Electroencephalogram during arousal from hibernation in the birchmouse

¹ Neurophysiological Laboratory, Anatomical Institute, University of Oslo; and University Institute for Experimental Medical Research, Ullevaal Hospital, Oslo, Norway

In the birchmouse, Sicista betulina, electrical activity of the brain was recorded at an oral temperature as low as 2.5°C. At body temperatures below about 10°C the activity consisted of bursts of slow waves separated by silent intervals. On increasing body temperature during the arousal this pattern was gradually replaced by activity of higher frequency until a normal electroencephalogram was recorded at about 30°C. No typical desynchronization of the EEG in response to sensory stimulation was noted until the body temperature reached that same level. The vocalization at low body temperatures induced by faint stimulation therefore seems to be unrelated to EEG desynchronization. The increase of recorded muscle-action potentials during the arousal from hibernation paralleled the increase in oxygen consumption and body temperature described previously (1).