Science posts

See science posts on page 27 below.

    • 2014
    • M. Economides et al.
    • Arbitration between controlled and impulsive choices
    • The impulse to act for immediate reward often conflicts with more deliberate evaluations that support long-term benefit. The neural architecture that negotiates this conflict remains unclear. One account proposes a single neural circuit that evaluates both immediate and delayed outcomes, while another outlines separate impulsive and patient systems that compete for behavioral control. Here we designed a task in which a complex payout structure divorces the immediate value of acting from the overall long-term value, within the same outcome modality. Using model-based fMRI in humans, we demonstrate separate neural representations of immediate and long-term values, with the former tracked in the anterior caudate (AC) and the latter in the ventromedial prefrontal cortex (vmPFC). Crucially, when subjects' choices were compatible with long-run consequences, value signals in AC were down-weighted and those in vmPFC were enhanced, while the opposite occurred when choice was impulsive. Thus, ..
    • 2015
    • Chelsea L. Robertson et al.
    • Striatal D1- and D2-type Dopamine Receptors Are Linked to Motor Response Inhibition in Human Subjects
    • Motor response inhibition is mediated by neural circuits involving dopaminergic transmission; however, the relative contributions of dopaminergic signaling via D1- and D2-type receptors are unclear. Although evidence supports dissociable contributions of D1- and D2-type receptors to response inhibition in rats and associations of D2-type receptors to response inhibition in humans, the relationship between D1-type receptors and response inhibition has not been evaluated in humans. Here, we tested whether individual differences in striatal D1- and D2-type receptors are related to response inhibition in human subjects, possibly in opposing ways. Thirty-one volunteers participated. Response inhibition was indexed by stop-signal reaction time on the stop-signal task and commission errors on the continuous performance task, and tested for association with striatal D1- and D2-type receptor availability [binding potential referred to nondisplaceable uptake (BPND)], measured using positron em..
    • 2015
    • J Joutsa et al.
    • Dopaminergic function and intertemporal choice
    • The discounting of delayed rewards, also known as temporal or delay discounting, is intrinsic to everyday decisions and can be impaired in pathological states such as addiction disorders. Preclinical and human studies suggest a role for dopaminergic function in temporal discounting but this relationship has not yet been verified using molecular imaging of the living human brain. Here, we evaluated dopaminergic function in temporal discounting using positron emission tomography (PET) with two different dopaminergic ligands assessing three populations in whom temporal discounting has been shown to be impaired. First, we show using [11C]raclopride PET that in pathological gamblers, greater temporal discounting correlates with decreased ventral striatal binding potential, convergent with translational findings of lower nucleus accumbens D2/D3 receptor density in high-impulsive rodents. Temporal discounting also correlates with lower ventral striatal dopamine release in response to high-r..
    • 2015
    • Paola Fuentes-Claramonte et al.
    • Reward Sensitivity Modulates Brain Activity in the Prefrontal Cortex, ACC and Striatum during Task Switching
    • Current perspectives on cognitive control acknowledge that individual differences in motivational dispositions may modulate cognitive processes in the absence of reward contingencies. This work aimed to study the relationship between individual differences in Behavioral Activation System (BAS) sensitivity and the neural underpinnings involved in processing a switching cue in a task-switching paradigm. BAS sensitivity was hypothesized to modulate brain activity in frontal regions, ACC and the striatum. Twenty-eight healthy participants underwent fMRI while performing a switching task, which elicited activity in fronto-striatal regions during the processing of the switch cue. BAS sensitivity was negatively associated with activity in the lateral prefrontal cortex, anterior cingulate cortex and the ventral striatum. Combined with previous results, our data indicate that BAS sensitivity modulates the neurocognitive processes involved in task switching in a complex manner depending on tas..
    • 2015
    • Agnes Norbury et al.
    • Sensation-seeking: Dopaminergic modulation and risk for psychopathology
    • Sensation-seeking (SS) is a personality trait that refers to individual differences in motivation for intense and unusual sensory experiences. It describes a facet of human behaviour that has direct relevance for several psychopathologies associated with high social cost. Here, we first review ways of measuring SS behaviour in both humans and animals. We then present convergent evidence that implicates dopaminergic neurotransmission (particularly via D2-type receptors) in individual differences in SS trait. Both high tonic dopamine levels and hyper-reactive midbrain dopaminergic responses to signals of forthcoming reward are evident in higher sensations-seekers. We propose that differences in the efficacy of striatal dopaminergic transmission may result in differential expression of approach-avoidance reactions to same intensity stimuli. This constitutes a quantitative trait of intensity preference for sensory stimulation that may underlie core features of the SS personality. We revi..
