Exercise-Induced Endocannabinoids Boost Brain Plasticity

15-30 minutes of cardio enhances synaptic plasticity via increased anandamide.

Posted Sep 24, 2020

dolomite-summits/Shutterstock
Source: dolomite-summits/Shutterstock

Neuroscientists have known for decades that physical activity improves memory functions. Since the early 2000s, numerous human and animal studies have identified a correlative link between cardiorespiratory exercise and better neuroperformance.

In August 2020, a systematic review (Blomstrand & Engvall, 2020) concluded that a single bout of moderate-to-vigorous physical activity (MVPA) boosts learning, memory, attention, and concentration for up to two hours immediately after a workout. (See "One Cardio Workout = Two Hours of Supercharged Brainpower")

Although this systematic review concludes that doing anywhere from 2-to-60 minutes of cardio can improve learning and memory for up to two hours after completing a workout, Peter Blomstrand and Jan Engvall could only speculate when it came to answering the million-dollar question: "How does aerobic exercise improve brain functions and boost cognitive performance?" Recently published research by a team of neuroscientists in Switzerland helps to answer this question.

This week, a new study (Bosch et al., 2020) on the effects of a single 15- or 30-minute indoor cycling workout at different exertion levels offers fresh clues about how moderate or vigorous aerobic exercise can improve one aspect of human memory called motor sequence learning. These findings by Blanca Marin Bosch and colleagues at the University of Geneva (UNIGE) were published on September 18 in Scientific Reports.

For this three-day experiment, the Swiss researchers had over a dozen study participants ride a stationary bike for 15 minutes at high intensity (75% of VO2 max) on one day; ride the bike for 30 minutes at moderate intensity (60% of VO2 max) another day; and on the third day, study participants came to the lab and sat still for 15-30 minutes but didn't ride the bike.

After each session, the researchers took blood samples and assessed motor sequence learning using a finger tapping task or serial reaction time task (SRTT). After each lab visit, the UNIGE neuroscientists also performed fMRI brain scans of every study participant (N = 15).

 Bosch et al., 2020/Scientific Reports, Open Access (CC-BY-4.0)
This diagram shows increased anandamide (AEA) levels after moderate physical exercise (MOD) and even higher AEA levels after high-intensity exercise in comparison to a "rest" condition.
Source: Bosch et al., 2020/Scientific Reports, Open Access (CC-BY-4.0)

Interestingly, the researchers found that high-intensity bike pedaling for 15 minutes created a dramatic surge of anandamide* (AEA), an endocannabinoid associated with runner's high that also promotes synaptic plasticity in the hippocampus. Although 30 minutes of moderate-intensity stationary bicycling also boosted anandamide levels and improved memory functions, the effects were less robust.  

In addition to increases in exercise-induced anandamide, the fMRI neuroimages showed that higher-intensity workouts were associated with more activity in the hippocampus (memory hub) and the caudate nucleus (a brain structure involved in motor functions). As the authors explain: 

"We show that [aerobic] exercise enhanced motor sequence memory, significantly for high-intensity exercise and tending towards significance for moderate-intensity exercise. This enhancement correlated with anandamide increases and dovetailed with local increases in caudate nucleus and hippocampus activity. These findings demonstrate that acute physical exercise promotes sequence learning, thus attesting the overarching benefit of exercise to hippocampus-related memory functions."

Taken together, these findings suggest that both moderate and vigorous workouts boost anandamide levels and improve motor sequence memory functions; however, higher-intensity workouts appear to produce more anandamide and have a more pronounced effect on motor-skill learning. "These [anandamide] molecules are involved in synaptic plasticity (i.e., the way in which neurons are connected to each other) and thus may act on long-term potentiation, the mechanism for optimal consolidation of memory," Bosch said in a news release.

Notably, a previous study (Bosch et al., 2017) by the same lab found that moderate-intensity exercise improved associative memory functions better than high-intensity exercise. This suggests that various intensities of aerobic activity affect brain mechanisms and memory function in slightly different ways. But in all cases, the researchers conclude that any type of moderate-to-vigorous physical activity has a positive effect on learning and memory.  

*For more on "the bliss molecule" anandamide see here, here, here and "The Brain's Critically Important Natural Cannabinoid System" by Timmen Cermak.

LinkedIn Image Credit: Rido/Shutterstock

References

Blanca Marin Bosch, Aurélien Bringard, Maria Grazia Logrieco, Estelle Lauer, Nathalie Imobersteg, Aurélien Thomas, Guido Ferretti, Sophie Schwartz & Kinga Igloi. "Effect of Acute Physical Exercise on Motor Sequence Memory." Scientific Reports (First published: September 18, 2020) DOI: 10.1038/s41598-020-72108-1

Blanca Marin Bosch, Aurélien Bringard, Giulio Ferretti, Sophie Schwartz, Kinga Iglói. "Effect of Cerebral Vasomotion During Physical Exercise on Associative Memory, a Near-Infrared Spectroscopy Study." Neurophotonics (First published: July 25, 2017) DOI: 10.1117/1.NPh.4.4.041404