DNA Ancestry, 1

One fine day (after watching a TV program about descendants of President Thomas Jefferson) I  decided to bite the bullet and send in some of my white blood cells to be analyzed for maternal mitochondrial DNA. Before I go into that, a bit of background. As you probably already know, your complete set of genetic information is encoded within 23 pairs of chromosomes in the nucleus of your cells. (Not all cells have a nucleus, however. Red-blood cells, for instance, have no nucleus.)  A chromosome is a single piece of coiled DNA, a bio-molecule that holds the blueprint for how living organisms are built. About 99% of all DNA (deoxyribonucleic acid) in your body is found in your chromosomes. DNA consists of a 64-letter (codon) alphabet that spells out your genetic code. The letters or codons are organized into words and sentences called genes―a segment of DNA passed down from parents to child that confers a trait to the offspring. Humans have 25,000-30,000 genes, usually in pairs (one from each parent). Part 2 tomorrow.

Blink of an Eye, 2

A study by MIT neuroscientists provides evidence that feedforward processing—the flow of information in only one direction, from retina through visual processing centers in the brain—is sufficient for the brain to identify concepts without having to do any further feedback processing. It also suggests that while the images are seen for only thirteen milliseconds before the next image appears, part of the brain continues to process those images for longer than that, senior author Mary Potter explained, because in some cases subjects weren’t asked whether a specified image was present until after they had seen the sequence. “If images were wiped out after 13 milliseconds, people would never be able to respond positively after the sequence. There has to be something in the brain that has maintained that information at least that long,” she says. This ability to identify images seen so briefly may help the brain as it decides where to focus the eyes, which dart from point to point in brief movements called fixations about three times per second. Deciding where to move the eyes can take 100 to 140 milliseconds, so very high-speed understanding must occur before that.

http://newsoffice.mit.edu/2014/in-the-blink-of-an-eye-0116

Blink of an Eye

It’s hard to keep up with the rapid advances of brain research. Funded by the National Institutes of Health, MIT neuroscientists found that the human brain can process entire images that the eye sees for as little as 13 milliseconds—the first evidence of such rapid processing speed—which works out to seventy-five frames per second. This is far faster than the 100 milliseconds suggested by previous studies. In the new study, which appears in the journal Attention, Perception, and Psychophysics, researchers asked subjects to look for a particular type of image, such as “picnic” or “smiling couple,” as they viewed a series of six or twelve images, each presented for between thirteen  and eighty milliseconds. “The fact that you can do that at these high speeds indicates to us that what vision does is find concepts. That’s what the brain is doing all day long — trying to understand what we’re looking at,” says Mary Potter, an MIT professor of brain and cognitive sciences and senior author of the study.

http://newsoffice.mit.edu/2014/in-the-blink-of-an-eye-0116

Happy National Day

According to Wikipedia, the National Day is a designated date on which celebrations mark the nationhood of a non-sovereign country. This nationhood can be symbolized by the date of becoming a republic, of becoming independent, or a significant date for a patron saint or a ruler. The day is not always called by the name National Day but can be considered as one. Often it is also a national holiday. Some countries have more than one National Day. Pakistan has three, for example, none of which is named the National Day. In the United States of America, its Independence Day, commonly known as the Fourth of July, is the country's National Day and is a federal holiday. It commemorates the approval and adoption of the Declaration of Independence on July 4, 1776, when the then colonies declared independence from the United Kingdom. In a remarkable coincidence, both John Adams and Thomas Jefferson, the only signers of the Declaration of Independence later to serve as US Presidents, died on the same day: July 4, 1826, which was the 50th anniversary of the Declaration. Whatever your plans, have a happy day and relish your freedom.

Casual Pot Use and Brain Changes, 3

Study results (recently published in the Journal of Neuroscience related to recreational use of marijuana and brain changes in the amygdala and nucleus accumbens) fit with animal studies that show when rats are given tetrahydrocannabinol (THC)—the mind-altering ingredient contained in marijuana—their brains rewire to form many new connections. In animals, these new connections indicate the brain is adapting to the unnatural level of reward and stimulation from marijuana. The result of these new connections is to make other natural rewards less satisfying. Lead author Jodi Gilman said, “It may be that we’re seeing a type of drug learning in the brain. “We think when people are in the process of becoming addicted, their brains form these new connections.”

Jodi M. Gilman et al., Cannabis Use is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users, Journal of Neuroscience, 2014, DOI: 10.1523/JNEUROSCI.4745-13.2014

Casual Pot Use and Brain Changes, 2

An article was published recently in the Journal of Neuroscience related to abnormal changes in the brain associated with the recreational use of marijuana. The degree of brain abnormalities in these regions is directly related to the number of joints a person smoked per week. The more joints a person smoked, the more abnormal the shape, volume and density of the brain regions. According to Dr. Breiter, this study raises a strong challenge to the idea that casual marijuana use isn’t associated with negative consequences. Some of the participants “used marijuana to get high once or twice a week. People think a little recreational use shouldn’t cause a problem if someone is doing okay with work or school. Our data directly says this is not the case.” Part 3 tomorrow.

Jodi M. Gilman et al., Cannabis Use is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users, Journal of Neuroscience, 2014, DOI: 10.1523/JNEUROSCI.4745-13.2014

Casual Pot Use and Brain Changes

The results of research led by Hans Breiter, MD, professor of Psychiatry and Behavioral Sciences at Northwestern University Feinberg School of Medicine and a psychiatrist at Northwestern Memorial Hospital, was recently published in the Journal of Neuroscience. Lead author Jodi Gilman, a researcher in the Massachusetts General Center for Addiction Medicine and an instructor in Psychology at Harvard Medical School, indicated this is the first study to show that the casual use of marijuana is related to major brain changes in two areas: the nucleus accumbens and the amygdala. Both these regions play a major role in emotion and motivation. Co-senior study author Anne Blood, director of the Mood and Motor Control Laboratory at Massachusetts General and assistant professor of psychiatry at Harvard Medical School, said that these brain areas form the basis for how you assess positive and negative features about things in the environment and make decisions about them. Part 2 tomorrow.