Neuroscience
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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. ⋯ 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.
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In recent years, an array of brain mapping techniques has been successfully employed to link individual differences in circuit function or structure in the living human brain with individual variations in the human genome. Several proof-of-principle studies provided converging evidence that brain imaging can establish important links between genes and behaviour. ⋯ While the rapidly emerging field of imaging genetics holds great promise, the integration of genetic and neuroimaging data also poses major methodological and conceptual challenges. Therefore, this special issue also focuses on how these challenges can be met to fully exploit the synergism of genetically informed brain imaging.
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Various genes are known to modulate the delicate balance of dopamine in prefrontal cortex and influence cortical information processing. Catechol-O-methyltransferase (COMT) on chromosome 22q11 is the most widely studied of these genes. ⋯ We review how Val158Met has been used to help develop and validate behavioral and neurophysiological phenotypes, as a critical tool in dissecting overlapping neural functional systems and exploring interactions within and between genes, and in exploring how gene effects on cognition are modulated by environmental, demographic and developmental factors. Despite the impressive range of findings, the COMT story is also a bracing reminder of how much work remains to translate this knowledge into practical clinical applications.
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Imaging techniques are a potentially powerful method of identifying phenotypes that are associated with, or are indicative of, a vulnerability to developing major depressive disorder (MDD). Here we identify seven promising MDD-associated traits identified by magnetic resonance imaging (MRI) or positron emission tomography (PET). We evaluate whether these traits are state-independent, heritable endophenotypes, or state-dependent phenotypes that may be useful markers of treatment efficacy. ⋯ Potentially indicative of inter-study variation in MDD etiology or mood state, both increased and decreased binding potential of the 5-HT transporter has been reported. Challenges facing the field include the problem of phenotypic and etiological heterogeneity, technological limitations, the confounding effects of medication, and non-disease related inter-individual variation in brain morphology and function. Further advances are likely as epigenetic, copy-number variant, gene-gene interaction, and genome-wide association (GWA) approaches are brought to bear on imaging data.
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Dopaminergic neurotransmission is widely recognized to be critical to the neurobiology of reward, motivation and addiction. Interestingly, social interactions and related behavior also activate the same neuronal system. Consequently, genetic variations of dopamine neurotransmission are thought influence reward processing that in turn may affect distinctive social behavior and susceptibility to addiction. This review focuses on advances made to date in an effort to link genetic individual variations and reward processing as a possible basis for addictive behaviors.