Wonder of the Moment

Memories Are Made of What? Part 2

2011-07-28T18:34:17Z

In my last post I began describing how memory or learning might occur in the brain of a mammal, as described by Dennis Bray in his wonderful book, Wetware.

It seems that learning and memory are somehow encoded in synapses between neurons. The more often a synapse is used, the stronger and more developed it becomes. But this strengthening depends on neuron A sending a signal to neuron B at the same moment that neuron B is also sending a signal.

Here’s how the chemistry may work. When A sends a signal to B, B may not be aware of the signal because its receptors are plugged up. But if B is also signaling, B’s electrical change may unplug its receptors. Then it can receive the signal from A.

If the signal from A to B is repeated, a protein called Cam II kinase starts changing itself in permanent ways, so that the synapse between A and B becomes permanently stronger and more sensitive. The changed protein is “…like a toggle switch that, once thrown, remains on forever.” This switch then turns neuron B on at the slightest twitch from neuron A.

But how is it possible for this situation to last a lifetime? For this is how long many memories and much learning do last. More on this next time.

Memories Are Made of What? Part 1

2011-07-26T17:41:59Z

How do we learn? How do we remember? How can a mass of neurons in the brain produce bodies of knowledge from our experiences?

Recently I came across an excellent description of what we know about this in Dennis Bray’s wonderful book, Wetware, which I have referred to a number of times in this blog.

Neurons communicate with other neurons via synapse. A synapse is a tiny gap (cleft) between the sending part of one neuron (the axon) and a receiving part of another neuron (a dendrite or cell body). When an electrical signal travels to the end of an axon, it causes the axon to spill out molecules of neurotransmitter. The neurotransmitter molecules spill into the tiny synaptic cleft. Then they diffuse across the synaptic cleft and lodge in receptors on the receiving neuron.

So far, all we have is a signal from neuron A to neuron B. But it turns out that if neuron B is simultaneously sending a signal (say to neuron C or D), the synapse between A and B will be strengthened.

Bray’s example here is the Pavlov experiment with dogs. The sound of the bell makes neuron A fire a signal so that the dog hears the bell. The smell of food makes neuron B fire a signal so that the dog salivates. The strengthened synapse results in the dog salivating when it merely hears the bell.

How does this synapse strengthening happen? More on this in my next post.

Dopamine and Eating Disorders: Obesity

2011-07-14T17:39:05Z

Judging by popular beliefs about obesity, we might think weight and eating, like drug use, are also controlled by dopamine, but this is only partly true.

We have a built-in “weight thermostat.” Our bodies store energy in the form of fat. When our fat cells are full, they secrete the hormone “leptin” and we feel less hungry.

Also, when we lack nutrients, our brain secretes “orexin” to make us feel hungry. When we eat and have plenty of circulating nutrients, the brain secretes “CRH” to make us feel full.

However, eating results in higher levels of dopamine as well. So the news isn’t completely clear when it comes to dopamine and obesity.

Genetic components of weight also include sensitivity to all these signals. We may have more or fewer receptors for the signals, or more or less sensitive receptors.

So weight regulation is more complex than drug addiction. We don’t “need” drugs and alcohol, so leaving them out of our lives is a more straightforward cure. But we do need to eat, so it’s not surprising to discover that regulation of eating is complicated.

Dopamine and Eating Disorders: Anorexia

2011-07-05T16:58:59Z

Recently, I’ve been posting about dopamine and addictions. Since dopamine is a “feel good” neurotransmitter, and has connections to food addiction, I’ve been wondering what it has to do with anorexia.

Research on eating disorders is really in its infancy. But there seem to be connections to dopamine. Apparently, people who suffer from anorexia have an unusual reaction to this substance. When dopamine flows in their brains, instead of feeling pleasure, they feel anxiety and fear.

Not only do anorexics feel anxiety when they eat, they feel anxiety and worry about other things as well. Some of their fears are similar to what happens in the brains of people suffering from obsessive/compulsive disorder. The lives of anorexics are unpleasant and scary, to say the least.

There are so many myths about anorexia, it’s a relief to realize that anorexia is very much a product of the anorexic’s brain chemistry. But there is clearly a great deal more to be learned about eating disorders in general and anorexia in particular.

Stay tuned

Dopamine, Learning, and Addiction

2011-06-28T16:48:06Z

Yet more about brain chemistry and addiction: A few years ago, the Harvard Mental Health Letter pointed out that the dopamine link is important with respect to learning.

That is, when we do something pleasurable, the neurotransmitter dopamine is released in our brain and tells us to repeat the experience.

But dopamine is also involved in parts of the brain having to do with forming memories and learning. So not only do we get the message to repeat the pleasurable experience, we also truly “learn” to repeat it. Hence, we may become addicted.

Of course, from the standpoint of evolution, we need to feel pleasure in learning, because learning was and is essential to our survival. And we still enjoy learning new things, whether they are in in academics or entertainment or gossip. I know I get a kick out of learning about the connection between dopamine and addiction—it explains a lot.

