Effect of catechol-O-methyltransferase val158met genotype on attentional control

Interaction of COMT val158met and externalizing behavior: relation to prefrontal brain activity and behavioral performance

A promising approach in neuroimaging studies aimed at understanding effects of single genetic variants on behavior is the study of gene-trait interactions. Variation in the catechol-O-methyl-transferase gene (COMT) is associated with the regulation of dopamine levels in the prefrontal cortex and with cognitive functioning. Given the involvement of dopaminergic neurotransmission in externalizing behavior, a trait characterized by impulsivity and aggression, especially in men, externalizing (as a trait) may index a set of genetic, environmental, and neural characteristics pertinent to understanding phenotypic effects of genetic variation in the COMT gene. In the current study, we used a gene-trait approach to investigate effects of the COMT val(158)met polymorphism and externalizing on brain activity during moments involving low or high demands on cognitive control. In 104 male participants, interference-related activation depended conjointly on externalizing and val(158)met: stronger activation in the dorsal anterior cingulate and lateral prefrontal cortex was found for val/val individuals with high trait externalizing while stronger activation in cingulate motor areas and sensorimotor precuneus was found for met/met individuals with low externalizing. Our results suggest that the val/val genotype, coupled with high levels of trait externalizing, lowers the efficiency of stimulus conflict resolution, whereas the met/met genotype, coupled with low levels of externalizing, lowers the efficiency of response selection.

A combination of dopamine genes predicts success by professional Wall Street traders

What determines success on Wall Street? This study examined if genes affecting dopamine levels of professional traders were associated with their career tenure. Sixty professional Wall Street traders were genotyped and compared to a control group who did not trade stocks. We found that distinct alleles of the dopamine receptor 4 promoter (DRD4P) and catecholamine-O-methyltransferase (COMT) that affect synaptic dopamine were predominant in traders. These alleles are associated with moderate, rather than very high or very low, levels of synaptic dopamine. The activity of these alleles correlated positively with years spent trading stocks on Wall Street. Differences in personality and trading behavior were also correlated with allelic variants. This evidence suggests there may be a genetic basis for the traits that make one a successful trader.

A Potential Role for a Genetic Variation of AKAP5 in Human Aggression and Anger Control

The A-kinase-anchoring protein 5 (AKAP5), a post-synaptic multi-adaptor molecule that binds G-protein-coupled receptors and intracellular signaling molecules has been implicated in emotional processing in rodents, but its role in human emotion and behavior is up to now still not quite clear. Here, we report an association of individual differences in aggressive behavior and anger expression with a functional genetic polymorphism (Pro100Leu) in the human AKAP5 gene. Among a cohort of 527 young, healthy individuals, carriers of the less common Leu allele (15.6% allele frequency) scored significantly lower in the physical aggression domain of the Buss and Perry Aggression Questionnaire and higher in the anger control dimension of the state-trait anger expression inventory. In a functional magnetic resonance imaging experiment we could further demonstrate that AKAP5 Pro100Leu modulates the interaction of negative emotional processing and executive functions. In order to investigate implicit processes of anger control, we used the well-known flanker task to evoke processes of action monitoring and error processing and added task-irrelevant neutral or angry faces in the background of the flanker stimuli. In line with our predictions, Leu carriers showed increased activation of the anterior cingulate cortex (ACC) during emotional interference, which in turn predicted shorter reaction times and might be related to stronger control of emotional interference. Conversely, Pro homozygotes exhibited increased orbitofrontal cortex (OFC) activation during emotional interference, with no behavioral advantage. Immunohistochemistry revealed AKAP5 expression in post mortem human ACC and OFC. Our results suggest that AKAP5 Pro100Leu contributes to individual differences in human aggression and anger control. Further research is warranted to explore the detailed role of AKAP5 and its gene product in human emotion processing.

DNA hypomethylation of MB-COMT promoter in the DNA derived from saliva in schizophrenia and bipolar disorder

The failure in the discovery of etiology of psychiatric diseases, despite extensive genetic studies, has directed the attention of neuroscientists to the contribution of epigenetic modulations, which play important roles in fine-tuning of gene expression in response to environmental factors. Previously, we analyzed 115 human post-mortem brain samples from the frontal lobe and reported DNA hypo methylation of the membrane-bound catechol-O-methyltransferase (MB-COMT) gene promoter, associated with an increased gene expression, as a risk factor for schizophrenia (SCZ) and bipolar disorder (BD). Since most epigenetic modifications are tissue specific and the availability of brain tissue to identify epigenetic aberrations in living subjects is limited, detection of epigenetic abnormalities in other tissues that represent the brain epigenetic marks is one of the critical steps to develop diagnostic and therapeutic biomarkers for mental diseases. Here, hypothesizing that; those factors that lead to the brain MB-COMT promoter DNA hypo-methylation may also cause concurrent epigenetic aberrations in peripheral tissues, we analyzed MB-COMT promoter methylation in DNA derived from the saliva in SCZ, BD and their first-degree relatives (20 cases each) as well as 25 control subjects. Using bisulfite DNA sequencing and quantitative methylation specific PCR (qMSP), we found that similar to the brain, MB-COMT promoter was hypo-methylated (∼50%) in DNA derived from the saliva in SCZ and BD compared to the control subjects (p = 0.02 and 0.037, respectively). These studies suggest that DNA methylation analysis of MB-COMT promoter in saliva can potentially be used as an available epigenetic biomarker for disease state in SCZ and BD.

Control networks and neuromodulators of early development

In adults, most cognitive and emotional self-regulation is carried out by a network of brain regions, including the anterior cingulate, insula, and areas of the basal ganglia, related to executive attention. We propose that during infancy, control systems depend primarily upon a brain network involved in orienting to sensory events that includes areas of the parietal lobe and frontal eye fields. Studies of human adults and alert monkeys have shown that the brain network involved in orienting to sensory events is moderated primarily by the nicotinic cholinergic system arising in the nucleus basalis. The executive attention network is primarily moderated by dopaminergic input from the ventral tegmental area. A change from cholinergic to dopaminergic modulation would be a consequence of this switch of control networks and may be important in understanding early development. We trace the attentional, emotional, and behavioral changes in early development related to this developmental change in regulative networks and their modulators.

Startle response related genes

The startle reaction (also known as the startle response, the startle reflex, or the alarm reaction) is the psychological and physiological response to a sudden unexpected stimulus, such as a flash of light, a loud noise (acoustic startle reflex), or a quick movement near the face. Abnormalities of startle response have been observed in many stress-related mental disorders, such as schizophrenia and post-traumatic stress disorder (PTSD). However, the molecular mechanisms of startle in stress-associated conditions--for example, whether the startle reaction is associated with any gene variance--is still unknown. In this paper, we will carry out a systematic review by retrieving, assessing, and combining, when applicable, individual studies investigating association of the molecular variation of candidate gene with the startle response. The systematic review is based on the search for numerous publications using the keywords "startle gene" on September 15, 2010 using PubMed, which comprises more than 20 million citations for biomedical literature from MEDLINE and life science journals. A total of 486 publications regarding genes associated with startle have been obtained and reviewed here. There are fewer than 20 publications associating genes with the startle response between 1979, when the first valuable paper was published, and 1999. However, publications have dramatically increase from 2001 and reaches over 70 in 2009. We have characterized them into three categories: startle-associated gene studies in humans, in animals, as well as in both human and animals. This review of research strategy may provide the information for identifying a biomarker for startle response, with the objective of translating research into clinical utility: diagnosis and treatment of stress-induced mental disorders.

