Firstly, after patients are admitted, the researchers will visit every patient, introduce the study protocol, the risks and rights of the subjects to them in detail, and obtain their signed informed consent. Then, researches will collect the baseline data of the patients and complete the baseline status data measurement, including cognitive function, sleep quality, anxiety and depression scores, multi-channel EEG recorder monitoring and functional magnetic resonance examination.~According to the results of randomization, the intervention will be carried out according to the study protocol.~The day before the operation, EEG cortical network connection status, cognitive function, sleep quality, anxiety and depression scores will be measured after the intervention to understand the effect of preoperative intervention on brain function.~On the day of operation, anesthesia and operation will be performed according to clinical routine. And the multi-channel EEG will be detected after induction of anesthesia and during the period of sedation and recovery.When the patient meets the appropriate conditions, cognitive function training will be started as soon as possible.~Researches will evaluate the patients' sleep quality and the incidence of delirium in the first six days after the operation. They will also evaluate cognitive function, sleep quality, anxiety and depression scores, and conduct postoperative delirium evaluation, multi-channel EEG recorder monitoring, functional magnetic resonance examination on the seventh day after operation.The cognitive function, sleep quality, anxiety and depression scores will be measured 30 days after operation.~The Clinical Research Institute of Peking University undertakes the work of data collection and analysis of this project. A electronic data acquisition system based on network is used for data acquisition, where researchers need to input the research data accurately, timely and comprehensively. The audit and quality control will be fed back to the researchers in time. The researchers need to check the feedback one by one and record the check results in detail.
Whether enough time and high-quality cognitive training will reduce the incidence of postoperative cognitive dysfunction after cardiac surgery.