Exercise can help improve both memory and mood after whole-brain radiation treatment, that's the conclusion of a new study in rodents.
The study has been presented by Duke University scientists at the Society for Neuroscience meeting.
"This is the first demonstration that exercise can prevent a decline in memory after whole-brain radiation treatment," said lead researcher and graduate student Sarah Wong-Goodrich of the Duke Department of Psychology and Neuroscience. Whole-brain radiation is sometimes used to treat brain cancers in humans.
In the experiment, one group of mice that had brain radiation stayed in their cages under normal conditions, living with other mice, eating and playing as they liked.
But a different group of mice that had radiation were given daily access to a cage with a running wheel, which they could use if they wanted to.
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 the three-month mark after their irradiation 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. We were expecting some memory retention issues with a longer delay and there weren't any," said Wong-Goodrich.
Wong-Goodrich said that exercise appears to actually protect against the loss of memory and the increase in depressive-like behaviors.
The 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.
Radiation knocks out the ability of the brain to produce new nerve cells, called neurons. Williams said that they were able to measure increases in certain growth factors in the exercising mice that might be necessary to help cells divide.
Wong-Goodrich said that exercise might help by increasing blood flow to the hippocampus area of the brain, which is an important structure for learning, memory, and spatial navigation.