Science posts

See science posts on page 21 below.

    • 2005
    • Reuter, Martin et al.
    • Association of the functional catechol-O-methyltransferase VAL158MET polymorphism with the personality trait of extraversion
    • Across different personality theories, there is agreement that dopamine is the neurochemical basis of extraversion. However, evidence from molecular genetics for the validity of this hypothesis is far from convincing. The functional polymorphism of the catechol-O-methyltransferase gene (COMT VAL158MET) has not been related to extraversion before, although it is a promising candidate gene locus for extraversion because of its great influence on the catabolism of dopamine. In a sample of n=363 healthy study participants, the catechol-O-methyltransferase VAL158MET polymorphism was related to extraversion and novelty seeking. Results showed a significant association between catechol-O-methyltransferase, extraversion and the subscale exploratory excitement (NS1) of novelty seeking but not with the total novelty-seeking scale supporting the psychometric analyses of the personality scales. The findings support the hypothesis that the dopamine system is involved in positive emotionality a..
    • 2006
    • Jan B. Engelmann
    • Personality Predicts Responsivity of the Brain Reward System
    • Food is a primary reward. There is no doubt that animals and humans find pleasure in the consumption of food and will work hard to obtain it under certain conditions. Foods differ in their rewarding value, with high-calorie foods typically being highly rewarding. In modern societies, food is readily available and food-related advertisements are ubiquitous. Thus, we can be easily motivated to consume rewarding foods even regardless of satiety. The over-consumption of appetizing high-caloric foods has contributed to the dramatic increase in obesity within the past 20 years, making obesity a top 10 global health threat, according to the World Health Organization.
    • 2008
    • Hidehiko Takahashi et al.
    • Differential Contributions of Prefrontal and Hippocampal Dopamine D1 and D2 Receptors in Human Cognitive Functions
    • Dopamine D1 receptors in the prefrontal cortex (PFC) are important for prefrontal functions, and it is suggested that stimulation of prefrontal D1 receptors induces an inverted U-shaped response, such that too little or too much D1 receptor stimulation impairs prefrontal functions. Less is known of the role of D2 receptors in cognition, but previous studies showed that D2 receptors in the hippocampus (HPC) might play some roles via HPC–PFC interactions. We measured both D1 and D2 receptors in PFC and HPC using positron emission tomography in healthy subjects, with the aim of elucidating how regional D1 and D2 receptors are differentially involved in frontal lobe functions and memory. We found an inverted U-shaped relation between prefrontal D1 receptor binding and Wisconsin Card Sorting Test performance. However, prefrontal D2 binding has no relation with any neuropsychological measures. Hippocampal D2 receptor binding showed positive linear correlations not only with memory fu..
    • 2015
    • Valentina Mione et al.
    • Both the COMT Val158Met single-nucleotide polymorphism and sex-dependent differences influence response inhibition
    • Reactive and proactive controls of actions are cognitive abilities that allow one to deal with a continuously changing environment by adjusting already programmed actions. They also set forthcoming actions by evaluating the outcome of the previous ones. Earlier studies highlighted sex-related differences in the strategies and in the pattern of brain activation during cognitive tasks involving reactive and proactive control. To further identify sex-dependent characteristics in the cognitive control of actions, in this study, we have assessed whether/how differences in performance are modulated by the COMT Val158Met single-nucleotide polymorphism (SNP), a genetic factor known to influence the functionality of the dopaminergic system—in particular, at the level of the prefrontal cortex. Two groups of male and female participants were sorted according to their genotype (Val/Val, Val/Met, and Met/Met) and tested in a stop signal task, a consolidated tool for measuring executive ..
    • 2012
    • David M. Cole et al.
    • Orbitofrontal Connectivity with Resting-State Networks Is Associated with Midbrain Dopamine D3 Receptor Availability
    • Animal research and human postmortem evidence highlight the importance of brain dopamine D3 receptor (D3R) function in multiple neuropsychiatric disorders, including addiction. Separate anatomical and functional neuroimaging findings implicate disrupted frontal cortical connectivity with distributed brain networks in processes relevant for these diseases. This potential conjunction between molecular and functional markers has not, however, been tested directly. Here, we used a novel combination of [11C]-(+)-PHNO positron emission tomography and resting-state functional magnetic resonance imaging in the same healthy individuals to investigate whether differences in midbrain D3R availability are associated with functional interactions between large-scale networks and regions involved in reward processing and cognition. High midbrain D3R availability was associated with reduced functional connectivity between orbitofrontal cortex (OFC) and networks implicated in cognitive control and sa..
    • 2011
    • Evan M. Gordon et al.