Inefficiently increased anterior cingulate modulation of cortical systems during working memory in young offspring of schizophrenia patients

BACKGROUND

Children and adolescent offspring of schizophrenia patients are at increased risk for schizophrenia and are also characterized by impairments in brain structure and function. To date, few studies have investigated whether functional interactions between brain regions are intact or altered. Using an established verbal working memory paradigm with variable levels of memory load, we investigated the modulatory effect of activity in cognitive control regions of the brain (specifically the dorsal anterior cingulate cortex) on activity in core working memory regions, in particular the dorsal prefrontal cortex and the parietal lobe.

METHODS

Forty four subjects participated. An n-back task with two levels of working memory load (1- and 2-back) was employed during fMRI (4 T Bruker MedSpec system). Data were processed with SPM5 and the modulatory effects of the anterior cingulate were investigated using psycho-physiological interaction (PPI).

RESULTS

In spite of only subtle activation differences, and no significant differences in performance accuracy, a significant group x memory load interaction in the parietal lobe, indicated aberrantly increased modulatory inputs to this region under conditions of high working memory load in schizophrenia offspring.

DISCUSSION

Increased modulatory inputs from a central control region like the anterior cingulate presumably reflect relative inefficiency in intra-cortical interactions in the vulnerable brain. This inefficiency may reflect a developmentally mediated impairment in functional brain interactions in this important vulnerable population. It is highly plausible that the resultant effect of these altered interactions is an increased vulnerability to impaired brain development, and therefore to psychiatric disorders including schizophrenia.

Genomic and epigenomic instability, fragile sites, schizophrenia and autism

Increasing evidence links genomic and epigenomic instability, including multiple fragile sites regions to neuropsychiatric diseases including schizophrenia and autism. Cancer is the only other disease associated with multiple fragile site regions, and genome and epigenomic instability is a characteristic of cancer. Research on cancer is far more advanced than research on neuropsychiatric disease; hence, insight into neuropsychiatric disease may be derived from cancer research results. Towards this end, this article will review the evidence linking schizophrenia and other neuropsychiatric diseases (especially autism) to genomic and epigenomic instability, and fragile sites. The results of studies on genetic, epigenetic and environmental components of schizophrenia and autism point to the importance of the folate-methionine-transulfuration metabolic hub that is diseases also perturbed in cancer. The idea that the folate-methionine-transulfuration hub is important in neuropsychiatric is exciting because this hub present novel targets for drug development, suggests some drugs used in cancer may be useful in neuropsychiatric disease, and raises the possibility that nutrition interventions may influence the severity, presentation, or dynamics of disease.

Prefrontal dopamine and the dynamic control of human long-term memory

Dopaminergic projections to the prefrontal cortex support higher-order cognitive functions, and are critically involved in many psychiatric disorders that involve memory deficits, including schizophrenia. The role of prefrontal dopamine in long-term memory, however, is still unclear. We used an imaging genetics approach to examine the hypothesis that dopamine availability in the prefrontal cortex selectively affects the ability to suppress interfering memories. Human participants were scanned via functional magnetic resonance imaging while practicing retrieval of previously studied target information in the face of interference from previously studied non-target information. This retrieval practice (RP) rendered the non-target information less retrievable on a later final test-a phenomenon known as retrieval-induced forgetting (RIF). In total, 54 participants were genotyped for the catechol-O-methyltransferase (COMT) Val(108/158)Met polymorphism. The COMT Val(108/158)Met genotype showed a selective and linear gene-dose effect on RIF, with the Met allele, which leads to higher prefrontal dopamine availability, being associated with greater RIF. Mirroring the behavioral pattern, the functional magnetic resonance imaging data revealed that Met allele carriers, compared with Val allele carriers, showed a greater response reduction in inhibitory control areas of the right inferior frontal cortex during RP, suggesting that they more efficiently reduced interference. These data support the hypothesis that the cortical dopaminergic system is centrally involved in the dynamic control of human long-term memory, supporting efficient remembering via the adaptive suppression of interfering memories.

Brain states and hypnosis research

Research in cognitive neuroscience now considers the state of the brain prior to the task an important aspect of performance. Hypnosis seems to alter the brain state in a way which allows external input to dominate over internal goals. We examine how normal development may illuminate the hypnotic state.

Intermediate phenotypes in psychiatric disorders

The small effect size of most individual risk factors for psychiatric disorders likely reflects biological heterogeneity and diagnostic imprecision, which has encouraged genetic studies of intermediate biological phenotypes that are closer to the molecular effects of risk genes than are the clinical symptoms. Neuroimaging-based intermediate phenotypes have emerged as particularly promising because they map risk associated gene effects onto physiological processes in brain that are altered in patients and in their healthy relatives. Recent evidence using this approach has elucidated discrete, dissociable biological mechanisms of risk genes at the level of neural circuitries, and their related cognitive functions. This approach may greatly contribute to our understanding of the genetics and pathophysiology of psychiatric disorders.

Developing Mechanisms of Self-Regulation in Early Life

Children show increasing control of emotions and behavior during their early years. Our studies suggest a shift in control from the brain's orienting network in infancy to the executive network by the age of 3-4 years. Our longitudinal study indicates that orienting influences both positive and negative affect, as measured by parent report in infancy. At 3-4 years of age, the dominant control of affect rests in a frontal brain network that involves the anterior cingulate gyrus. Connectivity of brain structures also changes from infancy to toddlerhood. Early connectivity of parietal and frontal areas is important in orienting; later connectivity involves midfrontal and anterior cingulate areas related to executive attention and self-regulation.

The impact of the Val158Met catechol-O-methyltransferase genotype on neural correlates of sad facial affect processing in patients with bipolar disorder and their relatives

BACKGROUND

The Met allele of the catechol-O-methyltransferase (COMT) valine-to-methionine (Val158Met) polymorphism is known to affect dopamine-dependent affective regulation within amygdala-prefrontal cortical (PFC) networks. It is also thought to increase the risk of a number of disorders characterized by affective morbidity including bipolar disorder (BD), major depressive disorder (MDD) and anxiety disorders. The disease risk conferred is small, suggesting that this polymorphism represents a modifier locus. Therefore our aim was to investigate how the COMT Val158Met may contribute to phenotypic variation in clinical diagnosis using sad facial affect processing as a probe for its neural action.

METHOD

We employed functional magnetic resonance imaging to measure activation in the amygdala, ventromedial PFC (vmPFC) and ventrolateral PFC (vlPFC) during sad facial affect processing in family members with BD (n=40), MDD and anxiety disorders (n=22) or no psychiatric diagnosis (n=25) and 50 healthy controls.

RESULTS

Irrespective of clinical phenotype, the Val158 allele was associated with greater amygdala activation and the Met158 allele with greater signal change in the vmPFC and vlPFC. Signal changes in the amygdala and vmPFC were not associated with disease expression. However, in the right vlPFC the Met158 allele was associated with greater activation in all family members with affective morbidity compared with relatives without a psychiatric diagnosis and healthy controls.

