Science posts

See science posts on page 32 below.

    • 2015
    • N.I. Landrø et al.
    • Serotonin transporter polymorphisms predict response inhibition in healthy volunteers
    • Serotoninergic transmission is reliably implicated in inhibitory control processes. The aim of this study was to test the hypothesis if serotonin transporter polymorphisms mediate inhibitory control in healthy people. 141 healthy subjects, carefully screened for previous and current psychopathology, were genotyped for the 5-HTTLPR and rs25531 polymorphisms. Inhibitory control was ascertained with the Stop Signal Task (SST) from the Cambridge Neuropsychological Test Automated Battery (CANTAB). The triallelic gene model, reclassified and presented in a biallelic functional model, revealed a dose-dependent gene effect on SST performance with Individuals carrying the low expressive allele had inferior inhibitory control compared to high expressive carriers. This directly implicates serotonin transporter polymorphisms (5-HTTLPR plus rs25531) in response inhibition in healthy subjects.
    • 2015
    • Laura Steenbergen et al.
    • Tyrosine promotes cognitive flexibility: Evidence from proactive vs. reactive control during task switching performance
    • Tyrosine (TYR), an amino acid found in various foods, has been shown to increase dopamine (DA) levels in the brain. Recent studies have provided evidence that TYR supplementation can improve facets of cognitive control in situations with high cognitive demands. Here we investigated whether TYR promotes cognitive flexibility, a cognitive-control function that is assumed to be modulated by DA. We tested the effect of TYR on proactive vs. reactive control during task switching performance, which provides a relatively well-established diagnostic of cognitive flexibility. In a double-blind, randomized, placebo-controlled design, 22 healthy adults performed in a task-switching paradigm. Compared to a neutral placebo, TYR promoted cognitive flexibility (i.e. reduced switching costs). This finding supports the idea that TYR can facilitate cognitive flexibility by repleting cognitive resources.
    • 2010
    • Koji Jimuraa et al.
    • Prefrontal cortex mediation of cognitive enhancement in rewarding motivational contexts
    • Increasing the reward value of behavioral goals can facilitate cognitive processes required for goal achievement. This facilitation may be accomplished by the dynamic and flexible engagement of cognitive control mechanisms operating in distributed brain regions. It is still not clear, however, what are the characteristics of individuals, situations, and neural activation dynamics that optimize motivation-linked cognitive enhancement. Here we show that highly reward-sensitive individuals exhibited greater improvement of working memory performance in rewarding contexts, but exclusively on trials that were not rewarded. This effect was mediated by a shift in the temporal dynamics of activation within right lateral prefrontal cortex, from a transient to predominantly tonic mode, with an additional anticipatory transient boost. In contexts with intermittent rewards, a strategy of proactive cognitive control may enable globally optimal performance to facilitate reward attainment. Reward-se..
    • 2001
    • Kay Young et al.
    • The Neurology of Narrative
    • Narrative is the inescapable frame of human existence. Thinkers as diverse as Aristotle, Barthes, and Bruner have recognized the centrality of narrative in human cognition, but have scanted its neurobiologic underpinning. Recent advances in cognitive neuroscience suggest a regionally distributed neural network mediates the creation of narrative in the human central nervous system. Fundamental network components include: 1) the amygdalo-hippocampal system, responsible for initial encoding of episodic and autobiographical memories, 2) the left peri-Sylvian region, where language is formulated, and 3) the frontal cortices and their subcortical connections, where individuals and entities are organized into real and fictional temporal narrative frames. We describe four types of dysnarrativia, states of narrative impairment experienced by individuals with discrete focal damage in different regions of this neural network subserving human self-narrative. Patients with these syndromes illustr..
    • 2005
    • Nadia Degonda et al.
    • Implicit Associative Learning Engages the Hippocampus and Interacts with Explicit Associative Learning
    • The hippocampus is crucial for conscious, explicit memory, but whether it is also involved in nonconscious, implicit memory is uncertain. We investigated with functional magnetic resonance imaging whether implicit learning engages the hippocampus and interacts with subsequent explicit learning. The presentation of subliminal faces-written profession pairs for implicit learning was followed by the explicit learning of supraliminal pairs composed of the same faces combined with written professions semantically incongruous to those presented subliminally (experiment 1), semantically congruous professions (experiment 2), or identical professions (experiment 3). We found that implicit face-profession learning interacted with explicit face-profession learning in all experiments, impairing the explicit retrieval of the associations. Hippocampal activity increased during the subliminal presentation of face-profession pairs versus face-nonword pairs and correlated with the later impairment of..
