Regular physical activity is a lifestyle factor known to benefit neuroplasticity and neurocognitive functions. Regular exercise enhances memory functions, synaptic plasticity in the hippocampus, and brain-derived neurotrophic factor (BDNF) levels. Evidence suggests that BDNF influences hippocampal synaptic plasticity. This is shown as physical exercise increases BDNF, mRNA and protein levels in the hippocampus but blocking BDNF action in the hippocampus blocks the beneficial effect of exercise on memory. These BDNF level changes are fast and momentary, rapidly increasing hippocampal subfields responding to exercise with enhanced long-term potentiation (LTP) and synaptic plasticity. These effects are also brief and may only enhance memory for a few hours. Similarly, physical exercise rapidly increases circulating endocannabinoids, which act on cannabinoid receptors CB1 and CB2. Endocannabinoids directly resolve forms of retrograde plasticity and can also regulate other forms of plasticity, including LTP and BDNF signalling.
The present study conducted by Bosch et al., 2021, analyzed the effects of short periods of exercise or acute exercise on memory and cognition. The researchers combined blood biomarkers and behavioural and functional magnetic resonance imaging (fMRI) measurements to assess the impact of a single physical exercise session on conjoined memory and underlying neurophysiological mechanisms in healthy male volunteers. This study included 18 participants between 18 and 34 years old who were all male, right-handed, without psychiatric and neurological history, reported exercising regularly (at least twice per week) and whose VO2max (volume of oxygen used during max exercise) was above 40ml/kg/min and below 65ml/km/min. All participants were to wear a Fitbit fitness tracker for five days before each experimental visit to monitor and record physical activity and cardiac frequencies. Participants were required to continue with their training habits during the five days and refrain from any strenuous exercise on day five. For each participant, memory was tested after three conditions: rest, moderate or high-intensity training. A hippocampus-dependent associative memory task was used where participants learned eight series of six successive pictures. These pictures belonged to different themes at each of the three visits (“office,” “shoe shop,” or “house”) to avoid interference between experimental visits for this within-subject design.
The main aims of the present study were to confirm these effects using an individually defined calibration for moderate (and high) physical effort derived from a maximal effort test (VO2max) and to unravel the underlying blood biomarker and neuroimaging correlation. Results showed that: increased Anandamide level (AEA) after moderate and high physical exercise compared to rest, increased right hippocampal activity for hits after moderate exercise compared to hits after rest correlated with the increase in AEA level after moderate exercise, increased BDNF levels after moderate and high-intensity exercise compared to after rest. After this analysis revealed that AEA levels were lower after rest than after physical exercise, for BDNF levels after moderate and high-intensity exercise differed from after rest. At the same time, there was no effect on exercising condition in endocannabinoid 2-arachidonoylglycerol (2-AG). Although this study observes promising links between changes in biomarker levels, brain activations and associative memory performance, there are likely many other molecules involved in the effect of exercise on memory.
This study concluded that acute physical exercise performed right after memory encoding resulted in both short and long-lasting improvements in memory recollection. This could potentially reduce the risk of cognitive decline associated with Dementia and Alzheimer`s disease.
Marin Bosch, B., Bringard, A., Logrieco, M.G., Lauer, E., Imobersteg, N., Thomas, A., Guido, F., Schwartz, S., & Igloi, K. (2021). A single session of moderate-intensity exercise influences memory, endocannabinoids and brain-derived neurotrophic factor levels in men. Sci Rep 11, 14371. https://doi.org/10.1038/s41598-021-93813-5
