It has become quite clear that physical exercise is an essential part of a brain-healthy lifestyle. Over the long term it helps both preserve the volume of gray matter in the brain and maintain cognitive functions. A recently published study goes further and shows for the first time that physical activity can have immediate positive effects on memory.
Participants were between 50 and 85 years old. There were two groups, one composed of healthy individuals and one of people diagnosed with Mild Cognitive Impairment.
The study design was simple. Participants were first presented with emotionally pleasant images (photographs of animals, nature, etc.). Then half of the participants were asked to exercise on a stationary bike for six minutes, at a moderate pace (that is, at 70% of their maximum capacity). Finally, 1h later, all participants were unexpectedly asked to recall the images they viewed earlier.
The results were striking: Whether they were healthy or cognitively impaired, older adults who had exercised did much better at the memory test than those who had not.
Why? The authors of the study had hypothesized a memory boost after exercising because exercise triggers an increase in the production of a neurotransmitter in the brain, norepinephrine, which is involved in memory processes (eg, memory consolidation).
They tested the saliva of the participants to look for a biological marker of norepinephrine activity in the brain. They noted that exercise did indeed increase norepinephrine production. This phenomenon could be observed most clearly in people who saw their memory improve after exercise.
Results from other studies suggest that the production of norepinephrine is not the only one affected by exercise. Brain-derived neurotrophic factor (BDNF) levels also increase while exercising. BDNF is a growth factor that can trigger the production of new neurons and connections between neurons, as well as help them survive. Increased BDNF production during exercise is believed to explain the longer term effect of exercise on the brain: that is when the volume of the brain matter grows in some areas of the brain after regular physical training.
Note that short term memory improvements have also been associated with BDNF increases. For instance it has been shown that, in college students, riding a stationary bicycle at an increasing speed until exhaustion improved memory for names of strangers (Griffin et al., 2011). This increased performance was accompanied by increased concentrations of BDNF in the brain.
A lot is thus going on in the brain while we exercise! And the results of this extra activity may be better brain health overall and better memory, immediately.
References: Segal, S. K. et al (2012). Exercise-Induced Noradrenergic Activation Enhances Memory Consolidation in Both Normal Aging and Patients with Amnestic Mild Cognitive Impairment. Journal of Alzheimer’s Disease, 2012