Transcranial Magnetic Stimulation MIT Artificial Intelligence Lab and Brigham and Women's Hospital Transcranial Magnetic Coil We implemented a real-time non-invasive functional mapping system using Transcranial Magnetic Stimulation (TMS). A magnetic coil is attached to a trackable probe (left) and placed on the scalp of a subject (right). The head position is tracked using LEDs fixed to the subject's forehead (right). Combining Position and Response The tracking system localizes and displays the position of the coil in real-time, relative to models of the patient's anatomy (left). When the coil is fired over motor cortex, a muscular response occurs. Electrodes are placed on the muscles, and the muscular response is recorded by the system (right). Functional Map of Motor Cortex Functional maps of the cortex are automatically generated on the fly from the position and response data. The arrows on the brain (left) are color-coded based on the intensity of the response of the forefinger (red = large, yellow = medium, green = small, gray = none). The map on the right shows the "hot spots" of five muscle groups (red = finger, green = wrist, yellow = biceps, blue & purple = left & right jaw). Visual Suppression Map The TMS stimulation is also used to map the visual cortex. A computer monitor is placed in front of the subject and three letters are flashed milliseconds before stimulation. The subject reports which letters were visible. The arrows are color-coded based on the region of the visual field suppressed by the stimulation (red = right suppression, blue = left suppression, green = no suppression). These results agree with the expected left-right cross-over of the visual cortex to the visual field.