Science posts

See science posts on page 46 below.

    • 2001
    • Anthony D. Wagner et al
    • Prefrontal Contributions to Executive Control: fMRI Evidence for Functional Distinctions within Lateral Prefrontal Cortex
    • The prefrontal cortex (PFC) plays a fundamental role in internally guided behavior. Although it is generally accepted that PFC subserves working memory and executive control operations, it remains unclear whether the subregions within lateral PFC support distinct executive control processes. An event-related fMRI study was implemented to test the hypothesis that ventrolateral and dorsolateral PFC are functionally distinct, as well as to assess whether functional specialization exists within ventrolateral PFC. Participants performed two executive control tasks that differed in the types of control processes required. During rote rehearsal, participants covertly rehearsed three words in the order presented, thus requiring phonological access and maintenance. During elaborative rehearsal, participants made semantic comparisons between three words held in working memory, reordering them from least to most desirable. Thus, in addition to maintenance, elaborative rehearsal required goal-re..
    • 2011
    • Green, Adam E et al
    • Neural correlates of creativity in analogical reasoning
    • 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 determinant of the creativity of analogical mapping (i.e., more distant analogies are generally more creative). Here, we used functional magnetic resonance imaging to assess brain activity during an analogy generation task in which we varied the semantic distance of analogical mapping (as derived quantitatively from a latent semantic analysis). Data indicated that activity within an a priori region of interest in left frontopolar cortex covaried parametrically with increasing semantic distance, even after removing effects of task difficulty. Results implicate increased recruitment of frontopolar cortex as a mechanism for integrating semantically distant information to generate solutions in creative analogical reasoning.
    • 2010
    • Soohyun Ch et al
    • Common and Dissociable Prefrontal Loci Associated with Component Mechanisms of Analogical Reasoning
    • The ability to draw analogies requires 2 key cognitive processes, relational integration and resolution of interference. The present study aimed to identify the neural correlates of both component processes of analogical reasoning within a single, nonverbal analogy task using event-related functional magnetic resonance imaging. Participants verified whether a visual analogy was true by considering either 1 or 3 relational dimensions. On half of the trials, there was an additional need to resolve interference in order to make a correct judgment. Increase in the number of dimensions to integrate was associated with increased activation in the lateral prefrontal cortex as well as lateral frontal pole in both hemispheres. When there was a need to resolve interference during reasoning, activation increased in the lateral prefrontal cortex but not in the frontal pole. We identified regions in the middle and inferior frontal gyri which were exclusively sensitive to demands on each component..
    • 2011
    • Michael L. Platt et al
    • Learning: Not Just the Facts, Ma'am, but the Counterfactuals as Well
    • Our brains allow us to consider rewards and other scenarios that could have happened but did not. Such counterfactual outcomes can influence our choices and hasten learning. A series of recent studies has begun to untangle the neural circuitry responsible for monitoring counterfactual outcomes. Here, we summarize several recent complementary discoveries, including a new article in the current issue of PLoS Biology. Neurons in several brain areas that process directly experienced rewards respond to counterfactual information about rewards as well. Among these brain regions, the frontal pole appears to be most specialized, and carries a decision variable representing the value of the best alternative option. Together, these findings suggest that counterfactual learning and thinking build upon scaffolding circuits that evolved to learn from direct experience. In the hit 1950s television series Dragnet, Detective Joe Friday methodically solved crimes by slowly accumulating knowledge o..
    • 2004
    • David Badre et al
    • Selection, Integration, and Conflict Monitoring: Assessing the Nature and Generality of Prefrontal Cognitive Control Mechanisms
    • Prefrontal cortex (PFC) supports flexible behavior by mediating cognitive control, though the elemental forms of control supported by PFC remain a central debate. Dorsolateral PFC (DLPFC) is thought to guide response selection under conditions of response conflict or, alternatively, may refresh recently active representations within working memory. Lateral frontopolar cortex (FPC) may also adjudicate response conflict, though others propose that FPC supports higher order control processes such as subgoaling and integration. Anterior cingulate cortex (ACC) is hypothesized to upregulate response selection by detecting response conflict; it remains unclear whether ACC functions generalize beyond monitoring response conflict. The present fMRI experiment directly tested these competing theories regarding the functional roles of DLPFC, FPC, and ACC. Results reveal dissociable control processes in PFC, with mid-DLPFC selectively mediating resolution of response conflict and FPC further medi..
