Exercise improves memory, boosts blood flow to brain
What is it about?
Our research shows that aerobic exercise is capable of improving memory function in patients with amnestic Mild Cognitive Impairment (aMCI), individuals who are at high risk for Alzheimer’s disease (AD) (Thomas et al.). This improvement might occur because our data show cerebral blood flow (CBF) to the Anterior Cingulate Cortex (ACC) and adjacent prefrontal regions of the brain increased in association with aerobic exercise. This blood flow increase was related to the improvement in memory performance. We also reported that one year of aerobic exercise training led to an increase in CBF in the hippocampus. Hippocampus is a region involved with memory formation. In particular, to our best knowledge, no studies have investigated CBF changes in aMCI participants following a longer period (12 months) of aerobic exercise. In the US there are about 5.5 million people living with AD-related memory impairment, and 11% of the population over the age of 65 has AD, which strain patients, caregivers and the healthcare system. To develop effective treatment strategies, we must understand the pathophysiologic mechanisms of AD, especially at the aMCI stage. 10% per year of those with aMCI progress to AD. Much research has focused on preventing the onset of AD, but negative outcomes from several AD clinical trials has led us to explore alternative strategies. Aerobic exercise may be an effective approach for preventing AD. It is known to improve cardiorespiratory and cognitive function in older adults with and without aMCI. A previous report stated that blood flow to the left ACC decreased after performing 12 weeks of aerobic exercise. The mechanisms of cognitive function improvement are not yet understood. We hypothesized that aerobic exercise improves brain vascular function, leading to brain function improvement. We used Magnetic Resonance Imaging (MRI) to non-invasively measure resting CBF in 30 patients with aMCI. Fifteen participants were assigned to perform aerobic exercise and 15 were assigned to perform non-aerobic stretching. Both groups were age, gender, education and BMI matched and underwent training for one year. Specifically, the aerobic exercise program started with a frequency of 3 exercise sessions per week for 25–30 minutes per session at the intensity of 75–85% of maximal heart rate. At week 11, participants started alternating between 3 and 4 exercise sessions per week for 30–35 minutes per session. During the weeks in which they performed 3 exercise sessions per week, a high intensity exercise session was introduced which consisted of 30 minutes of walking at the intensity of 85–90% of maximal heart rate (e.g., brisk uphill walking). After week 26, participants performed 4-5 exercise sessions per week for 30–40 minutes, including two high intensity sessions. Each exercise session included a 5-minute warm-up and a 5-minute cool-down. Any mode of aerobic exercise was allowed as long as they maintained the prescribed training dose and intensity, as monitored by changes in heart rate during each of the exercise sessions. The stretch group performed upper and lower body stretching and maintained their HR below 50% of max HR. The frequency and duration of the Stretch training program was the same as the aerobic exercise program. Memory function was assessed using a standard paragraph recall task, and resting CBF was measured at the start and end of training using MRI. After one year of training, cardiorespiratory fitness was found to be significantly improved in the exercise group, while the stretch group did not change. Delayed paragraph recall improved significantly in the aerobic exercise group, while the stretch group did not show improvement. CBF increased in the exercise group compared to the stretch group in the ACC and adjacent prefrontal regions of the brain. Shown in Figure 1 are change in CBF in the exercise group and stretch group. Increase in CBF in the ACC is similar to previous studies that found aerobic exercise induced increase in ACC CBF in cognitively normal older adults. It appears that ACC and adjacent prefrontal regions are involved in monitoring of memory and allocation of attention supporting memory. Improvement in memory function correlated positively with the regional increase in CBF in the ACC and prefrontal regions. These findings suggest that improvement in cognitive performance in aMCI was associated with increases in CBF with aerobic exercise. In summary, this study is the first to measure CBF in aMCI participants in response to 12 months of aerobic exercise. Aerobic exercise improved cardiorespiratory and memory function in aMCI and the improvement in memory performance was attributed to an increase in CBF in the ACC.
Why is it important?
One year long exercise intervention was shown to improve long term memory scores in Mild cognitive impairment (MCI) patients. Exercise was also shows to increase cerebral blood flow (CBF) to the hippocampus and the Anterior cingulate cortex. Exercise related increase in CBF most likely led to the memory function improvement.