Fun With Stress 2.8
Chronic Stress and our Brain, Nervous System, and Sleep
Reading time: 9 minutes
Close-up of a neuron (brain cell). Image: IMGMIDI
Effects of Chronic Stress on Our Memory
Let’s return to the beginning of our story, where in Chapter 1 Part 1 Farid’s buttons were pushed because he smelled an odour reminiscent of war casualties that he had encountered in his home country Syria. However, it wasn’t until after he discovered the connection between the odour of the waste bin next to the entrance to his apartment building and that of the dead bodies back in Syria, that he understood why his buttons were pushed. So even though the context in which the odour was perceived was totally different, the danger in Syria had been so great that as soon as anything reminiscent of that environment was going to be perceived by Farid’s senses, his brain would forever judge that as highly dangerous. Subsequently, it would initiate a full-on stress response to make him as alert as possible – and ready to run.
This phenomenon, where the stimulus of seeing and smelling war casualties created big anxiety buttons in Farid’s memory, is called implicit fear conditioning. It is a form of implicit memory and is closely connected to what we tend to call body memory.[1]
Of the many different types of memory, the most relevant to the areas of stress and learning are our implicit and explicit memory.
Explicit memory refers to our ability to know and remember facts: I was born in Holland, there are 24 hours in a day, fish live in water, and so on. Our conscious behaviour is based on active knowledge of these facts.
Implicit memory, by contrast, involves all our behaviours that have been internalized by our body (hence body memory). It does not require conscious thought, and is either genetically programmed, like most of our bodily functions; or acquired, like Farid’s reaction to any memorized stimuli reminiscent of a warzone.
An important part of the brain that is involved in explicit learning and memory, is the hippocampus.[2] This little structure is part of our limbic system (or: emotional brain) and can be regarded as our personal library, for every fact that we learn gets recorded in the ‘books’ of the hippocampus.
Implicit learning happens mostly in the part of the brain called the cerebellum. Since one of its main tasks is regulating our fine motor skills, it figures that this structure is heavily involved in implicit memory and conditioning, i.e. body memory.
Cross section of the brain; here we see the right hemisphere viewed from the inside with the cerebellum at the back of the brain, and the hippocampus in the middle as part of our limbic system.
The formation of memory is believed to be about strengthening pre-existing connections between brain cells (neurons) so that those connections last long term. This process is called long term potentiation and happens for a large part in the hippocampus.
Now, short term, or acute stress, does wonderful things for learning and memory. Thanks to an increasing heartrate and widening of the brain arteries, more oxygen and glucose (i.e. fuel) reach the brain which makes it work more effective. And with the onset of stress, the connections between the brain cells in the hippocampus become more sensitive, thus enhancing long term potentiation.[3]
Long term, or chronic stress, however, can cause memory disruption. After a few hours of stress, instead of delivering more oxygen and glucose to the brain, we deliver less. Brain cells in the hippocampus begin to atrophy (i.e. waste away) which disrupts the formation, storing, and accessibility of memories. In other words, chronic stress tends to burn books in our library, and makes the remaining ones harder to access.
Effects of Chronic Stress on Our Humanity
The frontal part of our brain is where processes regarding planning, judgement, personality formation, executive decisions, behaviour, and impulse control happen. It is the most recent developed part of our human brain and I like to call it the seat of humanity, since it is thanks to this frontal cortex that we can learn, develop, and cultivate, typical human traits like reason, love, humour, generosity, and compassion.[4]
It is a well documented phenomenon that acts of kindness make us feel much more jolly than mere selfishness. Image found on zenfulspirit.com
Long term stress seems to atrophy brain cells in the frontal cortex, and thin out its layers. Like the hippocampus, the frontal cortex tends to shrink under chronic stress, and with it the effectiveness of its functions. For example, where a normal functioning frontal cortex keeps us calm if someone starts yelling at us, an atrophied frontal cortex lacks that ability; so instead of remaining calm in reaction to the yelling, we slap the other person in the face because we lack the ability to control our impulses.
