Fig. 1.  An intravenous bolus dose of propofol (0.3 mg/kg) that produced sedation did not alter the overall discharge activity of subthalamic nucleus (STN). Recordings at the top show the discharge pattern of an STN neuron before (A  ¹control; top two recordings at a slow and fast timebase) and after propofol administration (A  ²lower two recordings). Rate meter graphs on the bottom (B ) show little effect after propofol administration in two individual patients. Rate meters demonstrate the relatively stable discharge activity of STN neurons, averaged over 5-s epochs, throughout the recording period. A single bolus injection of propofol was given at the time indicated by the arrows (0.3 mg/kg intravenously delivered within 10 s) to awake patients.