Tuesday, 24 April 2012

Even the coolest ones can loose it

Have you ever had one of those moments when your brain just blanks out? Was it a stressful situation? Was it maybe during an exam? Or when you were supposed to remember someone’s birthday and all you could think of was ... nothing ... Just embarrassment... 

Well, don’t worry, science has proven that stress is the reason why you blank out.

This month’s Scientific American has published a review article that explains how stressful situations can trigger signals in our brain, leading to a loss of control over its ‘executive functions’.

According to the authors “when things are going well, the prefrontal cortex acts as control centre that keeps our baser emotions and impulses in check. (...) Acute, uncontrollable stress sets off a series of chemical events that weaken the influence of the prefrontal cortex while strengthening the dominance of the older parts of the brain”.

Essentially, stress is giving control over thought and emotion to the so-called ancient structures of the brain - hypothalamus and other earlier evolved structures - the areas responsible for more basic functions as eating or having fear.

“The growing understanding that acute stress can severely compromise the function of higher “executive” areas in the human brain has drawn the interest of investigators. They are now not just trying to understand what happens in your head when you freeze but also developing behavioural and pharmacological interventions to help you keep your composure”, said the authors.

And now some interesting science bit and bobs. Why does this happen?

1.     The prefrontal cortex is so sensitive to stress because it makes up a full third of the human cortex; it matures more slowly than other brain areas (only reaches full maturity after the teen years have passed); it houses the neural circuits for abstract thoughts and allow us to concentrate and stay focused on task, while storing information and making memories.

2.     Under normal circumstances the prefrontal cortex controls our emotions, desires and habits. However, under stress, the brain is flooded with chemicals such as adrenaline or dopamine, which are released by neurons, and the prefrontal cortex is shut down, passing the control over to deeper, ancient areas of the brain, such as the hypothalamus or the amygdala.

3.     Recent studies have shown that some people may be more vulnerable than others to stress because of their genetic makeup or because of a previous exposure to stress.  Under normal situations, after hormones like adrenaline or dopamine switch off circuits in the prefrontal area, enzymes chew up these neurotransmitters so that the shutdown does not persist. In this way, we can return to our baseline when stress abates. Certain forms of a gene can weaken these enzymes, making people more vulnerable to stress and, in some cases, mental illness.

4.     John Morrison of the Mount Sinai School of Medicine and his colleagues have shown that chronic stress appears to expand the intricate web of connections in our lower emotional centers, whereas the areas in our prefrontal cortex actually shrink. They have shown that prefrontal dendrites can regrow if the stress disappears, but this ability to rebound may vanish if the stress is especially severe.  This chain of molecular events makes us more vulnerable to subsequent stress and most likely contributes to depression, addiction and anxiety disorders, including post-traumatic stress.

5.     Gender appears to be a factor in determining how we react to stress. In women, the hormone estrogen may amplify sensitivity. It has actually been proven that life stress poses a greater risk for depression in women than men and is more likely to reduce abstinence from certain addictive behaviors, such as smoking, for women as compared with men.

Why the brain has built-in mechanisms to weaken its highest cognitive functions, making it “dumber” at key life-decision moments, is still a very intriguing question. Researchers are investing greatly to bring insight in to this matter. In the meantime, the next time you are taking a test or speaking in public and your mind goes blank, say to yourself:  “This is just my brain loosing its grip, hold on, just calm down!”. It maybe not give you the correct answer, but it might bring you a comforting smile. 

Let's give this a thought, shall we?

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