A wireless system for monitoring a patient's brain tissue including (1) a plurality of electrodes abutting brain tissue, (2) main circuitry outside the patient's body to transmit power at radio frequencies and send/receive data using infrared energy, and (3) subcutaneously-implanted remote circuitry connected to the electrodes and configured to (a) receive transmitted RF power, (b) capture and digitize EEG signals from the electrodes, and (c) send/receive data to/from the main circuitry using IR energy, including sending digitized EEG signals from each electrode to capture the full bandwidth of each EEG signal. The system preferably includes circuitry to measure the electrical impedance of each electrode for real-time monitoring of the condition of the electrode/tissue interfaces to enhance interpretation of captured EEG signals.