Walking through Paris

Amongst the many changes I have experienced while in Paris, I noticed that I am walking considerably more than I usually do. While most people are aware of the positive impact walking and exercise can have on the body, I am dedicating this post to exploring the effects of exercise on the brain.

Thanks to my handy Fitbit (yes, I know I am a little obsessed), I am able to track my daily activity, so I have a very good idea about how much exercise I am getting. Between going to class, touring museums, and exploring getting lost in the streets of Paris, I am walking an average of over 8 miles every day. Paris is a very “walk-able” city, and my friends and I regularly opt to walk to our destinations instead of using the metro. I know that this must be affecting my cognitive ability, because even while operating on 4-6 hours of sleep every night, I am able to focus and work surprisingly well.

Fitbit evidence that 1) I am walking crazy amounts in Paris 2) I can justify eating multiple pastries a day*
*point 2 has not been scientifically proven

A recent study in college-aged females found that after only a single session of moderate exercise, participants showed increased brain activation during a working memory task (Li et al. 2014). Working memory is a limited brain resource that temporarily stores, processes and updates action-related thinking. It is utilized when you need to actively handle information, and your working memory capacity is an important measure of cognitive function. The researchers in this study used a modified N-back task to measure working memory. This task requires participants to attend to a sequence of stimuli, and determine if the current stimulus matches a stimulus that was “N” steps earlier in the sequence. The task gets more and more difficult as N increases, because it becomes harder to keep track of when a stimulus appeared.

A visual representation of the N-back task used in the study by Li et al. (2014)

To compare brain function, the subjects performed this task while in a functional magnetic resonance imaging (fMRI) machine, once following exercise, and once following a rest period. The fMRI measures blood oxygenation, which provides a visual image of brain activation. While there was no significant change in subject performance on the task, the data show more brain activation in the exercise condition, especially in the prefrontal cortex (PFC) and medial occipital cortex during the 2-back condition. The PFC is well recognized to be important for working memory, and the specific areas of the occipital lobe that changed are also involved in online processing. The lack of performance change limits the conclusions that can be drawn from this study, but it is reasonable for me to assume that my working memory capacity is positively influenced by the increased exercise I get in Paris. The researchers clearly showed that exercise influenced the brain areas important for working memory in subjects of my same age and sex, and this effect would likely be enhanced by an extended exercise routine like mine. A future study could explore the effect of chronic exercise, or use multiple behavioral measures to see if that leads to more pronounced changes in working memory performance.

Working memory is not the only brain function influenced by exercise. In fact, hundreds of studies explore how exercise can change the brain. One of the most common focus areas is how exercise increases brain-derived neurotropic factor (BDNF) in the hippocampus. BDNF is very important for brain plasticity, and the hippocampus is highly involved in learning and memory. One study found that exercise enhanced memory and cognition in rats, through the action of BDNF and the pathways it influences (Vaynman, et al. 2004). A different study focused on the non-neuronal cells in the brain, called glial cells (Brockett, et al. 2015). They found that running influenced synaptic plasticity in rats, producing widespread positive effects in both neurons and glial cells in areas associated with cognitive improvement. The last study looked at showed how exercise can help people’s mental health by reducing the stress hormone cortisol, through overall regulation of the hypothalamic-pituitary (HPA) axis (Zschucke et al. 2015).

I walked almost 10 miles before stumbling upon this set at Fete de la musique, and the journey was as fun as the event!

It is so interesting to hypothesize about the different ways that my brain may be changing in response to something as simple as walking. Evidence suggests that my working memory capacity, brain plasticity, and mental health are all influenced by exercise. Now that I only have one week left to enjoy Paris, I will make sure to walk everywhere to experience, learn and improve my brain as much as possible. With all of the positive effects Paris seems to have, I know I will be planning a return trip the second I get home!

References 

Brockett AT, LaMarca EA, Gould E (2015). Physical Exercise Enhances Cognitive Flexibility as Well as Astrocytic and Synaptic Markers in the Medial Prefrontal Cortex. PLoS ONE. 10(5): e0124859.

Li L, Men W-W, Chang Y-K, Fan M-X, Ji L, & Wei GX, (2014). Acute Aerobic Exercise Increases Cortical Activity during Working Memory: A Functional MRI Study in Female College Students. PLoS ONE. 9(6): e99222.

Vaynman S, Ying Z, and Gomez-Pinilla F, (2004). Hippocampal BDNF mediates the efficacy of exercise on synaptic plasticity and cognition. European Journal of Neuroscience. 20: 2580–2590.

Zschyke E, Renneberg B, Dimeo F, Wüstenberg T, & Ströhle A (2015). The stress-buffering effect of acute exercise: Evidence for HPA axis negative feedback. Psychoneuroendocrinology. 51: 414-425.