Science posts

See science posts on page 37 below.

    • 2010
    • Wei-Chun Wang et al.
    • The Medial Temporal Lobe Supports Conceptual Implicit Memory
    • The medial temporal lobe (MTL) is generally thought to be critical for explicit, but not implicit, memory. Here, we demonstrate that the perirhinal cortex (PRc), within the MTL, plays a role in conceptually-driven implicit memory. Amnesic patients with MTL lesions that converged on the left PRc exhibited deficits on two conceptual implicit tasks (i.e., exemplar generation and semantic decision). A separate functional magnetic resonance imaging (fMRI) study in healthy subjects indicated that PRc activation during encoding of words was predictive of subsequent exemplar generation. Moreover, across subjects, the magnitude of the fMRI and behavioral conceptual priming effects were directly related. Additionally, the PRc region implicated in the fMRI study was the same region of maximal lesion overlap in the patients with impaired conceptual priming. These patient and imaging results converge to suggest that the PRc plays a critical role in conceptual implicit memory, and possibly concept..
    • 2013
    • Stan B. Floresco
    • Prefrontal dopamine and behavioral flexibility: shifting from an “inverted-U” toward a family of functions
    • Studies on prefrontal cortex (PFC) dopamine (DA) function have revealed its essential role in mediating a variety of cognitive and executive functions. A general principle that has emerged (primarily from studies on working memory) is that PFC DA, acting on D1 receptors, regulates cognition in accordance to an “inverted-U” shaped function, so that too little or too much activity has detrimental effects on performance. However, contemporary studies have indicated that the receptor mechanisms through which mesocortical DA regulates different aspects of behavioral flexibility can vary considerably across different DA receptors and cognitive operations. This article will review psychopharmacological and neurochemical data comparing and contrasting the cognitive effects of antagonism and stimulation of different DA receptors in the medial PFC. Thus, set-shifting is dependent on a co-operative interaction between PFC D1 and D2 receptors, yet, supranormal stimulation of these re..
    • 2005
    • Nathaniel D Daw et al.
    • Uncertainty-based competition between prefrontal and dorsolateral striatal systems for behavioral control
    • A broad range of neural and behavioral data suggests that the brain contains multiple systems for behavioral choice, including one associated with prefrontal cortex and another with dorsolateral striatum. However, such a surfeit of control raises an additional choice problem: how to arbitrate between the systems when they disagree. Here, we consider dual-action choice systems from a normative perspective, using the computational theory of reinforcement learning. We identify a key trade-off pitting computational simplicity against the flexible and statistically efficient use of experience. The trade-off is realized in a competition between the dorsolateral striatal and prefrontal systems. We suggest a Bayesian principle of arbitration between them according to uncertainty, so each controller is deployed when it should be most accurate. This provides a unifying account of a wealth of experimental evidence about the factors favoring dominance by either system. Top of page
    • 2008
    • Dongju Seo et al.
    • Role of serotonin and dopamine system interactions in the neurobiology of impulsive aggression and its comorbidity with other clinical disorders
    • Impulsive aggression is characterized by an inability to regulate affect as well as aggressive impulses, and is highly comorbid with other mental disorders including depression, suicidal behavior, and substance abuse. In an effort to elucidate the neurobiological underpinnings of impulsive aggression and to help account for its connections with these other disorders, this paper reviews relevant biochemical, brain-imaging, and genetic studies. The review suggests that dysfunctional interactions between serotonin and dopamine systems in the prefrontal cortex may be an important mechanism underlying the link between impulsive aggression and its comorbid disorders. Specifically, serotonin hypofunction may represent a biochemical trait that predisposes individuals to impulsive aggression, with dopamine hyperfunction contributing in an additive fashion to the serotonergic deficit. The current paper proposes a modified diathesis–stress model of impulsive aggression in which the underl..
    • 2011
    • Nora T Walter et al.
    • A genetic contribution to cooperation: dopamine-relevant genes are associated with social facilitation.
    • Social loafing and social facilitation are stable behavioral effects that describe increased or decreased motivation, as well as effort and cooperation in teamwork as opposed to individual working situations. Recent twin studies demonstrate the heritability of cooperative behavior. Brain imaging studies have shown that reciprocity, cooperativeness, and social rewards activate reward processing areas with strong dopaminergic input, such as the ventral striatum. Thus, candidate genes for social behavior are hypothesized to affect dopaminergic neurotransmission. In the present study, we investigated the dopaminergic genetic contribution to social cooperation, especially to social loafing and social facilitation. N = 106 healthy, Caucasian subjects participated in the study and were genotyped for three polymorphisms relevant to the dopaminergic system (COMTval158met, DRD2 c957t, DRD2 rs#2283265). In addition to a main effect indicating an increased performance in teamwork situations, we ..