    • 2009
    • Silvia A. Bunge et al
    • Comparing the Bird in the Hand with the Ones in the Bush
    • So goes the fable of Aesop, versions of which have been transmitted around the world for over 2500 years. Indeed, a bird in the hand is worth two in the bush—unless, perhaps, the probability of catching the birds in the bush is very high. In a dynamic environment, it is adaptive to monitor the possible outcomes associated with alternative courses of action and to update our behavior accordingly. In the current issue of Neuron, Boorman, Behrens, Woolrich, and Rushworth provide compelling evidence for a neural mechanism by which this monitoring of alternative outcomes relative to current outcomes, and the subsequent updating of behavior, can occur ( Boorman et al., 2009). In particular, they show that our brains can keep track of the mounting evidence in favor of an alternative course of action, and that—when strong enough—this signal leads to a switch in behavior. The evidence favoring a switch to an alternative choice is tracked by lateral fronopolar cortex (FPC), and this informa..
    • 2011
    • Erie D. Boorman et al
    • Counterfactual Choice and Learning in a Neural Network Centered on Human Lateral Frontopolar Cortex
    • Decision making and learning in a real-world context require organisms to track not only the choices they make and the outcomes that follow but also other untaken, or counterfactual, choices and their outcomes. Although the neural system responsible for tracking the value of choices actually taken is increasingly well understood, whether a neural system tracks counterfactual information is currently unclear. Using a three-alternative decision-making task, a Bayesian reinforcement-learning algorithm, and fMRI, we investigated the coding of counterfactual choices and prediction errors in the human brain. Rather than representing evidence favoring multiple counterfactual choices, lateral frontal polar cortex (lFPC), dorsomedial frontal cortex (DMFC), and posteromedial cortex (PMC) encode the reward-based evidence favoring the best counterfactual option at future decisions. In addition to encoding counterfactual reward expectations, the network carries a signal for learning about counter..
    • 2013
    • Molly J. Crockett et al
    • Restricting Temptations: Neural Mechanisms of Precommitment
    • Humans can resist temptations by exerting willpower, the effortful inhibition of impulses. But willpower can be disrupted by emotions and depleted over time. Luckily, humans can deploy alternative self-control strategies like precommitment, the voluntary restriction of access to temptations. Here, we examined the neural mechanisms of willpower and precommitment using fMRI. Behaviorally, precommitment facilitated choices for large delayed rewards, relative to willpower, especially in more impulsive individuals. While willpower was associated with activation in dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex (PPC), and inferior frontal gyrus, precommitment engaged lateral frontopolar cortex (LFPC). During precommitment, LFPC showed increased functional connectivity with DLPFC and PPC, especially in more impulsive individuals, and the relationship between impulsivity and LFPC connectivity was mediated by value-related activation in ventromedial PFC. Our findings suppor..
    • 2012
    • Franck Amyot et al
    • Normative database of judgment of complexity task with functional near infrared spectroscopy—Application for TBI
    • The ability to assess frontal lobe function in a rapid, objective, and standardized way, without the need for expertise in cognitive test administration might be particularly helpful in mild traumatic brain injury (TBI), where objective measures are needed. Functional near infrared spectroscopy (fNIRS) is a reliable technique to noninvasively measure local hemodynamic changes in brain areas near the head surface. In this paper, we are combining fNIRS and frameless stereotaxy which allowed us to co-register the functional images with previously acquired anatomical MRI volumes. In our experiment, the subjects were asked to perform a task, evaluating the complexity of daily life activities, previously shown with fMRI to activate areas of the anterior frontal cortex. We reconstructed averaged oxyhemoglobin and deoxyhemoglobin data from 20 healthy subjects in a spherical coordinate. The spherical coordinate is a natural representation of surface brain activation projection. Our results sh..
    • 2015
    • Andrew E. Reineberg et al
    • Resting-state networks predict individual differences in common and specific aspects of executive function
    • The goal of the present study was to examine relationships between individual differences in resting state functional connectivity as ascertained by fMRI (rs-fcMRI) and performance on tasks of executive function (EF), broadly defined as the ability to regulate thoughts and actions. Unlike most previous research that focused on the relationship between rs-fcMRI and a single behavioral measure of EF, in the current study we examined the relationship of rs-fcMRI with individual differences in subcomponents of EF. Ninety-one adults completed a resting state fMRI scan and three separate EF tasks outside the magnet: inhibition of prepotent responses, task set shifting, and working memory updating. From these three measures, we derived estimates of common aspects of EF, as well as abilities specific to working memory updating and task shifting. Using Independent Components Analysis (ICA), we identified across the group of participants several networks of regions (Resting State Networks, RSN..