Washington, Oct 19 - Exercise is the key to improving both memory and mood after whole-brain radiation treatment that is used to treat brain cancer, says a new study.

"This is the first demonstration that exercise can prevent a decline in memory after whole-brain radiation treatment," said lead researcher Sarah Wong-Goodrich of Duke University.

"We found that exercise following radiation prevented a decline in erasable memory in mice and this is analogous to the type of memory problems people have after whole-brain radiation for brain tumours," said senior co-author Christina Williams, Duke professor of psychology and neuroscience.

"This is the type of short-term memory people use to find their car after they have parked it in a large lot. After radiation, this type of memory becomes impaired in many people," she said.

"It was remarkable that the irradiated, running mice were just like the normal, non-irradiated mice that didn't exercise," said Wong-Goodrich, who conducted the experiments in the Williams' lab. "We were expecting some memory retention issues with a longer delay and there weren't any."

Exercise appears to actually protect against the loss of memory and the increase in depressive-like behaviours, Wong-Goodrich said.

The mice also were tested for depressive-like behaviour, using gentle restraints which they worked to escape from. Two weeks after radiation, the irradiated mice gave up sooner than the normal mice.

Three months after radiation, the runners that had brain radiation, however, tried just as hard as the normal mice, while their non-running counterparts gave up more readily, said a Duke release.

Study author Lee W. Jones, professor of radiation oncology at Duke said the findings show "how powerful exercise is and how many benefits it can provide, and even restore, after radiation."