Transcranial photobiomodulation effects on resting state EEG activity in adults diagnosed with ADHD versus healthy controls (Hebrew)

Attention-Deficit/Hyperactivity Disorder (ADHD) in adults is characterized by atypical resting-state brain network activity. Transcranial photobiomodulation (tPBM) is a non-invasive brain stimulation method utilizing near-infrared light pulses, which demonstrates potential for neural and cognitive regulation. In this context, the literature indicates that during resting-state, adults with ADHD typically exhibit reduced alpha wave power and altered beta waves compared to healthy controls, patterns that may suggest cortical hyperarousal and impaired attentional regulation. This study examined the effects of a single tPBM intervention at a wavelength of 1060-1070 nm in the near-infrared spectrum on resting-state electroencephalography (EEG) patterns (eyes-open and eyes-closed) in adults diagnosed with ADHD compared to a healthy control group. Thirty-nine adults (19 with ADHD and 20 healthy controls) participated in the study, undergoing EEG measurements before and after an active tPBM intervention, delivered at an alpha frequency (10 Hz), applied to the frontal regions F3 and F4. Accordingly, the study investigated three main issues: (1) whether there are neurophysiological baseline differences prior to the intervention (in wave power and functional connectivity) between adults with ADHD and healthy controls, (2) how the tPBM intervention affects alpha and beta wave power in frontal and parietal regions in both groups, and (3) how the intervention affects functional connectivity between the Dorsolateral Prefrontal Cortex (DLPFC) and the Precuneus.

Examining baseline measures prior to the intervention, it was found that the control group was characterized by higher relative power of Alpha1 waves in the right frontal region, whereas the ADHD group exhibited higher Beta1 power in the right parietal region. Additionally, in baseline functional connectivity measures, the ADHD group demonstrated hyperconnectivity compared to the control group. Following the intervention, results showed that the treatment increased the relative power of Alpha1 (8-10 Hz) and Alpha2 (10-13 Hz) waves during the eyes-open condition. However, in Alpha2 waves, a topographical difference emerged: the control group exhibited a widespread increase across frontal and parietal regions, whereas the ADHD group showed a localized increase restricted solely to the frontal region. Contrary to expectations, no significant changes were observed in beta wave power following the treatment. Functional connectivity analysis revealed a marginal decrease in the Beta3 band (30-40 Hz) exclusively within the ADHD group. These findings provide preliminary evidence that tPBM affects resting-state brain oscillations in a state-dependent manner. That is, the differences observed in diagnosis and baseline (the lower alpha power and network inefficiency in ADHD prior to the intervention) dictated the response pattern to the stimulation: while in healthy controls the effect spread to widespread regions, in the ADHD group it remained limited to the frontal stimulation area. These results highlight the tool's potential as a non-pharmacological intervention, which should be tailored to the patient's neurophysiological profile.