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Exercise Boosts Brain Development

Introduction
Neuroscientific Context
Analysis
Appendix
References


Group Members:

Alanna Wong z3418547
Elisa Lau z3419391
Daniel Zhu z3417105
Vivien Lu z3417648


Link to Article: http://www.digitaljournal.com/article/355407



Introduction


“Walking to school will boost brain development in children” is an online media article, recently published on Digital Journal by Jay McClung, on the 28th July 2013. The article centres around the beneficial effects of exercise on the cognitive abilities of children. Evidences present include research conducted by Georgia Health Sciences University, noting modest improvements in mathematics and IQ after 13 weeks of a daily vigorous exercise regime.

Research in the field has confirmed that exercise affects many areas in the brain, relating to cognition, mood, and physical well-being. This field of interest has been increasingly significant, as society has become sedentary in their lifestyles, with less physical engagement (Manson et al. 2004). The recent Global Status Report (2010) by WHO has shown that obesity/overweight and physical inactivity are two of the leading risk factors for preventable deaths. As our group did little to no exercise, we were curious as to whether this was affecting our mental and cognitive health. In particular we are interested in investigating if such a decrease in physical activity in crucial stages of a child's development is negatively impacting future generations, thus hindering their ability to attain their full potential.


Neuroscientific Context


1. The Brain


1.1 Aerobic Exercise


Exercise is an extremely broad term and comes under many different forms, ranging from flexibility, through to anaerobic and aerobic exercises. Although all physical movements have various impacts on the human body, this page specifically concerns itself with the effects of aerobic exercise (AE) on the brain. It is therefore important to distinguish this type of exercise from others.

It must be understood that where anaerobic activity (such as strengthening exercise) primarily affects the development of skeletal muscles, with no change to oxygen intake, AE's impact on oxygen levels is noticeable (So, W.Y., 2012). Further comparison between anaerobic and AE has shown AE to positively impact brain development, while others have produced no evident neuroscientific impact (Hillman et al., 2008).

1.2 Short-Term Effects


1.2.1. Cardiovascular Effects
AE, encompassing a broader framework of physical activity, also includes cardiovascular fitness, which collectively improves cognitive performance in the short-term (Etnier et al., 2006). In a meta-analysis by Etnier et al. (2006), it was shown that AE alone did not consistently have a beneficial effect on cognitive performance. Ogoh and Ainslie (2009) show that AE increases cerebral blood flow, which delivers more oxygen and nutrients to the cerebral cortex. Subsequently, neuronal activity is higher and more efficient in the brain, thus enhancing cognitive performance.

1.2.2. Motor Control + Cerebellum
According to a meta-analysis, AE quickly alters brain structure through an increase in capillary density, in the cerebellum (Thomas et al., 2012). Since the former is responsible for motor control, this increase translates in blood flow increases, both in the cerebellum and to other parts of the body it controls, including the limbs. Hence, this leads to an increase in reaction accuracy, along with faster neural responses. This change in the cerebellum thus accounts for the benefits in terms of motor activity, as it communicates more efficiently with the body’s internal system.

1.2.3. Impact of Stress
Stress, whether it is acute or chronic, has particularly negative effects on the brain’s neural plasticity. Consequences include dendritic atrophy and spine reduction, both important in learning and memory development. Corticosteroids are produced in the presence of stressors, which can decrease brain-derived neurotrophic factors (BDNF) in the hippocampus. This results in neuronal death, and learning and memory impairments (Cotman & Berchtold, 2002). However, AE has positive effects on the body’s stress response, by lowering cortisol or norepinephrine levels. Instead, it releases chemicals such as endorphins, dopamine and serotonin, which results in feelings of elations. Therefore, AE is commonly advised as a short-term stress-relief strategy, quickly addressing the likelihood of neuronal death while improving the mood.

1.3 Long Term Effects


1.3.1. Brain-Derived Neurotrophic Factors (BDNF)
BDNF are trophic proteins, part of the neurotrophin family of growth factors, that are found in the brain (Bear et al., 2007). They have a very important role in neuronal survival and growth (neurogenesis) and are thus key mediators of synaptic transmission, communication and neuroplasticity (Cotman & Berchtold, 2002). BDNF is particularly active in the dentate gyrus (DG) and the CA3 region of the hippocampus (as shown by the highlighted hippocampal parts in Figure 1, a) and b)), which is important for learning and memory formation. Accordingly, Tokuyama et al. (2000) suggests that learning involves numerous changes in the brain’s plasticity, facilitated by BDNF.

