Ever wondered why teenagers take more risks and are more prone to addiction? It's because their brains respond differently to a situation than adults, says a new study.

In experiments on mice, researchers at the University of Pittsburgh have pinpointed some differences in brain response to a food reward between adolescent and adult rodents.
The findings, published in the journal Proceedings of the National Academies of Sciences, could explain why adolescents take more risks and are more prone to addiction, depression and schizophrenia, the researchers said.

"The brain region that is very critical in planning your actions and in habit formation is directly tapped by reward in adolescents, which means the reward could have a stronger influence in their decision-making, in what they do next, as well as forming habits in adolescents," study researcher Bita Moghaddam told LiveScience.

"Teens could do stupid things in response to a situation not because they are stupid, but because their brains are working differently. Somehow they perceive and react to a situation differently," Moghaddam said.

The study was performed in rats, but teenagers throughout the animal kingdom show the same risk-taking and impulsive behaviours as human teens, so the results are likely to be applicable in humans too, the researchers said.

Other studies have shown that the teen brain is also more susceptible to stress than the adult brain. Teenage brains are especially susceptible to addiction and mental illness, and the differences in the brain at that time may play a big role in these diseases. "If your brain is processing the exact same thing differently, that could give us clues as to why their brain is more vulnerable," Moghaddam said. "By understanding what is happening in the brains of adolescents we can better understand how to prevent disease."

The nucleus accumbens is the part of the brain that reacts with happy "reward" chemicals when we eat, have sex or do other things that ensure our survival. Drugs activate this region as well, creating an artificial reward signal by making these neurons send out their feel-good chemicals.

The researchers saw very similar reward responses in the nucleus accumbens when the rats received food pellets; the big difference between the brains of teenage and adult rats occurred in the dorsal striatum, where more activity showed up for teen rats about to get a food pellet.

This brain region gets activated by the reward signals from the nucleus accumbens and is involved in habit formation, sort of sealing in the memory of "I put my nose in here and I get a treat that makes me feel good."

These brain differences could manifest as the impulsive and risk-taking habits of your average teen, Moghaddam said.

"It could make the adolescent brain more vulnerable to what goes on around them in the environment, to things that are expected to be rewarding, and could make the brain more vulnerable to addiction," she said.

More bad news for office dwellers, all that sitting at your desk all day not only may put your health at risk but is bad for your mental well-being, at least according to a new study.

In research presented last week at the British Psychological Society's Annual Occupational Conference in Chester, England, scientists warn that the more you sit, the more risk you have for both a higher body mass index score and decreased mental well-being.

In a survey of more than 1,000 workers, nearly 70 percent surveyed did not meet recommended guidelines for exercise. The findings also revealed that the more you sit at work, the more you are likely to sit on your off hours, further raising your risks of health problems and mental strain.

According to the British Psychological Society, people spend on average five hours and 41 minutes per day sitting at their desks and eight hours sleeping at night -- and researchers warn that is "too much sitting."

Lead researcher Dr. Myanna Duncan, from Loughborough University in the UK, said the findings may be due to the fact workers "just forget" to stand up, she told the BBC last week.

"People don't need a psychologist to tell them to get up and walk around," she added in a press release. "But if it helps, I'd tell them to put a post-it note on their computer to remind them. Anyway go and talk to your colleagues face to face, it's a lot more sociable and better for you than emailing them."

The new study adds to growing scientific research suggesting that sitting can raise your risks for a host of problems, including obesity and diabetes -- this is especially true if you spend time outside of work lounging in front of the television or commuting. In one study, researchers found that people who spend more than two hours per day of leisure time watching television or sitting in front of a screen face double the risk of heart disease.

The short days, the weak sun, and the warm beds of winter can wreak havoc on your fitness routine.

As the outside temperature plummets, so too can the will to brave the elements for outdoor exercise. Experts say as long as you layer up, drink up and tune into how cold is just too cold it shouldn't impact your fitness.

"Come with a different game plan for the winter," advises Jessica Matthews, an exercise physiologist with the American Council on Exercise (ACE).

"Motivation tends to wane a bit, so explore different activities, including things you can do in your own home. Have a flexible approach to your fitness routine as the weather changes."

If you're keen to exercise outside in all seasons, says Matthews, learn to dress for workout success.

"Wear layers. That's really important when it's cold outside and make sure you're not becoming wet. Heavy cotton soaks up sweat, so you might want to stick with wool or polyester something water repellent."

Matthews suggests a first layer of lightweight synthetic.

"The second can be a little heavier, but still avoid heavy cotton," she said.

And don't leave home without hat and gloves. Heat loss from the head alone is about 50 percent at the freezing mark, according to ACE's safety tips for cold weather.

Keeping hands and feet warm is crucial because in cold the body shunts blood away from the extremities to warm internal organs at the center.

"In temperatures below zero, consider a scarf or face mask, kept loosely over mouth, to warm the air a little bit before it gets into your body," Matthews said.

Sometimes it's just too cold outside.

