Science

  • Issue 114 / November - December 2016



    When Our Brain Asks for Help Remembering

    Geffrey Olsen

    The first time you rode your bicycle, the first day of the school, or the time you ran into an old friend: all these may still be fresh in your memory. Immediately recognizing the faces of your friends is only one of many amazing functions that our brain performs every day. The human brain contains billions of nerve cells (neurons) and just as many connections between the cells, which carry information amongst them. These connections allow our brain to adapt to changing external factors, such as stressors. The scientific definition of “stress” is slightly different than the one we may use to describe a difficult work assignment or a long commute in traffic.


    As a phenomenon, stress is a must for humanity’s survival; however, it becomes harmful when encountered excessively. Stress is what makes you run away from a giant bear in the middle of the forest. And it is the same force that drives you to fight when cornered. This fight or flight response primarily involves the sympathetic nervous system, which initiates a chain of reactions in communications between the body and the brain. Within seconds, stress hormones (epinephrine and norepinephrine) are released into the bloodstream, which in turn increase heart rate and blood pressure. This response occurs rapidly, though the hormones clear out of the system just as quickly when the threat passes.


    What happens if our fight or flight response is constantly triggered? What if stress hormones become a normal part of our bodily system? For instance, you might have taken your first “F” on a calculus test; this is followed by many others later on in the semester. Or you may have wanted to start your day with a fresh cup of coffee; instead, you were stuck in traffic and were late for work, and then forgot to hand in a big report to your boss.


    Imagine that these kinds of events are repeated more often than not; now think about how they make your feel. The medical terminology for this phenomenon is chronic stress. The consequences of chronic stress affect all aspects of our health, primarily the neural control systems, i.e. the brain.


    The Hippocampus, an essential area for memory storage and recall, is located in the inner layers of the brain. The specific system within which this structure is located is called the Limbic System. This is the brain’s Emotion Center. Similar to computers, our brains have two main memory systems. One is called short-term memory, which stores the information received through our senses. This information is usually brief, e.g. seven letters or digits such as phone numbers, and is usually processed in just a few seconds. This feature of the human brain resembles RAM (random access memory) in computers, because it mainly serves as a temporary storage area.

    Conversely, the other type of memory, also referred to as our “real memory,” is long-term. This is where we permanently store information – unless, of course, our brain is impaired by physical traumas, aging, or stress. We can think of this as the equivalent of a hard drive in data processing machines.


    Despite contributions from many other areas, the hippocampus plays the leading role in memory storage by performing “information consolidation” and converting temporary memories into memories that are suitable for long term storage. The process by which our brain commits information to long term memory can take minutes, hours, or even days. Our brain can retain information for a very long time, until we start to lose either individual encoded nerve cells or the connections bridging them. Once info is stored, it becomes your permanent data, to be recalled when needed. For this reason, the hippocampus can be seen as our personal storage box.


    Despite the astonishing hippocampus and its ability to develop on its own, it is ultimately affected by the brain’s common enemies, such as strokes, neurodegenerative diseases, brain tumors, and trauma related injuries. Most of these conditions will impact the region by attacking the neurons and their network of connections, which may lead to memory loss, depending on the magnitude of the damage and the region where the impairment takes place. Alzheimer’s disease is a commonly observed condition that leads to memory loss. Although, it was first believed that Alzheimer’s primarily affects elderly people older than the age of 65, recent cases indicate that it can be diagnosed as early as one’s thirties. The signature symptom of the disease is a progressive memory loss due to the substantial loss of neurons in this area. This is called hippocampal deterioration. For this reason, the size of the hippocampus can be used as a measure to follow up the progress of the disease. Although age related factors are the prime suspects, there are more variables in the equation that can trigger this devastating condition.


    Stress can affect our memory. While normal and moderate levels of stress are necessary for our body to trigger protective mechanisms, excessive levels of stress can lead to temporary and chronic disorders. Signs of stress can be physical, behavioral, and emotional, but they can also be cognitive. These include memory deficits. To see the dramatic changes that result from chronic stress on nerve cells, see figure 3.


    The underlying mechanism of how stress affects the hippocampus can be explained by the fact that the hippocampus contains high levels of glucocorticoid receptors, which make it more vulnerable to long-term stress than most other brain areas. Stress-related steroids affect the hippocampus in at least three different ways: first, by reducing the excitability of some hippocampal neurons; second, by inhibiting the genesis of new neurons in the dentate gyrus; third, by causing the atrophy of dendrites in pyramidal cells (7).


     


    Interestingly, religion plays a role in how our memory works – and it can be both a positive and negative force. “Hippocampal atrophy can be introduced by the level of stress that has been suffered in selected religious groups,” found Amy Owen and her colleagues at Duke University. She hypothesizes that the observed hippocampal shrinkage is greater in those who are part of a minority group or struggle to express their beliefs in society. In their MRI (brain imaging method used to measure the volume of the hippocampus) studies, Owen et al. found significantly greater hippocampal shrinkage among born-again Protestants, Catholics, and those with no religious affiliation compared to others.


    Earlier studies regarding relations between religion and the brain demonstrated many undeniably positive effects of religion on the brain. It is believed that since religion leads to a more tranquil and less stressful lifestyle, religious practices have beneficial effects on the human brain, particularly on the hippocampus. However, controversial findings have caused speculation about the negative effects of religious experience on selected individuals by causing chronic stress and anxiety (1).