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Figure 1. (a) & (b). BDNF expressed in certain areas of the hippocampus including dentate gyrus and CA3 region. (c) Number of BDNF increased in subjects who undertook aerobic exercise compared to those that were sedentary (controls). (d) Positive correlation between BDNF levels and the amount of exercise.


Exercise has been shown to increase the number of BDNF protein and gene expression in the hippocampus, which is involved in learning and memory (Kesslak et al., 1998). Figure 1 c) and d) further supports the positive correlation between AE and BNDF levels, by comparing the former with length of exercise. Illustrated in Figure 2, BDNF participates in gene transcription and change the synaptic structure, by the transfer between synaptic neurons. This increases neuronal survival and resilience (Cotman & Berchtold, 2002). Regarding gene transcription, AE also increased the level of certain immediate early genes (IEG) that regulate neuronal growth and plasticity. For example, NARP, a homologous member of the pentraxin family, promotes neuronal growth and synaptic changes. NGFI-A is another type of gene affected, responsible for memory consolidation and long-term potentiation formation (Tong et al., 2001). Studies also show that mice, lacking in BDNF, exhibit impaired long-term potentiation, resulting in learning deficits. However, when BDNF was replaced in these mice, the findings were reversed, as learning was enhanced (Lu & Chow, 1999). This further illustrates the effect BDNF has on learning and memory in the long-term.

Screen Shot 2013-09-07 at 9.06.42 PM.png
Figure 2. (a) BDNF is being transported to synapses, undergoing synaptic transmission. (b) BDNF in the synapse binds to its receptor (TrkB) to modify neurotransmitter release e.g. NMDA receptors.


1.3.2. Effect on Neurotransmitters
Neurotransmitters are chemicals that transmit signals between neurons over a synapse. According to Cotman & Berchtold (2002), neurotransmitters such as glutamate, GABA and ACh also control BDNF gene expression patterns in the hippocampus. The medial septum, connected to the hippocampus via the GABAergic neurons (Hangya et al., 2009), helps with BDNF regulation after exercise. The combination of GABAergic neurons and ACh-mediated activation of the hippocampus has also been shown to regulate BDNF by exercise, because loss of GABAergic neurons and septal cholinergic afferents resulted in disruption of hippocampal BNDF regulation.

According to Etnier et al. (2006), the neuroadrenergic hypothesis states that AE changes neurotransmitters availability in the cerebral cortex. Because neurotransmitters, such as adrenaline and serotonin, are associated with better memory storage and recall, increasing their availability in the cortex may improve cognitive and memory performance. Overall, neurotransmitters play an important role in regulating hippocampal BDNF expression, while directly affecting the cerebral cortex to change plasticity, creating long-term potentiation with increased cell survival and growth, all of which enhance cognitive functioning.

1.3.3. Insulin-like Growth Factors (IGF-1)
Insulin-like Growth factors (IGF-1) play a role in neuronal growth and differentiation in the brain, while acting as a mediator of BDNF gene regulation, neurogenesis and brain insult prevention. Exercise increases the absorption of IGF-1 circulating in the brain and peripheral areas. When the IGF-1 in the periphery fuses across the blood-brain barrier, BDNF mRNA is induced in the brain. Consequently, BDNF brings about some protective effects of IGF-1 (Cotman & Berchtold, 2002). Therefore, evidence suggests that peripheral IGF-1 can alter ongoing plasticity, by regulating BDNF gene regulation and protecting the brain.



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Figure 3. Overview of how exercise affects the brain




1.4 Improvement in Cognitive Function


1.4.1. Memory and Learning
The hippocampus, located in the medial temporal lobe, is responsible for learning and memory processing. Studies show that children who exercise more, and have higher aerobic fitness levels, have larger bilateral hippocampal volumes, which is associated with better performance in relational memory tasks (Shaddock et al., 2010). More specifically, the dentate gyrus of the hippocampus sees an increase in cell proliferations and survival (Hillman, C.H. et al, 2008). Importantly, the duration and intensity of AE prior to cognitive memory tasks has a large effect on memory consolidation: results showed better memory recall after only 30 minutes of moderate intensity AE (Labban & Etnier, 2011). Therefore, AE is essential in improving memory consolidation, through increasing hippocampal volumes, which in turn increases its efficiency, to provide better cognitive performance in memory tasks.

