Brain-behavior Disconnect In Cocaine Addiction

Parts of the brain involved in monitoring behaviors and emotions show different levels of activity in cocaine users relative to non-drug users, even when both groups perform equally well on a psychological test. These results — from a brain-imaging study conducted at the U.S. Department of Energy's Brookhaven National Laboratory and published online the week of May 25, 2009, by the Proceedings of the National Academy of Sciences — suggest that such impairments may underlie addictive vulnerability, and that treatments aimed at improving these functions could help addicted individuals resist drugs."Many studies have found decreased brain activity in drug-addicted individuals relative to healthy control subjects during psychological tests," said lead author Rita Goldstein, a psychologist at Brookhaven Lab. "But it's never been clear if these differences were due to varying levels of interest or ability between the two groups. This is the first study to look at two groups matched for performance and interest — and we still see dramatic differences in the brain regions that play a very significant role in the ability to monitor behavior and regulate emotion, which are both important to resisting drug use.

"Whether these brain differences are an underlying cause or a consequence of addiction, the brain regions involved should be considered targets for new kinds of treatments aimed at improving function and self-regulatory control," Goldstein said.

The researchers studied 17 active cocaine users and 17 demographically matched healthy control subjects. Both groups were trained to push one of four colored buttons corresponding to the color of type used to present words that were either related to drug use (e.g., crack, addict) or neutral household terms. Subjects were given monetary rewards for fast, accurate performance — up to 50 cents for each correct answer on some tests, for a maximum of $75.

After training, both groups performed equally well on this same test while lying in a magnetic resonance imaging (MRI) scanner, with performance improving when they knew they'd be earning the highest monetary reward. During the tests, the scientists used functional MRI (fMRI) to indirectly measure the amount of oxygen being used by specific regions of the brain, as an indicator of brain activity in those regions.

There were three main differences between the cocaine-addicted subjects and the healthy controls:

* The cocaine users had reduced activity in a portion of the anterior cingulate cortex that usually becomes more active (compared to a passive baseline) when monitoring behavior. Activity levels were lowest during the least "interesting," or salient, version of the test — when there was no monetary reward and the words shown were neutral household terms. Within the cocaine-user group, activity levels were lowest in the people who had used cocaine most frequently in the 30 days prior to the test.
* The cocaine users also had reduced activity in another part of the anterior cingulate cortex that usually becomes less active (compared to a passive baseline) when someone is successfully suppressing emotional feelings. Within the cocaine-user group, activity levels during the high-salience version of the test — when each fast, correct answer was rewarded with 50 cents and the words presented were drug-related — were lowest in the people who were most successful in suppressing the task-induced craving. In healthy controls, who did not report craving, activation in this region was not significantly different from baseline.
* The functions within the behavior-monitoring and emotion-monitoring brain regions were interconnected in the healthy control subjects but not in the addicted individuals. In all, these group differences in brain function and interconnectivity were quite robust and all the more meaningful in that there were no differences between the groups in performance on or interest ratings for the task.

"When you really have to suppress a powerful negative emotion, like sadness, anxiety or drug craving, activity in this brain region is supposed to decrease, possibly to tune out the background 'noise' of these emotions so you can focus on the task at hand," Goldstein said.

"Our results show that activity in this region indeed went down in the drug-using group, suggesting they were actively trying to suppress craving. Indeed subjects who reported the highest levels of task-induced craving were the least able to suppress activity in this particular brain region.

"This could be because these drug users were still being distracted by background 'noise' stimuli, like memories of having taken drugs or anticipation of further use," Goldstein said.

"This work gives us some clues as to what happens when drug users are unable to suppress craving — and how that might work together with a decreased ability to monitor behavior, even during neutral, non-emotional situations, to make some people more vulnerable to taking drugs," Goldstein said.

The findings point to the importance of improving activity in the behavior-monitoring brain region, possibly by using behavioral and pharmacological approaches to increase motivation and top-down monitoring. Treatments aimed at strengthening activity in the emotion-monitoring brain region may further help addicted individuals regain self-control, especially during hard to suppress highly emotional situations (e.g., during craving). Treatments aimed at strengthening the interconnectivity between these brain regions may decrease impulsivity.

This study was supported by grants from the National Institute on Drug Abuse and the General Clinical Research Center of Stony Brook University.