CONCLUSIONS

Our results suggest that the COMT Val158Met polymorphism has a pleiotropic effect within the neural networks subserving emotional processing. Furthermore the Met158 allele further reduces cortical efficiency in the vlPFC in individuals with affective morbidity.

Variation in genes involved in dopamine clearance influence the startle response in older adults

The dopamine transporter (DAT) and the enzyme catechol-O-methyltransferase (COMT) both terminate synaptic dopamine action. Here, we investigated the influence of two polymorphisms in the respective genes: DAT1 (SLC6A3) VNTR and COMT val(158)met (rs4680). Startle magnitudes to intense noise bursts as measured with the eye blink response were recorded during the presentation of pictures of three valence conditions (unpleasant, pleasant and neutral) and during baseline without additional pictorial stimulation in a sample of healthy older adults (N = 94). There was a significant Bonferroni corrected main effect of COMT genotype on the overall startle responses, with met/met homozygotes showing the highest and participants with the val/val genotype showing the lowest startle response, while participants with the val/met genotype displayed intermediate reactions. There was also a DAT1 VNTR main effect, which, after Bonferroni correction, still showed a tendency toward significance with carriers of at least one 9-repeat (R) allele showing smaller overall startle responses compared to 10R/10R homozygotes. Thus, older adult carriers of COMT variants, which result in lower enzyme activity and therefore probably enhanced dopamine signaling, showed stronger startle activity. Although the functional significance of DAT1 VNTR is less defined, our results point to a potential influence of SLC6A3 on startle magnitude.

The effects of the COMT Val108/158Met polymorphism on BOLD activation during working memory, planning, and response inhibition: a role for the posterior cingulate cortex?

Catechol-O-methyl transferase (COMT) val(108/158)met polymorphism impacts on cortical dopamine levels and may influence functional magnetic resonance (fMRI) measures of task-related neuronal activity. Here, we investigate whether COMT genotype influences cortical activations, particularly prefrontal activations, by interrogating its effect across three tasks that have been associated with the dopaminergic system in a large cohort of healthy volunteers. A total of 50 participants (13 met/met, 23 val/met, and 14 val/val) successfully completed N-Back, Go-NoGo, and Tower of London fMRI tasks. Image analysis was performed using statistical parametric mapping. No significant relationships between COMT genotype groups and frontal lobe activations were observed for any contrast of the three tasks studied. However, the val/val group produced significantly greater deactivation of the right posterior cingulate cortex in two tasks: the Go-NoGo (NoGo vs Go deactivation contrast) and N-Back (2-back vs rest deactivation contrast). For the N-Back task, the modulated deactivation cluster was functionally connected to the precuneus, left middle occipital lobe, and cerebellum. These results do not support findings of prefrontal cortical modulation of activity with COMT genotype, but instead suggest that COMT val/val genotype can modulate the activity of the posterior cingulate and may indicate the potential network effects of COMT genotype on the default mode network.

Dysbindin-1 genotype effects on emotional working memory

We combined functional imaging and genetics to investigate the behavioral and neural effects of a dysbindin-1 (DTNBP1) genotype associated with the expression level of this important synaptic protein, which has been implicated in schizophrenia. On a working memory (WM) task for emotional faces, participants with the genotype related to increased expression showed higher WM capacity for happy faces compared with the genotype related to lower expression. Activity in several task-related brain areas with known DTNBP1 expression was increased, including hippocampal, temporal and frontal cortex. Although these increases occurred across emotions, they were mostly observed in areas whose activity correlated with performance for happy faces. This suggests effects of variability in DTNBP1 on emotion-specific WM capacity and region-specific task-related brain activation in humans. Synaptic effects of DTNBP1 implicate that altered dopaminergic and/or glutamatergic neurotransmission may be related to the increased WM capacity. The combination of imaging and genetics thus allows us to bridge the gap between the cellular/molecular and systems/behavioral level and extend the cognitive neuroscience approach to a comprehensive biology of cognition.

Double dissociation of dopamine genes and timing in humans

A number of lines of evidence implicate dopamine in timing [Rammsayer, T. H. Neuropharmacological approaches to human timing. In S. Grondin (Ed.), Psychology of time (pp. 295-320). Bingley, UK: Emerald, 2008; Meck, W. H. Neuropharmacology of timing and time perception. Brain Research, Cognitive Brain Research, 3, 227-242, 1996]. Two human genetic polymorphisms are known to modulate dopaminergic activity. DRD2/ANKK1-Taq1a is a D(2) receptor polymorphism associated with decreased D(2) density in the striatum [Jönsson, E. G., Nothen, M. M., Grunhage, F., Farde, L., Nakashima, Y., Propping, P., et al. Polymorphisms in the dopamine D(2) receptor gene and their relationships to striatal dopamine receptor density of healthy volunteers. Molecular Psychiatry, 4, 290-296, 1999]; COMT Val158Met is a functional polymorphism associated with increased activity of the COMT enzyme such that catabolism of synaptic dopamine is greater in pFC [Meyer-Lindenberg, A., Kohn, P. D., Kolachana, B., Kippenhan, S., McInerney-Leo, A., Nussbaum, R., et al. Midbrain dopamine and prefrontal function in humans: Interaction and modulation by COMT genotype. Nature Neuroscience, 8, 594-596, 2005]. To investigate the role of dopamine in timing, we genotyped 65 individuals for DRD2/ANKK1-Taq1a, COMT Val158Met, and a third polymorphism, BDNF Val66Met, a functional polymorphism affecting the expression of brain-derived neurotrophic factor [Egan, M. F., Kojima, M., Callicott, J. H., Goldberg, T. E., Kolachana, B. S., Bertolino, A., et al. The BDNF val66met polymorphism affects activity-dependent secretion of BDNF and human memory and hippocampal function. Cell, 112, 257-269, 2003]. Subjects were tested on a temporal discrimination task with sub- and supra-second intervals (500- and 2000-msec standards) as well as a spontaneous motor tempo task. We found a double dissociation for temporal discrimination: the DRD2/ANKK1-Taq1a polymorphism (A1+ allele) was associated with significantly greater variability for the 500-msec duration only, whereas the COMT Val158Met polymorphism (Val/Val homozygotes) was associated with significantly greater variability for the 2000-msec duration only. No differences were detected for the BDNF Vall66Met variant. Additionally, the DRD2/ANKK1-Taq1a polymorphism was associated with a significantly slower preferred motor tempo. These data provide a potential biological basis for the distinctions between sub- and supra-second timing and suggest that BG are integral for the former whereas pFC is implicated in the latter.

Neurogenetics and pharmacology of learning, motivation, and cognition

Many of the individual differences in cognition, motivation, and learning-and the disruption of these processes in neurological conditions-are influenced by genetic factors. We provide an integrative synthesis across human and animal studies, focusing on a recent spate of evidence implicating a role for genes controlling dopaminergic function in frontostriatal circuitry, including COMT, DARPP-32, DAT1, DRD2, and DRD4. These genetic effects are interpreted within theoretical frameworks developed in the context of the broader cognitive and computational neuroscience literature, constrained by data from pharmacological, neuroimaging, electrophysiological, and patient studies. In this framework, genes modulate the efficacy of particular neural computations, and effects of genetic variation are revealed by assays designed to be maximally sensitive to these computations. We discuss the merits and caveats of this approach and outline a number of novel candidate genes of interest for future study.

