Going Green–Literally.

Paris is unique in its ability to blend modernity and antiquity. In the heart of Paris, buildings are decades if not centuries old, with intricate designs and rows of windows, all neatly laced in criss-crossing streets and alleyways. It’s a dizzying sight, but one that sparks all of my imaginations and Google searches of the city view. In the peripheral regions of the city are giant skyscrapers, metal behemoths proving that Paris is not just an old city, but still vibrant and thriving well in the 21st century.

Square trees--welcome to Paris?

Amidst all of this man-made wonder, still I feel that something is amiss—greenery. Sure there are parks, and trees carefully planted in rows along the streets, but I can’t help but miss that part of home. I grew up in the suburbs of metro-Atlanta, where trees grew haphazardly and buildings were constructed around them. Nature is one of the reasons for which I am excited to return home–to get my hands messy with dirt and tree sap instead of congesting my lungs with cigarette smoke and exhaust fumes. I guess that’s to be expected in the city, but that is the reason why I would not feel ‘at home’ here. When I do find some odd time, I like to venture into the park across Cite U. It’s huge, with rolling hills, monstrous trees, and a laidback atmosphere with people hoping to escape the hustle and bustle of Paris—if only for a moment.

A map of Parc Montsouris

The freshness of nature is what draws me to the great outdoors. It’s rejuvenating, like taking a nice hot shower on a cold day. I feel connected to Mother Earth, and free of the dusty rooms and buildings that seem to trap more than shelter. Though I have come to appreciate the emotional (and even spiritual) boost I receive when taking nature walks, I began to wonder if there are more tangible benefits to walking in the woods. As luck would have it, research has shown the possibility of improving cognition by surrounding oneself in nature.

Parc Montsouris

A study by Berman et al. focused on understanding how nature can affect individuals with major depressive disorder (MDD) (2012). This disorder affects working memory and is characterized by a constant negative mood.  Nature may help these people improve cognitively, or conversely cause them to ruminate and thus worsen their mood. The researchers used 20 participants diagnosed with MDD. Before starting the nature walks, the participants’ short term memory span and mood were measured using the BDS task and PANAS, respectively. BDS (backward digit span) task involves patients repeating a number auditorily presented each second. PANAS (positive and negative affect schedule) is a questionnaire in which participants rate in terms of intensity a list of emotions (both positive and negative) that they may be feeling. Lastly, the participants were asked to ruminate on a negative event in their life, to see if nature walks would alleviate or aggravate the ruminations.

A park near the Bastille, on an archway above the busy streets below

Participants walked on a designated path for about 50 minutes (2.8 miles) in either a secluded park or traffic-heavy downtown area. Upon returning, they again completed the BDS task and PANAS. The researchers also asked the patients what they thought about during their walks, to roughly see if ruminations persisted on the walk. The experiment was repeated a week later, with the participants walking along the path they had not walked in the first session. Results show that the participants had relatively similar BDS score before the tests, but those in the nature walk had higher scores (i.e. a larger memory capacity) than those in the city walk. In terms of mood, the participants scored higher on more positive emotions and lower on negative emotions after the nature walk than after the urban walk. Lastly, participants in either walk ruminated on the negative event to the relatively same degree.

Garden in the Chateau de Villandry

Garden in the Chateau de Villandry

These results of the study are interesting because they suggest that perhaps one can improve memory and mood simply through walking through nature. Even though the ruminations didn’t differ during either walk, still the participants demonstrated better short term memory and mood, indicating that just avoiding those negative thoughts is not why they scored higher on the tests. Maybe environment does play a stronger role in our cognition than previously thought.

Still, I was curious to learn more about the root of cognitive improvement through these nature walks. After some research, I found data that blew my mind. A study investigated the role of a bacteria, Mycobacterium vaccae in mice behavior and learning (Matthews and Jenks, 2013). These bacteria are found in soil, water, and plants, i.e. the basic ingredients of a nature walk. Previous research has studied the symbiotic (both parties benefiting) relationship between microbes and animal hosts, and the possible brain-gut connection through these animals improve cognitive abilities after ingesting the bacteria.

Lopsided tree, perfect for climbing

Skipping the gory details, mice were tested for anxiety-related behaviors and speed of completion of maze navigation. Those fed the bacteria had reduced anxiety-related behaviors and completed the maze twice as quickly as mice not given the bacteria. The level of activity did not differ between the experimental and control mice, since both groups used the running wheel a similar amount of time. The results are astonishing because they show that by simply ingesting certain bacteria, mice can improve learning and reduce their anxiety.

If we can somehow test this in humans, and ascertain to what degree the Mycobacterium vaccae bacteria exist in our environment and our bodies, maybe we can come to similar conclusions. These data could potentially show that walking in nature does not only give a psychological boost—we may be actually replenishing our stock of that bacteria, becoming cognitively stronger without even realizing it. Though we may be far from truly understanding this effect in humans, I will take these results as a cue to continue my nature walks. If not for the healthy boost of bacteria, at least I can leave the crowded, polluted city for fresh air, green trees, and a glimpse of untouched beauty.

-Mayur Patel

Relaxing on a giant branch

Relaxing on a giant branch

References:

Berman M, Kross E, Krpan K, Askren M, Burson A, Deldin P, Kaplan S, Sherdell L, Gotlib I, Jonides J (2012) Interacting with nature improves cognition and affect for individuals with depression. Journal of Affective Disorders 140: 300-305

Matthews D, Jenks S (2013) Ingestion of Mycobacterium vaccae decreases anxiety-related behavior and improves learning in mice. Behavioral Processes 96: 27-35

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