Sunday, October 03, 2010

Your Brain’s Capacity Limits, Dopamine, and Food

I am fascinated by the marvelous transmission system that our  nervous system, including our brain and neurotransmitters, is. Typically, the internal processes seamlessly forms that which we are throughout our daily lives are.  The orbitofrontal cortex, located just above your eyes (light blue in the graphic below), is an important brain region for the processing of rewards and punishments,  a qualification for the complex yet flexible emotional and social behavior which has contributed to the evolutionary success of humans.

But first I have a complaint. While reading science and psychology articles this week about dopamine and how our bodies have been made to signal pleasure to our brain I detected a removed tone about the "other". It is often "the obese" or "the addictive" people that are referred to. To me, it sounds dangerously elitist. Perhaps it is the style to which science is written for journals and publications; but I take issue with it because it also pointlessly segregates. 

Biologically, it is this, our attraction to sex and high calorie foods that has kept our species going through the ages. Some of us are more susceptible than others but, especially when it comes to food majority of us are prone to over-indulging. (Typically, people with damage to the orbitofrontal cortex have a harder time disengaging from impulsive behavior.)

And these statistics suggest we are all susceptible:

Cancer deaths are projected to double in the next two decades. A report issued by the International Agency for Research on Cancer (IARC) says that by 2030, there will be almost 21.4 million new cases diagnosed annually and that there will be over 13.2 million deaths from cancer. (Science Centric. Web. 2010)

In the 2006 American Cancer Society (ACS) Guidelines on Nutrition and Physical Activity one third of more than 500,000 cancer deaths each year can be attributed to diet and physical activity habits. (Kushi, et al 254) …hum…seems like we need a wakeup call…that "other" person is the majority of us.

What about the alarming rise in instances of cardiovascular disease, diabetes and other autoimmune diseases. (HELLO!?!?!)

The Invisible Person

not pregnant
Well, I am done talking about the invisible person.  I am going to throw myself into the group of "other". I love my chocolate chip cookies and controlling food impulses can be challenging for me. I have been known to eat a whole plateful of cookies on days I feel overwhelmed and lack impulse control. I gained 60-ish pounds with each of my 3 pregnancies. I was also raised with a mother who told me that it was highly likely I would someday be overweight too. And  she was right. The genetics for being overweight lie within my DNA.  I got to experience it for the 9 months my weight went up and the 9 (or maybe more) months I worked to get it off - three times. One side note about each of my pregnancies, I did eat more meat and processed food during those times. I wonder if my brain was low on dopamine during this huge hormonal shift?

Programed to be Open to Change

There is hope.  We do know that just because the genetic code for something such as obesity, cancer, diabetes, etc. lie within our DNA molecules does not mean that our bodies will express (or turn on) that gene. It is about choices, sometimes our choices and sometimes our reaction to other people's choices that affect our lives. 

One somewhat new science finding  - one that gives me hope -  is neuroplasticity (aka cortical re-mapping) which is the thought that the brain is malleable; that the brain has the ability to change as a result of experience. It takes place in the lateral orbitofrontal cortex. It is here we evaluate negative things, which may lead us to a change in behavior.

The realization that preferences are something that can be hard to free ourselves perhaps is the first step to making better choices in the long run. Likewise, understanding that our brains have a capacity limit is also important.

The Limits of Self Control

Science journalist and author of How We Decide, Jonah Lehrer, during a 2009 interview on NPR told Terri Gross:

