Why Smokers Can't Quit Easily

Every smoker knows it's tough to kick the habit. In fact,

just seeing a photo of someone smoking is enough for

would-be quitters to ditch their best intentions and light up

"just one more," research now shows.

New brain scans taken during normal smoking activity and

24 hours after quitting show a marked increase in a

particular kind of brain activity when quitters see

photographs of people smoking, said Joseph McClernon,

an associate professor in the department of psychiatry

and behavioral sciences at Duke University Medical

Center.

The brain area in question turns out to be the dorsal

striatum, a region responsible for automatic responses 

(such as controlling the movements needed to ride a bike

or brush one's teeth), which means that quitting smoking

may be out of a person's conscious control, McClernon

said.

"Only five percent of unaided quit attempts result in

successful abstinence," McClernon said. "Quitting

smoking dramatically increases brain activity in response

to seeing smoking cues, which seems to indicate that

quitting smoking is actually sensitizing the brain to these

smoking cues," thus explaining why most smokers who try

to quit tend to relapse.

"If we're really going to help people quit, this emphasizes

the need to do more than tell people to resist temptation.

We also have to help them break that habitual response,"

McClernon said.

The study is detailed online in the journal

Psychopharmacology. Further research is focusing on the

use of a nicotine patch prior to quitting smoking to break

the mental link between cigarettes and nicotine.

·           10 Easy Paths to Self Destruction 

·           Smoking's Many Myths Examined 

·           More News about Smoking 

轉貼自︰

http://news.yahoo.com/s/livescience/20090106/sc_livescience/whysmokerscantquiteasily;_ylt=Ao4J0yk_fs2JfLyPphYZiu4br7sF

Why We Take Risks - It's the Dopamine

By ALICE PARK

Risk-taking, by definition, defies logic. Reason can't

explain why people do unpredictable things - like betting

on blackjack or jumping out of planes - for little or,

sometimes, no reward at all. There's the thrill, of course,

but those brief moments of ecstasy aren't enough to keep

most risk takers coming back for more - which they do,

again and again, like addicts.

A new study by researchers at Vanderbilt University in

Nashville and Albert Einstein College of Medicine in New

York City suggests a biological explanation for why

certain people tend to live life on the edge - it involves the

neurotransmitter dopamine, the brain's feel-good

chemical. (See the Year in Health, from A to Z.)

Dopamine is responsible for making us feel satisfied after

a filling meal, happy when our favorite football team wins,

or really happy when we use stimulating drugs like

amphetamines or cocaine, which can artificially squeeze

more dopamine out of the nerve cells in our brain. It's also

responsible for the high we feel when we do something

daring, like skiing down a double black diamond slope or

skydiving out of a plane. In the risk taker's brain,

researchers report in the Journal of Neuroscience, there

appear to be fewer dopamine-inhibiting receptors -

meaning that daredevils' brains are more saturated with

the chemical, predisposing them to keep taking risks and

chasing the next high:

driving too fast, drinking too much, overspending or even

taking drugs.

David Zald, a professor of psychology and psychiatry at

Vanderbilt, studied whether the brains of those thrill

seekers differed in any way from those of the less

adventuresome when it comes to dopamine. He gave 34

men and women a questionnaire to assess their novelty-

seeking tendencies, then scanned their brains using a

technique called positron emission tomography to figure

out how many dopamine receptors the participants had. Zald and his team were on the lookout for a particular

dopamine-regulating receptor, which monitors levels of

the neurotransmitter and signals brain cells to stop

churning it out when there's enough.

Earlier studies in rats had shown that animals that tend to

explore and take more risks in new environments also

tend to have fewer of these inhibitory receptors, and Zald

wanted to find out if the same was true in people.

"This is one of those situations where the data came out

essentially perfectly," he says. "The results were exactly

as we predicted they would be, based on the animal

data." That is, like the rats, humans who were more

spontaneous and eager to take risks had fewer

dopamine-regulating receptors than those who were more

cautious.

The findings support Zald's theory that people who take

risks get an unusually big hit of dopamine each time they

have a novel experience, because their brains are not

able to inhibit the neurotransmitter adequately. That blast

makes them feel good, so they keep returning for the rush

from similarly risky or new behaviors, just like the addict

seeking the next high.

"This finding is really interesting," says Dr. Bruce Cohen,

director of the Frazier Research Institute at McLean

Hospital in Boston and a professor of psychiatry at

Harvard Medical School. "It's a piece of the puzzle to

understanding why we like novelty, and why we get

addicted to substances ... Dopamine is an important piece

of reward."

Cohen suggests that a better understanding of novelty-

seeking behavior may even help researchers find more

effective treatments for addiction. If future studies

validate Zald's findings and show that addicts also have

fewer dopamine-inhibiting receptors than average, then

medicines designed to replace the function of those

receptors may help bring their dopamine levels down to

normal and weaken their addiction.

On a more theoretical level, Zald's results may also help

inform a long-ranging debate in the addiction field. Some

experts believe that addicts suffer from a natural deficit of

dopamine and self-medicate with drugs; others think

addicts' brains make normal amounts of the

neurotransmitter but just can't break it down and regulate

it properly.

"We think a person who finds novelty and excitement

more rewarding does so because he gets more dopamine

release, or more of a boost," says Zald. "But it's one of

the big controversies in the field of addiction research

now." And it's yet another area for researchers to explore

in trying to come up with a better treatment for substance

abuse.

See the top 10 scientific discoveries of 2008.

轉貼自︰

http://news.yahoo.com/s/time/20081231/hl_time/08599186910600

(Time)