Other interesting research shows that where chronic stress atrophies brain cells in the frontal cortex, the subsiding of stress seems to reverse that process, but with different sorts of connections. Despite current unclarity of what that means, it seems to point towards the possibility of a change in perspective.
A possible implication thereof is that for a change in perspective to occur, we might actually need a certain ‘preparatory’ period of chronic stress as a kind of ‘ploughing the field’, on which ‘the seeds of new perspectives’ can be sown. Perhaps that is why, when we hit a brick wall and wish to change our (mostly) automated thought and behavioural patterns, we first have to ‘fight our demons and conquer our dragons’, which are huge stressors if there are any. Then again, the rewards are so worth the challenge.
An image of a human brain viewed from the left side.
Effects of Chronic Stress on Our Learning, Remembering & Energy Restoration
In Part 2 Chapter 3 we’ve already established that energy restoration happens mainly when we sleep. Furthermore, sleep seems to be equally important for our ability to learn and remember, i.e. the creation of, and accessibility to, the books in our mental library. These functions happen during the second and third phases of our sleep cycle.
When we go to bed, we first enter the Light Sleep phase. That is followed by the Deep Sleep phase, which is characterized by very little brain activity; hence ideal circumstances for energy restoration, since the body is in its dormant state. The third phase is called the Vivid Dreaming phase (aka REM-sleep). In this phase there is much activity in the brain which we experience as dreams, and is believed to have much to do with our capacity to learn and remember.
A full sleep cycle consists of these three phases (see Figure 1A).
In a healthy situation, a good night’s sleep consists of multiple sleep cycles. Both energy restoration and learning & remembering processes happen at various moments during our sleep (see Figure 1B), and we wake up energized and a little more cognitively developed in the morning. But what happens when we throw chronic stress into the mix?
Figure 1A (left): Image of one complete sleep cycle, consisting of the three phases of light sleep, deep sleep, and vivid dreaming (REM sleep). Figure 1B (right): A schematic representation of one night’s sleep, which consists of multiple sleep cycles. Images: sleepfoundation
Long term stress tends to create incessant chatter in our minds that usually starts when we wish to go to sleep. If that develops into sleep deprivation, or even insomnia, it figures that we go through less sleep cycles every night, with detrimental effects for our learning, remembering, and energy restoration.
When we don’t get the hours of sleep we need (which is different for everyone), we don’t learn and remember as well. Add to that the capacity of chronic stress to burn the books in our library (the atrophied hippocampus) and we see a deterioration of important cognitive processes.
Furthermore, energy restoration also begins to falter if we don’t get enough sleep, because our digestive system has less and less time to produce new fuel.
However, even when we do get many hours of sleep, energy restoration can still deteriorate. How is that possible? Well, chronic stress also tends to have a deteriorating effect on the quality of our sleep. Effectively that means that even though we sleep many hours, there is no more predominance of Deep Sleep in the sleep cycles. When that part of the cycle goes missing, so does its capacity to re-fuel our internal fuel tank, which we are going to directly experience with intensifying fatigue and possible other emerging low-on-fuel-signs and symptoms.[5]
It is a known fact that sleep is important for our recovery and healing processes. Image: Claudio_Scott
Sense of Security: A Story About Our Burglar Alarm
In anatomy we’ve divided our nervous system into a central and a peripheral part.
The central nervous system (CNS) consists of the brain, brain stem and spinal cord (inside our spine).
The peripheral nervous system (PNS) consists of all the nerves as soon as they exit our spine, and connects the CNS to our sense organs and to sensors in all our tissues, glands, organs and limbs, a bit like electricity cables.
Now, the human nervous system can be compared to a burglar alarm. In normal circumstances, the alarm goes off when a burglar breaks a window or forces a lock. But sometimes it is set too sharp, causing it to go off when someone merely walks by. Here’s a story to illustrate how that can develop in a human being.
Janice is excited to start her new job as computer expert. Since she is hired as an expert, she suggests some IT improvements to her manager. He reacts enthusiastically and ensures he’ll get right on it. Janice leaves his office feeling heard and appreciated.
