Archive for November 2007
Watching media violence significantly increases the risk that a viewer or video game player will behave aggressively in both the short and long term, according to a University of Michigan study published today in a special issue of the Journal of Adolescent Health.
The study, by L. Rowell Huesmann, reviews more than half a century of research on the impact of exposure to violence in television, movies, video games and on the Internet.
“The research clearly shows that exposure to virtual violence increases the risk that both children and adults will behave aggressively,” said Huesmann, the Amos N. Tversky Collegiate Professor of Communication Studies and Psychology, and a senior research scientist at the U-M Institute for Social Research (ISR).
In his article, Huesmann points out that U.S. children spend an average of three to four hours a day watching television. “More than 60 percent of television programs contain some violence,” he said, “and about 40 percent of those contain heavy violence.
“Children are also spending an increasingly large amount of time playing video games, most of which contain violence. Video game units are now present in 83 percent of homes with children,” he said.
According to research conducted by Huesmann and ISR colleague Brad Bushman, media violence significantly increases the risk that both children and adults will behave aggressively.
“Exposure to violent electronic media has a larger effect than all but one other well-known threat to public health. The only effect slightly larger than the effect of media violence on aggression is that of cigarette smoking on lung cancer,” Huesmann said.
“Our lives are saturated by the mass media, and for better or worse, violent media are having a particularly detrimental effect on the well-being of children,” he said.
“As with many other public health threats, not every child who is exposed to this threat will acquire the affliction of violent behavior. But that does not diminish the need to address the threat — as a society and as parents by trying to control children’s exposure to violent media to the extent that we can.” The reading is clearly indebted to the author’s piagetian concepts about psychosocial development. But even in the light of a Vygotskian “zone of proximal development”, narrative constructivism or REBT, the social consequences of these findings would not be any less concerning.
Dev Psychol. 2007 Jul;43(4):1038-44.
Department of Communication Science, VU University Amsterdam, Amsterdam, Netherlands. firstname.lastname@example.org
This study tested the hypothesis that violent video games are especially likely to increase aggression when players identify with violent game characters. Dutch adolescent boys with low education ability (N=112) were randomly assigned to play a realistic or fantasy violent or nonviolent video game. Next, they competed with an ostensible partner on a reaction time task in which the winner could blast the loser with loud noise through headphones (the aggression measure). Participants were told that high noise levels could cause permanent hearing damage. Habitual video game exposure, trait aggressiveness, and sensation seeking were controlled for. As expected, the most aggressive participants were those who played a violent game and wished they were like a violent character in the game. These participants used noise levels loud enough to cause permanent hearing damage to their partners, even though their partners had not provoked them. These results show that identifying with violent video game characters makes players more aggressive. Players were especially likely to identify with violent characters in realistic games and with games they felt immersed in. Copyright 2007 APA.
Arch Pediatr Adolesc Med. 2006 Apr;160(4):348-52.
Vrije Universiteit, Amsterdam, the Netherlands. email@example.com
OBJECTIVES: To test whether the results of the accumulated studies on media violence and aggressive behavior are consistent with the theories that have evolved to explain the effects. We tested for the existence of both short-term and long-term effects for aggressive behavior. We also tested the theory-driven hypothesis that short-term effects should be greater for adults and long-term effects should be greater for children. DESIGN: Meta-analysis. PARTICIPANTS: Children younger than 18 years and adults. MAIN EXPOSURES: Violent media, including TV, movies, video games, music, and comic books. MAIN OUTCOME MEASURES: Measures of aggressive behavior, aggressive thoughts, angry feelings, physiological arousal (eg, heart rate, blood pressure), and helping behavior. RESULTS: Effect size estimates were combined using meta-analytic procedures. As expected, the short-term effects of violent media were greater for adults than for children whereas the long-term effects were greater for children than for adults. The results also showed that there were overall modest but significant effect sizes for exposure to media violence on aggressive behaviors, aggressive thoughts, angry feelings, arousal levels, and helping behavior. CONCLUSIONS: The results are consistent with the theory that short-term effects are mostly due to the priming of existing well-encoded scripts, schemas, or beliefs, which adults have had more time to encode. In contrast, long-term effects require the learning (encoding) of scripts, schemas, or beliefs. Children can encode new scripts, schemas, and beliefs via observational learning with less interference and effort than adults.
