OMG, More Stairs?!?

When I came to Paris, I thought I was prepared for everything: the bakeries, the museums, the landmarks, the culture — but nothing could have prepared me for the walking I was about to do. Unlike the suburban areas around Emory or my hometown of Topeka, Kansas, where a car is considered necessary for most outings, the streets of Paris are easily traversable by foot, and public transportation is much more accessible. And in a city so beautiful, I had a hard time refusing the ease of foot travel. Still, with the recent muggy weather, walking hasn’t felt quite as pleasant. People always say “no pain, no gain,” and I began to wonder what all my walking was doing for me brain-wise.

My steps before and after I came to Paris. As one can see, my steps significantly increased after I came to Paris, May 22th.

Turns out, there’s a lot to be gained from regular aerobic exercise. Consistent research has pointed to the role of physical activity in cognitive function and has grown in volume over the past decade (Soga et al., 2015). General movement has been suggested to contribute to brain plasticity, which in turn facilitates interaction between cognitive and motor functioning (Doyon and Benali, 2005). Furthermore, research has also linked physical activity to academic performance (Castelli et al., 2007). While these results doesn’t necessarily mean that taking up routine walking or running will guarantee better grades or memory, the two do seem to be invariably related.

Amidst this burgeoning research, Colcombe and colleagues decided to research the cortical mechanisms beneath cardiovascular fitness-related changes in cognitive function (Colcombe et al., 2004). Functional magnetic resonance imaging (fMRI) was used to study how changes in fitness might affect the brain. Researchers particularly focused on the anterior circular cingulate (ACC), an area of the limbic system linked to brain structures responsible for sensory, motor, emotional, and cognitive information (Bush et al., 2000).

The study took place in 2 segments, with Study 1 involving high-fit (HF) older adults, and Study 2 involving adults randomly assigned to either a cardiovascular fitness training (CFT) group or a stretching and toning group (control) (Colcombe et al., 2004). All participants in both groups underwent a flanker task in which they filtered and identified incongruent cues (Colcombe et al., 2004). The flanker test allowed researchers to study participants’ ability to filter and respond to relevant information (Colcombe et al., 2004). Researchers then compared cortical mechanisms triggered by incongruent clues to those triggered by congruent ones, to see whether HF adults would demonstrate higher activation in attention- and control-related regions (Colcombe et al., 2004).

fMRI scans of the ACC illustrate activation of different cortical areas in the task-related activity (Colcombe et al., 2004).

Sure enough, fMRI scans supported the study’s hypothesis that older adults with high levels of measured cardiovascular fitness would demonstrate significantly more activation in cortical regions linked with attention selection and control (Colcombe et al., 2004). These cortical regions include the medial frontal gyrus (MFG), superior frontal gyrus (SFG), and superior parietal lobe (SPL) (Colcombe et al., 2004). Significantly less activation was observed in the ACC, which is linked with behavioral conflict and adaptation of attentional control (Colcombe et al., 2004).

One weakness of the study by Colcombe and colleagues is the cross-sectional approach taken in Study 1. Being observational, cross-sectional studies are vulnerable to non-response bias, which can lead to a participant pool unrepresentative of the population (Sedgwick, 2014). Furthermore, data can only be collected during one set period of time, leaving researchers unable to create long-term representations of cause and effect (Sedgwick, 2014). However, it is important to note that longitudinal studies might also be difficult to complete with older participants, due to possible interference from disease or other age-related complications (Sedgwick, 2014). Ultimately, the research by Colcombe and colleagues was important at the time of its publication because it expanded upon existing research regarding the underlying cortical mechanisms of cardiovascular fitness.

More recent research by Brockett and colleagues suggests that physical exercise may contribute to extensive plasticity and increased cognitive functioning (Brockett et al., 2015). Rats who ran for moderate durations of 12 days were able to better discriminate than control rats in a task testing medial prefrontal cortex (mPFC) function, though little difference was seen between both groups in a task testing perirhinal cortex (PRC) function (Brockett et al., 2015). In a second experiment, runner rats took less trials and errors than control sedentary rats to reach criteria for simple discrimination, reversal, extradimensional shift (Brockett et al., 2015). Researchers also tested whether running influences astrocytes, non-neural brain cells that communicate with neurons and suggest links to synaptic plasticity, learning, and memory (Brockett et al., 2015). Co-labelling of astrocytes with visual markers revealed increase in astrocytes cell body area in the hippocampus, mPFC, and OFC (Brockett et al., 2015). These results aligned with data from the behavioral tests, suggesting that physical exercise can enhance cognitive performance in tasks that activate the hippocampus, mPFC, and OFC (Brockett et al., 2015). The lack of significant change to the PRC suggests that routine running lacks observable relation to the PRC. Ultimately, results suggest greater cognitive performance in tasks reliant on the prefrontal cortex, as well as enhanced synaptic, dendritic, and astrocytic measures in several regions. This evidence supports the hypothesis that physical exercise contributes positively to plasticity and cognitive functioning. Together, both papers by Colcombe, Brockett, and their colleagues have contributed to the growing understanding that exercise generally promotes greater cognitive functioning.

Brockett and colleagues’ research has made me wonder how much I would have to run to achieve the human equivalent of a rat’s 12-day regimen. As a student, it’s incredibly easy to get sucked into the grind and become deskbound. But the grind is exactly why brain power is important for the students, and optimizing my brain power in exchange for a few minutes and some physical effort has started to sound like a much better idea than the old me would have thought.

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. Public Library of Science ONE 10(5): e0124859. https://doi.org/10.1371/journal.pone.0124859.

Bush G, Luu P, Posner MI (2000) Cognitive and emotional influences in anterior cingulate cortex. Trends in Cognitive Sciences. 4(6):215-222. https://doi.org/10.1016/S1364 6613(00)01483-2.

Castelli DM, Hillman CH, Buck SM, Erwin HE (2007) Physical fitness and academic achievement in third- and fifth-grade students. Journal of Sport and Exercise Psychology 29(2):239-252. https://doi.org/10.1123/jsep.29.2.239.

Colcombe SJ, Kramer AF, Erickson KI, Scalf  P, McAuley E, Cohen NJ, Webb A, Jerome GJ, Marquez DX, Elavsky S (2004) Cardiovascular fitness, cortical plasticity, and aging. Proceedings of the National Academy of Sciences of the United States of America            101(9):3316-3321. https://doi.org/10.1073/pnas.0400266101.

Doyon J, Benali H (2005) Reorganization and plasticity in the adult brain during learning of motor skills. Current Opinion in Neurobiology 15(2):161-167. https://doi.org/10.1016/j.conb.2005.03.004.

Sedgwick P (2014) Cross sectional studies: Advantages and disadvantages. BMJ 348. https://doi.org/10.1136/bmj.g2276.

Soga K, Shishido T, Nagatomi R (2015) Executive function during and after acute moderate aerobic exercise in adolescents. Psychology of Sport and Exercise 16:7-17. https://doi.org/10.1016/j.psychsport.2014.08.010.

Image 1 taken by myself.

Image 2 from Colcombe et al., 2004.

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