Exercise enhances the brain's activity during daydreaming

Do you ever wonder what your brain does while you daydream? The majority of adults daydream at least once a day and for many of us, this behavior occurs periodically through the day.

Daydreaming often occurs during our downtime or when we have a moment to rest. From an outside perspective, it might look as though we are resting; however, the brain is doing anything but.

The brain produces electric fields, and scientists have harnessed this fact to measure brain activity through a technique called electroencephalography or EEG. To do this, scientists place a cap covered in electrodes over the heads of participants and record the brain’s activity – which looks like a series of oscillations or sine waves that are composed of many different frequencies.

By doing this while we are daydreaming, scientists have revealed exciting things about the brain at rest.

One of these frequencies, known as the alpha wave, occurs in the range of 7.5 to 12.5 Hertz (or times per second). As EEG records populations of neurons, this means that groups of neurons are firing between 7.5 to 12.5 times per second. When the brain is at rest, alpha activity increases. Though it was originally thought that alpha activity was simply a marker of the brain at rest, recent research has shown that individuals with higher alpha activity show improvements in reaction time and both short- and long-term memory. In addition, alpha activity is impaired in patients with Alzheimer’s disease, major depression, attention deficit hyperactivity disorder, cerebral ischemia, and carotid artery disease.

Considering that exercise produces many beneficial effects on the brain including those cognitive processes related to alpha activity, a group of scientists at the Institute of Movement and Neurosciences in Germany asked whether exercise could produce an enhancement in alpha activity of the brain.

Ten young adult men who participated in regular exercise (>30 minutes/day on >3 days/week) for the past 2 years engaged in 4 weeks of cycling training. During these 4 weeks, participants engaged in 3, 30-minute cycling sessions that were conducted at approximately 70% of the individual’s maximal heart rate. The brain’s activity during rest was recorded both before and after the exercise intervention. In addition, prior to and after this experience, brain activity was recorded both before and after a steady state exercise session (similar to the one participants engaged in during the study) and an exhaustive exercise session (to measure their cardiopulmonary fitness).

So how did exercise affect the daydreaming brain? Acute exercise caused a significant increase in the peak level of alpha activity, which lasted for up to 10 minutes after the cessation of exercise. However, long-term exercise did not have any additional effects on the peak level of alpha activity. The authors state that, “the results of the present study indicate [that] an acute bout of strenuous physical exercise [activates] mechanisms in the brain which facilitate information processing.”

As acute exercise has been shown to improve attention and information processing speed, these are the exact neural mechanisms that may underlie these exercise-induced improvements in cognition. Future research will be needed to investigate this relationship. In the meantime, it is exciting to see that exercise changes the firing activity of the brain’s neurons – even when we are daydreaming!