It is a well-researched and empirically proven fact that physical activity and fitness are integrally linked to neurological health and cognitive functionality. Every year, however, thousands of individuals are placed in a position of sedentariness beyond their control, in the form of long-term bed rest.
To better understand the deleterious effects of long-term bed rest and, inversely, the benefits of exercise, a team of researchers exposed 22 informed and consenting males participants to 60 days of bed rest, with half the participants following a high-intensity interval training (HIIT) regiment. The study, “Exercise-induced changes in brain activity during memory encoding and retrieval after long-term bed rest”, appeared in NeuroImage.
The study represented a rare opportunity, in that the researchers were able to strictly control level of activity and nutrition. It is also one of the first instances of a longitudinal rather than cross-sectional study of the effect of a sedentary lifestyle on cognition, allowing for the authors to pose and verify hypotheses of causality.
The authors focused on memory functionality and its neural basis, using a pattern separation task to test behavioral aspects of episodic memory and fMRI scans to examine neurophysiological changes in the brain during and after the experiment.
The results of the study lend further evidence to the relation between physical activity and improved cognition, but also underline the effects that long-term bed rest can have on patients in controlled, clinical settings, like one might experience in a hospital following serious injury.
One of the most interesting findings related to blood oxygen levels, which were found to be increased during memory encoding and retrieval in the control group compared to the HIIT group. This allowed the researchers to draw connections between bed rest and the effects of physiological aging, thus broadening its applications. In both cases, the increased blood oxygenation can be seen as a compensatory response to dysfunctional encoding mechanisms.
However, the differences in the group’s brain activity did not result in differences in performance on the memory tasks. While this may seem contradictory, it actually fits quite well with the proposed compensatory mechanism of increased blood flow. That is, the compensation worked, and thus performance was maintained. However, the authors underline that this line of reasoning is, for the moment, only speculative and must be tested empirically.
Despite some limitations, including a small sample size and its relative homogeneity to young, healthy men, the results have implications both for patients assigned long term bed rest and for aging individuals, and may eventually lead to effective therapies to combat reduced cognition in both cases.