    • 2007
    • Marcus R. Munafò et al.
    • Association of the Dopamine D4 Receptor (DRD4) Gene and Approach-Related Personality Traits: Meta-Analysis and New Data
    • Background Two variants in the dopamine D4 receptor (DRD4) gene have been reported to be associated with human approach-related traits such as novelty seeking and extraversion. However, the strength of evidence for this association remains uncertain. Methods We conducted a meta-analysis of published studies of the association between the DRD4 gene variable number of tandem repeats (VNTR) and C-521T polymorphisms and human approach-related personality traits, including novelty seeking, extraversion, and impulsivity, restricted to adult samples recruited from nonpsychiatric populations, and extended on this literature by attempting to confirm any evidence of association in a replication sample (n = 309) selected for extreme scores on the extraversion subscale of the Eysenck Personality Questionnaire from a large (n = 40,090) population-based sample. Results Our initial meta-analysis supported the association of the DRD4 C-521T polymorphism, but not the VNTR polymorphism, wit..
    • 2002
    • M R Munafò et al.
    • Genetic Polymorphisms and Personality in Healthy Adults: A systematic review and meta-analysis
    • A meta-analysis was conducted on studies reporting data on associations between candidate genes and human personality. Studies reporting data for psychiatric populations (including organic disease and substance abuse) were excluded. A total of 46 studies contributed to the analysis. Pooled data using a fixed-effects model suggested significant associations between the 5HTT LPR, DRD4 c>t, DRD4 length, DRD2 A1/A2, DRD3 A1/A2 polymorphisms and personality traits. A multivariate analysis using a mixed-effects model and including age, sex and predominant ethnicity as covariates was applied to the analyses of 5HTT LPR and DRD4 length polymorphism data. Only the association between the 5HTT LPR polymorphism and avoidance traits remained significant (P=0.038). However, sensitivity analyses excluding data from studies reporting allele frequencies not in Hardy–Weinberg equilibrium and unpublished data resulted in this association no longer being significant. Implications for the desig..
    • 2007
    • Caroline Davis et al.
    • Reward sensitivity and the D2 dopamine receptor gene: A case-control study of binge eating disorder
    • Objective The sensitivity of dopamine reward pathways has been implicated in the risk for various psychiatric disorders including compulsive overeating. The evidence is divided, however, about the direction of causal association. One argument is that a Reward Deficiency Syndrome is the risk factor, while others contend that hyper-sensitivity to reward enhances the motivation for pleasurable activities like eating. Unfortunately, little human research has bridged the gap between psychological and neurobiological approaches to brain reward functioning and disorder. The present study addressed this issue by implementing psychological and biological markers of reward sensitivity in the assessment protocol. Methods Adults with binge eating disorder (BED) were compared to samples of normal-weight and obese controls on two personality measures of reward sensitivity and were genotyped for six markers of the DRD2 dopamine receptor gene. Results Genotype × Group ANOVAs reveale..
    • 1995
    • K Blum et al.
    • The D2 Dopamine Receptor Gene as a Determinant of Reward Deficiency Syndrome
    • The dopaminergic system, and in particular the dopamine D2 receptor, has been profoundly implicated in reward mechanisms in the brain. Dysfunction of the D2 dopamine receptors leads to aberrant substance seeking behaviour (alcohol, drug, tobacco, and food) and other related behaviours (pathological gambling, Tourette's syndrome, and attention deficit hyperactivity disorder). We propose that variants of the D2 dopamine receptor gene are important common genetic determinants of the ‘reward deficiency syndrome’.
    • 2014
    • Brendan Behan et al.
    • Right prefrontal and ventral striatum interactions underlying impulsive choice and impulsive responding
    • Although a multifaceted concept, many forms of impulsivity may originate from interactions between prefrontally-mediated cognitive control mechanisms and limbic, reward or incentive salience approach processes. We describe a novel task that combines reward and control processes to probe this putative interaction. The task involves elements of the monetary incentive delay task (Knutson et al., [2000]: Neuroimage 12:20–27) and the Go/No-Go task (Garavan et al., [1999]: Neuroimage 17:1820–1829) and requires human subjects to make fast responses to targets for financial reward but to occasionally inhibit responding when a NoGo signal rather than a target is presented. In elucidating the dynamic between reward anticipation and control we observed that successful inhibitions on monetary trials, relative to unsuccessful inhibitions, were associated, during the anticipation phase, with increased activation in the right inferior frontal gyrus (rIFG), decreased activity in the vent..