1.4.2. Executive Functioning
Executive functioning involves planning, reasoning, problem solving, scheduling and multi-tasking, all of which the pre-frontal cortex controls. According to Hillman et al. (2008), subjects with higher levels of aerobic fitness had larger volumes of prefrontal cortex, more temporal grey matter (more neurons) and more anterior white matter (myelination). These brain regions may function more efficiently, since more grey matter allows for more effective communication and connection between neurons; and more white matter allows for faster and smoother signal transduction. As illustrated in Figure 4, exercise significantly enhances overall cognitive processes, compared to controls, and has greater effects on executive functioning.
Screen Shot 2013-09-08 at 5.04.41 PM.png
Figure 4. Meta-analytic results of exercise training and its effects on adults’ cognitive processes.


These results are further replicated in other studies, in which there were increases in bilateral prefrontal cortex activity, and a decrease in bilateral posterior parietal cortex in the exercise group, relative to the inactive group (Davis et al., 2011). The effortful mental involvement during exercise may stimulate executive functioning areas as a “warm up” in the brain for further cognitive tasks.

2. A Child's Brain


Effects of AE on young brains seem to be different, despite the similar positive correlation being observed. AE has longer lasting (Chaddock et al., 2010) and more remarkable impact on children’s behaviours (Hillman et al., 2005). This is because childhood is quite a significant period to develop habits and routines, as found by So (2012). In fact, approximately 80% of obese kids grow to stay obese. With this in mind, benefits from AE would be amplified, since children would have started AE at a young age. Furthermore, the preadolescent period allows for cognitive, medial temporal lobe, grey matter structure and neural developments (Brocki & Bohlin, 2004). As a result, AE’s positive impact on children lasts longer, while their brains are still actively developing.

3. Gender Differences


AE also yields distinctive outcomes between genders, with women having higher recall rates and AE-related cognitive benefits (Labban & Ethnier, 2011; Spencer et al., 2008). Spencer et al. (2008) hypothesise that higher levels of estrogen in women positively correlates with BDNF production. Consequently, gains from AE are higher in females, when tested under same conditions.
Furthermore, estrogen replacement therapy in older women, which elevates estrogen levels, improves cognitive functioning (ibid). Hence, cognitive improvements from AE have a more articulate impact on women, compared to men.


4. Implications in real life practices

Many schools, such as the Naperville Central High School in Illinois (CBS News, 2009), have already started implementing scientific findings, by re-modelling traditional education methods. Indeed, students undergoing AE before the classes they struggle with, successfully experience net academic improvements. This leaves us to wonder about the implications of existing scientific research, and the extent to which these results should be implemented in present education systems. To bridge the gap between science and education, Goswami (2006) suggested the development of societies such as the International Mind, Brain and Education Society, along with the introduction of communicators, to interpret scientific results to educators.
Importantly, other major studies have linked cardiovascular fitness (through AE) to higher academic success, through an increase in perceptual, verbal and calculation skills, along with general IQ and increased creativity (Tomporowski et al., 2007). However, AE in extensive amount not only left students evidently tired and unable to focus, but also consumed studying time (So, 2012). Furthermore, other randomized studies (Donelly & Lambourne, 2011; Tomporowski et al., 2007) found no evident correlation between AE and academic performance.


Hence, conclusions imply AE to not compromise academics, at best.




5. Conclusion


Although the experiments showing no correlation between AE and academic performance cannot be ignored, results have yet to show negative impacts with adequate AE, irrespective of age or gender. On the other hand, many mediating factors considered by Donelly J.E. and Lambourne K. (2011) to impact on experiment results, also need to be taken into account, and are summarised in Figure 5 below:


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Figure 5. Possible experiments mediating factors


Alternatively, convincing evidence and repeated results imply a positive correlation between AE and academic improvements, as suggested in the media item. AE seems to trigger a cascading chain of events, ultimately leading to general cognitive improvements. Nonetheless, it is undeniable that additional research needs to be done in this area before further implementation in real-life practices, ensuring that no unnecessary risks and costs are undertaken.



Analysis


This media piece was published on Digital Journal, an online media network displaying content from both professional and amateur contributors. Topics covered by the website, like the authors, are extremely diverse and generates traffic and interest of millions of viewers. It is clear though that their target audience are parents concerned about their child’s health as the related links direct to parenting articles and guides.

The article caters to its wide audience by simplifying its terms and summarising the studies without over sensationalism. However, it fails to explain specific details such as what defines aerobic exercise and how the areas of intelligence were tested. Furthermore the author has avoided explaining any underlying mechanisms in which exercise could affect cognitive ability and summarising its influence to a generic statement of “activating nerve cells and aiding healthy brain development”.

