How electroacupuncture parameters shape brain responses

Electroacupuncture (EA) is often treated as a uniform intervention, although its central effects vary with electrical parameters and stimulation site. This narrative review, supported by a structured search of PubMed/MEDLINE, Embase, Web of Science Core Collection, China National Knowledge Infrastructure, and SinoMed through August 4, 2026, synthesizes human and animal evidence on how frequency, current intensity, waveform, stimulation duration, and acupoint selection shape regional, network-level, electrophysiological, neurochemical, neurovascular, neuroimmune, and plasticity-related brain responses. Evidence was separated into direct comparative studies and an illustrative subset of single-protocol studies, with complementary transcutaneous electrical acupoint stimulation evidence considered separately. Frequency had the largest and most diverse evidence base. Low-, intermediate-, high-, and alternating-frequency protocols recruited overlapping sensorimotor, insular-cingulate, thalamic, limbic, hypothalamic, midbrain, and medullary systems, but differed in the relative distribution of regional activity and in associated neurochemical, neuronal, neurovascular, and plasticity-related processes. The available heterogeneous evidence does not establish a universally optimal frequency. The smaller current-intensity literature indicates recruitment thresholds, non-linear response ranges, and plateaus. Evidence for waveform and duration is limited and concentrated mainly in animal models of brain injury; waveform comparisons frequently involved concurrent differences in frequency composition and train structure, whereas duration effects varied by model and endpoint. Direct brain-level comparative evidence for pulse width remains insufficient. Acupoint and stimulation-site comparisons further showed site-, laterality-, and point-combination-related differences in cerebral, sensorimotor, neurovascular, and autonomic responses. Single-protocol studies characterized networks, receptors, cell populations, and defined circuits engaged under selected protocols, whereas parameter specificity was assessed from direct comparisons. Collectively, these findings support a multidimensional framework in which electrical dose and acupoint selection jointly shape brain responses. Future studies should use controlled, target-oriented comparisons, report complete stimulation characteristics, and link mechanistic brain measures to clinically relevant outcomes.