Changes in aperiodic EEG activity following acupuncture stimulation in stroke

Electroencephalography (EEG) enables the direct measurement of stroke-related brain activity, which is crucial for objectively evaluating therapeutic effects of neuromodulatory interventions in stroke. Numerous studies indicate that EEG spectra comprise a mixture of periodic oscillations and aperiodic background; however, how aperiodic activity, distinct from oscillatory components, characterizes and quantifies external stimulation remains unclear. In this paper, we parameterized the power spectra of EEG recorded from 30 stroke subjects with acupuncture stimulation and investigated the changes of oscillatory and aperiodic brain activity following acupuncture stimulation. For the oscillatory components, we found that acupuncture increased both the power and center frequency of alpha oscillations in the left fronto-parietal cortex, indicating a shift toward faster and more strongly synchronized activity in the lesioned regions. Next, analysis of aperiodic brain activity demonstrated widespread decreases in the aperiodic exponent and offset, most prominently in the ipsilesional hemisphere. These globally and spatially coherent changes suggest that aperiodic dynamics are highly sensitive to acupuncture, reflecting coordinated changes in the background spectral organization. Furthermore, analyses of both periodic and aperiodic features revealed that acupuncture improved interhemispheric symmetry, with particularly pronounced effects observed in alpha center frequency, alpha power, and the aperiodic exponent. Collectively, this study extracted oscillatory and aperiodic spectral features to characterize EEG activity, identified alpha center frequency, alpha power, and the aperiodic exponent as potential biomarkers of acupuncture-induced changes in stroke, and provided evidence for the modulatory effects of peripheral acupuncture stimulation on brain activity.