Effect of Transcutaneous Auricular Vagus Nerve Stimulation on Perioperative Negative Emotions in Breast Cancer Surgery Patients

Inclusion Criteria: * Aged ≥18 years. Scheduled for elective breast cancer surgery. ASA physical status I-III. Willing and able to provide informed consent. Exclusion Criteria: * Preoperative MMSE score \< 24; severe communication barriers. History of diagnosed dementia, Parkinson's disease, schizophrenia, bipolar disorder, major depressive disorder, or long-term use of psychotropic drugs. Skin lesions, infection, or deformity of bilateral ears; history of ear surgery or nerve injury; allergy to electrode materials. Severe arrhythmia; implanted electronic devices (e.g., pacemaker, ICD). Participation in another interventional trial within 3 months. Other conditions deemed unsuitable by investigators.