This one is interesting too and explains a good part of actual Bush administration’s foreign politics:
Psychol Sci. 2007 Mar;18(3):204-7.
Institute for Social Research, University of Michigan, 426 Thompson St., Ann Arbor, MI 48106, USA. firstname.lastname@example.org
Violent people often claim that God sanctions their actions. In two studies, participants read a violent passage said to come from either the Bible or an ancient scroll. For half the participants, the passage said that God sanctioned the violence. Next, participants competed with an ostensible partner on a task in which the winner could blast the loser with loud noise through headphones (the aggression measure). Study 1 involved Brigham Young University students; 99% believed in God and in the Bible. Study 2 involved Vrije Universiteit-Amsterdam students; 50% believed in God, and 27% believed in the Bible. In Study 1, aggression increased when the passage was from the Bible or mentioned God. In Study 2, aggression increased when the passage mentioned God, especially among participants who believed in God and in the Bible. These results suggest that scriptural violence sanctioned by God can increase aggression, especially in believers.
Pedophilia might be the result of faulty connections in the brain, according to new research released by the Centre for Addiction and Mental Health (CAMH). The study used MRIs and a sophisticated computer analysis technique to compare a group of pedophiles with a group of non-sexual criminals. The pedophiles had significantly less of a substance called “white matter” which is responsible for wiring the different parts of the brain together.
The study challenges the commonly held belief that pedophilia is brought on by childhood trauma or abuse. This finding is the strongest evidence yet that pedophilia is instead the result of a problem in brain development.
Previous research from this team has strongly hinted that the key to understanding pedophilia might be in how the brain develops. Pedophiles have lower IQs, are three times more likely to be left-handed, and even tend to be physically shorter than non-pedophiles.
“There is nothing in this research that says pedophiles shouldn’t be held criminally responsible for their actions,” said Dr. James Cantor, CAMH Psychologist and lead scientist of the study, “Not being able to choose your sexual interests doesn’t mean you can’t choose what you do.” This is pretty much the same bigotry as the Vatican’s attitude about homosexuality: gays can be redeemed and enter paradise, if they refute their heinous sins, renouncing sexuality alltogether.
This discovery suggests that much more research attention should be paid to how the brain governs sexual interests. Such information could potentially yield strategies for preventing the development of pedophilia. The old nurture/nature-debate in new outfit? A previous study, with much higher numbers of participants of correctional institutions in Canada and U.S., showed that people with intellectual disability were also found to be typically very conservative when it came to sexual attitudes. However, the researchers found that serious sex offenders actually expressed much more liberal attitudes when it came to sex, including same-sex relationships, than sex offenders who only committed sexual inappropriate behaviors, such as public masturbation or inappropriate touching. Conclusion: “This study provides support for the need to assess sexual knowledge, sexual attitudes and prior sex education when an individual commits a sexual offence… Only a careful diagnosis will reveal whether the offence is motivated by sexual urges and fantasies consistent with serious sexual offence or by other factors.” It is expectable then, that among the 65 “men who demonstrated illegal or clinically significant sexual behaviors or interests” there were some belonging to either of the two, or both of the above mentioned categories, which limits the value of the interpreted data. (A total of 127 men participated in the study; approximately equal numbers of pedophiles and non-sexual offenders.)
The Kurt Freund Laboratory at CAMH was established in 1968 and remains one of the world’s foremost centres for the research and diagnosis of pedophilia and other sexual disorders.
CAMH is a Pan American Health Organization/World Health Organization Collaborating Centre, and is fully affiliated with Tthe University of Toronto.
