Attention Deficit Hyperactivity Disorder is one of the most widespread psychiatric diagnoses in children. Parents who are faced with the decision to medicate or not medicate their children may wonder if their child – given a bit more time – won’t just “grow out of it”, as many children seem to do. With this in mind, it would obviously be helpful to have biomarkers that could predict whether certain children are more likely to simply acquire better attentional control on their own, and those children that might not. In their paper, “Polymorphisms of the Dopamine D4 Receptor, Clinical Outcome, and Cortical Structure in Attention-Deficit/Hyperactivity Disorder” (Arch Gen Psychiatry Vol 64 (no. 8), Aug 2007) a veritable dream team of child developmental neuroscientists working across several medical institutions report on two such biomarkers. One biomarker is the thickness of the orbitofrontal cortex and posterior parietal cortex. MRI-based measurments of these parts of the brain (just about 5mm thick!) show that children who carry a diagnosis of ADHD have a thinner cortical sheet in these regions. Another biomarker is genetic variation in an intracytoplasmic loop of the G-protein coupled dopamine D4 receptor (DRD4). Children with ADHD are more likely to carry a longer 7-repeat version of this VNTR polymorphism than the more common 4-repeat. Interestingly, the research team found that healthy children who carry the 7-repeat genetic variant also have slightly thinner cortex in the orbitofrontal and posterior parietal cortex, suggesting that this genetic variant may influence the risk of ADHD by way of an effect on cortical development. Additionally, the research team found that the cortex of ADHD children who carry this 7-repeat genetic variant “catches up” from age 8 and eventually falls within the range of healthy children by age 15. Lastly, the team reports that ADHD children who carry the 7-repeat had better clinical outcomes (albeit, many of the ADHD children in this study were treated with medication). Nevertheless, it appears that some progress has been made in identifying biomarkers that might predict favorable developmental trajectories.
Archive for the ‘Posterior parietal cortex’ Category
Posted in COMT, DLPFC, Dopamine, Frontal cortex, Orbitofrontal cortex, Parahippocampal gyrus, Posterior parietal cortex, tagged 23andMe, Dopamine, Frontal lobe, Functional magnetic resonance imaging on January 1, 2008| Leave a Comment »
Holiday time is full of all things delicious and fattening. Should I have a little chocolate now, or wait till later and have a bigger dessert ? Of course, this is not a real forced choice (in my case, the answer too often seems – alas – “I’ll have both!”), but there are many times in life when we are forced to decide between ‘a little now’ or ‘more later’. Sometimes, its clear that the extra $20 in your pocket now would be better utilized later on, after a few years of compound interest. Other times, its not so clear. Consider the recent ruling by the Equal Employment Opportunity Commission, which allows employers to drop retirees’ health coverage once they turn 65 and become eligible for Medicare. Do I save my resources now to provide for my geezerdom healthcare spending, or do I enjoy (spend) my resources now while I’m young and able ? How do I make these decisions ? How does my life experience and genome interact to influence the brain systems that support these computations ? Boettiger and company provide some insight to these questions in their paper, “Immediate Reward Bias in Humans: Fronto-Parietal Networks and a Role for the Catechol-O-Methyltransferase 158Val/Val Genotype” (DOI). The authors utilize an assay that measures a subject’s preference for rewards now or later and use functional brain imaging to seek out brain regions where activity is correlated to preferences for immediate rewards. Dopamine rich brain regions such as the posterior parietal cortex, dorsal prefrontal cortex and rostral parahippocampal gyrus showed (+) correlations while the lateral orbitofrontal cortex showed a (-) correlation. Variation in the dopaminergic enzyme COMT at the rs165688 SNP also showed a correlation with preferences for immediate reward as well as with brain activation. The authors’ results suggest that improving one’s ability to weigh long-term outcomes is a likely therapeutic avenue for helping impulsive folks (like me) optimize our resource allocation. I have not yet had my genome deCODEd or Google-ed, but strongly suspect I am a valine/valine homozygote.
Indeed it seems I am a GG (Valine/Valine) at this site according to 23andMe !