The topic of this review is the physiological changes produced by local
brain cooling. The review also includes a description of the techniques of
cooling and an assessment of its usefulness as a research tool.
In warmblooded animals, communication between neurons ceases
when neural temperature is lowered to about 20°C. Normal function returns
upon rewarming, if freezing is avoided. Cooling usually first raises
and then lowers neural excitability, depending on ambient temperature
levels, as well as the extent and rate of temperature change. There is no
systematic knowledge of this at present, but the results to be described
suggest that local cooling alters membrane permeabilities for specific ions,
such as Na ÷, K ÷, and Ca ÷*. Physiological effects are diverse because they
are composed of cellular effects that can differ for various parts of the
central nervous system and for various types of neurons (see Fig. 11).