Does a warmed brain learn better.

When laboratory rats explore new mazes or learn to find objects, specific areas of their brains change the type of electrical signals they give off, increasing the strength of some aspects of these signals. Neurobiologists monitor these changes to try to correlate nerve cell activity with the animal's behavior. In this way, they study how animals learn to get around in their environments.

But Norwegian researchers now report that alterations in the signals may simply reflect changes in brain temperature. When the body gets moving, the brain gets hotter, and the nerve cells produce faster signals, says Per Andersen of the University of Oslo.

He monitored temperatures in different parts of the brains of rats allowed to explore new cages and to swim in cool water. Blood warmed by moving muscles increases brain temperature by as much as 3 (deg) C, he and his colleagues report in the Feb. 26 SciENCE.

They also warmed the rats' brains slightly with probes and monitored whether exploring a new place causes further alteration of the electrical signal. It did not, Andersen says.

Thus, temperature rise - not the act of learning - alters the character of electrical signals generated by these nerve cells, they conclude. "The temperature effect does not say. that the animal does not learn," Andersen told SCIENCE NEWS. "It just says that the brain is not as homeothermic as we think."

The Norwegian finding hints that changes in brain temperature may affect the way information is transmitted or stored in the brain, notes Bruce L. McNaughton, a neurobiologist at the University of Arizona in Tucson. Scientists still need to confirm that mammals other than rodents undergo changes in brain temperature. Nevertheless, "we are vigorously pursuing that [temperature] may be an important modulator," he adds.