    • 2008
    • Paul J. Reber
    • Cognitive Neuroscience of Declarative and Nondeclarative Memory
    • The study of memory within cognitive neuroscience is an attempt to synthesize an account of both the fundamental mnemonic component processes and the neural basis of these processes. This chapter focuses on cognitive neuroscience of declarative and nondeclarative memory. Declarative memory refers to the acquisition and retrieval of facts, events, and episodes. A nearly synonymous term, explicit memory, emphasizes the fact that these types of memory are available to awareness—that is, one can consciously recall these memories during retrieval. The bulk of what is thought of as the ordinary, everyday operation of memory depends on declarative memory. The conventional use of the term memory generally refers to the retrieval process, but before memories can be retrieved, they have to be acquired (stored), and this process depends on the intact function of the MTL (medial temporal lobe). The terms nondeclarative and implicit memory are synonymous (but not completely). The chapter re..
    • 2004
    • Rajendra D. Badgaiyan
    • Conscious awareness of retrieval: an exploration of the cortical connectivity
    • A review of the patterns of brain activation observed in implicit and explicit memory tasks indicates that during conscious retrieval studied items are first retrieved nonconsciously and are retained in a buffer at the extrastriate cortex. It also indicates that the awareness of the retrieved item is made possible by the activation of a reentrant signaling loop between the extrastriate and left prefrontal cortices.
    • 2006
    • Kristine M. Knutson et al.
    • Neural correlates of automatic beliefs about gender and race
    • Functional MRI was used to identify the brain areas underlying automatic beliefs about gender and race, and suppression of those attitudes. Participants (n = 20; 7 females) were scanned at 3 tesla while performing the Implicit Association Test (IAT), an indirect measure of race and gender bias. We hypothesized that ventromedial prefrontal cortex areas (PFC) would mediate gender and racial stereotypic attitudes, and suppression of these beliefs would recruit dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC). Performance data on the IAT revealed gender and racial biases. Racial bias was correlated with an explicit measure of racism. Results showed activation of anteromedial PFC and rostral ACC while participants implicitly made associations consistent with gender and racial biases. In contrast, associations incongruent with stereotypes recruited DLPFC. Implicit gender bias was correlated with amygdala activation during stereotypic conditions. Results sugges..
    • 2006
    • Nicholas B. Turk-Browne et al.
    • Linking Implicit and Explicit Memory: Common Encoding Factors and Shared Representations
    • Dissociations between implicit and explicit memory have featured prominently in theories of human memory. However, similarities between the two forms of memory have been less studied. One open question concerns whether implicit and explicit memory share encoding resources. To explore this question, we employed a subsequent memory design in which several novel scenes were repeated once during an fMRI session and explicit memory for the scenes was unexpectedly tested afterward. Subsequently remembered scenes produced more behavioral priming and neural attenuation—two conventional measures of implicit memory—than did subsequently forgotten scenes. Moreover, brain-behavior correlations between these two implicit measures were mediated by subsequent memory. Finally, tonic activity, possibly reflecting the natural time course of attention, was predictive of subsequent memory. These results suggest that implicit and explicit memory are subject to the same encoding factor..
    • 2011
    • Brian A. Nosek et al.
    • Implicit social cognition: from measures to mechanisms
    • Most human cognition occurs outside conscious awareness or conscious control. Some of these implicit processes influence social perception, judgment and action. The past 15 years of research in implicit social cognition can be characterized as the Age of Measurement because of a proliferation of measurement methods and research evidence demonstrating their practical value for predicting human behavior. Implicit measures assess constructs that are distinct, but related, to self-report assessments, and predict variation in behavior that is not accounted for by those explicit measures. The present state of knowledge provides a foundation for the next age of implicit social cognition: clarification of the mechanisms underlying implicit measurement and how the measured constructs influence behavior.