Science posts

See science posts on page 52 below.

    • 2013
    • Ashley C. Chen et al
    • Causal interactions between fronto-parietal central executive and default-mode networks in humans
    • Information processing during human cognitive and emotional operations is thought to involve the dynamic interplay of several large-scale neural networks, including the fronto-parietal central executive network (CEN), cingulo-opercular salience network (SN), and the medial prefrontal-medial parietal default mode networks (DMN). It has been theorized that there is a causal neural mechanism by which the CEN/SN negatively regulate the DMN. Support for this idea has come from correlational neuroimaging studies; however, direct evidence for this neural mechanism is lacking. Here we undertook a direct test of this mechanism by combining transcranial magnetic stimulation (TMS) with functional MRI to causally excite or inhibit TMS-accessible prefrontal nodes within the CEN or SN and determine consequent effects on the DMN. Single-pulse excitatory stimulations delivered to only the CEN node induced negative DMN connectivity with the CEN and SN, consistent with the CEN/SN’s hypothesized negati..
    • 2015
    • Klara Spalek et al
    • Sex-Dependent Dissociation between Emotional Appraisal and Memory: A Large-Scale Behavioral and fMRI Study
    • Extensive evidence indicates that women outperform men in episodic memory tasks. Furthermore, women are known to evaluate emotional stimuli as more arousing than men. Because emotional arousal typically increases episodic memory formation, the females memory advantage might be more pronounced for emotionally arousing information than for neutral information. Here, we report behavioral data from 3398 subjects, who performed picture rating and memory tasks, and corresponding fMRI data from up to 696 subjects. We were interested in the interaction between sex and valence category on emotional appraisal, memory performances, and fMRI activity. The behavioral results showed that females evaluate in particular negative (p below 10−16) and positive (p = 2 × 10−4), but not neutral pictures, as emotionally more arousing (pinteraction below 10−16) than males. However, in the free recall females outperformed males not only in positive (p below 10−16) and negative (p below 5 × 10−5), but also in..
    • 2007
    • Timothy J. Buschman et al
    • Top-Down Versus Bottom-Up Control of Attention in the Prefrontal and Posterior Parietal Cortices
    • Attention can be focused volitionally by “top-down” signals derived from task demands and automatically by “bottom-up” signals from salient stimuli. The frontal and parietal cortices are involved, but their neural activity has not been directly compared. Therefore, we recorded from them simultaneously in monkeys. Prefrontal neurons reflected the target location first during top-down attention, whereas parietal neurons signaled it earlier during bottom-up attention. Synchrony between frontal and parietal areas was stronger in lower frequencies during top-down attention and in higher frequencies during bottom-up attention. This result indicates that top-down and bottom-up signals arise from the frontal and sensory cortex, respectively, and different modes of attention may emphasize synchrony at different frequencies.
    • 2015
    • Robert P. Spunt et al
    • The Default Mode of Human Brain Function Primes the Intentional Stance
    • Humans readily adopt an intentional stance to other people,comprehending their behavior as guided by unobservable mentalstates such as belief, desire, and intention. We used fMRI inhealthy adults to test the hypothesis that this stance is primedby the default mode of human brain function present when themind is at rest. We report three findings that support this hypothesis. First, brain regions activated by actively adopting an intentional rather than nonintentional stance to another person wereanatomically similar to those demonstrating default responses toa fixation baseline condition. Second, moment-to-moment variation in default activity in the dorsomedial pFC was related to theease with which participants applied an intentional—but not non-intentional—stance to a social stimulus presented moments later.Finally, individuals who showed stronger dorsomedial pFC activity at baseline in a separate task were generally more efficientwhen adopting the intentional stance and reported hav..
    • 2012
    • D. Prochnow et al
    • The neural correlates of affect reading: An fMRI study on faces and gestures
    • As complex social beings, people communicate, in addition to spoken language, also via nonverbal behavior. In social face-to-face situations, people readily read the affect and intentions of others in their face expressions and gestures recognizing their meaning. Importantly, the addressee further has to discriminate the meanings of the seen communicative motor acts in order to be able to react upon them appropriately. In this functional magnetic resonance imaging study 15 healthy non-alexithymic right-handers observed video-clips that showed the dynamic evolution of emotional face expressions and gestures evolving from a neutral to a fully developed expression. We aimed at disentangling the cerebral circuits related to the observation of the incomplete and the subsequent discrimination of the evolved bodily expressions of emotion which are typical for everyday social situations. We show that the inferior temporal gyrus and the inferior and dorsal medial frontal cortex in both cerebr..
