EEG Oscillations and the Modulation of tES and TMS in Patients with Mild Cognitive Impairment

Mild cognitive impairment (MCI) is characterized by objective cognitive decline that does not severely impact daily independence. This clinical stage may stem from various underlying causes, including Alzheimer's disease pathology. MCI provides a valuable opportunity to study interventions that could slow cognitive decline. Individuals with MCI show alterations in neural oscillations linked to cognitive impairment. Non-invasive brain stimulation (NIBS) techniques, including transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES), along with their major forms, transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), can effectively modulate neural oscillations and improve cognition in MCI patients. Due to the potential of NIBS in the treatment of MCI, this review focuses on EEG abnormalities of neural oscillations in MCI patients and examines how repetitive TMS (rTMS), tDCS, and tACS improve cognitive function by targeting specific EEG frequency bands. A literature review was conducted for this study using the PubMed database, including studies published up to May 2025. Studies demonstrated that MCI patients have significant changes in EEG activity, with increases in the low-frequency band (δ-θ, 0.5-8 Hz) and decreases in the high-frequency band (β-γ, 12-100 Hz), and there are few reports on changes in mid-frequency α (8-12 Hz) EEG activity. Notably, tDCS improves cognition in MCI patients by decreasing low-frequency and increasing highfrequency EEG activity, whereas rTMS and tACS achieve similar effects mainly by increasing highfrequency EEG activity. Overall, this review provides an understanding of the role of NIBS in modulating neural oscillations and improving cognition in MCI, which may guide future therapeutic strategies. Future studies could explore the specific molecular pathways of neural oscillatory dysfunction in MCI and investigate the correlation between neural oscillations and other biomarkers, such as amyloid plaques and tau tangles, for a more comprehensive understanding of the disease.