Effect of Low-intensity Transcranial Magnetic Stimulation on Response Inhibition of Adults With...

Response inhibition is an impaired cognitive function in attention-deficit/hyperactivity disorder (ADHD) individuals. This primary deficit during the cancelation of an intended movement is observed even in the minimal demanding cognitive tasks. Studies have shown that transcranial magnetic stimulation (TMS), especially on the dorsolateral prefrontal cortex (DLPFC), can improve response inhibition. Nevertheless, TMS has a low spatial resolution, and its effect may not be observed in a single-session intervention. Studies show that low-intensity TMS has higher spatial resolution. Therefore, in this study, we aimed to evaluate the effectiveness of this method for intervention of response inhibition in ADHD individuals.

In a double-blind paradigm, the performance of the adults with ADHD while executing a Stroop color and word test (SCWT) was measured during a sham or a real stimulation of the DLPFC. Subsequently, the response inhibitions of the participants were measured before and after the stimulation. The number of correct, wrong, and missed answers to 96 computerized trials and the response times of the answers were measured. In addition, changes in electro-cortical activities during the rest phase before and after the stimulation were also evaluated.

After checking for data normality, the paired t-test between behavioral data showed that low-intensity magnetic stimulation of the DLPFC can improve response inhibition (reduce errors) even in a single-session intervention of ADHD individuals. The answering times did not change significantly. The behavioral changes were associated with significant changes in the power of EEG in delta and beta frequency bands at the frontal areas.

The proposed stimulation protocol with low-intensity TMS had a fair effect on the response inhibition in adults with ADHD. Therefore, it could be suggested as a treatment protocol for response inhibition in ADHD individuals.