Low-frequency anodal Transcranial pulsed current stimulation (0.5-5 Hz): effects on EEG band amplitude, interhemispheric coherence, and cognitive performance.

Transcranial pulsed current stimulation (tPCS) is a frequency-dependent neuromodulation technique. However, its mechanisms remain unclear. This study examined the effects of low-frequency (0.5, 1, 3, 5 Hz, and sham stimulation) anodal monophasic tPCS (a-tPCSM) on interhemispheric coherence, electroencephalography (EEG) band power, cognitive behaviours, and adverse effects. Seventeen healthy adults completed five sessions in a double-blinded, randomised, counterbalanced crossover design (2 mA stimulation for 20 min over M1) with a 48-hour washout period. Before and immediately after stimulation, absolute EEG band power and interhemispheric coherence were measured using quantitative EEG. Behavioural performance was assessed using the simple choice reaction time task (SCRTT), which evaluates cognitive processing speed, attention, and response selection ability. Stimulation-related adverse effects were also evaluated. Results indicated that 1 Hz stimulation with eyes closed significantly increased interhemispheric coherence across the delta, theta, alpha, and sensory-motor rhythm (SMR) bands in frontal, temporal, and central regions. However, 0.5, 3, and 5 Hz stimulation produced selective reductions in delta and alpha power during the eyes-open condition across frontal, temporal, parietal, and occipital regions. No significant differences were observed in simple and choice reaction time or error rates. Mild transient adverse effects, including itching, tingling, burning sensations, and occasional phosphene perception, were reported during stimulation. In conclusion, low-frequency a-tPCSM produced selective modulation of resting-state EEG coherence and spectral power without measurable changes in cognitive-behavioural performance. Thus, low-frequency a-tPCSM can modulate selected EEG measures in healthy adults; however, the functional and clinical significance of these neurophysiological effects remains uncertain and requires further investigation.