J Psychiatr Res. 2007 Nov 24; [Epub ahead of print]
Law and Mental Health Program, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, Canada M5T 1R8.
The present investigation sought to identify which brain regions distinguish pedophilic from nonpedophilic men, using unbiased, automated analyses of the whole brain. T1-weighted magnetic resonance images (MRIs) were acquired from men who demonstrated illegal or clinically significant sexual behaviors or interests (n=65) and from men who had histories of nonsexual offenses but no sexual offenses (n=62). Sexual interest in children was assessed by participants’ admissions of pedophilic interest, histories of committing sexual offenses against children, and psychophysiological responses in the laboratory to erotic stimuli depicting children or adults. Automated parcellation of the MRIs revealed significant negative associations between pedophilia and white matter volumes of the temporal and parietal lobes bilaterally. Voxel-based morphometry corroborated the associations and indicated that the regions of lower white matter volumes followed, and were limited to, two major fiber bundles: the superior fronto-occipital fasciculus and the right arcuate fasciculus. No significant differences were found in grey matter or in cerebrospinal fluid (CSF). Because the superior fronto-occipital and arcuate fasciculi connect the cortical regions that respond to sexual cues, these results suggest (1) that those cortical regions operate as a network for recognizing sexually relevant stimuli and (2) that pedophilia results from a partial disconnection within that network.
Scientists from Queen Mary, University of London, have discovered a new way to separate the therapeutic benefits of cannabis from its mood-altering side-effects.
Cannabis contains a chemical called THC, which binds to, and activates, proteins in the brain known as ‘CB1 cannabinoid receptors’. Activating these receptors can relieve pain and prevent epileptic seizures; but it also causes the mood-altering effect experienced by people who use cannabis as a recreational drug. (Credit: iStockphoto/Dmitriy Norov)
Cannabis contains a chemical called THC, which binds to, and activates, proteins in the brain known as ‘CB1 cannabinoid receptors’. Activating these receptors can relieve pain and prevent epileptic seizures; but it also causes the mood-altering effect experienced by people who use cannabis as a recreational drug.
Now, Professor Maurice Elphick and Dr Michaela Egertová from Queen Mary’s School of Biological and Chemical Sciences may have found a way of separating out the effects of cannabis – a discovery which could lead to the development of new medicines to treat conditions such as epilepsy, obesity and chronic pain. The research is described in the December issue of the journal Molecular Pharmacology.
Working in collaboration with scientists based in the USA*, they have identified a protein that binds to the CB1 receptors in the brain. But unlike THC, this ‘Cannabinoid Receptor Interacting Protein’ or CRIP1a, suppresses the activity of CB1 receptors.
Professor Elphick explains: “Because CRIP1a inhibits the activity of the brain’s cannabinoid receptors, it may be possible to develop drugs that block this interaction, and in turn enhance CB1 activity. This may give patients the pain relief associated with CB1 activity, without the ‘high’ that cannabis users experience.”
Leslie Iversen FRS, Professor of Pharmacology at the University of Oxford and author of The Science of Marijuana, commented on the new findings: “This interesting discovery provides a completely new insight into the regulation of the cannabinoid system in the brain – and could offer a new approach to the discovery of cannabis-based medicines in the future.”
Mol Pharmacol. 2007 Dec;72(6):1557-66. Epub 2007 Sep 25.
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912, USA.