"Check the air temperature and wind chill factor before exercising in the cold," Matthews said. "Data from the National Safety Council suggest that when the wind chill factor falls below -20 degrees Fahrenheit (-29 Celsius), a danger zone exists."

Hypothermia is a potentially fatal condition. Warning signs include light-headedness, dizziness and lethargy.

"Those are the beginning stages," Matthews said.

Most people are not likely to forget to layer up in the cold, but they will more easily neglect to hydrate.

"It's too easy to forget to hydrate in the cold, and it's so important to stay hydrated in winter," said Matthews. "You are going to sweat."

She suggests drinking up to 20 ounces (0.59 liters) of water two or three hours before working out.

Deborah Plitt is a trainer with the Illinois-based equipment company Life Fitness, which recently broke down the calorie burn of 30 minutes of winter activities, such as sledding (250 calories), ice skating (230 calories), shoveling snow (230 calories).

"Of course there's a lot of wiggle room (in the calculations). It's based on an average woman of 145 pounds," said Plitt. "And sledding and snow shoveling depends on whether the snow is wet or fluffy."

Plitt said the point is to stay physically active, regardless of the weather, even if that means just taking the dog for a walk (125 calories).

"They're mixing things up; they're enjoying what they're doing," she said. "And believe it or not you burn more calories when you're shivering."

Experts have revealed that breast cancer survivors may experience problems with certain mental abilities several years after treatment, regardless of whether they were treated with chemotherapy plus radiation or radiation only.

The study indicated that there might be common and treatment specific ways that cancer therapies negatively affect cancer survivors` mental abilities.


Previous research had suggested that chemotherapy could cause problems with memory and concentration in breast cancer survivors.

To compare the effects of different types of cancer treatment on such mental abilities, Paul Jacobsen, PhD, of the Moffitt Cancer Centre and Research Institute in Tampa, and his colleagues examined 62 breast cancer patients treated with chemotherapy plus radiation, 67 patients treated with radiation only, and 184 women with no history of cancer.

Study participants completed neuropsychological assessments six months after completing treatment and again 36 months later.

The study confirmed that chemotherapy could cause cognitive problems in breast cancer survivors that persist for three years after they finish treatment.

In addition, the investigators found that breast cancer survivors who had been treated with radiation (and not chemotherapy) often experienced problems similar to those in breast cancer survivors treated with both chemotherapy and radiation.

They did not find that hormonal therapy (such as tamoxifen) caused cognitive difficulties.

"These findings suggest that the problems some breast cancer survivors have with their mental abilities are not due just to the administration of chemotherapy," said Dr. Jacobsen.

"Our findings also provide a more complete picture of the impact of cancer treatment on mental abilities than studies that did not follow patients as long or look at mental abilities in breast cancer survivors who had not been treated with chemotherapy," he added.

India, once the epicentre of polio, marked its first full year without a new case of the crippling disease on Friday, but the US taxpayer, who has been generously supporting India's polio fight, may be pulling the plug on funding.

India's success leaves just three countries where polio is still endemic. When India was polio ravaged, it was one of the four countries along with Pakistan, Afghanistan and Nigeria to be known by the acronym PAIN.
India's success in fighting polio, which has cost almost $2 billion and several nationwide immunisation programs, has been credited to decades of work by the Indian government, Rotary International, along with the US government-funded Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and UNICEF. According to the Washington Post, the US has spent more than $2 billion around the world since the WHO launched the global eradication campaign in 1988.

"Federal funding for global health programs now faces sharp cuts from Tea Party lawmakers and others worried about the deficit," warned The Hill.

"House Republicans last year voted to cut funding for global health by more than $1 billion from 2010 levels. A House and Senate conference committee last month ended up agreeing to slash President Obama's request for $9.1 billion by 9.2 percent, or $840 million."

Lawmakers have had to resort to sharp cuts in global health programs as America is running a $15 trillion debt and its own entitlement programs are on the brink of insolvency.

Officials with the CDC say US funding and experience were key to beating back polio in India.

"Since 1999, CDC has provided more than $113 million to India for technical, programmatic and laboratory support and purchase of oral polio vaccine," Kevin De Cock, the CDC's director for global health, told The Hill.

In India, De Cock said, the CDC "worked side-by-side with the government of India in designing and maintaining WHO's highly effective national polio surveillance system" while "CDC disease detectives and laboratory experts [were] on the ground working with global and local partners to investigate outbreaks and rapidly stop their spread."

Back at CDC headquarters in Atlanta, De Cock said, health experts "collect and analyze the latest information on eradication progress and share with those on the ground so strategies are adjusted based on the science."

The US government has shown huge commitment to eradicating polio in India, but if state funding dries up India will have to rely more heavily on Bill Gates who has made eliminating polio a centerpiece of his efforts to use his Microsoft fortune to change the world.

"We must build on this historic moment and ensure that India's polio program continues to move full-steam ahead," Gates said in a statement released by the Bill & Melinda Gates Foundation.

Gates said India had demonstrated that polio can be halted "when countries combine the right elements political will, quality immunisation campaigns, and an entire nation's determination."