Stressed-Out Rats: Nature vs. Nurture

Let’s start this day’s column off with a somewhat famous story of two rats. 

Once upon a time, some scientists decided to study a couple of baby rats (what a surprise!)  One baby rat received a great deal of attention from its mother as she licked its fur many times a day.  The other baby rat was neglected most of the time:  its mother rarely licked its fur.  The two rats grew and began to behave in very different ways compared to each other.

The rat which had received all the licking (the love, the nurturing) was not easily startled, showed more curiosity by exploring places away from its mother, and did not suffer surges of stress hormones.  The rat which had been, for the most part neglected, was easily startled by noises, was reluctant to explore away from its mother, and suffered surges of stress hormones. 

Hundreds of lab experiments have duplicated these results and these findings have been extrapolated to humans via further brain-based research. 

Our brains develop according to a formula encoded in our genes – our inheritable factors.  “Each of our brain cells contains the same set of genes we are born with and uses those genes to build proteins and other molecules throughout its life.  The sequence of DNA in those genes is pretty much fixed.  For experiences to produce long-term changes in how we behave, they must somehow” (1) be able to do something akin to rewriting the genes in our brains.

Thousands of molecules attached to our DNA shut some genes down while allowing others to be active.  These molecule switches, it turns out, can be rearranged by our experiences.  This changes the way our brain cells work.

“Two families of molecules perform that kind of genetic regulation.  One family consists of methyl groups, molecular caps made of carbon and hydrogen.  A string of methyl groups attached to a gene can prevent a cell from reading its DNA sequence.  As a result, the cell can’t produce proteins or other molecules from that particular gene.  The other family is made up of coiling proteins, molecules that wrap DNA into spools.  By tightening the spools, these proteins can hide certain genes; by relaxing the spools, they can allow genes to become active.

Together, the methyl groups and coiling proteins – what scientists call the epigenome – are essential for the brain to become a brain in the first place.  An embryo starts out as a tiny clump of identical stem cells.  As the cells divide, they all inherit the same genes, but their epigenetic marks change.  As division continues, the cells pass down not only their genes, but their epigenetic marks on those genes.  Each cell’s particular combination of active and silent genes helps determine what kind of tissue it will give rise to – liver, heart, brain, and so on.  Epigenetic marks are remarkably durable, which is why you don’t wake up to find that your brain has started to turn into a pancreas.”(2) (Based on the current wave of cinematic sci-fi thrillers, though, perhaps this concept is not a bad idea for a movie: doctors race against time to ensure that everyone’s brains do not become livers.  How will they stop the epidemic!)

A lack of folate available to a developing fetus from its mother’s body is a nutritional factor that can change epigenetic marks prior to birth.  Another nutritional factor which can also effect a change to the brain in utero occurs when the mother consumes a lot of alcohol.  After birth experiential factors can change the epigenetic marks in the brain as evidenced by the rat experiments.

Neurons in the hippocampus – a part of the brain which helps organize memories – regulate the response to stress hormones by making special receptors.  “When the receptors grab a hormone, the neurons respond by pumping out proteins that trigger a cascade of reactions.  These reactions ripple through the brain and reach the adrenal glands, putting a brake on the production of stress hormones.”(3)

It turned out (in more rat experiments) that the stretch of DNA that works as the switch for one of the hippocampus’ genes, the glucocorticoid receptor gene, was different in the rats which received many licks compared to the rats which received very few.  In the latter group, the molecule switch for the glucocorticoid receptor gene was capped by methyl groups.  The neurons, therefore, could not produce as many stress receptors.  “The hippocampus neurons were, therefore, less sensitive to stress hormones and were less able to tamp down the animals’ stress response”(4).

And, the neglected rats – the ones which received few licks – were permanently stressed out as a result.  And, that's the end of the story of two rats.

D.

(1-4) were taken from an article by Carl Zimmer published online June 16, 2010.  The article was originally from the June 2010 issue of Discover magazine.

