So why is this stress thing so important?


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So why is this stress thing so important?

Let’s think about the different domains where stress occurs and why it makes a difference if there is less stress.

We are all the product of evolution.  To move from one generation to the next we had to survive long enough to have children, getting our genetic representation into the next generation.  Why this was so important is a different question, but for now let’s assume that the evolutionary theorists, who came up with this, starting with Darwin, are right.  How do we create an environment in which we can reach that potential?

But there is a problem with measuring evolution due to the enormous disconnect between how long it takes to have an effect, and the limitation of our own personal life.  Scientists have got around this to a degree, by agreeing to the following:  let’s study animals that have shorter lives so we can observe what happens over several generations.  For example, bacteria can reproduce in optimal conditions every twenty minutes. In fact, if you are a scientist studying bacteria you can see the effects of evolution, via the transmission of genetic material from one generation to the next sometimes within the matter of weeks.

It is common knowledge that three things dominate what needs to go into this creation:  Food, shelter, and the ability to reproduce or mate.  Of course, they are all intimately connected but for now let’s start with two of these three, mating and shelter, in many ways some of things you want at home!

Now it is a bit of a stretch to say that things that happen in the life of a bacterium can be used to draw any conclusions at all about us humans.  But what if you start studying animals that are a bit more complex like slugs or fish?  Some fish appear to be able to learn, they have relatively short lives, (of course significantly shorter in some of the studies!), but have very similar neuroendocrine systems, with many of the same chemicals used in the complex and elegant dance between our brains and bodies.  Fish use cortisol in a very similar “fishon” to us.

Popular among researchers today is a particular species of fish, the African cichlid fish (Astatotilapia burtoni).

Believing that animals who learn have the best chance of survival, scientists in Stanford California designed a task relevant to the natural behavior of male African cichlid fish (Astatotilapia burtoni), to determine if they could be trained on a spatial task to gain access to females and shelter.

We measured both how successfully animals completed this task over time and whether and how immediate early gene and hormone expression profiles were related to success. While training fish in a maze, we measured time to task completion, circulating levels of three key hormones (cortisol, 11-ketotestosterone, and testosterone) and mRNA abundance of seven target genes including three immediate early genes (that served proxies for brain activity) in nine brain regions. Data from our subjects fell naturally into three phenotypes: fish that could be trained (learners), fish that could not be trained (non-learners) and fish that never attempted the task (non-attempters). Learners and non-learners had lower levels of circulating cortisol compared to fish that never attempted the task. Learners had the highest immediate early gene mRNA levels in the homologue of the hippocampus (dorsolateral telencephalon; Dl), lower cortisol (stress) levels and were more motivated to accomplish the task as measured by behavioral observations. Fish that never attempted the task showed the lowest activity within the Dl, high stress levels and little to no apparent motivation. Data from non-learners fell between these two extremes in behavior, stress, and motivation.

I know it’s fish but it is still interesting.  Fish that were more able to learn had lower levels of cortisol. And fish that never even made the attempt to learn had the highest levels of cortisol.  Ok, so here comes the stretch:  does this mean that fish who were so stressed out could not even get it together enough to try?  In human equivalents does this translate to feeling defeated before you even start, so why bother starting at all?  No matter which comes first, high stress levels leading to cortisol, or for some reason excreting too much cortisol leading to feeling stress, it impedes perhaps not the capacity to learn, but even the choice to do so.  And this also makes sense.  The body interprets cortisol as a stress hormone, which is meant to mean there is some imminent danger so be on the alert. With that much distraction how are you meant to learn anything?  Your body is on alert, you could be something’s lunch at any second.  That becomes the priority, to simply survive.  I’ll deal with shelter and mating later!

So one reason why controlling stress is so important is that it interferes with learning.  Home is meant to be the safest place you have to go.  A shelter, in the truest sense of the word: protection, safe haven, refuge, sanctuary.  Just the words alone conjure feelings, images, another manifestation of the intimate connection between our thoughts and feelings.  Home should not be a source of stress at all, but it can be.  And what a waste!

Neurobiol Learn Mem. 2010 Dec 9.
Effects of stress and motivation on performing a spatial task.
Wood LS, Desjardins JK, Fernald RD.
Department of Biology, Stanford University, Stanford, CA, USA.