Research update

CrossCurrents

By Mark de la Hey

Cognitive impairments may play role in alcohol dependency

Differences in certain regions of the brains of people with alcohol dependency impair the ability to compare short-term versus long-term rewards, according to research from the Ernest Gallo Clinic and Research Centre in Emeryville, California. Scientists used functional magnetic resonance imaging to study the brains of nine abstinent participants with alcohol dependency and 10 controls with no history of alcohol dependency. Participants were asked to choose between a smaller monetary reward available immediately and a larger amount to be received later. As expected, those with alcohol dependency chose the immediate reward almost three times more often than did the controls. The tendency to choose immediate rewards was associated with increased activity in the parietal cortex, dorsal prefrontal cortex and rostral parahippocampal gyrus. In contrast, increased activity in the lateral orbitofrontal cortex was associated with the tendency to wait for larger rewards. These regions have all been experimentally linked to the comparison of value and outcome. The study also found that participants carrying a less active variant of the catechol-O-methyltransferase (COMT) gene, which helps control dopamine activity in the brain, were more likely to choose immediate rewards and showed increased activity in the dorsal prefrontal cortex and posterior parietal cortex. The presence of this variant of the COMT gene appears to deplete dopamine in the brain’s cortex. The authors suggest that these findings may lead to cognitive therapies that would help people improve their decision making as part of a recovery plan.

Journal of Neuroscience, December 26, 2007, v. 27: 14383–14391. Charlotte A. Boettiger et al., Ernest Gallo Clinic and Research Center, Emeryville, California.

Abnormalities in brain associated with borderline personality disorder

New research from Weill Medical College of Cornell University in New York has highlighted the role of brain abnormalities underlying borderline personality disorder (BPD). Scientists used functional magnetic resonance imaging to study brain activity in response to negative emotions among 16 individuals with BPD and 14 controls. Participants were scanned while performing an emotional linguistic go/no-go task. They were asked to press a button when shown a word in normal font or refrain from doing so when shown a word in italics. Researchers contrasted participants’ responses to negative words with their responses to emotionally neutral words. As expected, individuals with BPD rated the negative words more negatively than did controls. When responding to negative words, individuals with BPD displayed less activity than controls in two parts of the ventromedial prefrontal cortex involved in the regulation of emotions: the medial orbitofrontal cortex and the subgenual anterior cingulate cortex. The responses of individuals with BPD to negative words also showed increased activity in the limbic regions of the brain, notably the amygdala – regions also associated with the regulation of emotions. The authors state that their findings may help develop better diagnostic instruments and treatments. One limitation of the study is that 11 of the individuals with BPD were taking medication for their illness, although this was taken into account in the analysis.

American Journal of Psychiatry, December 2007, v. 164: 1832–1841. David Silbersweig et al., Weill Medical College of Cornell University, New York, New York.

Diagnostic criteria for generalized anxiety disorder may exclude many

New research from the Stanford University School of Medicine in Stanford, California, indicates that the current DSM-IV diagnostic criteria for generalized anxiety disorder (GAD) exclude many individuals who experience chronic anxiety and hyperarousal. The study examined 18 participants seeking treatment for frequent, unpleasant tension over the previous six weeks, as well as 18 participants who could be considered calm. Only five of the tense group could be diagnosed as having GAD using DSM-IV criteria. Each participant was examined using structured interviews and questionnaires. Tests of skin conductance level (SCL) were also given over a 24-hour period to measure sweat gland activity as an indicator of stress levels. The tense group reported more worry, more stress, more depression and poorer sleep than the calm group. The calm group had fewer periods of sleep disruption than the tense group. Calm individuals showed longer runs of SCL declines both when awake and asleep, indicating longer periods of relaxation among calm participants. One-minute waking SCL levels were higher among the tense group, indicating an inability to relax. Overall, the results indicate fewer and shorter periods of relaxation among tense participants. Interestingly, people in the tense group were able to achieve SCL declines comparable to those achieved by the calm group when they were instructed to sit quietly and relax after a three-minute walk. Since the majority of participants who showed symptoms could not be diagnosed as having GAD, the authors conclude that the current DSM-IV criteria for the disorder define a subtype that is not typical for chronic anxiety in general, leaving many individuals excluded from psychological and pharmaceutical research.

Journal of Psychiatric Research, February 2008, v. 42: 205–212. Walton T. Roth et al., Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California.

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