Further scepticism arises from the quoted researchers not being a part of the original study and their questionable areas of expertise. Dr. Gwen Dewar is the owner of a parenting website whose official qualifications are limited only to biological anthropology and her presence in the article generates the false sense of expertise to reinforce reputability. Yet it is good that a second professional Palma Chillon in the area of physical education can second the opinion.


In regards to the referenced sources, the relevancy and reliability is questionable. The author provides links to secondary sources such as other blogs and online articles but has neglected scientific journals, raising doubt on reliability. Moreover, the referenced articles talk about the same research with only one providing extra background research. The studies cited are also correlational with no direct manipulation and hence it is possible that there are other unexplored mediating factors that affect cognitive abilities and correlate to physical activity such as diet (Junger & van Kampen, 2010). Furthermore, the title using “will” implies a direct causal relationship that is contrary to the cited articles. Additional studies introduced to the article would provide a more balanced view and reduce bias


Nevertheless, the media article is easy to comprehend in its delivery and is an adequate outlet to inform the general public of recent research and its implications in daily lives. The lack of over sensationalism is also quite commendable but it is suggested the article be taken at face value and further research should be undertaken before making any radical lifestyle changes.



Appendix


When discussing the media item to use for this project, we had narrowed it down to a few topics and unanimously decided on the effect of exercise on the brain especially in young children. We thought this would be an interesting area to research since it appeared to be of practical benefit that people could easily implement into their children’s lives if confirmed. A quick search also showed there was a vast amount of investigation in this area which meant we would have access to enough information to conduct our research and analysis of the topic.

We also found that the media piece we chose was a great starting point for us to start our elaborate research into the topic. It delivered information in a brief and succinct manner and due to this nature of the article it allowed us to expand on the existing information and focus on the areas of interest.

Throughout this project, we used google documents as a method to collate our ideas and sources. As a group we all had access to the document and could submit any new and interesting research on the topic we had gathered throughout our search. Here we also summarised journal articles and linked other related video clips and articles for each other to approve and decide on as a team.

As a group, we welcomed and appreciated the constructive criticism of the reviewers, their comments gave us fresh insight into how we could improve our wiki page.
The general positive comments noted the logical organisation of the ideas and information making it easy to read and understand. Remarks were also made on the coherent manner in which we were able to relevantly tie in the neuroscientific context well with the information presented in the media article. Our execution of summarising and supporting our conclusions through graphs and figures were also well received.

Certain areas of improvements required as pointed out by the reviewers were addressed through elaborating on certain points and ideas to include further links and context with the support of empirical research particularly in the aerobic exercise section. Specifically, we followed the suggestion of a particular reviewer and made it more explicit that the research we referred to in the introduction was not the only source in the media article. In the body of the information we also elaborated on the figures to explain its relevance.

Following the advice, we also updated our sources to be more recent and relevant to reinforce the validity of our information. A chart of mediating factors was also included to allow readers to be aware of other contributing factors that could affect the link between exercise and brain development

Due to limitations on the word count we were unable to address all of the reviewers' concerns particularly in regards to expanding on certain areas of the topic. This was also necessary to keep the information succinct and significant to the main ideas.


References


Bear, M. F., Connors, B. W., & Paradiso, M. A. (2006). Neuroscience: Exploring the brain. Philadelphia: Lippincott Williams & Wilkins. 706-707.

CBS News (2009). Exercise gives the brain a workout too. The Early Show, retrieved from http://www.cbsnews.com/2100-500165_162-4764523.html.

Chaddock, L., Erickson, K. I., Prakash, R. S., Kim, J. S., Voss, M. W., VanPatter, M., … Kramer, A. F. (2010). A neuroimaging investigation of the association between aerobic fitness, hippocampal volume, and memory performance in preadolescent children. Brain Research, 1358, 172-183.

Cotman, C. W., & Berchtold, N. C. (2002). Exercise: a behavioural intervention to enhance brain health and plasticity. TRENDS in Neuroscience, 25(6), 295-301.

Davis, C, L., Yanasak, N. E., Allison, J. D., Tomporowski, P. D., McDowell, J. E., Austin, B. P., … Nalieri, J. A. (2011). Exercise improves executive function and achievement and alters brain activation in overweight children: a randomised, controlled trial. Health Psychology, 30(1), 91-98.