Notes on Attraction

I once dated a man because I liked the sound of his voice over the telephone.  Needless to say, our ‘connection’ soon fizzled after only a few dates, pleasant as they were, because I just wasn’t ‘into him’. When you meet someone that you’re attracted to, your whole body seems to switch on as certain neurotransmitters rev into high gear (like dopamine) while others (like serotonin) decrease in production.  In fact, several regions of the brain know anywhere from one-200^th of a second to a half-second (studies vary widely) before we consciously do, that we are attracted to someone.  

I also dated a very charming, very handsome, very attentive man for a while.  I ignored the red flags which went off in my brain (the adventurer that I was) as he pursued me and gradually broke down my defenses, and sure enough, this man ended up to be major bad news - harassing me, stalking me, and putting me through a harrowing criminal trial which stretched over the course of several months.  What can I say, my primary goal in dating has never been to land a husband and the electricity of our connection drew me in big time… When I tried to leave the relationship after realizing the guy was a psychopath (extremely low self-esteem, lacked empathy, and so on - read my December 2010 blog about psychopathy), things became difficult.  Let me just say, I’m glad I survived this decades-old debacle.  

Researchers believe that our strongest perceptions of mutual attraction develop in those first encounters where two people have a measurable physiological reaction to one another:  something akin to electricity rather than the oft-touted ‘chemistry’.  And, researcher, Pieternel Dijkstra, of the University of Groningen says that initial infatuation is driven largely by lust.(1)   Lust is not, however, necessarily a death sentence to a relationship in the long term and if that type of passion can be maintained throughout it is definitely a plus; provided, of course, that it’s not the only thing you are using to try to sustain the relationship.  A 2007 study of 137 couples found no difference in commitment, intimacy, or relationship quality after 25 years between those who fell in love (lust) at first sight and those who were friends before they fell in love .(2)  

In a somewhat related vein, if you are excited about someone, uncertainty about their interest in you can heighten your attraction to them.  You have a drive within you to reduce the uncertainty of the situation which causes you to obsess, which in turn deepens your feelings of attraction.  The previously mentioned increase in the production of dopamine also enhances focus on the object of your desire.   Many of your senses can become quite over-stimulated on the high of infatuation. 

Until very recently, I was normally a person who was not ‘easily available’.  I didn’t, however, ‘play hard to get’ which seems to be prescribed as something to do in all popular dating advice columns and books these days, but was naturally ambivalent and not easily available due to the simple fact that I had my own life in which I was thriving.  I loved the companionship, adventure and connection of having an intimate relationship, but was never on the marriage track, which I’m sure I signaled, albeit subconsciously.  In the twist of fate that life often holds for us, because marriage was not on my agenda, many of the men I dated, in fact, ended up wanting to marry me.

When in dating mode, if “you don’t seem too available, it makes you mysterious,” states Robert Greene, author of The Art of Seduction.(3)  But beware, you have to walk a fine line here because playing hard to get can backfire.  We like people who like us back, according to Peter Jonason, a researcher at New Mexico State University.(4)  Although playing hard to get works because it increases a person’s perceived value – the simple economics of lower availability increasing demand, like those high-end, extremely expensive purses that are made by hand at the rate of about six per year – it can be a dangerous game.  If you seem too unattainable, the other person may simply give up.  Use your ‘lack of availability’ with caution.

D.

(1) and (2), Psychology Today, February 2008, p. 34

(3) and (4), Psychology Today, February 2008, p. 77

Laughter Revisited

Thought I would write some more about laughter and the brain - to augment my previous column - for all you brainiacs out there. (Okay, I admit it, I've been obsessed with the brain for years...)

Researchers at the Stanford University School of Medicine found that the brains of introverts respond differently to humour than do the brains of extroverts. (Personally, though, I 'm not sure what my own brain does with humour because, after allowing myself to be tested a few times, I consistently sit on the fence between the two personality types as I'm sure some of you do, as well.)