The roles of COMT val158met status and aviation expertise in flight simulator performance and cognitive ability

The polymorphic variation in the val158met position of the catechol-O-methyltransferase (COMT) gene is associated with differences in executive performance, processing speed, and attention. The purpose of this study is: (1) replicate previous COMT val158met findings on cognitive performance; (2) determine whether COMT val158met effects extend to a real-world task, aircraft navigation performance in a flight simulator; and (3) determine if aviation expertise moderates any effect of COMT val158met status on flight simulator performance. One hundred seventy two pilots aged 41-69 years, who varied in level of aviation training and experience, completed flight simulator, cognitive, and genetic assessments. Results indicate that although no COMT effect was found for an overall measure of flight performance, a positive effect of the met allele was detected for two aspects of cognitive ability: executive functioning and working memory performance. Pilots with the met/met genotype benefited more from increased levels of expertise than other participants on a traffic avoidance measure, which is a component of flight simulator performance. These preliminary results indicate that COMT val158met polymorphic variation can affect a real-world task.

DRD2/AKT1 interaction on D2 c-AMP independent signaling, attentional processing, and response to olanzapine treatment in schizophrenia

The D2/AKT1/GSK-3β signaling pathway has been involved in the downstream intracellular effects of dopamine, in the pathophysiology of cognitive deficits and related brain activity in schizophrenia, as well as in response to treatment with antipsychotics. Polymorphisms in the D2 (DRD2 rs1076560) and AKT1 (AKT1 rs1130233) genes have been associated with their respective protein expression and with higher-order cognition and brain function, including attention. Given the strong potential for their relationship, we investigated the interaction of these polymorphisms on multiple molecular and in vivo phenotypes associated with this signaling pathway. We measured AKT1 and GSK-3β proteins and phosphorylation in human peripheral blood mononuclear cells, functional MRI cingulate response during attentional control, behavioral accuracy during sustained attention, and response to 8 wk of treatment with olanzapine in a total of 190 healthy subjects and 66 patients with schizophrenia. In healthy subjects, we found that the interaction between the T allele of DRD2 rs1076560 and the A allele of AKT1 rs1130233 was associated with reduced AKT1 protein levels and reduced phosphorylation of GSK-3β, as well as with altered cingulate response and reduced behavioral accuracy during attentional processing. On the other hand, interaction of these two alleles was associated with greater improvement of Positive and Negative Syndrome Scale scores in patients with schizophrenia after treatment with olanzapine. The present results indicate that these functional polymorphisms are epistatically associated with multiple phenotypes of relevance to schizophrenia. Our results also lend support to further investigation of this downstream molecular pathway in the etiology and treatment of this disorder.

Atypical development of the executive attention network in children with chromosome 22q11.2 deletion syndrome

Impairment in the executive control of attention has been found in youth with chromosome 22q11.2 deletion syndrome (22q11.2DS). However, how this impairment is modified by other factors, particularly age, is unknown. Forty-six typically developing and 53 children with 22q11.2DS were tested with the attention networks task (ANT) in this cross-sectional study. We used logarithmic transform and linear modeling to assess age effects on the executive index of the ANT. Mixed modeling accounted for between subject variability, age, handedness, catecholamine-O-transferase (COMT; codon 158) genotype, and gender on performance for all experimental conditions (cue × flanker) and their two-level interactions. Children with 22q11.2DS showed a relative, age-dependent executive index impairment but not orienting or alerting network index impairments. In factorial analysis, age was a major predictor of overall performance. There was a significant effect of the 22q11.2DS on overall performance. Of note, children with 22q11.2DS are specifically vulnerable to incongruent flanker interference, especially at younger ages. We did not find an overall effect of COMT genotype or handedness. Children with 22q11.2DS demonstrated age-related impairment in the executive control of attention. Future investigation will likely reveal that there are different developmental trajectories of executive attentional function likely related to the development of schizophrenia in 22q11.2DS.

COMT Val108/158Met genotype modulates human sensory gating

BACKGROUND

The catechol-O-methyltransferase (COMT) Val(108/158)Met polymorphism of the dopamine system is essential for prefrontal cortex processing capacity and efficiency. In addition, dopaminergic neurotransmission is also associated with the sensory gating phenomenon protecting the cerebral cortex from information overload. It is however unclear if COMT genotype as a predictor of prefrontal efficiency modulates sensory gating on the level of the auditory cortex, i.e. the gating of the auditory evoked P50 and N100 components.

METHODS

P50 and N100 gating and COMT Val(108/158)Met genotype were determined in 282 healthy subjects of German descent carefully screened for psychiatric or neurological disorders.

RESULTS

A significant effect of the COMT genotype was observed for N100 gating (F=4.510, df=2, p=0.012) but not for P50 gating (F=0.376, df=2, p=0.687). Contrast analysis showed that Met/Met individuals had poorer N100 gating compared to Val/Met (F=-12.931, p=0.003) and the Val/Val individuals (F=-11.056, p=0.057).

CONCLUSION

The results indicate that a high prefrontal efficiency as suggested by the COMT Met/Met genotype is associated with to a poor sensory gating of the N100 component. This would fit in a model where a high prefrontal processing capacity allows a pronounced afferent input of sensory information from the auditory cortex as reflected by a poor sensory gating. The more pronounced prefrontal contribution to the N100 compared to the P50 component may explain the exclusive genotype association with the N100 sensory gating. This preliminary model should be replicated and validated in future investigations.

D2 receptor genotype and striatal dopamine signaling predict motor cortical activity and behavior in humans

OBJECTIVE

Pre-synaptic D2 receptors regulate striatal dopamine release and DAT activity, key factors for modulation of motor pathways. A functional SNP of DRD2 (rs1076560 G>T) is associated with alternative splicing such that the relative expression of D2S (mainly pre-synaptic) vs. D2L (mainly post-synaptic) receptor isoforms is decreased in subjects with the T allele with a putative increase of striatal dopamine levels. To evaluate how DRD2 genotype and striatal dopamine signaling predict motor cortical activity and behavior in humans, we have investigated the association of rs1076560 with BOLD fMRI activity during a motor task. To further evaluate the relationship of this circuitry with dopamine signaling, we also explored the correlation between genotype based differences in motor brain activity and pre-synaptic striatal DAT binding measured with [(123)I] FP-CIT SPECT.

METHODS

Fifty healthy subjects, genotyped for DRD2 rs1076560 were studied with BOLD-fMRI at 3T while performing a visually paced motor task with their right hand; eleven of these subjects also underwent [(123)I]FP-CIT SPECT. SPM5 random-effects models were used for statistical analyses.

RESULTS

Subjects carrying the T allele had greater BOLD responses in left basal ganglia, thalamus, supplementary motor area, and primary motor cortex, whose activity was also negatively correlated with reaction time at the task. Moreover, left striatal DAT binding and activity of left supplementary motor area were negatively correlated.

