In time, he figured out why. Slight differences in the temperature of the rats' brains, resulting from things like the lab temperature and air currents, had a huge impact on the extent of the animals' strokes. The cooler the brain, it turned out, the smaller the stroke. But even a modest drop in temperature seemed to be highly protective, while a little extra heat made things vastly worse. In a cool head, enzymes stop working.
Oxygen consumption slows.
Glucose metabolism plummets. The processes of cell death shut down. We evolved at this temperature. We don't work if we lower it. Doctors consider this to be mild hypothermia, and they hope patients will be able to stand it while conscious.