Research led by neuroscientist, Alllan L. Reiss at Stanford U., indicates that in extroverted individuals, the prefrontal cortex and nearby orbitofrontal cortex "light up preferentially when a person reacts to funny cartoons."*  In introverts, the amygdala and the front portion of the temporal lobe become active.  This research suggests that these brain structures mediate the rewarding feelings people experience when they respond to humour and that pleasurable emotions originate from different brain sites depending on personality type.

Related to our ability to appreciate humour is how cheerful we tend to be on a day to day basis.  The more cheerful we tend to be, the more easily we are amused and the more readily we laugh.  One benefit of a cheerful personality is resilience:  a psychic robustness that emotionally buffers an individual against crises such as the dissolution of a marriage, or the loss of a job.  This type of person tends to survive setbacks well, preferring to see the silver lining in major disappointments rather than doom and gloom. 

And, a sense of humour strengthens the psyche, according to Willibald Ruch of the University of Zurich.**  In one test, students at the University were tested to determine whether they were generally cheerful, or generally somber.  They then had to spend time in three different environments doing rote jobs such as filling out questionnaires and drawing pictures.  The first environment was a sunny room with large windows, yellow walls, funny posters and colourful drapes.  The second was a dark room painted black and lit only by a small lamp, while the third room connoted seriousness with its display of scientific equipment, books, manuals and presentation posters.  It turned out that the ambience of the rooms had a more profound effect upon those students who rated low on general cheerfulness:  their moods became worse after spending time in the 'dark' room and also became worse after spending time in the 'serious' room.  The mood of the generally more cheerful students was not affected by environment.

One question I've had on occasion is:  why is it that some people appreciate the loud and boisterous laughter of another and are actually stimulated to laugh even more because of it, whereas others are irritated by this display of laughter?  Is there a laughter etiquette that is not being followed by those that freely and exuberantly laugh, chortle and guffaw?  Why do others find this offensive?  I, for one, love it and  tend to laugh more as a result of this type of free flowing laughter. 

I've also noticed that when I once tried laughter yoga, all I got was a headache from the forced nature of it all, but laughing naturally at, say, a comedic movie or schtick of some sort feels so darn good.  Well, the other day I came across research that indicates that forced laughter does not produce the same 'feel good' chemicals that are produced when one is laughing more naturally, and that any positive benefits one feels during laughter yoga may simply be due to the social nature of the group activity.

Another study I came across recently indicates that forcing our mouths into a smile before viewing funny cartoons produces more activity in the pleasure centres of the brain than does forcing our mouths into a disappointed expression or frown.  (Volunteers were to hold a pen either with their teeth - thereby creating an artificial smile - or with their lips, thereby producing a frown. Those forced to exercise their smile muscles reacted more exuberantly to the cartoons than did those whose mouths were contracted into a frown.)  And, from other studies I've read, it seems that just 'putting on a happy face' (smiling) when you are feeling down can trick your brain into thinking you feel happy and improvement in mood then follows.  I've actually tried this particular tactic myself a few times and it does seem to work. 

D.

* and **(Scientific American Mind, April/May/June 2009, pp. 28 - 29).  

 

So Laughter's a Drug, Too?

Next time you're at a party, you may want to skip the cocaine and prowl around for some laughter, instead. Just as love has been coined "a drug" based on the effects it has on our brain's neurotransmitters - especially dopamine - it turns out that laughter can invoke a high in your mind similar to that found after snorting some "blow".

Functional MRI scans are frequently used today in order to determine how a person's brain reacts to all sorts of stimuli.  In a research study carried out at Stanford University in California, a comical cartoon activated one of the same brain regions as a shot of cocaine did - the nucleus accumbens.

The nucleus accumbens lit up seconds after the subjects involved in the study found the comic hilarious while comics that were deemed to not be so funny by the subjects failed to affect the region.  This nucleus of the brain is awash with the feel good chemical, dopamine, which is one of the brain chemicals involved when we are high on love, or high on cocaine.

The other great thing about laughter is that it doesn't damage the brain.  I can't say the same thing about cocaine, and perhaps I will write a column one of these days about all the nasty things street drugs do to our brains.

D.