INTERPRETATION

The present results suggest that DRD2 genetic variation was associated with focusing of responses in the whole motor network, in which activity of predictable nodes was correlated with reaction time and with striatal pre-synaptic dopamine signaling. Our results in humans may help shed light on genetic risk for neurobiological mechanisms involved in the pathophysiology of disorders with dysregulation of striatal dopamine like Parkinson's disease.

Perinatal risk factors interacting with catechol O-methyltransferase and the serotonin transporter gene predict ASD symptoms in children with ADHD

BACKGROUND

Symptoms of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) often co-occur. Given the previously found familiality of ASD symptoms in children with ADHD, addressing these symptoms may be useful for genetic association studies, especially for candidate gene findings that have not been consistently replicated for ADHD.

METHODS

We studied the association of the catechol O-methyltransferase (COMT) Val158Met polymorphism and the serotonin transporter (SLC6A4/SERT/5-HTT) 5-HTTLPR insertion/deletion polymorphism with ASD symptoms in children with ADHD, and whether these polymorphisms would interact with pre- and perinatal risk factors, i.e., maternal smoking during pregnancy and low birth weight. Analyses were performed using linear regression in 207 Dutch participants with combined type ADHD of the International Multicenter ADHD Genetics (IMAGE) study, and repeated in an independent ADHD sample (n =439) selected from the TRracking Adolescents' Individual Lives Survey (TRAILS). Dependent variables were the total and subscale scores of the Children's Social Behavior Questionnaire (CSBQ).

RESULTS

No significant main effects of COMT Val158Met, 5-HTTLPR, maternal smoking during pregnancy and low birth weight on ASD symptoms were found. However, the COMT Val/Val genotype interacted with maternal smoking during pregnancy in increasing stereotyped behavior in the IMAGE sample (p =.008); this interaction reached significance in the TRAILS sample after correction for confounders (p =.02). In the IMAGE sample, the 5-HTTLPR S/S genotype interacted with maternal smoking during pregnancy, increasing problems in social interaction (p =.02), and also interacted with low birth weight, increasing rigid behavior (p =.03). Findings for 5-HTTLPR in the TRAILS sample were similar, albeit for related CSBQ subscales.

CONCLUSIONS

These findings suggest gene-environment interaction effects on ASD symptoms in children with ADHD.

COMT Val158Met polymorphism, cognitive stability and cognitive flexibility: an experimental examination

Background

Dopamine in prefrontal cortex (PFC) modulates core cognitive processes, notably working memory and executive control. Dopamine regulating genes and polymorphisms affecting PFC - including Catechol-O-Methyltransferase (COMT) Val158Met - are crucial to understanding the molecular genetics of cognitive function and dysfunction. A mechanistic account of the COMT Val158Met effect associates the Met allele with increased tonic dopamine transmission underlying maintenance of relevant information, and the Val allele with increased phasic dopamine transmission underlying the flexibility of updating new information. Thus, consistent with some earlier work, we predicted that Val carriers would display poorer performance when the maintenance component was taxed, while Met carriers would be less efficient when rapid updating was required.

Methods

Using a Stroop task that manipulated level of required cognitive stability and flexibility, we examined reaction time performance of patients with schizophrenia (n = 67) and healthy controls (n = 186) genotyped for the Val/Met variation.

Results

In both groups we found a Met advantage for tasks requiring cognitive stability, but no COMT effect when a moderate level of cognitive flexibility was required, or when a conflict cost measure was calculated.

Conclusions

Our results do not support a simple stability/flexibility model of dopamine COMT Val/Met effects and suggest a somewhat different conceptualization and experimental operationalization of these cognitive components.

Antero-posterior EEG spectral power gradient as a correlate of extraversion and behavioral inhibition

Several studies have shown that individual-specific patterns of cortical spectral power distribution are relatively stable across time and experimental conditions. The antero-posterior EEG spectral power gradient (APSPG) emerged as the most prominent feature associated with important personality characteristics. In this study this phenomenon is further investigated in relation to its stability and association with different personality traits. It has been shown that APSPG is generally more pronounced during resting baseline than during inter-trial interval and post-stimulus period. Its association with personality variables is similar for different frequency bands and is mostly preserved during different experimental conditions. Relatively higher oscillatory activity in frontal than in posterior cortical sites is more frequently observed in subjects with higher behavioral inhibition (BIS) and lower Sociability. Source localization analysis showed that both high BIS/low Sociability and high APSPG are associated with higher oscillatory activity in medial cortices associated with emotion processing (mostly the cingulate gyrus). This association could be tentatively explained by higher vigilance and emotional tension in introverted and behaviorally inhibited subjects.

Modulatory effects of modafinil on neural circuits regulating emotion and cognition

Modafinil differs from other arousal-enhancing agents in chemical structure, neurochemical profile, and behavioral effects. Most functional neuroimaging studies to date examined the effect of modafinil only on information processing underlying executive cognition, but cognitive enhancers in general have been shown to have pronounced effects on emotional behavior, too. We examined the effect of modafinil on neural circuits underlying affective processing and cognitive functions. Healthy volunteers were enrolled in this double-blinded placebo-controlled trial (100 mg/day for 7 days). They underwent BOLD fMRI while performing an emotion information-processing task that activates the amygdala and two prefrontally dependent cognitive tasks-a working memory (WM) task and a variable attentional control (VAC) task. A clinical assessment that included measurement of blood pressure, heart rate, the Hamilton anxiety scale, and the profile of mood state (POMS) questionnaire was also performed on each test day. BOLD fMRI revealed significantly decreased amygdala reactivity to fearful stimuli on modafinil compared with the placebo condition. During executive cognition tasks, a WM task and a VAC task, modafinil reduced BOLD signal in the prefrontal cortex and anterior cingulate. Although not statistically significant, there were trends for reduced anxiety, for decreased fatigue-inertia and increased vigor-activity, as well as decreased anger-hostility on modafinil. Modafinil in low doses has a unique physiologic profile compared with stimulant drugs: it enhances the efficiency of prefrontal cortical cognitive information processing, while dampening reactivity to threatening stimuli in the amygdala, a brain region implicated in anxiety.

Behavior, brain, and genome in genomic disorders: finding the correspondences

OBJECTIVE

Within the last decade or so, there has been an acceleration of research attempting to connect specific genetic lesions to the patterns of brain structure and activation. This article comments on observations that have been made based on these recent data and discusses their importance for the field of investigations into developmental disorders.

METHODS

In making these observations, the authors focus on one specific genomic lesion, the well-studied, yet still incompletely understood, 22q11.2 deletion syndrome.

RESULTS

The authors demonstrate the degree of variability in the phenotype that occurs at both the brain and behavioral levels of genomic disorders and describe how this variability is, on close inspection, represented at the genomic level.

CONCLUSION

The authors emphasize the importance of combining genetic/genomic analyses and neuroimaging for research and for future clinical diagnostic purposes and for the purposes of developing individualized, patient-tailored treatment and remediation approaches.

