 Adaptive Capacity: An evolutionary-neuroscience model linking exercise, cognition, and brain health NEUROPLASTICITY An overview of the current scientific understanding of neuroplasticity and the brain, (Costandi, 2016):
A brief overview of the historical discovery of neuroplasticity The discovery of neuroplasticity extends back approximately 200 years. In the 1780’s Swiss naturalist, Charles Bonnet, and Italian anatomist, Michele Vincenzo Malacarne, corresponded about the brain's ability to grow and change from practicing “mental exercise”. Then in 1791 German physician, Samuel Thomas von Sömmerring, published a textbook titled “Does use and exertion of mental power gradually change the material structure of the brain.” He pondered that in the same way we used our muscles to become stronger the possibly existed that the same could happen within the brain. In the 1890’s Spanish neuroanatomist Santiago Ramón y Cajal whose advancements in microscopy and (cell) staining methods propelled examination of nervous tissues that led to the discovery of cells called neurons. And the list goes on and on, (Costandi, 2016). From the beginning, advancements in neuroscience have and continue to be a multidisciplinary effort. In 1969 Paul Bach-y-Rita published an article in a European science journal citing his research using a machine that sent signals to the damaged area of a brain that ultimately cured retinal damage in some cases. Bach-y-Rita’s research demonstrated that our brains were capable of neuroplasticity and using other area’s to restructure and create new neural growth. The research publication and its avant-garde nature caused isolation from some of his peers. Bach-y-Rita had a multi-disciplinary background and approach and tended to follow ideas as they evolved. As a neuroscientist, he had expertise in medicine, psychopharmacology, ocular neurophysiology, visual neurophysiology, and bio-medical engineering. Doidge (2007) asserts that Paul Bach-y-Rita stated “we see with our brains” and that if one area is damaged, another area can take over. He referred to this process as “sensory substitution”. It was Eric Kandel who “was the first to show that as we learn, our individual neurons alter their structure and strengthen the synaptic connections between them…” Doidge (2007) explained that Kandel’s work demonstrated that learning produces new neurons in the brain that influence our genes and that psychotherapy changes people’s brain structure, “it presumably does so through learning, by producing changes in gene expression that alter the anatomical pattern of interconnections between nerve cells”. Neuroplasticity and the CNS Neuroplasticity is the ability of the central nervous system (CNS) to adapt to environmental changes and experiences and to adapt to injury or disease. This plasticity ability in the CNS allows modifications to successfully cope with new circumstances, allow for recruitment of new neural networks, and creates neural changes in areas of the brain, (Sharma, N., Classen, J., & Cohen, L. G., 2013). Mechanisms of plasticity and metaplasticity (activity-dependent changes in neural functions that modulate subsequent synaptic-plasticity such as long-term potentiation “LTP” and long-term depression “LTD”) are important for learning and memory, and in functional recovery from lesions in the CNS, and stroke. Plasticity changes occur at the cortical levels and reorganize subcortical structures. “…neural substrates of recovery of function are likely distributed over multiple sites at different levels of the neuroaxis and not restricted to one specific location…”, (Sharma, N., Classen, J., & Cohen, L. G., 2013). It is recent that our understanding neuroplasticity can occur in the adult CNS and in elderly people. This mechanism includes the recruitment of multiple brain regions in the elderly and in stroke recovery patients. Neuroplasticity occurs when the nervous system responds to experiences, thus experience-dependent. Experiences create a stimulus that ignites neural firing patterns in the brain to imprint or to re-transcribe an experience, or to reorganize the infrastructure of previous experiences via new neural pathways. Researchers Cramer, Sur, Dobkin, O'Brien, Sanger, Trojanowski, & Vinogradov (2011) examine the function of neuroplasticity in the context of clinical psychology via interventions and treatments, including CNS trauma recovery. “To advance the translation of Neuroplasticity research towards clinical applications, the National Institutes of Health Blueprint for Neuroscience Research sponsored a workshop in 2009. Basic and clinical researchers in disciplines from central nervous system injury/stroke, mental/addictive disorders, pediatric/developmental