The CB1 cannabinoid receptor is a G-protein coupled receptor that has important physiological roles in synaptic plasticity, analgesia, appetite, and neuroprotection. We report the discovery of two structurally related CB1 cannabinoid receptor interacting proteins (CRIP1a and CRIP1b) that bind to the distal C-terminal tail of CB1. CRIP1a and CRIP1b are generated by alternative splicing of a gene located on chromosome 2 in humans, and orthologs of CRIP1a occur throughout the vertebrates, whereas CRIP1b seems to be unique to primates. CRIP1a coimmunoprecipitates with CB1 receptors derived from rat brain homogenates, indicating that CRIP1a and CB1 interact in vivo. Furthermore, in superior cervical ganglion neurons coinjected with CB1 and CRIP1a or CRIP1b cDNA, CRIP1a, but not CRIP1b, suppresses CB1-mediated tonic inhibition of voltage-gated Ca2+ channels. Discovery of CRIP1a provides the basis for a new avenue of research on mechanisms of CB1 regulation in the nervous system and may lead to development of novel drugs to treat disorders where modulation of CB1 activity has therapeutic potential (e.g., chronic pain, obesity, and epilepsy).
What GWB’s manners do suggest, seems highly likely in the light of genetic research: Americans are Siberians by provenance. 😉 Native Americans should not feel offended by this, we all know, that the Bush Clan is not native to the Americas. Seriously now, did a relatively small number of people from Siberia who trekked across a Bering Strait land bridge some 12,000 years ago give rise to the native peoples of North and South America?
The U-M study, which analyzed genetic data from 29 Native American populations, suggests a Siberian origin is much more likely than a South Asian or Polynesian origin. (Credit: University of Michigan)
Or did the ancestors of today’s native peoples come from other parts of Asia or Polynesia, arriving multiple times at several places on the two continents, by sea as well as by land, in successive migrations that began as early as 30,000 years ago?
The questions — featured on magazine covers and TV specials — have agitated anthropologists, archaeologists and others for decades.
University of Michigan scientists, working with an international team of geneticists and anthropologists, have produced new genetic evidence that’s likely to hearten proponents of the land bridge theory. The study, published online in PLoS Genetics, is one of the most comprehensive analyses so far among efforts to use genetic data to shed light on the topic.
The researchers examined genetic variation at 678 key locations or markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups. The analysis shows:
o genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait — adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.
o a unique genetic variant is widespread in Native Americans across both American continents — suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources. The variant, which is not part of a gene and has no biological function, has not been found in genetic studies of people elsewhere in the world except eastern Siberia.
The researchers say the variant likely occurred shortly prior to migration to the Americas, or immediately afterwards.
“We have reasonably clear genetic evidence that the most likely candidate for the source of Native American populations is somewhere in east Asia,” says Noah A. Rosenberg, Ph.D., assistant professor of human genetics and assistant research professor of bioinformatics at the Center for Computational Medicine and Biology at the U-M Medical School and assistant research professor at the U-M Life Sciences Institute.
“If there were a large number of migrations, and most of the source groups didn’t have the variant, then we would not see the widespread presence of the mutation in the Americas,” he says.
Rosenberg has previously studied the same set of 678 genetic markers used in the new study in 50 populations around the world, to learn which populations are genetically similar and what migration patterns might explain the similarities. For North and South America, the current research breaks new ground by looking at a large number of native populations using a large number of markers.
The pattern the research uncovered — that as the founding populations moved south from the Bering Strait, genetic diversity declined — is what one would expect when migration is relatively recent, says Mattias Jakobsson, Ph.D., co-first author of the paper and a post-doctoral fellow in human genetics at the U-M Medical School and the U-M Center for Computational Medicine and Biology. There has not been time yet for mutations that typically occur over longer periods to diversify the gene pool.
In addition, the study’s findings hint at supporting evidence for scholars who believe early inhabitants followed the coasts to spread south into South America, rather than moving in waves across the interior.
“Assuming a migration route along the coast provides a slightly better fit with the pattern we see in genetic diversity,” Rosenberg says.
The study also found that:
- Populations in the Andes and Central America showed genetic similarities.
- Populations from western South America showed more genetic variation than populations from eastern South America.
- Among closely related populations, the ones more similar linguistically were also more similar genetically.
PLoS Genet 3(11): e185 doi:10.1371/journal.pgen.0030185
Genetic Variation and Population Structure in Native Americans.
