Figure 1. Recording location, behavioral task, and behavioral response to propofol. A, Location of recording sites in S1, S2, and PMv. CS, Central sulcus; IPS, intraparietal sulcus; LS, lateral sulcus; AS, arcuate sulcus. B, Sequence of events during behavioral trials. At the start tone (pure tone 1000 Hz, 100 ms), the animal initiates a trial by placing the hand on the button (using a hand ipsilateral to the recording hemisphere). The animal is required to keep its hand on the button until the end of the trial to be able to gain a liquid reward and then to release the button during the intertrial interval (ITI). During each trial, after a random delay, one of the four sensory stimulus sets is delivered regardless of the animal's behavioral response: nonaversive air puff at 12 psi to the lower face (250 ms, contralateral to the recording hemisphere), pure tone at 4000 Hz at 80 dB SPL (250 ms), simultaneous air puff and sound, or no stimulus. C, Typical behavioral response during propofol infusion. The animal's trial-by-trial behavioral response is recorded as a correct response (blue), failed attempt (black), or no response (red). Propofol was infused for 60 min at a fixed rate (200 μg/kg/min for Monkey E, 230 or 270 μg/kg/min for Monkey H). After the start of propofol infusion, failed attempts increased for 3–4 min before LOC (magenta arrow).