    • 2014
    • Chris Baeken et al.
    • The influence of COMT Val158Met genotype on the character dimension cooperativeness in healthy females
    • Objectives Although the Val158Met catechol-O-methyltransferase (COMT) gene has been linked with the temperament dimension Novelty Seeking (NS), new insights in this polymorphism might point to a major role for character features as well. Given that individual life experiences may influence Val158 and Met158 allele carriers differently it has been suggested that the character trait cooperativeness could be implicated. Case report A homogeneous group of eighty right-handed Caucasian healthy female university students were assessed with the TCI and genotyped for the COMT Val158Met polymorphism (rs4680). Gene determination showed that eighteen were Val158 homozygotes, forty-four Val/Met158 heterozygotes, and eighteen were Met158 homozygotes. All were within the same age range and never documented to have suffered from any neuropsychiatric illness. Bonferroni corrected non-parametric analyses showed that only for the character scale cooperativeness Val158 homozygotes displayed sign..
    • 2015
    • Ignacio Sáez et al.
    • Dopamine Modulates Egalitarian Behavior in Humans
    • Egalitarian motives form a powerful force in promoting prosocial behavior and enabling large-scale cooperation in the human species [ 1 ]. At the neural level, there is substantial, albeit correlational, evidence suggesting a link between dopamine and such behavior [ 2, 3 ]. However, important questions remain about the specific role of dopamine in setting or modulating behavioral sensitivity to prosocial concerns. Here, using a combination of pharmacological tools and economic games, we provide critical evidence for a causal involvement of dopamine in human egalitarian tendencies. Specifically, using the brain penetrant catechol-O-methyl transferase (COMT) inhibitor tolcapone [ 4, 5 ], we investigated the causal relationship between dopaminergic mechanisms and two prosocial concerns at the core of a number of widely used economic games: (1) the extent to which individuals directly value the material payoffs of others, i.e., generosity, and (2) the extent to which they are averse to ..
    • 2014
    • Panos Athanasopoulos et al.
    • Two Languages, Two Minds Flexible Cognitive Processing Driven by Language of Operation
    • People make sense of objects and events around them by classifying them into identifiable categories. The extent to which language affects this process has been the focus of a long-standing debate: Do different languages cause their speakers to behave differently? Here, we show that fluent German-English bilinguals categorize motion events according to the grammatical constraints of the language in which they operate. First, as predicted from cross-linguistic differences in motion encoding, bilingual participants functioning in a German testing context prefer to match events on the basis of motion completion to a greater extent than do bilingual participants in an English context. Second, when bilingual participants experience verbal interference in English, their categorization behavior is congruent with that predicted for German; when bilingual participants experience verbal interference in German, their categorization becomes congruent with that predicted for English. These findin..
    • 2014
    • Keith M. Welker et al.
    • Individual Differences in Testosterone Predict Persistence in Men
    • Persistence is an important predictor of future successes. The present research addresses the relationship between testosterone and persistence in men. One hundred eighteen men were randomly assigned to win or lose a competitive number tracing task against a confederate or complete the task alone in a non-competitive control condition. Saliva samples were collected prior to and after the competition or control conditions. Participants were then given a maximum time of 30 min to spend attempting to solve unsolvable puzzles, with the option to quit at any time. In contrast to our prediction, changes in testosterone concentrations in response to the competitive interaction did not predict persistence behaviour. However, individual differences in testosterone concentrations (pre-competition/non-competition) were positively correlated with persistence. These findings are the first to examine associations between neuroendocrine function and persistence behaviour in people and sugges..
    • 2014
    • Donné van der Westhuizen et al.
    • Social dominance and the Affective Neuroscience Personality Scales
    • The tendency for cohabiting mammals to organise themselves into dominance hierarchies is a well-documented phenomenon and has consistently been linked to the activity of testosterone and cortisol. However, a systematic account of it within the “basic emotion” taxonomy proposed by Panksepp remains uncharted. The Affective Neuroscience Personality Scales (ANPS), developed to measure the influence of basic affective systems on human temperamental variability, were used as a tool through which to dissociate incentives that promote social dominance from other personality stereotypes. 36 Males were assayed for baseline testosterone and cortisol. Dominance, conceptualised as an egocentric incentive for gaining social influence, was found to positively correlate with the testosterone: cortisol ratio but not with any existing subscales of the ANPS. While these findings suggest that trait dominance can be monitored as an independent personality variable according to a disti..