We examined genetic diversity and population structure in the American landmass using 678 autosomal microsatellite markers genotyped in 422 individuals representing 24 Native American populations sampled from North, Central, and South America. These data were analyzed jointly with similar data available in 54 other indigenous populations worldwide, including an additional five Native American groups. The Native American populations have lower genetic diversity and greater differentiation than populations from other continental regions. We observe gradients both of decreasing genetic diversity as a function of geographic distance from the Bering Strait and of decreasing genetic similarity to Siberians—signals of the southward dispersal of human populations from the northwestern tip of the Americas. We also observe evidence of: (1) a higher level of diversity and lower level of population structure in western South America compared to eastern South America, (2) a relative lack of differentiation between Mesoamerican and Andean populations, (3) a scenario in which coastal routes were easier for migrating peoples to traverse in comparison with inland routes, and (4) a partial agreement on a local scale between genetic similarity and the linguistic classification of populations. These findings offer new insights into the process of population dispersal and differentiation during the peopling of the Americas.
Studies of genetic variation have the potential to provide information about the initial peopling of the Americas and the more recent history of Native American populations. To investigate genetic diversity and population relationships in the Americas, we analyzed genetic variation at 678 genome-wide markers genotyped in 29 Native American populations. Comparing Native Americans to Siberian populations, both genetic diversity and similarity to Siberians decrease with geographic distance from the Bering Strait. The widespread distribution of a particular allele private to the Americas supports a view that much of Native American genetic ancestry may derive from a single wave of migration. The pattern of genetic diversity across populations suggests that coastal routes might have been important during ancient migrations of Native American populations. These and other observations from our study will be useful alongside archaeological, geological, and linguistic data for piecing together a more detailed description of the settlement history of the Americas.
Bad news for directors of photography and similar professions: even dogs are able to classify complex color photographs and place them into categories in the same way that humans do. Friederike Range and colleagues from the University of Vienna in Austria have shown for the first time that dogs can form abstract concepts. And the dogs successfully demonstrate their learning through the use of computer automated touch-screens, eliminating potential human influence.
Researchers have shown for the first time that dogs can classify complex color photographs and place them into categories in the same way that humans do. (Credit: iStockphoto/Rami Ben Ami)
In order to test whether dogs can visually categorize pictures, and transfer their knowledge to new situations, four dogs were shown landscape and dog photographs, and expected to make a selection on a computer touch-screen.
In the training phase, the dogs were shown both the landscape and dog photographs simultaneously and were rewarded with a food pellet if they selected the dog picture (positive stimulus). The dogs then took part in two tests.
In the first test, the dogs were shown completely different dog and landscape pictures. They continued to reliably select the dog photographs, demonstrating that they could transfer their knowledge gained in the training phase to a new set of visual stimuli, even though they had never seen those particular pictures before.
In the second test, the dogs were shown new dog pictures pasted onto the landscape pictures used in the training phase, facing them with contradictory information: on the one hand, a new positive stimulus as the pictures contained dogs even though they were new dogs; on the other hand, a familiar negative stimulus in the form of the landscape.
When the dogs were faced with a choice between the new dog on the familiar landscape and a completely new landscape with no dog, they reliably selected the option with the dog. These results show that the dogs were able to form a concept i.e. ‘dog’, although the experiment cannot tell us whether they recognized the dog pictures as actual dogs.
The authors also draw some conclusions on the strength of their methodology: “Using touch-screen computers with dogs opens up a whole world of possibilities on how to test the cognitive abilities of dogs by basically completely controlling any influence from the owner or experimenter.” They add that the method can also be used to test a range of learning strategies and has the potential to allow researchers to compare the cognitive abilities of different species using a single method.
Journal reference: Range F et al (2007). Visual categorization of natural stimuli by domestic dogs (Canis familiaris). Animal Cognition (DOI 10.1007/s10071-007-0123-2).
