Quantitative Neurofeedback Techniques for Treating Perioperative Cognitive Disorders in Elderly Patients

The goal of this clinical trial is to learn if quantitative measurement of brain and neurofeedback intervention techniques works to prevent perioperative neurocognitive deficits in elderly oncology patients who are to undergo elective major surgery. The main questions it aims to answer are: * Can neurofeedback intervention training reduce the incidence of postoperative delirium in elderly oncology patients? Researchers will compare the incidence of postoperative delirium in elderly oncology patients after training in neurofeedback intervention with those after living a normal life, to see if training in neurofeedback intervention before surgery is effective in preventing the development of postoperative delirium. Participants will: * Take neurocognitive feedback intervention training for 14 days prior to surgery (recommended to be used for at least 1 hour per day for a cumulative preoperative use of 14 hours). * Received preoperative and postoperative assessments of cognitive function by a third-party researcher, as well as daily delirium assessments for 7 days postoperatively. * The subjects in the control group lived a normal life every day before the operation, and the rest of the measures were the same as those in the intervention group.