    • Effect of Dopamine Transporter Genotype on Intrinsic Functional Connectivity Depends on Cognitive State
    • Functional connectivity between brain regions can define large-scale neural networks and provide information about relationships between those networks. We examined how relationships within and across intrinsic connectivity networks were 1) sensitive to individual differences in dopaminergic function, 2) modulated by cognitive state, and 3) associated with executive behavioral traits. We found that regardless of cognitive state, connections between frontal, parietal, and striatal nodes of Task-Positive networks (TPNs) and Task-Negative networks (TNNs) showed higher functional connectivity in 10/10 homozygotes of the dopamine transporter gene, a polymorphism influencing synaptic dopamine, than in 9/10 heterozygotes. However, performance of a working memory task (a state requiring dopamine release) modulated genotype differences selectively, such that cross-network connectivity between TPNs and TNNs was higher in 10/10 than 9/10 subjects during working memory but not during rest. This ..
    • 2002
    • David Williams et al.
    • Dopamine‚Äźdependent changes in the functional connectivity between basal ganglia and cerebral cortex in humans
    • We test the hypothesis that interaction between the human basal ganglia and cerebral cortex involves activity in multiple functional circuits characterized by their frequency of oscillation, phase characteristics, dopamine dependency and topography. To this end we took recordings from macroelectrodes (MEs) inserted into the subthalamic nucleus (STN) in eight awake patients following functional neurosurgery for Parkinson’s disease. An EEG was also recorded, as were the signals from MEs in the globus pallidus interna (GPi) in two of the cases. Coherence between EEG and ME potentials was apparent in three major frequency bands, 2–10 Hz, 10–30 Hz and 70–85 Hz. These rhythmic activities differed in their cortical topography, although coherence was always strongest over the midline. Coherence between EEG and ME potentials in the 70–85 Hz band was only recorded in patients treated with levodopa. Cortical activity phase led that in the basal ganglia in those osc..
    • 2012
    • David M. Cole et al.
    • Dopamine-Dependent Architecture of Cortico-Subcortical Network Connectivity
    • Maladaptive dopaminergic mediation of reward processing in humans is thought to underlie multiple neuropsychiatric disorders, including addiction, Parkinson's disease, and schizophrenia. Mechanisms responsible for the development of such disorders may depend on individual differences in neural signaling within large-scale cortico-subcortical circuitry. Using a combination of functional neuroimaging and pharmacological challenges in healthy volunteers, we identified opposing dopamine agonistic and antagonistic neuromodulatory effects on distributed functional interactions between specific subcortical regions and corresponding neocortical “resting-state” networks, known to be involved in distinct aspects of cognition and reward processing. We found that, relative to a placebo, levodopa and haloperidol challenges, respectively, increased or decreased the functional connectivity between (1) the midbrain and a “default mode” network, (2) the right caudate and a rig..
    • 2008
    • Atsuko Nagano-Saito et al.
    • Dopamine Depletion Impairs Frontostriatal Functional Connectivity during a Set-Shifting Task
    • We investigated the effect of transient dopamine depletion on functional connectivity during performance of the Wisconsin Card Sorting Task. Functional magnetic resonance imaging data were analyzed as a psychophysiological interaction, a statistical method used to identify functional connectivity during experimental manipulations. Nineteen healthy subjects were scanned, double blind, on 2 separate days: once after drinking an amino acid mixture deficient in the dopamine precursors tyrosine and phenylalanine, and once after drinking a nutritionally balanced mixture. In the balanced drink session, statistically significant connectivity between the frontal lobes and striatum was observed during set shifting, and the greater the prefrontostriatal connectivity, the faster the response time after a shift. Neither of these associations were observed after dopamine depletion. Moreover, dopamine depletion also reduced the degree of deactivation in areas normally suppressed during attention-de..
    • 2008
    • Daniel Durstewitz et al
    • The Dual-State Theory of Prefrontal Cortex Dopamine Function with Relevance to Catechol-O-Methyltransferase Genotypes and Schizophrenia
    • There is now general consensus that at least some of the cognitive deficits in schizophrenia are related to dysfunctions in the prefrontal cortex (PFC) dopamine (DA) system. At the cellular and synaptic level, the effects of DA in PFC via D1- and D2-class receptors are highly complex, often apparently opposing, and hence difficult to understand with regard to their functional implications. Biophysically realistic computational models have provided valuable insights into how the effects of DA on PFC neurons and synaptic currents as measured in vitro link up to the neural network and cognitive levels. They suggest the existence of two discrete dynamical regimes, a D1-dominated state characterized by a high energy barrier among different network patterns that favors robust online maintenance of information and a D2-dominated state characterized by a low energy barrier that is beneficial for flexible and fast switching among representational states. These predictions are consistent with ..