Exercise is a key factor in improving both memory and mood after whole-brain radiation treatments in rodents, according to data presented this week at the Society for Neuroscience (SfN) meeting in Chicago.
"This is the first demonstration that exercise can prevent a decline in memory after whole-brain radiation treatment," often used to treat brain cancer, according to lead researcher and graduate student Sarah Wong-Goodrich from the department of psychology and neuroscience at Duke University in Durham, N.C.
"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 tumors," said senior researcher Christina Williams, PhD, professor of psychology and neuroscience at Duke. "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."
In the experiment, one group of mice that had brain radiation stayed in their cages under normal conditions, living with other mice. But a different group of mice that had radiation were given daily access to a cage with a running wheel, which they could use at will.
According to the researchers, the animals were tested for how well they remembered spatial features in their environment for locating a preferred escape hole to exit a well-lit maze and hide. The mice completed tests at the two-week and three-month mark after their irradiation, in order to get a baseline and then to see how they fared over time.
Mice that had radiation plus access to running did as well at remembering where the hole was as normal mice that didn't exercise. Irradiated mice that had no access to an exercise wheel eventually showed no particular preference for the section of the maze with the escape hole.
"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. "We were expecting some memory retention issues with a longer delay and there weren't any."
The researchers reported that mice also were tested for depressive-like behavior, 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.
Researcher Lee W. Jones, PhD, associate professor in the Duke department of radiation oncology, said the findings show "how powerful exercise is and how many benefits it can provide, and even restore, after radiation."
Jones said that he is beginning to look at neurocognitive outcomes for cancer patients at Duke who undergo radiation, in addition to their body health indicators.
"Once a patient gets a doctor's clearance, I think exercise is a good thing during whole-brain radiation," he said. "[T]elling patients to take it easy is the worst advice we can give, because we know they will become deconditioned physically, and this study shows exercise potentially could provide cognitive and psychological benefits."