This study will be conducted on patients aged 65 and older scheduled for surgery due to lumbar or cervical disc herniation. General anesthesia is routinely used for these types of surgeries in the hospital. In patients receiving general anesthesia, anesthesia depth monitoring is performed. As part of the study, a preoperative anesthesia evaluation will be conducted, which will include age, weight, height, comorbidities, regularly used medications, previous surgical or anesthesia experiences, nutritional habits, mental status, and daily activity levels. On the day of surgery, upon arrival in the operating room, the following will be measured and recorded: * Blood pressure using a non-invasive blood pressure monitor * Heart rate and rhythm via electrocardiogram (ECG) * Blood oxygen level with a pulse oximeter * Anesthesia depth using a forehead-applied sensor All monitoring procedures are non-invasive and painless. Following the placement of these monitoring devices and initial measurements, anesthesia induction and surgery will commence. Throughout surgery, blood pressure, heart rate, and brain activity will be continuously recorded. After the surgical procedure, anesthesia emergence and mental status will be assessed. Preoperative evaluation data and intraoperative recordings will be used solely for research purposes, with patient identity information remaining confidential.