The Teen Brain on Weed

April 24, 2015

By Medical Discovery News

A brain

It is now legal to use marijuana (recreationally and/or medically) in more than 20 states and the District of Columbia, and as more places debate legalizing the substance, more people are asking about its consequences on human health. There are many myths and misconceptions out there, but this is what science has to say about the subject.

As with all substances, the health effects depend on the potency, amount, and a person’s age. An independent scientific committee in the United Kingdom evaluated how harmful various drugs were based on 16 criteria and ranked heroin, crack cocaine, and methamphetamine as the most harmful drugs to individuals using them, and ranked alcohol, heroin, and crack cocaine as the drugs that cause the most harm to others. Marijuana ranks eighth, with slightly more than one-quarter the harm of alcohol.

Short-term use is associated with impaired short-term memory, making it difficult to learn and retain information while under the influence. Short-term use can also impair motor coordination, interfering with tasks such as driving. The overall risk of an accident doubles if a person drives soon after using marijuana. In comparison, those with blood alcohol levels above the legal limit are five times more likely to have an accident, and the combination of alcohol and marijuana is higher than either one alone.

Long-term or heavy use is associated with diminished life satisfaction and achievement overall. At high doses, marijuana can cause paranoia and psychosis, and long-term marijuana use increases the risk of developing schizophrenia or other chronic psychotic illnesses. Nine percent of all marijuana users, or 2.7 million people, develop an addiction to it. That figure jumps to 25-50 percent for those who use marijuana daily, and 17 percent of people who begin using marijuana as adolescents become addicted. Cannabis withdrawal syndrome is real and includes symptoms of irritability, sleep disturbance, dysphoria, craving, and anxiety.

Adults who occasionally use marijuana do so with little to no risk, but adolescent brains are not fully developed, making them more vulnerable to the adverse effects of marijuana. Using marijuana during adolescence can alter brain development, causing impaired cognition and lower IQs. This is probably because the active ingredient in marijuana, tetrahydrocannabinol, affects the brain’s ability to make connections between neurons in certain regions of the brain. Adolescent marijuana users also have a smaller hippocampus, which is important in learning and memory, and a less active prefrontal cortex, which is important in cognitive tasks such as planning and problem-solving.

Since acute marijuana intoxication can impair cognitive functions for days, students who use marijuana may function well below their natural abilities, causing academic difficulties. High school dropouts do report higher marijuana usage than their peers. Some evidence suggests that these cognitive impairments could be long-lasting or permanent in long-term users who started at younger ages, which can impact their abilities to succeed academically and professionally.

There is no clear association between long-term marijuana use and any deadly disease, although chronic marijuana smokers have increased rates of respiratory infections and pneumonia and an increased risk of heart attack and stroke. The effects of marijuana on a developing embryo and the effects of second-hand or third-hand marijuana smoke have not been well-studied, but as marijuana legalization continues to be an issue the science behind it will as well.

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Nobel Prize for the Brain’s GPS

Jan. 2, 2015

By Medical Discovery News

Nobel Prize for the Brain's GPS

How do we know where we are at any time – what is up and down? How do we know that we have been in a place before, and how do we know what to expect around the corner? This may sound like a simple task, but it is actually a complex, dynamic problem for our brains. That is why the scientists who have shed light on this system have received science’s highest honor.

The 2014 Nobel Prize for Physiology or Medicine is awarded by the Nobel Assembly at Karolinksa Institute in Stockholm, Sweden, to recognize the most outstanding achievements in science. This year the prize was awarded to a trio of scientists who have unraveled the brain’s internal GPS system. Like it sounds, this allows us to know where we are in three-dimensional space in our environment. This year’s $1.1 million prize was split half-and-half between Dr. John O’Keefe of University College in London and Drs. May-Britt Moser of the Centre for Neural Computation in Trondheim, Norway, and Edvard I. Moser of the Kavli Institute for Systems Neuroscience in Trondheim, Norway. The Mosers are the fifth married couple to receive a Nobel. Together their work reveals the basic principles of how our brains create a figurative map of the space we occupy and how we are able use and store this information to navigate from one place to another.