disorders, and neurodegenerative/ aging identified cardinal examples of Neuroplasticity, underlying mechanisms, therapeutic implications and common denominators”, (p. 1592, 2011). Experience-dependent clinical interventions based on the principles of neuroplasticity require a multimodal treatment approach. Implementing the Hebbian principles, a neuroscience theory explaining the process of neurogenesis during learning, with cognitive behavioral techniques, achieving tasks and goals, socializing and exercising, can produce a measurable outcome. “A key principle in neuroplasticity is the value of coupling a plasticity-promoting intervention with behavioral reinforcement…” (Cramer, Sur, Dobkin, O'Brien, Sanger, Trojanowski, & Vinogradov, p. 1598, 2011). Participating in regular physical exercise and learning something new illuminate the experience-dependent neural growth aspect of neuroplasticity and neurogenesis. “Aerobic exercise is associated with increased neurogenesis and angiogenesis…”, “…aerobic exercise programs lasting even just a few months significantly benefit cognitive functioning…have been shown to increase brain volume in a variety of regions (Colcombe et al., 2006; Pajonk et al., 2010)…and to enhance brain network functioning…” (p. 1600, 2011). Exercise enhances cognitive functioning which increases our learning capacity. Interventions and treatments designed with the intention of working with the principles of neuroplasticity are used for various CNS injuries, like traumatic brain injury. These treatment interventions are measurable in terms of outcome. “Interestingly, after spinal cord injury, treatment-induced brain plasticity can be measured in the absence of behavioral change”, (p. 1594). The mechanisms of neuroplasticity apply to a range of CNS injuries and treatments. “Studies of motor recovery after stroke illustrate the principle that many forms of neuroplasticity can be ongoing in parallel. Injury to a region of the motor network can result in spontaneous intra-hemispheric changes, such as in representational maps, e.g. the hand area can shift dorsally to invade the shoulder region (Nudo et al., 1996; Muellbacher et al., 2002) or face region (Weiller et al., 1993; Cramer and Crafton, 2006)”, , (Sur, Dobkin, O'Brien, Sanger, Trojanowski, & Vinogradov, p. 1592-3, 2011). A rehabilitative perspective includes patients who’ve suffered CNS injury, stroke, and spinal cord injury. In particular, patients recovering from stroke are dependent upon new neural growth, neurogenesis, and new neural patterns and pathways, neuroplasticity. The brain of a recovering stroke victim begins reorganizing itself. EPIGENETICS fundamentals (“what-is-epigenetics”, 2018). Epigenetics is a (complex) biological mechanism that switches genes off and on. The process of epigenetics affects how genes are read by certain cells.
In general terms, it’s understood that our genetic inheritance plays a key role in either our ability to have a long healthy life or for developing a chronic disease and illness. Epigenetics is a recent scientific discovery to the study of genetics. Epigenetics shows us that behavioral and environmental lifestyle choices may influence up to 50% of our genetically inherited predisposition. Both endogenous (growing from within an organism) and exogenous (growing from outside an organism) epigenetic influences can determine how our genes are expressed. “A recent addition to genetics has been epigenetics, which includes the role of the environment, both social and natural, including day-to-day habits, lifestyle and personal experiences on human health. Epigenetics establishes a scientific basis for how external factors and the environment can shape an individual both physically and mentally”, (Kanherkar, R. R., Bhatia-Dey, N., & Csoka, A. B., 2014). Epigenetics refers to how our inherited genes are used or expressed. Behavioral and lifestyle choices affect which genes are switched on, or “expressed”, and which genes are switched off, or “silenced”. During the course of our lives, depending on environmental factors we are exposed to, epigenetics is capable of either positive or negative changes to our gene expression. (Kanherkar, R. R., Bhatia-Dey, N., & Csoka, A. B. (2014). EPIGENOME The epigenome integrates all the molecular and chemical cues from the cells and from the environment. It represents the ability of the genetic organism to adapt and evolve in response to environmental stimuli. It is therefore dynamic and flexible. “Ultimately, the environment presents these various factors to the individual that influence the epigenome, and the unique epigenetic and genetic profile of each individual also modulates the specific response to these