In the next weeks she notices that chatting colleagues by the coffee machine abruptly leave as she approaches. Also, when she needs information from them, they begin to ignore her. Not understanding what’s going on, she plans a meeting with her manager to inquire.
During that meeting he ignores her question regarding the colleagues. Instead, with a raised voice and an authoritarian pose, he tells her that the IT improvements she suggested are impracticable and way too expensive. The current system runs fine and she should do well to not cause any more trouble in the future. With that message she’s sent away.
Janice started this job open-minded. That means she wasn’t bracing herself for any hostile impact because she wasn’t expecting one. Therefore she entered this company feeling secure and relaxed.
The first time when chatting colleagues left the coffee machine as she approached, she probably didn’t think too much of it. As this kept reoccurring though, little doubts began to creep in her mind. What could be going on? In order to find out, she arranged the meeting with her manager.
Up to that point, she’s still convinced there must be some misunderstanding causing her colleagues’ behavior. However, her hope is dashed with the attitude and message from her manager. Thus, this meeting serves as a precedent: can she or can she not trust him, or her colleagues?
When people in leadership positions send mixed messages to their subordinates, a culture of fear is often the outcome. Image: PublicDomainPictures
From now on, every new incident will increase her feeling of insecurity. The more incidents happen, the more she will go to work bracing herself for hostile impacts. This is meant literally, because where she first walked into the office nice and relaxed with her head held high, chest forward, and shoulders low; after seven months she walked in like the Hunchback of Notre Dame: gazing at the floor, shoulders up high with her head buried in-between, a cramped gait, and frantically trying not to be noticed. How does that translate in her nervous system?
Well, she began her job with a normal functioning burglar alarm because she felt safe. After the second meeting with her manager, however, a new memory has been created: “He lied to me!” And what happens once, can happen again. So from that moment on, her nervous system has become more sensitive to mistreatment in her work environment. In other words: her burglar alarm has been set sharper as she now begins to suspect, conscious or unconsciously, mistreatment from her manager and colleagues. Every subsequent time she feels mistreated, whether or not it’s accurate, her burglar alarm will be set a little sharper,[6] which can even go so far as feeling mistreated by merely thinking about her workplace while being in the safety of her own home.
She then is liable to fall into a vicious circle: her feeling mistreated triggers the stress response, which sets her burglar alarm sharper, through which she will feel mistreated even quicker than before, triggering the stress response, setting her burglar alarm even more sharp, etcetera. With that, her sense of security is being flushed down the toilet.
Brain and Balance
It is no secret that health usually consists of an alternation between challenges (stress) and rest, and our brain thrives on a healthy balance between those two. However, when we enter a life situation that turns out to be toxic (which we can easily assess via this method), yet we keep returning to it day after day, we are then entering the realm of chronic stress. Our brain and nervous system, like all other body systems, can then begin to malfunction, which eventually can translate into more and more severe illnesses.
Therefore, as scary as it might feel to abandon a certain life situation, be it a marriage or a job, if you have no possibilities to change the situation; the wise thing to do would be to listen to your flight instinct. For as much as that might be regarded as weak, from the standpoint of your balance and health, it’s actually the strongest decision you can possibly make.
The next chapter will discuss the effects of chronic stress on our cardiovascular system. Until then,
Jolly greetings,
Erik Stout
[1] A wonderful elaboration on the phenomenon of implicit fear conditioning can be found in the book The Body Keeps The Score by Bessel van der Kolk.
[2] Dr. Robert M. Sapolsky - Why Zebras Don’t Have Ulcers (chapter 10)
[3] Ibid.
[4] Ibid.
[5] Dr. Robert M. Sapolsky - Why Zebras Don’t Have Ulcers (chapter 11)
[6] This process is called sensitization of the nervous system. Most likely it’s an important explanation for chronic pain syndromes like fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, or chronic whiplash associated disorders. Furthermore, it can also be involved in other unexplained chronic pain problems.
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