The Underlying Neural Mechanism of TMS in Improving the Imbalance of "Microbiota-brain-gut Axis" in Alzheimer 's Disease Population

What is this study about? This study focuses on Alzheimer's Disease (AD), a common neurodegenerative disease that affects memory, thinking, and daily life. We aim to explore whether a non-invasive treatment called Repetitive Transcranial Magnetic Stimulation (rTMS) can improve AD symptoms by regulating the "gut-brain-intestine axis" - a connection between gut bacteria, the brain, and the intestines. Who can participate? * \*\*AD patients\*\*: Aged 50-80, diagnosed with mild to moderate AD (MMSE score 18-27, MoCA score 10-26), with stable condition for at least 6 months, and able to cooperate with tests and treatment. * \*\*Healthy controls\*\*: Aged 50-80, with normal cognitive function (MMSE ≥28, MoCA ≥27), no AD family history, and matched in age and gender with AD patients. Those with epilepsy, severe mental illness, recent use of antibiotics/probiotics, or inability to complete MRI scans are not eligible. What will participants experience? * \*\*AD patients\*\*: Will be randomly divided into two groups. Both groups will receive 4 weeks of treatment (5 days/week) with a helmet-like device. One group gets real rTMS (safe magnetic stimulation to the brain), and the other gets sham stimulation (no effective magnetic field, but same sound/feel). * \*\*Healthy controls\*\*: No treatment, but will complete the same tests as AD patients. * \*\*Tests during the study\*\*: Cognitive assessments (memory, thinking skills via questionnaires), stool/blood sample collection (to check gut bacteria and body markers), and MRI scans (to look at brain structure/function) at baseline, 1 month, 3 months, 6 months, and 1 year. What are the potential benefits? * Free rTMS treatment (for AD patients), free MRI scans (valued at 700 RMB), and a 200 RMB subsidy. * Free health checks (gut bacteria analysis, metabolic tests) and cognitive evaluations to understand personal health status. * Contribution to developing new AD treatments that may help future patients. Is it safe? rTMS is