Genetic modulation of GABA levels in the anterior cingulate cortex by GAD1 and COMT

Gamma-aminobutyric acid (GABA)-ergic transmission is critical for normal cortical function and is likely abnormal in a variety of neuropsychiatric disorders. We tested the in vivo effects of variations in two genes implicated in GABA function on GABA concentrations in prefrontal cortex of living subjects: glutamic acid decarboxylase 1 (GAD1), which encodes GAD67, and catechol-o-methyltransferase (COMT), which regulates synaptic dopamine in the cortex. We studied six single nucleotide polymorphisms (SNPs) in GAD1 previously associated with risk for schizophrenia or cognitive dysfunction and the val158met polymorphism in COMT in 116 healthy volunteers using proton magnetic resonance spectroscopy. Two of the GAD1 SNPs (rs1978340 (p=0.005) and rs769390 (p=0.004)) showed effects on GABA levels as did COMT val158met (p=0.04). We then tested three SNPs in GAD1 (rs1978340, rs11542313, and rs769390) for interaction with COMT val158met based on previous clinical results. In this model, rs11542313 and COMT val158met showed significant main effects (p=0.001 and 0.003, respectively) and a trend toward a significant interaction (p=0.05). Interestingly, GAD1 risk alleles for schizophrenia were associated with higher GABA/Cre, and Val-Val homozygotes had high GABA/Cre levels when on a GAD1 risk genotype background (N=6). These results support the importance of genetic variation in GAD1 and COMT in regulating prefrontal cortical GABA function. The directionality of the effects, however, is inconsistent with earlier evidence of decreased GABA activity in schizophrenia.

COMT Val158Met polymorphism and socioeconomic status interact to predict attention deficit/hyperactivity problems in children aged 10-14

The functional Val158Met COMT polymorphism appears to affect a host of behaviours mediated by the pre-frontal cortex, and has been found associated to the risk for disruptive behaviours including ADHD. Parental socioeconomic status (SES) has also been reported as a predictor for the same childhood disorders. In a general population sample of 575 Italian pre-adolescents aged 10-14, we examined the association of the functional Val158Met COMT polymorphism and SES-both as linear and interactive effects-with oppositional defiant problems, conduct problems, and attention deficit/hyperactivity problems, as defined by the newly established Child Behaviour Check-List/6-18 DSM oriented scales. Multivariate- and subsequent univariate-analysis of covariance showed a significant association of COMT x SES interaction with CBCL 6/18 DOS attention deficit/hyperactivity problems (p = 0.004), and revealed higher scores among those children with Val/Val COMT genotype who belonged to low-SES families. We also found a significant association of SES with attention deficit/hyperactivity problems and conduct problems DOS (p = 0.04 and 0.01, respectively). Our data are consistent with a bulk of recent literature suggesting a role of environmental factors in moderating the contribution of specific genetic polymorphisms to human variability in ADHD. While future investigations will refine and better clarify which specific environmental and genetic mechanisms are at work in influencing the individual risk to ADHD in pre-adolescence, these data may contribute to identify/prevent the risk for ADHD problems in childhood.

COMT Val 158 Met polymorphism is related with interpersonal problem solving in schizophrenia

OBJECTIVE

The aim of this study was to investigate associations between COMT Val(158)Met polymorphism, and interpersonal problem solving capacity and cognitive functions in schizophrenia.

METHODS

COMT Val(158)Met polymorphism was studied with ARMS-PCR method in 99 outpatients with schizophrenia. Brief Psychiatric Rating Scale was used to assess symptom severity. The Assessment of Interpersonal Problem Solving Skills (AIPSS) was used to evaluate problem solving capacity. Continuous Performance Test (CPT) and Wisconsin Card Sorting Test (WCST), were used to measure cognition.

RESULTS

Patients with Met/Met genotype had higher AIPSS subscores for detecting the problem, than those with Val/Val at baseline (p=0.02). Met allele was also found to be related with higher AIPSS-receiving skills (p=0.04). Val allele was found to be related with more commission errors in CPT (p=0.03). There was no relation between Val(158)Met polymorphism and WCST and clinical measurements.

CONCLUSION

Our findings suggest that Val allele might be related to poor performance on detecting the interpersonal problems, and attention in schizophrenia.

Monitoring antisaccades: inter-individual differences in cognitive control and the influence of COMT and DRD4 genotype variations

Conscious monitoring of behavior is an essential control function for adaptation and learning. Antisaccade performance was investigated in a large sample of young healthy men in two tasks, one that required conscious error monitoring and one that did not. Conscious error monitoring did not lead to changes in error rate between the two tasks, while other antisaccade parameters were significantly modulated. Application of signal detection theory showed a large inter-individual variability in error detection sensitivity: the majority of individuals were unable to monitor antisaccade errors (chance error detection group), while a minority that successfully monitored their errors (non-chance error detection group) were worse in antisaccade performance in both tasks. These results were explained by the hypothesis of two modes of antisaccade processing favored by each one of the two groups: a mode of conscious cortical cognitive control leading to error monitoring, worse performance and no post-error adaptation and a mode of non-conscious subcortical control leading to chance error monitoring, post-error slowing and better performance of the antisaccade task. This hypothesis was corroborated by the results of the genotype analysis. Error-monitoring sensitivity in the non-chance error detection group was modulated by COMT genotype variations that in turn did not have an effect on error rate. On the other hand, DRD4 genotype variations were related to differences in antisaccade error rate while not affecting error-monitoring sensitivity.

COMT Val158Met polymorphism in relation to activation and de-activation in the prefrontal cortex: A study in patients with schizophrenia and healthy subjects

The Val158Met polymorphism in the COMT gene has been found to be associated with differences in brain activation in both healthy subjects and patients with schizophrenia. The predominant finding has been increased prefrontal activation associated with the Val allele; however, genotype-related de-activations have not been studied. In this study 42 schizophrenia patients and 31 controls underwent fMRI while performing the n-back task. Brain differences related to presence/absence of disease and presence/absence of the Val/Val genotype were examined. Both disease and Val/Val genotype were associated with failure of de-activation in a cluster centred in the medial prefrontal cortex. There was no interaction between disease and genotype at this location, but clusters where there were significant interactions emerged in the right prefrontal cortex and left temporal/parietal cortex. These findings suggest that Val158Met polymorphism influences task-related de-activations in the default mode network in both healthy subjects and schizophrenia patients to an equivalent extent. However the Val158Met polymorphism also has disease-specific effects on DLPFC activation in schizophrenia.

Polymorphisms in dopamine system genes are associated with individual differences in attention in infancy

Knowledge about the functional status of the frontal cortex in infancy is limited. This study investigated the effects of polymorphisms in four dopamine system genes on performance in a task developed to assess such functioning, the Freeze-Frame task, at 9 months of age. Polymorphisms in the catechol-O-methyltransferase (COMT) and the dopamine D4 receptor (DRD4) genes are likely to impact directly on the functioning of the frontal cortex, whereas polymorphisms in the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes might influence frontal cortex functioning indirectly via strong frontostriatal connections. A significant effect of the COMT valine(1)methionine (Val 158 Met) polymorphism was found. Infants with the Met/Met genotype were significantly less distractible than infants with the Val/Val genotype in Freeze-Frame trials presenting an engaging central stimulus. In addition, there was an interaction with the DAT1 3; variable number of tandem repeats polymorphism; the COMT effect was present only in infants who did not have two copies of the DAT1 10-repeat allele. These findings indicate that dopaminergic polymorphisms affect selective aspects of attention as early as infancy and further validate the Freeze-Frame task as a frontal cortex task.