"…. we should definitely be conscious of the fact that we have limited machines, that our brain isn't omnipotent and that it can only take in so much information at any one time.
One of the studies I talk about in the book concerns a study done by a Stanford psychologists who - they had two groups of people. One group they had memorize a two-digit number; the other group they had memorize a seven-digit number. Then they marched these two groups down the hall and gave them a choice between two snacks.
One snack was a rich, gooey slice of chocolate cake. The other snack was a responsible fruit salad. The people who memorized a two-digit number were twice as likely to choose the fruit salad as the people who memorized the seven-digit number, who were twice as likely to choose the chocolate cake. And the reason is that those extra five digits - doesn't seem like very much information at all, just five extra numbers - so overwhelmed the prefrontal cortex that there wasn't enough processing power leftover to exert self-control.
So that gives us a sense of just how limited in capacity our brain actually is and I think points to the fact that we should absolutely be aware of these limitations.
So that doesn't necessarily mean, you know, you have to block out information and never use Google. I think it just means that we should be aware of this and that if you've had a hard day at work or if you're trying to - you know, if you just spent all morning on a crossword puzzle, then be aware that your willpower's going to be a little bit weaker, that especially these rational faculties of the brain are very limited in capacity."


For me, it helps to understand the biology of what is causing me to go back for yet another chocolate chip cookie even when I am full.

In May of 2009 host, Terri Gross, of NPR's radio show Fresh Air interviewed Dr. David Kessler author of The End of Overeating, pediatrician, former FDA commissioner, and former Dean of the medical schools at Yale and the University of California. 

During the interview Dr. Kessler explained. "We used to think of - food was something we ate to fill us up, to satiate us. But in fact, much of the food that we're eating, this trifecta of sugar, fat and salt, stimulate us. And what we now see is the science that shows that much of the food that we're eating, this very highly palatable food, is excessively activating the neurocircuitry of many of our brains. We used to just think that, you know, food tasted good, but we now know what's behind that, and for many of us the reason we keep on eating is because of this sustained stimulation."


So what is happening when we bit into something sweet, salty and with a good chuck of fat within it?

From the PBS show Moyers on Addiction:

"Different parts of the brain govern different functions. Here, you can see the areas of the brain that control such things as movement, thought, judgment, memory, and "reward," or the feeling of pleasure that comes after one does something enjoyable (tasting a piece of cake, receiving a compliment from the boss)." (See this link for an animation)

On the same website dopamine is explained as:

 "One important neurotransmitter involved in the experience of pleasure is called dopamine. Here, dopamine, shown in yellow, is produced in the neuron shown at the top and packaged in containers called vesicles. As an electrical impulse arrives at the neuron's terminal, the vesicle moves to the neural membrane and releases its load of dopamine into the synaptic cleft. The dopamine crosses the gap and binds to receiver sites, or receptors, on the membrane of the next neuron. When dopamine occupies a receptor, various actions take place in that neuron so that a new electrical impulse is generated in this neuron, and the "message" continues on. After the dopamine has bound to the receptor, eventually it comes off again and is removed from the synaptic cleft and back into the first neuron by reuptake pumps. (For normal nerve transmission, it is important that the dopamine not stay in the cleft.)" See this link for an animation.

Many of our key bodily functions have evolved (or were designed; depending on the belief system at hand) to help us to survive and continue our species. Dopamine is released while consuming rich, salty, fatty food. Being attracted to high calories foods has helped our numbers explode into an estimated 6,872,597,995 humans walking this earth (estimate as of October 2, 2010). But this is what is starting to kill us now because "food" companies have figured out that if they process fruits, grains, vegetables, even meat (think chicken nuggets) mixed with salt and fat enough we will become addicted to their products. And those products affect who we are, who we become. They affect our moods, our weight, and our lives.

Author, Gary Wenk, points out in his 2010 book, Your Brain on Food: How Chemicals Control Your Thoughts and Feelings, that "the drugs you take, the foods you eat – can affect how your neurons behave and, subsequently, how you think and feel."

An interesting fact also is the power of human touch. Touch can light up the same area of the brain. But I think I will leave this topic for another day or you can learn more here.

One last thought. Almost every time I open "food" that is in a package I consciously know what I am doing to myself. And for me, that is half the battle….on most days.

As I finish writing I find I am reaching for the chocolate pie in the fridge (I'm only having one though!). I think my brain has reached capacity and impulse control has become questionable; and I still have lots of studying for midterms to do!

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