In the early 1970s, O’ Keefe identified a population of nerve cells in a part of the brain called the hippocampus that activate as the result of an animal recognizing it was in a specific location. These activated brain cells were named place cells. They create a map in the brain of locations corresponding to the external environment. This means that a person’s perception of location is determined by the activation of a specific group of place cells in a precise orientation in the hippocampus. Before O’Keefe’s discovery, scientists did not have a good understanding of how humans perceived positional locations.

Over 30 years later, the Mosers took this concept to a new level. They discovered that nerves in a nearby area of the brain called the entorhinal cortex activated when rats were in known locations. These grid cells formed hexagonal patterns, which together produced a system that is the basis for positional navigation. It works like this: the grid cells sense the directional motion of the head and the dimensions of a room. This creates a network of cells in the brain, functioning much like the Global Positioning System (GPS) used in cars and phones. This brain network tells you where you are, the direction you are moving, and what to expect in the environment ahead. Consider how difficult it would be to walk around your neighborhood without this type of information available to you. Just like with a GPS, recalculating is something the brain does all the time.

The Nobel Committee for Physiology or Medicine, which has awarded 105 prizes to 207 laureates since 1901, has once again identified a significant scientific contribution that has a profound impact on our understanding of how we function as human beings.

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Altering Memories

March 21, 2014

By Medical Discovery News

Altering Memories

In the film “Eternal Sunshine of the Spotless Mind,” people can request a medical procedure that targets memories pertaining to a specific subject or person and change or delete them. Several characters choose to have their memories of unrequited love and failed relationships erased. While the plot is purely fictional, new research does provide intriguing new details on how memories are stored, and how they might be manipulated.

Memories are stored in the temporal lobe and the hippocampus of the brain. Experiences produce physical and chemical changes in specific brain cells. Connections between brain cells that help with memory storage can also change. Scientists can identify the precise cells in a network involved with a specific experience. These are called memory traces or engrams.

Nobel Prize winner Susumu Tonegawa and his team wanted to explore how these memory traces are stored in cells. They used cells from the hippocampus that contained a light-sensitive protein called channelrhodopsin. When a memory pertaining to these cells is accessed within the brain, the light-sensitive protein activates. To discover which cells are associated with which memories, a memory is triggered and the cells respond with the light-sensitive protein. 

To do this experiment with mice, researchers assessed an easily observed behavior – the fear response. They first placed mice a chamber to allow memories of that environment to be formed. While this memory formed, channelrhodopsin was being produced in specific cells to record this memory. The next day the mice were placed in a completely different chamber and received a mild electric shock to their feet and a pulse of light simultaneously, prompting a fear response. But the pulse of light activated the memory of the chamber from the first day. And the following day when the mice were placed back in the first chamber, they displayed fear even though there was no electric shock associated with that chamber.

This means that activation of memory cells while receiving a shock in a different chamber produced fear associated with the first chamber. Now the mice connected the shock with the first chamber even though nothing bad happened there. This means scientist were able to implant a false memory by activating the trace of the original memory. This experiment identified the location of specific memories and showed that they could be manipulated. 

Not to sound too much like a sci-fi thriller, but this means in the future human memory may be able to be altered. There are positive, therapeutic applications, such as altering stress-inducing memories for war veterans with post-traumatic stress disorder. But in the wrong hands, this could be used for more sinister purposes, like mind control in “The Matrix.” Is it wise to alter any memories at all – does that change the person as a whole? Scientists and society will need to consider these questions if such experiments progress.  

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Stress-Relieving Gene

By Medical Discovery News

Oct. 20, 2012

Stress can lead to high blood pressure, mood disorders, and can have other negative health effects

One word serves as an instant conversation starter: stress. It’s inescapable, and comes from common experiences like deadlines and demanding bosses, a spouse who doesn’t understand and children who don’t obey, or bills to pay and endless chores to do. The added burden of a health crisis or relative’s death can cause stress to become acute. Though people throw the word around, unchecked stress takes a physiological and psychological toll.

Research shows chronic stress leads to mood disorders such as depression, which has enormous effects on the brain. It changes brain cell behavior and the structure of brain tissues. For example, the hippocampus, which is the brain’s memory center, can shrink in people with a history of depression. And neurons, which are cells that transmit brain signals, can slow down.

