Estimating transition point of anesthetic-induced loss of consciousness in mice by detecting motion in response to forced movement

To characterize transition periods of entrance to and emergence from anesthetic-induced unconsciousness in terms of thalamocortical neural activity, we devised a new method estimating a transition point of anesthetic-induced loss of consciousness. The method continuously monitors an animal´s head motion in response to forced movement on treadmill and uses the motion signals as a criterion of the transition. Anesthetics were administered via previously secured intraperitoneal injection route in order not to disturb the animal´s spontaneous movement. Resulting signals from the motion detector could discriminate the points of entrance into and emergence from the anesthetic-induced unconsciousness with resolution corresponding to the sampling frequency. This method makes it possible to track the anesthetic transition period continuously without contaminating EEGs and LFPs.