… it’s about self-sabotage. New research shows that how people view their abilities in the workplace impacts how they respond to success. Dr. Jason Plaks, a social psychologist at the University of Toronto and Kristin Stecher, a research scientist at the University of Washington, found that those who thought of their capabilities as fixed were more likely to become anxious and disoriented when faced with dramatic success, causing their subsequent performance to plummet, compared to those who thought of their abilities as changeable.
“People are driven to feel that they can predict and control their outcomes. So when their performance turns out to violate their predictions, this can be unnerving — even if the outcome is, objectively speaking, good news,” says Plaks. He points out that the notion that people often sacrifice their success in the name of greater certainty has some intuitive appeal but it has never been put to a rigorous test.
In one representative study, Plaks and Stecher used a questionnaire to classify participants into those who endorsed a fixed view of intelligence and those who endorsed a malleable view. Then participants took three versions of what was purported to be an intelligence test. After the first test, all participants were given a lesson on how to improve their score. After the second test, participants were randomly assigned to be told that their performance had improved, stayed constant, or declined.
Among those who believed they had improved, those with the fixed view became more anxious and performed worse on the third test than those with the malleable view. However, among participants who believed that their performance had failed to improve, it was the malleable view participants who grew anxious and underperformed compared to their fixed view counterparts.
Plaks notes that if people gain an understanding of how they view their abilities, as fixed or changeable, then they can be aware of the advantages and pitfalls of both perspectives. This in turn may better equip them to adopt alternative theories to explain life’s ups and downs. “Both approaches are highly intuitive and that makes them relatively easy to teach,” says Plaks. “If we can get people to change their underlying assumptions about their abilities then they may improve their performance and that is positive news for those charged with the task of getting people to reach their full potential.”
J Pers Soc Psychol. 2007 Oct;93(4):667-84.
Department of Psychology, University of Toronto, Ontario, Canada. email@example.com
The authors hypothesized that reactions to performance feedback depend on whether one’s lay theory of intelligence is supported or violated. In Study 1, following improvement feedback, all participants generally exhibited positive affect, but entity theorists (who believe that intelligence is fixed) displayed more anxiety and more effort to restore prediction confidence than did incremental theorists (who believe that intelligence is malleable). Similarly, when performance declined, entity theorists displayed more anxiety and compensatory effort than incremental theorists. However, when performance remained rigidly static despite a learning opportunity, incremental theorists evinced more anxiety and compensatory effort than entity theorists. In Study 2, this pattern was replicated when the entity and incremental theories were experimentally manipulated. Study 3 demonstrated that for both groups, theory violation impairs subsequent task performance. Taken together, these studies provide evidence that lay theory violation and damaged prediction confidence have significant and measurable effects on emotion and motivation. The authors discuss the implications of these findings for the literature on achievement success and failure. (PsycINFO Database Record (c) 2007 APA, all rights reserved).
Cambridge researchers have discovered that individuals with obsessive compulsive disorder (OCD) and their close family members have distinctive patterns in their brain structure. This is the first time that scientists have associated an anatomical trait with familial risk for the disorder.
Obsessive compulsive disorder, positive correlation. Positive correlation with obsessive compulsive disorder symptom intensities while contaminants placed in folded hands. WOEXP: 323.
Philip K. McGuire; C. J. Bench; C. D. Frith; I. M. Marks; Richard S. J. Frackowiak; R. J. Dolan. Functional anatomy of obsessive-compulsive phenomena. British Journal of Psychiatry 164(4):459-468, 1994. PMID: 8038933. WOBIB: 104. These new findings could help predict whether individuals are at risk of developing OCD and lead to more accurate diagnosis of the disorder.
Obsessive compulsive disorder is a prevalent illness that affects 2–3 % of the population. OCD patients suffer from obsessions (unwanted, recurrent thoughts, concerns with themes of contamination and ‘germs’, the need to check household items in case of fire or burglary, the symmetrical order of objects or fears of harming oneself or others) as well as compulsions (repetitive behaviours related to the obsessions such as washing and carrying out household safety checks). These symptoms can consume the patient’s life, causing severe distress, alienation and anxiety.
