Science posts

See science posts on page 59 below.

    • 2006
    • Alessandro Bertolino et al
    • Additive Effects of Genetic Variation in Dopamine Regulating Genes on Working Memory Cortical Activity in Human Brain
    • Functional polymorphisms in the catechol-O-methyltransferase (COMT) and the dopamine transporter (DAT) genes modulate dopamine inactivation, which is crucial for determining neuronal signal-to-noise ratios in prefrontal cortex during working memory. We show that the COMT Met158 allele and the DAT 3′ variable number of tandem repeat 10-repeat allele are independently associated in healthy humans with more focused neuronal activity (as measured with blood oxygen level-dependent functional magnetic resonance imaging) in the working memory cortical network, including the prefrontal cortex. Moreover, subjects homozygous for the COMT Met allele and the DAT 10-repeat allele have the most focused response, whereas the COMT Val and the DAT 9-repeat alleles have the least. These results demonstrate additive genetic effects of genes regulating dopamine signaling on specific neuronal networks subserving working memory.
    • 2007
    • Paul K. Hitchcott et al
    • Bidirectional Modulation of Goal-Directed Actions by Prefrontal Cortical Dopamine
    • Instrumental actions are a vital cognitive asset that endows an organism with sensitivity to the consequences of its behavior. Response–outcome feedback allows responding to be shaped in order to maximize beneficial, and minimize detrimental, outcomes. Lesions of the medial prefrontal cortex (mPFC) result in behavior that is insensitive to changes in outcome value in animals and compulsive behavior in several human psychopathologies. Such insensitivity to changes in outcome value is a defining characteristic of instrumental habits: responses that are controlled by antecedent stimuli rather than goal expectancy. Little is known regarding the neurochemical substrates mediating this sensitivity. The present experiments used sensitivity to posttraining outcome devaluation to index the action–habit status of instrumental responding. Infusions of dopamine into the ventral mPFC (vmPFC), but not dorsal mPFC, restored outcome sensitivity bidirectionally—decreasing responding following outcome..
    • 2005
    • Yukiori Goto et al
    • Dopaminergic modulation of limbic and cortical drive of nucleus accumbens in goal-directed behavior
    • Goal-directed behavior is believed to involve interactions of prefrontal cortical and limbic inputs in the nucleus accumbens (NAcc), and their modulation by mesolimbic dopamine (DA) seems to be of primary importance in NAcc function. Using in vivo electrophysiological recordings simultaneously with DA system manipulation in rats, we show that tonic and phasic DA release selectively modulates hippocampal and prefrontal cortical inputs through D1 and D2 receptors, respectively. In addition, we also found that D1 activation and D2 inactivation in the NAcc produced behaviorally selective effects (learning versus set shifting of response strategy) that correspond to specific afferents. These results suggest that the dynamics of DA release regulate the balance between limbic and cortical drive through activation and inactivation of DA receptor subtypes in the accumbens, and this regulates goal-directed behavior.
    • 2007
    • Joseph F. Cheer et al
    • Coordinated Accumbal Dopamine Release and Neural Activity Drive Goal-Directed Behavior
    • Intracranial self-stimulation (ICSS) activates the neural pathways that mediate reward, including dopaminergic terminal areas such as the nucleus accumbens (NAc). However, a direct role of dopamine in ICSS-mediated reward has been questioned. Here, simultaneous voltammetric and electrophysiological recordings from the same electrode reveal that, at certain sites, the onset of anticipatory dopamine surges and changes in neuronal firing patterns during ICSS are coincident, whereas sites lacking dopamine changes also lack patterned firing. Intrashell microinfusion of a D1, but not a D2 receptor antagonist, blocks ICSS. An iontophoresis approach was implemented to explore the effect of dopamine antagonists on firing patterns without altering behavior. Similar to the microinfusion experiments, ICSS-related firing is selectively attenuated following D1 receptor blockade. This work establishes a temporal link between anticipatory rises of dopamine and firing patterns in the NAc shell during..
    • 2012
    • Norman A. S. Farb et al
    • The Mindful Brain and Emotion Regulation in Mood Disorders
    • Mindfulness involves nonjudgmental attention to present-moment experience. In its therapeutic forms, mindfulness interventions promote increased tolerance of negative affect and improved well being. However, the neural mechanisms underlying mindful mood regulation are poorly understood. Mindfulness training appears to enhance attentional monitoring systems in the brain, supported by the anterior cingulate and lateral prefrontal cortices. In emotion regulation, this prefrontal training seems to promote the stable recruitment of a non-conceptual sensory pathway, an alternative to conventional cognitive reappraisal strategies. In neural terms, the transition to non-conceptual awareness involves reducing habitual evaluative processing supported by midline structures of the prefrontal cortex. Instead, attentional resources are directed towards a limbic pathway for present-moment sensory awareness, involving the thalamus, insula, and primary sensory regions. In patients with affective diso..
    • 2010
    • Claus Lamm et al
    • Meta-analytic evidence for common and distinct neural networks associated with directly experienced pain and empathy for pain