Functional variation of the dopamine D2 receptor gene is associated with emotional control as well as brain activity and connectivity during emotion processing in humans

Personality traits related to emotion processing are, at least in part, heritable and genetically determined. Dopamine D(2) receptor signaling is involved in modulation of emotional behavior and activity of associated brain regions such as the amygdala and the prefrontal cortex. An intronic single nucleotide polymorphism within the D(2) receptor gene (DRD2) (rs1076560, guanine > thymine or G > T) shifts splicing of the two protein isoforms (D(2) short, mainly presynaptic, and D(2) long) and has been associated with modulation of memory performance and brain activity. Here, our aim was to investigate the association of DRD2 rs1076560 genotype with personality traits of emotional stability and with brain physiology during processing of emotionally relevant stimuli. DRD2 genotype and Big Five Questionnaire scores were evaluated in 134 healthy subjects demonstrating that GG subjects have reduced "emotion control" compared with GT subjects. Functional magnetic resonance imaging in a sample of 24 individuals indicated greater amygdala activity during implicit processing and greater dorsolateral prefrontal cortex (DLPFC) response during explicit processing of facial emotional stimuli in GG subjects compared with GT. Other results also demonstrate an interaction between DRD2 genotype and facial emotional expression on functional connectivity of both amygdala and dorsolateral prefrontal regions with overlapping medial prefrontal areas. Moreover, rs1076560 genotype is associated with differential relationships between amygdala/DLPFC functional connectivity and emotion control scores. These results suggest that genetically determined D(2) signaling may explain part of personality traits related to emotion processing and individual variability in specific brain responses to emotionally relevant inputs.

Prefrontal-related functional connectivities within the default network are modulated by COMT val158met in healthy young adults

Previous studies have supported the concept that the default network is an intrinsic brain system that participates in internal modes of cognition. Neural activity and connectivity within the default network, which are correlated with cognitive ability even at rest, may be plausible intermediate phenotypes that will enable us to understand the genetic mechanisms of individuals' cognitive function or the risk for genetic brain diseases. Using resting functional magnetic resonance imaging and imaging genetic paradigms, we investigated whether individual default network connectivity was modulated by COMT val(158)met in 57 healthy young subjects. Compared with COMT heterozygous individuals, homozygous val individuals showed significantly decreased prefrontal-related connectivities, which primarily occurred between prefrontal regions and the posterior cingulate/restrosplenial cortices. Further analyses of the topological characteristics of the default network showed homozygous val individuals had significantly fewer node degrees in the prefrontal regions. This finding may partially elucidate previous reports that the COMT val variant is associated with inefficient prefrontal information processing and poor cognitive performance. Our findings suggest that default network connectivity that involves the prefrontal cortex is modulated by COMT val(158)met through differential effects on prefrontal dopamine levels.

Emotion-related self-regulation and its relation to children's maladjustment

The development of children's emotion-related self-regulation appears to be related to, and likely involved in, many aspects of children's development. In this review, the distinction between effortful self-regulatory processes and those that are somewhat less voluntary is discussed, and literature on the former capacities is reviewed. Emotion-related self-regulation develops rapidly in the early years of life and improves more slowly into adulthood. Individual differences in children's self-regulation are fairly stable after the first year or two of life. Such individual differences are inversely related to at least some types of externalizing problems. Findings for internalizing problems are less consistent and robust, although emotion-related self-regulation appears to be inversely related to internalizing problems after the early years. Self-regulatory capacities have been related to both genetic and environmental factors and their interaction. Some interventions designed to foster self-regulation and, hence, reduce maladjustment, have proved to be at least partially effective.

Emotion-related self-regulation and its relation to children's maladjustment

The development of children's emotion-related self-regulation appears to be related to, and likely involved in, many aspects of children's development. In this review, the distinction between effortful self-regulatory processes and those that are somewhat less voluntary is discussed, and literature on the former capacities is reviewed. Emotion-related self-regulation develops rapidly in the early years of life and improves more slowly into adulthood. Individual differences in children's self-regulation are fairly stable after the first year or two of life. Such individual differences are inversely related to at least some types of externalizing problems. Findings for internalizing problems are less consistent and robust, although emotion-related self-regulation appears to be inversely related to internalizing problems after the early years. Self-regulatory capacities have been related to both genetic and environmental factors and their interaction. Some interventions designed to foster self-regulation and, hence, reduce maladjustment, have proved to be at least partially effective.

ADHD candidate gene (DRD4 exon III) affects inhibitory control in a healthy sample

BACKGROUND

Dopamine is believed to be a key neurotransmitter in the development of attention-deficit/hyperactivity disorder (ADHD). Several recent studies point to an association of the dopamine D4 receptor (DRD4) gene and this condition. More specifically, the 7 repeat variant of a variable number of tandem repeats (VNTR) polymorphism in exon III of this gene is suggested to bear a higher risk for ADHD. In the present study, we investigated the role of this polymorphism in the modulation of neurophysiological correlates of response inhibition (Go/Nogo task) in a healthy, high-functioning sample.

RESULTS

Homozygous 7 repeat carriers showed a tendency for more accurate behavior in the Go/Nogo task compared to homozygous 4 repeat carriers. Moreover, 7 repeat carriers presented an increased nogo-related theta band response together with a reduced go-related beta decrease.

CONCLUSIONS

These data point to improved cognitive functions and prefrontal control in the 7 repeat carriers, probably due to the D4 receptor's modulatory role in prefrontal areas. The results are discussed with respect to previous behavioral data on this polymorphism and animal studies on the impact of the D4 receptor on cognitive functions.

The effect of the COMT val(158)met polymorphism on neural correlates of semantic verbal fluency

Variation in the val(158)met polymorphism of the COMT gene has been found to be associated with cognitive performance. In functional neuroimaging studies, this dysfunction has been linked to signal changes in prefrontal areas. Given the complex modulation and functional heterogeneity of frontal lobe systems, further specification of COMT gene-related phenotypes differing in prefrontally mediated cognitive performance are of major interest. Eighty healthy individuals (54 men, 26 women; mean age 23.3 years) performed an overt semantic verbal fluency task while brain activation was measured with functional magnetic resonance imaging (fMRI). COMT val(158)met genotype was determined and correlated with brain activation measured with fMRI during the task. Although there were no differences in performance, brain activation in the left inferior frontal gyrus [Brodmann area 10] was positively correlated with the number of val alleles in the COMT gene. COMT val(158)met status modulates brain activation during the language production on a semantic level in an area related to executive functions.