    • 2009
    • Adam Green et al
    • Connecting Long Distance: Semantic Distance in Analogical Reasoning Modulates Frontopolar Cortex Activity
    • Solving problems often requires seeing new connections between concepts or events that seemed unrelated at first. Innovative solutions of this kind depend on analogical reasoning, a relational reasoning process that involves mapping similarities between concepts. Brain-based evidence has implicated the frontal pole of the brain as important for analogical mapping. Separately, cognitive research has identified semantic distance as a key characteristic of the kind of analogical mapping that can support innovation (i.e., identifying similarities across greater semantic distance reveals connections that support more innovative solutions and models). However, the neural substrates of semantically distant analogical mapping are not well understood. Here, we used functional magnetic resonance imaging (fMRI) to measure brain activity during an analogical reasoning task, in which we parametrically varied the semantic distance between the items in the analogies. Semantic distance was derived q..
    • 2001
    • Todd S. Braver et al
    • Direct Comparison of Prefrontal Cortex Regions Engaged by Working and Long-Term Memory Tasks
    • Neuroimaging studies have suggested the involvement of ventrolateral, dorsolateral, and frontopolar prefrontal cortex (PFC) regions in both working (WM) and long-term memory (LTM). The current study used functional magnetic resonance imaging (fMRI) to directly compare whether these PFC regions show selective activation associated with one memory domain. In a within-subjects design, subjects performed the n-back WM task (two-back condition) as well as LTM encoding (intentional memorization) and retrieval (yes–no recognition) tasks. Additionally, each task was performed with two different types of stimulus materials (familiar words, unfamiliar faces) in order to determine the influence of material-type vs task-type. A bilateral region of dorsolateral PFC (DL-PFC; BA 46/9) was found to be selectively activated during the two-back condition, consistent with a hypothesized role for this region in active maintenance and/or manipulation of information in WM. Left frontopolar PFC (FP-PFC) wa..
    • 2003
    • Todd S Braver et al
    • Neural Mechanisms of Transient and Sustained Cognitive Control during Task Switching
    • A hybrid blocked and event-related functional magnetic resonance imaging (fMRI) study decomposed brain activity during task switching into sustained and transient components. Contrasting task-switching blocks against single-task blocks revealed sustained activation in right anterior prefrontal cortex (PFC). Contrasting task-switch trials against task-repeat and single-task trials revealed activation in left lateral PFC and left superior parietal cortex. In both sets of regions, activation dynamics were strongly modulated by trial-by-trial fluctuations in response speed. In addition, right anterior PFC activity selectively covaried with the magnitude of mixing cost (i.e., task-repeat versus single-task trial performance), and left superior parietal activity selectively covaried with the magnitude of the switching cost (i.e., task-switch versus task-repeat trial performance). These results indicate a functional double dissociation in brain regions supporting different components of cog..
    • 2002
    • Todd S. Braver et al
    • The Role of Frontopolar Cortex in Subgoal Processing during Working Memory
    • Neuroimaging studies have implicated the anterior-most or frontopolar regions of prefrontal cortex (FP-PFC, e.g., Brodmann's Area 10) as playing a central role in higher cognitive functions such as planning, problem solving, reasoning, and episodic memory retrieval. The current functional magnetic resonance imaging (fMRI) study tested the hypothesis that FP-PFC subserves processes related to the monitoring and management of subgoals, while maintaining information in working memory (WM). Subjects were scanned while performing two variants of a simple delayed response WM task. In the control WM condition, subjects monitored for the presence of a specific concrete probe word (LIME) occurring following a specific abstract cue word (FATE). In the subgoal WM condition, subjects monitored for the presence of any concrete probe word immediately following any abstract cue word. Thus, the task required semantic classification of the probe word (the subgoal task), while the cue was simultaneous..
    • 2014
    • Francisco Aboitiz et al
    • Irrelevant stimulus processing in ADHD: catecholamine dynamics and attentional networks
    • A cardinal symptom of attention deficit and hyperactivity disorder (ADHD) is a general distractibility where children and adults shift their attentional focus to stimuli that are irrelevant to the ongoing behavior. This has been attributed to a deficit in dopaminergic signaling in cortico-striatal networks that regulate goal-directed behavior. Furthermore, recent imaging evidence points to an impairment of large scale, antagonistic brain networks that normally contribute to attentional engagement and disengagement, such as the task-positive networks and the default mode network (DMN). Related networks are the ventral attentional network (VAN) involved in attentional shifting, and the salience network (SN) related to task expectancy. Here we discuss the tonic–phasic dynamics of catecholaminergic signaling in the brain, and attempt to provide a link between this and the activities of the large-scale cortical networks that regulate behavior. More specifically, we propose that a disbalan..