Effects of acupuncture on brain functional networks in patients with mild cognitive impairment and Alzheimer's disease: a systematic review and activation likelihood estimation meta-analysis of neuroimaging studies.

Background: The increasing prevalence of Alzheimer's disease (AD) and mild cognitive impairment (MCI) presents a significant societal and familial burden. Acupuncture has shown promise in modulating brain function; however, systematic evidence on its effects on brain functional networks in individuals with AD and MCI remains limited. This study aimed to quantitatively synthesize neuroimaging findings using activation likelihood estimation (ALE) meta-analyses. Methods: We systematically searched PubMed, PsycINFO, Google Scholar, SinoMed, and China National Knowledge Infrastructure (CNKI) for neuroimaging studies on acupuncture in AD and MCI. Activation coordinates were analyzed using GingerALE software. Separate ALE meta-analyses were conducted for AD and MCI with family-wise error (FWE) correction (P<0.05) and a cluster-forming threshold of P<0.001 (5,000 permutations), achieving >80% post hoc power. Contrast analyses used P<0.01, a minimum cluster size of 200 mm3 (10,000 permutations), and 95% confidence intervals from permutation distributions. Results: Thirteen studies (702 participants: 105 with AD, 312 with MCI, and 285 controls) with 303 activation foci (153 increased and 150 decreased) were included in the analysis. In patients with AD, acupuncture enhanced activation in the right superior frontal gyrus (BA10), left cerebellar regions, and right inferior occipital gyrus (BA19), while reducing activation in the right middle frontal gyrus (BA6). In an individual with MCI, increased activation was found in the right superior and middle temporal gyri (BA38 and BA21), parahippocampal gyrus (BA28), bilateral posterior cerebellar lobes, and left superior parietal lobe (BA7), which was accompanied by decreased activity in the right superior frontal gyrus (BA6) and cerebellar regions. Combined analyses revealed convergent activation in the bilateral cerebellar tonsils, parahippocampal gyrus, right middle temporal gyrus, left superior parietal lobe, and right superior frontal gyrus, indicating shared modulatory effects across both disorders. Conclusions: Acupuncture consistently activates the frontal, temporal, parietal, and cerebellar regions linked to cognitive and sensorimotor functions. Stronger effects in individuals with MCI suggest greater neuroplastic responsiveness. These findings provide quantitative evidence supporting acupuncture as a potential adjunctive therapy for cognitive impairment in neurodegenerative diseases.