Variations in catechol-O-methyltransferase gene interact with parenting to influence attention in early development

Attention influences many aspects of cognitive development. Variations in the catechol-O-methyltransferase (COMT) gene, known to affect dopamine neurotransmission, have frequently been found to influence attention in adults and older children. In this paper we examined 2 year old children and found that variation in the COMT gene influenced attention in a task involving looking to a sequence of visual stimuli. Because the influence of another dopamine-related gene (DRD4) has been shown to interact with parenting quality at this age, we explored parenting in relation to variations in the COMT gene. Variations in COMT interacted with parenting quality to influence our attention measure. The Val(108/158)Met polymorphism of COMT is commonly used to determine allelic groups, but recently haplotypes of several polymorphisms within this gene have been shown to be more strongly associated with perceived pain. Since attention and pain both involve the activation of the anterior cingulate gyrus in imaging studies, we compared the Val(108/158)Met influence with the COMT haplotypes and found the latter to be more predictive of attention. Our results confirm that important aspects of cognitive development including attention depend on the interaction of genes and early environment.

The effectiveness of exercise intervention on inhibitory control in children with developmental coordination disorder: using a visuospatial attention paradigm as a model

Children with developmental coordination disorder (DCD) have been demonstrated to show a deficit of inhibitory control in volitional shifts of attention. The aim of this study was to use ecological intervention to investigate the efficacy of table-tennis training on treating both problems with attentional networks and motor disorder in children with DCD. Forty-three children aged 9-10 years old were screened using the Movement Assessment Battery for Children and divided into DCD (n=27) and typically developing (TD, n=16) groups. Children with DCD were then quasi-randomly assigned to either a DCD-training group who underwent a ten-week table-tennis training program with a frequency of 3 times a week or a DCD non-training group. Before and after training, the capacity of inhibitory control was examined with the endogenous Posner paradigm task for DCD and TD groups. Table-tennis training resulted in significant improvement of cognitive and motor functions for the children with DCD. The study demonstrated that exercise intervention employed within the school setting can benefit the inhibitory control and motor performance in children with DCD. However, future research efforts should continue to clarify whether the performance gains could be maintained over time.

Introduction: genes, cognition and neuropsychiatry

Numerous genes modulate dopamine and consequently prefrontal cortical function. Some of these genes - notably catechol-O-methyltransferase - have been shown to impact a variety of core cognitive processes that are dependent upon the prefrontal cortex. This demonstration that a single functional polymorphism can contribute so dramatically to individual differences heralds a new era for neuropsychiatry. Although enormous detail remains to be discovered about these various genes that regulate neurotransmitters, how they interact and how they affect brain systems, there is much excitement and promise regarding new neuropsychopharmacological possibilities. However, this new research program is magnitudes more complex than any enterprise embarked on hitherto and requires the development, validation and deployment of novel behavioural and neurophysiological phenotypes in order to unravel the pathologies within neural functional systems. This research foundation is essential if these genetic breakthroughs are to be translated to successful clinical agents.

Genetic vulnerability to affective psychopathology in childhood: a combined voxel-based morphometry and functional magnetic resonance imaging study

BACKGROUND

The majority of affective psychopathology is rooted early in life and first emerges during childhood and adolescence. However, little is known about how genetic vulnerability affects brain structure and function in childhood since the vast majority of studies published so far have been conducted on adult participants. The present investigation examined for the first time the effects of catechol-O-methyltransferase (COMT) valine (val) 158 methionine (met) (val158met) polymorphism, which has been shown to moderate predisposition to negative mood and affective disorders, on brain structure and function in children.

METHODS

Voxel-based morphometry and functional magnetic resonance imaging were used to measure gray matter volume and emotional reactivity in 50 children aged between 10 and 12 years. We tested the hypothesis that met158 allele affects structural brain development and confers heightened reactivity within the affective frontolimbic circuit in children.

RESULTS

The met158 allele was positively associated with gray matter volume in the left hippocampal head where genotype accounted for 59% of interindividual variance. In addition, the met158 allele was positively associated with neuronal responses to fearful relative to neutral facial expressions in the right parahippocampal gyrus where genotype accounted for 14% of the interindividual variance.

CONCLUSIONS

These results indicate that the met158 allele is associated with increased gray matter volume and heightened reactivity during emotional processing within the limbic system in children as young as 10 to 12 years of age. These findings are consistent with the notion that genetic factors affect brain function to moderate vulnerability to affective psychopathology from childhood.

Epistasis between the DAT 3' UTR VNTR and the COMT Val158Met SNP on cortical function in healthy subjects and patients with schizophrenia

Dopamine has a crucial role in the modulation of neurocognitive function, and synaptic dopamine activity is normally regulated by the dopamine transporter (DAT) and catechol-O-methyltransferase (COMT). Perturbed dopamine function is a key pathophysiological feature of schizophrenia. Our objectives were (i) to examine epistasis between the DAT 3' UTR variable number of tandem repeats (VNTR) and COMT Val158Met polymorphisms on brain activation during executive function, and (ii) to then determine the extent to which such interaction is altered in schizophrenia. Regional brain response was measured by using blood-oxygen-level-dependent fMRI during an overt verbal fluency task in 85 subjects (44 healthy volunteers and 41 patients with DSM-IV schizophrenia), and inferences were estimated by using an ANOVA in SPM5. There was a significant COMT x DAT nonadditive interaction effect on activation in the left supramarginal gyrus, irrespective of diagnostic group (Z-score = 4.3; family-wise error (FWE) p = 0.03), and in healthy volunteers alone (Z-score = 4.7; FWEp = 0.006). In this region, relatively increased activation was detected only when COMT Met-158/Met-158 subjects also carried the 9-repeat DAT allele, or when, reversely, Val-158/Val-158 subjects carried the 10/10-repeat genotype. Also, there was a significant diagnosis x COMT x DAT nonadditive interaction in the right orbital gyrus (Z-score = 4.3; FWEp = 0.04), where, only within patients, greater activation was only associated with a 9-repeat allele and Val-158 conjunction, and with a 10-repeat and Met-158 conjunction (Z-score = 4.3; FWE p = 0.04). These data demonstrate that COMT and DAT genes interact nonadditively to modulate cortical function during executive processing, and also, that this effect is significantly altered in schizophrenia, which may reflect abnormal dopamine function in the disorder.

Nonlinear response of the anterior cingulate and prefrontal cortex in schizophrenia as a function of variable attentional control

Previous studies have reported abnormal prefrontal and cingulate activity during attentional control processing in schizophrenia. However, it is not clear how variation in attentional control load modulates activity within these brain regions in this brain disorder. The aim of this study in schizophrenia is to investigate the impact of increasing levels of attentional control processing on prefrontal and cingulate activity. Blood oxygen level-dependent (BOLD) responses of 16 outpatients with schizophrenia were compared with those of 21 healthy subjects while performing a task eliciting increasing levels of attentional control during event-related functional magnetic resonance imaging at 3 T. Results showed reduced behavioral performance in patients at greater attentional control levels. Imaging data indicated greater prefrontal activity at intermediate attentional control levels in patients but greater prefrontal and cingulate responses at high attentional control demands in controls. The BOLD activity profile of these regions in controls increased linearly with increasing cognitive loads, whereas in patients, it was nonlinear. Correlation analysis consistently showed differential region and load-specific relationships between brain activity and behavior in the 2 groups. These results indicate that varying attentional control load is associated in schizophrenia with load- and region-specific modification of the relationship between behavior and brain activity, possibly suggesting earlier saturation of cognitive capacity.