factors”, (Kanherkar, R. R., Bhatia-Dey, N., & Csoka, A. B. (2014). Epigenome biology A genome “marker” is the epigenomic compound that attached to (our) DNA with instructions, we inherited this as it was passed down generationally, (https://www.genome.gov/27532724/epigenomicsfact-sheet/). While “genome” refers to the whole DNA sequence and the “epigenome” refers to the entire pattern of epigenetic modifications across all genes, including methylation DNA tags. “The epigenome is a multitude of chemical compounds that can tell the genome what to do. The human genome is the complete assembly of DNA (deoxyribonucleic acid)-about 3 billion base pairs - that makes each individual unique. ... Rather, they change the way cells use the DNA's instructions”, which means they can be influenced to either turn on or off. Exercise effects epigenome How we may influence our gene expression, switching genes off and on, this mechanism can be harnessed via exercise. “Exercise is a non-pharmacological life-style factor, which plays an important role in maintaining a healthy brain through out life and in human ageing. It is a powerful environmental intervention capable of gene expression change, improved neurogenesis, enhanced synaptic plasticity and signaling pathways, and involving epigenetic regulation in the brain and cerebellum in humans, Raji et al. 2016...", (Rea, I. M. (2017). Exercise can be considered a preventative medicine. It can reduce the risk of developing a chronic illness and enhance one's overall well-being. Scientific research has identified some molecular pathways that show how physical exercise produces changes in the human epigenome. This finding indicates the potential for cognitive enhancement, improved psychological health, better muscular fitness, and extends to overall better aging and improved quality of life throughout one's lifespan. “Exercise is a key factor in maintaining our functional autonomy and can protect us from sarcopenic loss of muscle mass and strength which occurs with increasing age, and which is a major contributor to the frailty syndrome, Walston 2012; Cruz-Jentoft et al. 2010; Morley et al. 2001”, (Rea, I. M., 2017). Exercise activates certain genes by adding tags to DNA via methylation. These tags turn on or off gene switches. A regular exercise routine can cause a “modification in the genome-wide methylation pattern of DNA…”. Even a single exercise event causes immediate changes in the methylation pattern of certain genes in our DNA, and thus affects gene expression, (Rea, I. M., 2017). EXERCISE- EPIGENOME-EPIGENETICS Making healthy lifestyle choices like regular exercise is a way each person can actively modify their epigenome, and thus their epigenetics, in an effort to preserve and prolong their lifespan. Exercise activates epigenetic tags added to our DNA, such as methylation, which allows our DNA to better regulate metabolism and create beneficial changes to the skeletal muscle. “The health benefits of physical exercise, especially on a long term and strenuous basis, has a positive effect on epigenetic mechanisms and ultimately may reduce incidence and severity of disease, Sanchis-Gomar et al., 2012”, Kanherkar, R. R., Bhatia-Dey, N., & Csoka, A. B. (2014). Exercise activates a cellular stress response. Aerobic and anaerobic exercise re-energizes the mitochondria. Our muscle growth during a lifespan is regulated by anabolic, the chemical reactions that synthesize molecules in metabolism, and catabolic, the destructive metabolism and breaking down of more complex substances with the release of energy, mechanisms of our gene expressions. Exercise revitalizes the mitochondrial function in our muscles. “It not only improves muscle function but also quality of life, with exercise improving mitochondrial function in older individuals as much as in younger exercising individuals. “Enzymatic activity in response to the environment promotes addition or removal of epigenetic tags on DNA and/or chromatin, sparking a cavalcade of changes that affect cellular memory transiently, permanently or with a heritable alteration”, (Kanherkar, R. R., Bhatia-Dey, N., & Csoka, A. B., 2014). While the research referenced in this article focuses on exercise as a way to influence of epigenetics (gene expression), this concept can be applied to many other activities like learning new things, exposure to novel challenges and engaging in new tasks. Additionally, these research includes epigenetics in response to addiction and unhealthy lifestyle activities. I've chosen to focus my article on exercise and healthy lifestyle benefits. Express your gene's wisely! References
 Copyright © Lisa Lukianoff, Psy.D., 201
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