Dopamine apparently is part of becoming addicted to alcohol, drugs, gambling, food, thrill seeking, etc.

But ironically, dopamine also rewards use of recovery techniques, especially in twelve-step programs. Recovering addicts experience the pleasures of spiritual practice and fellowship. Clearly, we have a lot to learn about dopamine, the human brain, neurotransmitters, and who knows what else?

The Human Brain and Addiction, 2

2011-06-23T16:39:00Z

In my last post, I spoke of Dr. Nora D. Volkow, Director of the National Institute on Drug Abuse, and her message about addiction. Dr. Volkow sees addiction as a psychological, or brain disease because it is a product of brain chemicals.

In her appearance at a high school in Harlem in New York City, Volkow answered student questions about drugs and drug use and abuse. Volkow’s answers were honest, based in brain science. She told the students about brain development in adolescence and young adulthood. She explained that the frontal cortex, the decision center of the brain, matures more slowly than, say, the amygdala, a center for emotion. In adolescents, this temporary difference in development of two parts of the brain can lead to risk taking, Risk taking is essential to stepping out on your own and to learning new things, but it can also lead to drug addiction or unsafe sex.

Students asked Volkow about brain changes with marijuana use, and she told them about brain receptors involved in both marijuana use and learning. Cannabinoid receptors get tied up by marijuana, and so cannot be used for learning!

The Human Brain and Addiction, 1

2011-06-21T17:45:56Z

A week ago, The New York Times published a profile of Dr. Nora D. Volkow, Director of the National Institute on Drug Abuse. She is a very appealing person to begin with, which helps a lot with her various campaigns: She wants to interest people in the subject of addiction. She wants to educate people about addiction. And she wants to prevent and cure drug abuse.

Dr. Volkow is physically attractive, with a shock of curly hair and a slim build. She is a fascinating speaker, direct and straightforward, with a charming Mexican accent. Her audience appeal includes teenagers, parents, journalists, and scientists.

When Dr. Volkow speaks of brain neurotransmitters, especially dopamine, she is very convincing. She explains addiction as a disease, and speaks of how to prevent or cure this disease. She clearly cares deeply about human beings and wants to keep them from addiction or help them recover from addiction.

Systems, a Powerful Part of Evolution

2011-06-10T16:18:15Z

Speaking of ant rafts (my last post), I recently read The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies, by Bert Holldobler and E. O. Wilson.

“Superorganism” is a good name for an ant colony or a bee colony or a termite colony. The individual insects in such colonies are not like you and me. They don’t strive for individuality. Instead, they are part of a highly efficient, highly successful system.

To quote Holldobler and Wilson, “The principal target of natural selection in the social evolution of insects is the colony, while the unit of selection is the gene.” Ants truly live the principle of “All for one, and one for all.” Though the worker ants do not themselves reproduce, the expression of genes in each individual responds to colony-wide signals from the queen and from one another; so the individual genes that lead to success are favored.

Then there is a quite different book, Wetware: A Computer in Every Living Cell, by Dennis Bray. Much simplified, Bray’s point is that in a unit as small as a cell, the activities of thousands and millions of molecules are like electric circuits, providing information and carrying messages that lead to actions.

Bray describes the complex, overlapping systems of molecular signals within a cell. Then he considers the possibility that it is not just genes, but systems that control the expression or non-expression or slight expression of genes that actually evolve. Some combinations of expression are more successful than others for a particular species. So not only the genes in question, but the control systems that lead to successful expression patterns, are conserved.

I find this whole idea of evolving systems just breathtaking. How about you?

Wonders of Evolution: Ant Rafts

2011-06-07T18:06:39Z

Having seen the following fire-ant raft experiment:

I went in search of more, and found the following exquisite film.

Inflammation: Help, Hindrance, and Snake Oil Opportunity

2011-06-02T22:28:33Z

Chronic inflammation has been found to have some connection with heart disease, stroke, Alzheimer’s, arthritis, diabetes, overweight, autism, and cancer.

Cause? Effect? Neither?

Though testing for inflammation is not routine, it can be done. When there is inflammation in your body, your liver produces C-reactive protein. When CRP levels are high in your bloodstream, this indicates the presence of inflammation. How high is too high? Should you do something about elevated CRP?

So far, we only know inflammation is associated with certain diseases. And we know that inflammation is part of the way our bodies fight infection. Would it be healthful to try to eliminate chronic inflammation? Or should we leave inflammation alone and try to eliminate the associated disease condition?

No one knows for sure.

But that doesn’t stop the snake oil salespeople. As you can see from my posts on May 17 and May 19, plenty of people have inflammation cures to sell you.

A better suggestion comes from the U C Berkeley Wellness Letter of January, 2008:

“How to ‘tamp down’ inflammation—The same steps that help prevent cardiovascular disease may reduce chronic inflammation.

Don’t smoke.

Ask your doctor about low-dose aspirin.

If you take a statin, it also works agains inflammation.

Control your blood pressure.

If you are overweight, lose weight.

Exercise.

What do you know, living healthy might keep you healthy or bring you back to health.