Recording of brain potentials with FET-circuits: hazard of inadvertent lesions

Head-mounted field-effect transistors are frequently used for electrophysiological recording of brain potentials in freely moving animals. The low output impedance of these transistors reduces noise pickup and artifacts caused by movement of the cable that connects the animal to the amplifier. However, inadvertent brain lesions can occur if the positive pole of the DC power supply is disconnected, without simultaneous interruption of the connections to the negative pole and ground.