br Discussion The COMT Val Met polymorphism

Discussion The COMT Val158Met polymorphism is related to the PFC cognitive functions. Studies that associated the COMT polymorphism and cognition in clinical (Nolan et al., 2004; Rosa et al., 2010; Sagud et al., 2010; Sun et al., 2014) and non-clinical (Malloy-Diniz et al., 2013; Costa et al., 2016) populations indicated an association between the PFC state and the type of cognitive processing required. Differences in the patterns of the prefrontal cortical activation and higher order cognitive performance are observed (Egan et al., 2001; Rosa et al., 2010), as the effects of the COMT genotypes on information processing are critically dependent on the nature of the information being processed (Tunbridge et al., 2006). Although the cognitive areas are closely connected to the areas of motor planning and execution, little is known about the association between the COMT Val158Met polymorphism and motor behavior. Also, investigation of the relation of the COMT Tankyrase Inhibitors 49 on the roles played by phasic and tonic DA and the type of motor task is needed. Thus, this study aimed to review studies that investigated the association between the COMT Val158Met polymorphism and motor behavior. The results were consistent regarding the association between the COMT polymorphism and motor behavior. That is, all the investigated studies showed some sort of association between these constructs. However, the results were inconsistent in relation to our hypotheses that the COMT Val158Met polymorphism would be associated with: (a) stability in sequential motor learning and (b) flexibility in visuomotor adaptation. Inconsistencies were found regarding the association between the roles played by phasic and tonic DA and the nature of the task, as half of the studies did not show an association between Met/Met and Val/Val genotypes and cognitive stability and flexibility, respectively. Moreover, opposing to the cognitive studies, the motor behavior studies showed no association between the COMT polymorphism and WM. Furthermore, interactions of the COMT genotypes and genotypes of different polymorphisms seem to predict motor performance and motor adaptation by means of a polygenic index that represents the number of high performance alleles.
Conclusion
Funding This study was supported by Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) (grant APQ-03305-15).
Conflict of interest
Introduction Problem gambling represents a significant public health problem characterized by persistent and recurrent maladaptive patterns of gambling and is associated with impaired functioning (Hodgins et al., 2011). Problem gambling-related functional impairment may impact on every aspect of a person\'s life and many feel ill equipped to cope (Thon et al., 2014). Neuropsychological studies of adults with problem gambling indicate impairments in many cognitive areas including inhibition, working memory, decision-making, cognitive flexibility, and executive planning (Ledgerwood et al., 2012, Goudriaan et al., 2006). Dopamine is a neurotransmitter that regulates cognitive functions dependent on the fronto-striatal circuitry, and dopamine dysregulation has been suggested as playing a key role in a range of impulsive behaviors, particularly those related to inhibitory control and decision-making (Malloy-Diniz et al., 2013). The catechol-O-methyltransferase (COMT) enzyme plays a unique role in the regulation of dopamine in the prefrontal cortex (Tunbridge et al., 2004) and has been posited as a potential pharmacological target for the treatment of cognitive dysfunction in a number of psychiatric illnesses, especially those characterized by high rates of impulsivity (Scheggia et al., 2012). A recent treatment study for problem gambling found that the COMT inhibitor, tolcapone, improved gambling behavior and that this improvement was associated with enhanced fronto-parietal brain activation during planning (Grant et al., 2013).