A new report further supports this causal link between stress and mood disorders. It shows chronic stress blocks a gene called neuritin that normally protects the brain from such disorders. A research team from Yale University studied how rats, which also possess the neuritin gene, responded to 35 days of stress induced by isolation, no food or play, and a change in their light and dark cycles.

As expected, the rats showed signs of depression. They lost interest in food, sweetened drinks, and didn’t swim when placed in water. An analysis showed these rats had significantly lower neuritin gene activity compared with rats in a control group. While some of the depressed rats were given antidepressants to recover, others were injected with a genetically engineered virus to increase neuritin gene activity. These rats recovered just as well as those given antidepressants, which suggests neuritin is effective at blocking stress and mood disorders.

To further prove neuritin can protect the brain from depression, researchers blocked the neuritin gene in healthy rats and saw them exhibit the same depressed states as rats exposed to chronic stress. The study supports past evidence that already began to link stress to the development and progression of mood disorders.

Past studies show a person suffering depression has lower levels of something called brain-derived growth neurotrophic factor (BDNF).  This protein factor is important in keeping neurons active and healthy. Other findings also suggested low neuritin gene activity diminished the coding of a protein that protects the brain’s ability to adapt to new experiences.

The findings will help scientists target a new method for treating the one in four Americans affected by mood disorders in any given year, according to the National Institute on Mental Health. Though antidepressants are currently available, only 30 percent of people taking them fully recover. Finding a new therapy that can promise better results can be life changing.

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Have Another Cup

By Medical Discovery News

May 19, 2012

I Own Myself... Don't I?

During the morning rush or the afternoon lull, Americans all seem to reach for a pick-me-up using the same thing – caffeine, whether it be coffee, soda or tea. The human love affair with caffeine dates back 500,000 years when Paleolithic man drank tea. While people today use caffeine as a stimulant, experiments have not been able to prove it actually improves cognitive performance, meaning it doesn’t help someone memorize or retain facts for an upcoming exam.

That hasn’t stopped scientists from studying caffeine to understand its effects on the brain. Now, a new report joins a short list of studies showing a shot of Red Bull could enhance mental acuity.  Serena Dudek of the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., is co-author of the study. In experiments with rats, her team found caffeine jolts neurons in an area deep inside the brain responsible for forming, organizing and storing memory.

Caffeine alters brain chemistry because the molecule is small enough to enter the brain and interrupt normal nerve cell functions. In particular, it interferes with a process responsible for sleepiness. People get sleepy because as the day wears on, a chemical in the brain called adenosine builds up. This neurotransmitter protects the brain and keeps it from overworking by binding with nerve cells to slow their activity. As neurons slow down, a person gets sleepy; however, as they sleep, adenosine levels drop, which resets the sleep clock.

Caffeine interrupts this cycle by competing with adenosine for binding to nerve cells. Since caffeine is structurally similar, it can bind to nerve cells, blocking adenosine and stopping the sleep signal. Rather than slow down, the neurons keep working and, in Dudek’s study, they do so in an area of the brain not seen before.

When researchers gave rats the caffeine equivalent to two cups of coffee, a small amount compared with the massive doses used in other studies, they measured the electrical signals of neurons in an area of the hippocampus called CA2. The cells there responded with a huge burst of electrical activity, and the higher the dose of caffeine, the greater the response.

Scientists were able to replicate the experiment on CA2 nerve cells grown in a petri dish.  After only five minutes of exposure to caffeine, these nerve cells were still activated three hours later. If human CA2 neurons respond the same way, this area of the brain may be the most sensitive to caffeine.

The results suggest caffeine may temporarily stimulate mental sharpness and could have a role in learning, which makes sense because the hippocampus, a set of seahorse-shaped organs behind the ears, is responsible for organizing and developing memory. That’s why London cab drivers who learn incredibly complex traffic routes have an enlarged hippocampus.

The study’s results, though on rats, may give a better understanding of caffeine’s effects on the human brain. If caffeine does enhance memory, the 80 to 90 percent of Americans who swear by their daily caffeine habit have more reason to get another cup.

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