OCD is known to run in families. However, the complex set of genes underlying this heritability and exactly how genes contribute to the illness are unknown. Such genes may pose a risk for OCD by influencing brain structure (e.g. the amount and location of grey matter in the brain) which in turn may impact upon an individual’s ability to perform mental tasks.
In order to explore this idea, the researchers used cognitive and brain measures to determine whether there are biological markers of genetic risk for developing OCD. Using magnetic resonance imaging (MRI), the Cambridge researchers captured pictures of OCD patients’ brains, as well as those of healthy close relatives (a sibling, parent or child) and a group of unrelated healthy people.
Participants also completed a computerised test that involved pressing a left or right button as quickly as possible when arrows appeared. When a beep noise sounded, volunteers had to attempt to stop their responses. This task objectively measured the ability to stop repetitive behaviours.
Both OCD patients and their close relatives fared worse on the computer task than the control group. This was associated with decreases of grey matter in brain regions important in suppressing responses and habits.
Lara Menzies, in the Brain Mapping Unit at the University of Cambridge, explains, “Impaired brain function in the areas of the brain associated with stopping motor responses may contribute to the compulsive and repetitive behaviours that are characteristic of OCD. These brain changes appear to run in families and may represent a genetic risk factor for developing the condition. The current diagnosis of OCD available to psychiatrists is subjective and therefore knowledge of the underlying causes may lead to better diagnosis and ultimately improved clinical treatments.
“However, we have a long way to go to identify the genes contributing to the distinctive brain structure found in OCD patients and their relatives. We also need to identify other contributing factors for OCD, to understand why close relatives that share similar brain structures don’t always develop the disorder.”
Brain. 2007 Sep 13; [Epub ahead of print]
Brain Mapping Unit, University of Cambridge, Department of Psychiatry, Queen Elizabeth II Hospital, Welwyn Garden City, Department of Experimental Psychology, Behavioural and Clinical Neurosciences Institute, University of Cambridge, Cambridge, CB2 3EB, Department of Psychiatry, Addenbrooke’s Hospital, Cambridge, CB2 2QQ and Clinical Unit Cambridge, Addenbrooke’s Centre for Clinical Investigations, Clinical Pharmacology & Discovery Medicine, GlaxoSmithKline, Cambridge CB2 2QQ, UK.
Endophenotypes (intermediate phenotypes) are objective, heritable, quantitative traits hypothesized to represent genetic risk for polygenic disorders at more biologically tractable levels than distal behavioural and clinical phenotypes. It is theorized that endophenotype models of disease will help to clarify both diagnostic classification and aetiological understanding of complex brain disorders such as obsessive-compulsive disorder (OCD). To investigate endophenotypes in OCD, we measured brain structure using magnetic resonance imaging (MRI), and behavioural performance on a response inhibition task (Stop-Signal) in 31 OCD patients, 31 of their unaffected first-degree relatives, and 31 unrelated matched controls. Both patients and relatives had delayed response inhibition on the Stop-Signal task compared with healthy controls. We used a multivoxel analysis method (partial least squares) to identify large-scale brain systems in which anatomical variation was associated with variation in performance on the response inhibition task. Behavioural impairment on the Stop-Signal task, occurring predominantly in patients and relatives, was significantly associated with reduced grey matter in orbitofrontal and right inferior frontal regions and increased grey matter in cingulate, parietal and striatal regions. A novel permutation test indicated significant familial effects on variation of the MRI markers of inhibitory processing, supporting the candidacy of these brain structural systems as endophenotypes of OCD. In summary, structural variation in large-scale brain systems related to motor inhibitory control may mediate genetic risk for OCD, representing the first evidence for a neurocognitive endophenotype of OCD