Exercise does wonders for the human body. An international team of neuroscientists led by researchers at the University of Iowa (USA) uncovered an interesting mechanism: after a single 20-minute session of easy or moderate cycling, people show positive changes in brain activity that are linked to memory.
The scientists explained that sharp wave activity begins with synchronized patterns of neuron firing in the hippocampus — the brain region responsible for converting short-term memories into long-term memories. Those signals then spread to other brain regions, reaching much of the cortex and some subcortical areas.
Most of what researchers know about these events has come from animal studies and from work in people who have implanted electrodes that measure brain activity.
Measuring sudden changes in brain activity immediately after exercise is harder. Researchers usually do that with neuroimaging, which only indirectly shows how exercise improves brain function — for example, by revealing increases in oxygen-rich blood.
But now scientists have finally produced what they call the “first direct evidence” of hippocampal pulsations in the human brain after physical activity. The team had a rare chance to observe neuronal activity inside the human brain after exercise, said cognitive neuroscientist Michelle Voss, the study’s lead author.
“Using direct recordings of brain activity, our study shows in humans for the first time that even a single bout of exercise can rapidly change the neural rhythms and brain networks involved in cognition,” she said.
How researchers measured brain activity after exercise
The team recorded brain activity from 14 patients with epilepsy, aged 17 to 50. Clinicians implanted electrodes in their brains “exclusively for clinical reasons determined by a team of epileptologists and neurosurgeons,” the scientists wrote in an article published in the journal Brain Communications.
All participants had drug-resistant epilepsy and were undergoing pre-surgical evaluation. The implanted electrodes allowed the researchers to record intracranial electroencephalography (iEEG) data, which can clarify brain phenomena such as hippocampal pulsations.
After a short warm-up, participants pedaled on a stationary bike for 20 minutes at a pace they could sustain for the entire session. The iEEG recordings captured their brain activity before and after the session, revealing how exercise can strengthen brain function.
The exercise caused accelerated pulsations in the hippocampus. The activity also strengthened the connection between those hippocampal pulsations and activity in other brain regions, including the limbic system and the brain’s default mode network (DMN).
Those changes appeared after a single session of light or moderate exercise, confirming results from earlier neuroimaging studies.
The researchers also found a link between higher exercise intensity — measured by heart rate during the session — and stronger pulsation dynamics in specific neural networks, such as the DMN, during rest after exercise.
Although the sample was relatively small, the study gave scientists a rare window into human brain activity after physical exercise.
“The post-exercise changes we observed largely match what has been seen in healthy adults using noninvasive neuroimaging,” Michelle Voss said.