    When we consider the principles of memory processing and its ability to store the information gained by sensory perception, it is not surprising that “life-changing experiences” would have a great impact on our body. When we are surprised, we learn. Who does not remember the first time we were burned by a hot stove? Or falling off a bicycle? The strength of our memories depends on the degree of impact the event has on us. It is known that the experiences that have greater impacts, such as an affiliation with a new religion, are more likely to be stored in the long-term memory part of the brain and be recalled as active memories.


    It’s understandable, then, why religious experiences can have such an impact on a person’s brain. Just as a strong religious community leads to a healthy brain, it makes sense that a minority in a religious community might be stressed (2). Though “religion” is frequently referred to as an important coping mechanism, it may also have contrasting effects in such cases. This raises two important questions: why and how?


    Starting at an early age, we are susceptible to environmental changes like growing up in a family, building friendships, and living in society. Living as a minority in our society or have conflicting beliefs with others may cause short-term or long-term stress, if the experiences also produce a change in one’s social network.


    “Life changing experiences in religion” are not easy to interpret since many variables are involved, such as age, sex, ethnicity, and existing traditions. Do these factors also play a critical role in this equation?


    One might ask, what if we test younger subjects, who have fewer life experiences, to see if they are better at adapting to new conditions? This might reveal the underlying causes of stress, i.e. whether religious practices cause stress and if they have an effect on hippocampal atrophy.


    The hippocampus is not completely developed until the age of two. During this early period, its development is extremely sensitive to the effects of chronic stress. It has been documented that hippocampal shrinkage is highly possible among those who are born healthy but exposed to stressful conditions. Growing in a healthy family and gaining supportive parental care is an important part of eliminating early stress in young children.


    The difficulties that certain individuals experience while trying to adapt to new communities or societies may be similar to what children experience in a less caring family. Studies show that stress and chaos at home impair the development of self-regulatory behaviors, which can lead to underdeveloped decision making skills.


    To understand the underlying mechanism of stress-induced hippocampal atrophy in certain individuals, we might have to reconsider our current understanding of the environmental conditions that cause stress. In other words, in what circumstances are we most likely to experience stress and feelings that lead to stress, and what is the product of these events?


    Nevertheless, stress is necessary, to a certain extent. It allows us to understand the significance of an obstacle. Imagine yourself studying for one of the most important tests of your life; the level of stress and pain during the pre-test period would be described as “suffering.” However, once the test is over, you’ll likely feel a sense of great relief.


    This leads to another question researchers must ask: how do individuals handle stress when they have been prepared to face it? Once again, the student-test example is useful. In one extreme, student A studies very diligently and feels confident about the test. Although the student spends a good amount of time stressing out about the test, this stress will be temporary and replaced by gratitude once the goal is achieved. On the other hand, student B is lazy and does not prepare at all. Though deceptively happy at first, he or she is ultimately wasting his or her time by playing around. Overwhelming stress will take over as the deadline approaches. The Qur’an comments on this:


    There is no clear answer as to whether religious affiliation leads to increased or decreased levels of stress, especially in people who have survived critical changes in their lives. Is the stress we experience because we struggle with our beliefs in society, or is it because of difficulties in adapting our beliefs to those of society? This is a chicken and egg problem. Although we are not certain how religion affects the human brain, we now know there is an absolute correlation. It seems that this uncertainty will prevail until some studies that can shed light on the issue become available.


     


    References



    1. Owen AD, Hayward RD, Koenig HG, Steffens DC, Payne ME, 2011 Religious Factors and Hippocampal Atrophy in Late Life. PLoS ONE 6(3): e17006. doi:10.1371/journal.pone.0017006


     



    1. Rong-Jian Liu * and George K. Aghajanian, Stress blunts serotonin-and hypocretin-evoked EPSCs in prefrontal cortex: Role of corticosterone-mediated apical dendritic atrophy, PNAS January 8, 2008 vol. 105 no. 1 359-364



    1. Marks L., Fam Process. 2004 Jun;43(2):217-31. Sacred practices in highly religious families: Christian, Jewish, Mormon, and Muslim perspectives.


     



    1. Prull MW, Gabrieli JDE, Bunge SA (2000). "Ch 2. Age-related changes in memory: A cognitive neuroscience perspective". In Craik FIM, Salthouse TA. The handbook of aging and cognition. Erlbaum. ISBN 978-0-8058-2966-2.].



    1. Nature Reviews Neuroscience 7, 30-40 (January 2006) | doi:10.1038/nrn1809


     



    1. Sapolsky RM, Krey LC, McEwen BS (1986) The neuroendocrinology of stress and aging: the glucocorticoid cascade hypothesis. Endocr Rev 7: 284–301.



    1. Bremner JD. Does Stress Damage the Brain? Understanding Trauma-related Disorders from a Mind-Body Perspective. New York: W.W. Norton; 2002.


     



    1. D. Kapogiannis, A. K. Barbey, M. Su, G. Zamboni, F. Krueger, and J. Grafman, “Cognitive and Neural Foundations of Religious Belief,” Proceedings of the National Academy of Sciences USA 106, no. 12 (2009): 4876–4881.


    8. Aging, stress and the hippocampus. Miller DB, O'Callaghan JP. Ageing Res Rev. 2005 May; 4(2):123-40

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