    • A growing body of evidence suggests that empathy for pain is underpinned by neural structures that are also involved in the direct experience of pain. In order to assess the consistency of this finding, an image-based meta-analysis of nine independent functional magnetic resonance imaging (fMRI) investigations and a coordinate-based meta-analysis of 32 studies that had investigated empathy for pain using fMRI were conducted. The results indicate that a core network consisting of bilateral anterior insular cortex and medial/anterior cingulate cortex is associated with empathy for pain. Activation in these areas overlaps with activation during directly experienced pain, and we link their involvement to representing global feeling states and the guidance of adaptive behavior for both self- and other-related experiences. Moreover, the image-based analysis demonstrates that depending on the type of experimental paradigm this core network was co-activated with distinct brain regions: While..
    • 2012
    • Xiao-Fei Yang et al
    • Intrinsic Default Mode Network Connectivity Predicts Spontaneous Verbal Descriptions of Autobiographical Memories during Social Processing
    • Neural systems activated in a coordinated way during rest, known as the default mode network (DMN), also support autobiographical memory (AM) retrieval and social processing/mentalizing. However, little is known about how individual variability in reliance on personal memories during social processing relates to individual differences in DMN functioning during rest (intrinsic functional connectivity). Here we examined 18 participants’ spontaneous descriptions of autobiographical memories during a 2 h, private, open-ended interview in which they reacted to a series of true stories about real people’s social situations and responded to the prompt, “how does this person’s story make you feel?” We classified these descriptions as either containing factual information (“semantic” AMs) or more elaborate descriptions of emotionally meaningful events (“episodic” AMs). We also collected resting state fMRI scans from the participants and related individual differences in frequency of described..
    • 2012
    • Donna L. Murdaugh et al
    • Differential Deactivation during Mentalizing and Classification of Autism Based on Default Mode Network Connectivity
    • The default mode network (DMN) is a collection of brain areas found to be consistently deactivated during task performance. Previous neuroimaging studies of resting state have revealed reduced task-related deactivation of this network in autism. We investigated the DMN in 13 high-functioning adults with autism spectrum disorders (ASD) and 14 typically developing control participants during three fMRI studies (two language tasks and a Theory-of-Mind (ToM) task). Each study had separate blocks of fixation/resting baseline. The data from the task blocks and fixation blocks were collated to examine deactivation and functional connectivity. Deficits in the deactivation of the DMN in individuals with ASD were specific only to the ToM task, with no group differences in deactivation during the language tasks or a combined language and self-other discrimination task. During rest blocks following the ToM task, the ASD group showed less deactivation than the control group in a number of DMN reg..
    • 2010
    • Mohamed L. Seghier et al
    • Functional Subdivisions in the Left Angular Gyrus Where the Semantic System Meets and Diverges from the Default Network
    • The left angular gyrus (AG) is reliably activated across a wide range of semantic tasks, and is also a consistently reported component of the so-called default network that it is deactivated during all goal-directed tasks. We show here that there is only partial overlap between the semantic system and the default network in left AG and the overlap defines a reliable functional landmark that can be used to segregate functional subdivisions within AG. In 94 healthy human subjects, we collected functional magnetic resonance imaging (fMRI) data during fixation and eight goal directed tasks that involved semantic matching, perceptual matching or speech production in response to familiar or unfamiliar stimuli presented in either verbal (letters) or nonverbal (pictures) formats. Our results segregated three different left AG regions that were all activated by semantic relative to perceptual matching: (1) a midregion (mAG) that overlapped with the default network because it was deactivated d..
    • 2007
    • Norman A. S. Farb et al
    • Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference
    • It has long been theorised that there are two temporally distinct forms of self-reference: extended self-reference linking experiences across time, and momentary self-reference centred on the present. To characterise these two aspects of awareness, we used functional magnetic resonance imaging (fMRI) to examine monitoring of enduring traits (’narrative’ focus, NF) or momentary experience (’experiential’ focus, EF) in both novice participants and those having attended an 8 week course in mindfulness meditation, a program that trains individuals to develop focused attention on the present. In novices, EF yielded focal reductions in self-referential cortical midline regions (medial prefrontal cortex, mPFC) associated with NF. In trained participants, EF resulted in more marked and pervasive reductions in the mPFC, and increased engagement of a right lateralised network, comprising the lateral PFC and viscerosomatic areas such as the insula, secondary somatosensory cortex and inferior pa..

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