Monday, August 8, 2011

My Personal Experience with Chronic Stress: Facilitated Movement

Chronic stress changes the brain. It reprograms certain brain areas to become more active and other brain areas to become less active. Studies looking at soldiers being deployed for war, a major stressor for most soldiers, have documented that stressed individuals have lower cognitive performance on difficult and abstract thinking tasks but have facilitated reflexes and faster response times on tests of simple muscular responses. The same effects have been shown by animal studies. I personally have allowed stressors to influence me to a clinically significant extent and what follows is my recounting of the behavioral changes. After months of particularly acute, chronic stress I realized that I could do things physically that I could not do before. During these bouts of chronic stress my reflexes were potentiated so much that even other people were able to notice the changes.

I always wanted to be good at catching things that were falling, and I liked to think that I was good at it. After the acute stress though, I was very good at it. As long as I did not hesitate, I could even catch things that other people dropped. Many friends and acquaintances put their surprise into words, commenting on my quick, nimble reactions. The best way to describe it would be to say that it felt like my body was on autopilot and my dexterity linked sequences of movements together without me having to preside over the selection process. Playing a familiar sport seemed unconstrained and effortless. Trying to learn the strategies of a new sport was very difficult, however, as I had a hard time trying to systemize new rules and agendas.

In the past, I liked to think that I was decent at dancing, but truth be told, I would lose a beat pattern after just a few beats. Back then, I would try to concentrate on the timing of the music, but the simple act of paying attention to it caused me to lose the beat – I would expect it too early or too late – as if the act of trying to attend to it pulled me out of my sensory world. I would continue to attempt to execute dance moves without being able to synchronize them with the music. After the acute stress, it was impossible to lose cadence. My estimation of when the next beat would strike was much more precise. It felt very natural to coordinate my movements to a repeating rhythm, as if I had practiced doing it my entire life. In fact, I could smoothly alternate from a certain beat-per-second, into half-time or double-time, and then back again, something I had never even conceptualized before. Moreover, I seemed to be faster at familiar activities, my balance was better and my ability to gesticulate had taken on a smoother, more wholesome quality.

Growing up my personality was repressive and stoic and you could hear this in my speech, feel it in my demeanor and see it in my movements. In the past my movements were reserved, deliberate and discrete but stress made it so that they became spontaneous, relatively autonomous and it caused what would have been discrete motions to blend together seamlessly without cognitive guidance. I would notice that I would act or speak without deliberating beforehand. It was frightening at first because it felt like I lost the filter between thought and action. I would do something without first modeling the outcome. I would skip the normal checking, double-checking and planning that used to accompany the initiation of every move. In the past, I would veto every other imagined action before it had a chance to come out. Because of this, I didn’t move or act half as much especially in social situations. After the stress, I felt like a roving automaton that was in a state of constant impromptu activity. Before the stress I felt like I was a creature that, like a chess player, can only make one premeditated move at a time. After the stress I felt like I had become a flurry of well-coordinated but unplanned motions. This had the general effect of giving my behavior the unsupervised quality of punch drunkenness or slaphappiness and led to irreverent, impulsive, unprioritized and unproductive self-management. Interestingly, even though I feel that I have partially recovered from some of the cognitive deficits associated with chronic stress, I feel that I have retained much of the coordination and motoric adroitness.    

How did my motor control and procedural activities become effortless and how did my movements take on a life of their own? It is generally thought that there are three forms of movement: reflex, rhythm, and voluntary movement (Kandel et al., 2000). The prefrontal cortex, an area that is widely disturbed by chronic stress, mediates voluntary movement. Once its dominion over behavior is weakened, brain areas responsible for more automatic behaviors are given free reign. It is clear that the cortex, via the corticospinal tract, puts a great deal of inhibitory pressure on central pattern generators in the spinal cord which are responsible for reflexes and rhythmicity. For example, all healthy infants are born with certain reflexes, such as the Babinski reflex, which disappear within the first year of life. The reason that they disappear is because many axons in the corticospinal tract become myelinated during the first 12 months of life, and they allow the frontal cortex to tonically inhibit certain spinal reflexes which can be unmasked if this tract is damaged or if certain reflexes are highly practiced (Afifi & Bergman, 2005). Frontal brain damage has also been known to unmask motoric patterns that ordinarily would necessitate higher neural activation energy to surface (to overcome the neural inhibitory energy). I imagine that the release of inhibition, not just of the spinal cord but of the basal ganglia, extrapyramidal system, or other early motor centers might be responsible for my physical fluency. It is known that after motoric motions are sequenced consciously in the premotor and supplementary motor areas, implicit knowledge of this sequencing migrates to the basal ganglia and other lower motor centers.  

One really interesting example of a facilitated reflex involves recovering from being tripped. When your foot swings forward to take a step, it is very susceptible to being tripped. The foot swings forward briskly and automatically during a step, and if at any time during this movement the foot collides with an object or is caught on something, the person can trip very easily. The only way to keep yourself from stumbling or tripping is to stop the forward movement of the foot (switching quickly from using the quadriceps muscle to the hamstring), and to pull it up or over the obstacle that is impinging on your stride. This is very hard to do, because it requires split-second timing and if it necessitated conscious control, it would probably not occur in time to avoid most stumbles. I was rarely able to avoid tripping by engaging the hamstring quickly enough growing up. However, after the period of chronic stress it became second nature. I am very resistant to tripping over cracks, wires, tree roots or people’s legs now. Friends of mine have even commented on how briskly and effortlessly I have recovered from tripping. The funny thing is that I erroneously thought that the grace and agility required to do this was under my conscious control. In quick movements like this one, consciousness plays a small role if any. The movements controlling recovery of footfall, as in most aspects of walking, are mediated by the spinal cord (Kandel et al., 2000). I realized that I could not give my conscious self credit for the avoidance maneuver, because one day it became obvious to me that consciousness can be fractionated from it: when my foot swings forward sometimes it collides with a flimsy obstacle, one that gives way easily and would not trip me at all.

If the foot maneuver is a conscious one, I should be able to assess whether or not the collision was sufficient to trip me, and if not, I should be able to inhibit it. No such luck. I often find that my hamstring pulls my swinging foot back quickly when the obstacle is as light as a pillow, or as insubstantial as a loose cord. This is a perfect example of the tradeoff between fast inflexible movements and slower adjustable ones. Fast movements are quick enough to accomplish things that conscious ones are too slow to accomplish, but again, are susceptible to pragmatic errors and to being miscued. The effortless coordination of simple motor planning that I experienced was, in my opinion, striking and unmistakable. The effects were interesting and rather entertaining to experience despite the sobering reality that they were actualized by the decline of higher-order brain centers.

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