Ultraviolet LEDs Create Darker, Redder Lettuce Richer In Antioxidants

Salad dressing aside, a pile of spinach has more nutritional value than a wedge of iceberg lettuce. That's because darker colors in leafy vegetables are often signs of antioxidants that are thought to have a variety of health benefits. Now a team of plant physiologists has developed a way to make lettuce darker and redder—and therefore healthier—using ultraviolet light-emitting diodes (LEDs).Steven Britz of the U.S. Department of Agriculture in Beltsville, Md., and colleagues will present the research at the 2009 Conference on Lasers and Electro Optics/International Quantum Electronics Conference (CLEO/IQEC), which takes place May 31 to June 5 at the Baltimore Convention Center.

The dark red tinges on a leaf of red leaf lettuce are the plant kingdom's equivalent of suntan lotion. When bombarded with ultraviolet rays from the sun, the lettuce leaf creates UV-absorbing polyphenolic compounds in its outer layer of cells. Some of these compounds are red and belong to the same family that gives color to berries and apple skin. They help block ultraviolet radiation, which can mutate plant DNA and damage the photosynthesis that allows a plant to make its food.

Polyphenolic compounds,which include flavonoids like quercetin and cyanidin, are also powerful antioxidants. Diets rich in antioxidants are thought to provide a variety of health benefits to human beings, from improving brain function to slowing the wear and tear of aging.

To create red leaf lettuce plants enriched with these compounds, Britz purchased low-power LEDs that shine with UVB light, a component of natural sunlight. In small quantities, this ultraviolet light allows humans to produce vitamin D, which has been cited for its health benefits. Britz exposed the plants to levels of UVB light comparable to those that a beach goer would feel on a sunny day, approximately 10 milliwatts per square meter.

After 43 hours of exposure to UVB light, the growing lettuce plants were noticeably redder than other plants that only saw white light. Though the team has yet to quantify this effect, it appears to increase as the intensity of the light increases. The effect also seems to be particularly sensitive to the wavelength used – peaking at 282 and 296 nanometers, and absent for longer wavelength UV. "We've been pleasantly surprised to see how effective the LEDs are, and are now testing how much exposure is required, and whether the light should be pulsed or continuous," says Britz.

To cut transportation costs and feed the market in the wintertime, more produce is grown in greenhouses. Crops grown in the winter in northern climes receive very little UVB to begin with, and plants in greenhouses are further shielded from UVB by the glass walls. Ultraviolet LEDs could provide a way to replace and enhance this part of the electromagnetic spectrum to produce darker, more colorful lettuces.

Britz also discussed the potential for using UV LEDs to preserve nutrients in vegetables that have already been harvested. Previous experiments have shown that the peel of a picked apple stays redder for a longer period of time when exposed to ultraviolet light. UVB LEDs are a promising technology for irradiating vegetables stored at low temperatures to maintain or even boost the amount of phytonutrients they contain.

Presentation PTuA3, "Shedding light on nutrition," Steven Britz, June 2.

Fish Really Is 'Brain Food': Vitamin D May Lessen Age-related Cognitive Decline

Eating fish – long considered ‘brain food’ – may really be good for the old grey matter, as is a healthy dose of sunshine, new research suggests.University of Manchester scientists in collaboration with colleagues from other European centres have shown that higher levels of vitamin D – primarily synthesised in the skin following sun exposure but also found in certain foods such as oily fish – are associated with improved cognitive function in middle-aged and older men.

The study, published in the Journal of Neurology, Neurosurgery and Psychiatry, compared the cognitive performance of more than 3,000 men aged 40 to 79 years at eight test centres across Europe.

The researchers found that men with higher levels of vitamin D performed consistently better in a simple and sensitive neuropsychological test that assesses an individual’s attention and speed of information processing.

“Previous studies exploring the relationship between vitamin D and cognitive performance in adults have produced inconsistent findings but we observed a significant, independent association between a slower information processing speed and lower levels of vitamin D,” said lead author Dr David Lee, in Manchester’s School of Translational Medicine.

“The main strengths of our study are that it is based on a large population sample and took into account potential interfering factors, such as depression, season and levels of physical activity.

“Interestingly, the association between increased vitamin D and faster information processing was more significant in men aged over 60 years, although the biological reasons for this remain unclear.”

“The positive effects vitamin D appears to have on the brain need to be explored further but certainly raise questions about its potential benefit for minimising ageing-related declines in cognitive performance.”