This paper focuses on the cognitive performance of ADHD patients before and after treatment and compared to non-ADHD controls.

Methods: Ninety-six ADHD and 57 non-ADHD subjects underwent cognitive assessment using computerized battery. Forty-nine ADHD patients completed HF dTMS or sham treatment (n=26 real and 23 sham). Completers underwent a second Mindstreams assessment.

Results: Reaction times (RT) and their standard deviations (RT SD) were significantly higher in the ADHD group compared to non-ADHD. Reduced accuracy was evident within the ADHD group in tasks with high cognitive load and also in a verbal memory and a problem-solving task. HF dTMS resulted in a significant improvement in two tasks, as well as higher effect sizes in other tasks, compared to sham treatment.

Conclusions: Cognitive deficits related to ADHD are manifested in the Mindstreams battery mostly in terms of RT, and in some cases in accuracy. HF dTMS may improve cognitive abilities but an increase of sample sizes is required.