Donnelly, J. E. & Lambourne, K. (2011). Classroom-based physical activity, cognition, and academic achievement. Preventive Medicine, 52, S36-S42.

Etnier, J. L., Nowell, P. M., Landers, D. M., & Sibley, B. A. (2006). A meta-regression to examine the relationship between aerobic fitness and cognitive performance. Brain Research Reviews, 52, 119-130.

Goswami, U. (2006). Neuroscience and education: from research to practice? Nature Reviews Neuroscience, 7(5), 406.

Hangya, B., Borhegyi, Z., Szilagyi, N., Freund, T. F., & Varga, V. (2009) GABAergnic neurons of the medial septum lead the hippocampal network during theta activity, The Journal of Neuroscience, 29(25), 8094-8102.

Hillman, C. H., Erickson, K. I., & Kramer, A. F. (2008). Be smart, exercise your heat: exercise effects on brain and cognition. Nature Reviews Neuroscience, 9(1), 58-65.

Hillman, C. H., Castelli, D. M., & Buck, S. M. (2005). Aerobic Fitness and Neurocognitive Function in healthy Preadolescent Children. Medicine and science in sports and exercise, 37(11), 1967.

Junger, M., & Van Kampen, M. (2010). Cognitive ability and self-control in relation to dietary habits, physical activity and bodyweight in adolescents. International Journal of Behavioural Nutrition and Physical Activity, 7, 22-33.

Kesslak, P. J., So, V., Choi, J., Cotman, C. W., Gomez-Pinilla, F. (1998). Learning upregulates brain-deprived neutrophic factor messenger ribonucleic acid: a mechanism to facilitate encoding and circuit maintenance? Behavioural Neuroscience, 112(4), 1012-1019.

Labban, J. D., & Etnier, J. L. (2011). Effects of acute exercise on long-term memory. Research Quarterly for Exercise and Sport, 82(4), 712-721.

Lu, B., & Chow, A. (1999). Neurotrophins and hippocampal synaptic transmission and plasticity. Journal of Neuroscience Research, 58, 76-87.

Manson, J. E., Skerrett, P. J., Greenland, P., & VanItallie, T. B. (2004). The escalating pandemics of obesity and sedentary lifestyle: A call to action for clinicians. Archives of Internal Medicine, 164(3), 249-258.

McClung, J. (2013, Jul 28). Walking to school will boost brain development in children. Retrieved from http://www.digitaljournal.com/article/355407.

Ogoh, S., & Ainslie, P. N. (2009). Cerebral blood flow during exercise: Mechanisms of regulation. Journal of Applied Physiology, 107, 1370-1380.

So, W. Y. (2012). Association between physical activity and academic performance in Korean adolescent students. BMC Public Health, 12(1), 258.

Spencer, J. L., Waters, E. M., Romeo, R. D., Wood, G. E., Milner, T. A., & McEwen, B. S. (2008). Uncovering the mechanisms of estrogen effects on hippocampal function. Frontiers in Neuroendocrinology, 29(2), 219-237.

Thomas, A. G., Dennis, A., Bandettini, P. A., & Johansen-Berg, H. (2012). The effects of aerobic activity on brain structure. Frontiers in Psychology, 3(86), 1-9.

Tomporowski, P. D., Lambourne, K, & Okumura, M. S. (2011). Physical activity interventions and children's mental function: An introduction and overview. Preventive Medicine, 52, S3-S9.

Tong, L., Shen, H., Perreau, V. M., Balazs, R., & Cotman, C. W. (2001). Effects of exercise on gene-expression profile in the rat hippocampus, Neurobiology of Disease, 8, 1046-1056.



Workload Allocation:
Alanna - Neuroscientific Context
Daniel - Introduction & Analysis
Elisa - Neuroscientific Context
Vivien - Analysis & Appendix

Minutes:
Meeting 1 Minutes
Meeting 2 Minutes
Brainstorming, Research, General Structure - draft
Page Structure (draft).docx

Team Photo
DSC_0803.JPG

Deadlines:

17/08/13 - Find a collection of sources
21/08/13 - Select relevant sources
29/08/13 - Make a detailed plan/map of page and information to be included, and hand it over to Daniel and Vivien
05/09/13 - Complete Draft of Neuroscientific Context + References

05/09/13 - Complete Draft of Introduction, Analysis & Appendix

07/09/13 - Finalise Draft of Project
14/09/13 - Review comments on allocated projects
22/09/13 - Submit Final Project

Introduction | Neuroscientific Context | Analysis | Appendix | References