Science posts

See science posts on page 47 below.

    • 2009
    • Kalina Christoff et al
    • Prefrontal organization of cognitive control according to levels of abstraction
    • The prefrontal cortex (PFC) plays a crucial role in cognitive control and higher mental functions by maintaining working memory representations of currently relevant information, thereby inducing a mindset that facilitates the processing of such information. Using fMRI, we examined how the human PFC implements mindsets for information at varying levels of abstraction. Subjects solved anagrams grouped into three kinds of blocks (concrete, moderately abstract, and highly abstract) according to the degree of abstraction of their solutions. Mindsets were induced by cuing subjects at the beginning of every block as to the degree of abstraction of solutions they should look for. Different levels of abstraction were matched for accuracy and reaction time, allowing us to examine the effects of varying abstraction in the absence of variations in cognitive complexity. Mindsets for concrete, moderately abstract, and highly abstract information were associated with stronger relative recruitment ..
    • 2004
    • K. Richard Ridderinkhof et al
    • Neurocognitive mechanisms of cognitive control: The role of prefrontal cortex in action selection, response inhibition, performance monitoring, and reward-based learning
    • Convergent evidence highlights the differential contributions of various regions of the prefrontal cortex in the service of cognitive control, but little is understood about how the brain determines and communicates the need to recruit cognitive control, and how such signals instigate the implementation of appropriate performance adjustments. Here we review recent progress from cognitive neuroscience in examining some of the main constituent processes of cognitive control as involved in dynamic decision making: goal-directed action selection, response activation and inhibition, performance monitoring, and reward-based learning. Medial frontal cortex is found to be involved in performance monitoring: evaluating outcome vis-à-vis expectancy, and detecting performance errors or conflicting response tendencies. Lateral and orbitofrontal divisions of prefrontal cortex are involved in subsequently implementing appropriate adjustments.
    • 2006
    • David M. Amodio et al
    • Meeting of minds: the medial frontal cortex and social cognition
    • Social interaction is a cornerstone of human life, yet the neural mechanisms underlying social cognition are poorly understood. Recently, research that integrates approaches from neuroscience and social psychology has begun to shed light on these processes, and converging evidence from neuroimaging studies suggests a unique role for the medial frontal cortex. We review the emerging literature that relates social cognition to the medial frontal cortex and, on the basis of anatomical and functional characteristics of this brain region, propose a theoretical model of medial frontal cortical function relevant to different aspects of social cognitive processing.
    • 2007
    • J. B. Pochon et al
    • The neural system that bridges reward and cognition in humans: An fMRI study
    • We test the hypothesis that motivational and cognitive processes are linked by a specific neural system to reach maximal efficiency. We studied six normal subjects performing a working memory paradigm (n-back tasks) associated with different levels of monetary reward during an fMRI session. The study showed specific brain activation in relation with changes in both the cognitive loading and the reward associated with task performance. First, the working memory tasks activated a network including the dorsolateral prefrontal cortex [Brodmann area (BA) 9/46] and, in addition, in the lateral frontopolar areas (BA 10), but only in the more demanding condition (3-back task). This result suggests that lateral prefrontal areas are organized in a caudo-rostral continuum in relation with the increase in executive requirement. Second, reward induces an increased activation in the areas already activated by working memory processing and in a supplementary region, the medial frontal pole (BA 10),..
    • 2007
    • John-Dylan Haynes et al
    • Reading Hidden Intentions in the Human Brain
    • When humans are engaged in goal-related processing, activity in prefrontal cortex is increased 1 and 2. However, it has remained unclear whether this prefrontal activity encodes a subject's current intention [3]. Instead, increased levels of activity could reflect preparation of motor responses 4 and 5, holding in mind a set of potential choices [6], tracking the memory of previous responses [7], or general processes related to establishing a new task set. Here we study subjects who freely decided which of two tasks to perform and covertly held onto an intention during a variable delay. Only after this delay did they perform the chosen task and indicate which task they had prepared. We demonstrate that during the delay, it is possible to decode from activity in medial and lateral regions of prefrontal cortex which of two tasks the subjects were covertly intending to perform. This suggests that covert goals can be represented by distributed patterns of activity in the prefrontal corte..
    • 2003
    • Jiro Okuda et al
    • Thinking of the future and past: the roles of the frontal pole and the medial temporal lobes
    • Human lesion data have indicated that the frontal polar area might be critically involved in having an insight into one’s future. Retrospective memory mediated by medial temporal lobes and related structures, on the other hand, could be used to extract one’s future prospects efficiently. In the present study, we investigated the roles of these two brain structures in thinking of the future and past by using positron emission tomography (PET) and a naturalistic task setting. We measured regional cerebral blood flow (rCBF) in healthy subjects while they were talking about their future prospects or past experiences, with regard to two different temporal windows (in years or days). Many areas in the frontal and the medial temporal lobes were activated during the future and past tasks compared with a control task requiring semantic retrieval. Among these, areas in anteromedial frontal pole showed greater activation during the future tasks than during the past tasks, showing significant ef..
    • 2003
    • Paul W Burgess et al
    • The role of the rostral frontal cortex (area 10) in prospective memory: a lateral versus medial dissociation
    • Using the H215O PET method, we investigated whether previous findings of regional cerebral blood flow (rCBF) changes in the polar and superior rostral aspects of the frontal lobes (principally Brodmann’s area (BA) 10) during prospective memory (PM) paradigms (i.e. those involving carrying out an intended action after a delay) can be attributed merely to the greater difficulty of such tasks over the baseline conditions typically employed. Three different tasks were administered under four conditions: baseline simple RT; attention-demanding ongoing task only; ongoing task plus a delayed intention (unpracticed); ongoing task plus delayed intention (practiced). Under prospective memory conditions, we found significant rCBF decreases in the superior medial aspects of the rostral prefrontal cortex (BA 10) relative to the baseline or ongoing task only conditions. However more lateral aspects of area 10 (plus the medio-dorsal thalamus) showed the opposite pattern, with rCBF increases in the ..
    • 2008
    • Chun Siong Soon et al
    • Unconscious determinants of free decisions in the human brain
    • Abstract There has been a long controversy as to whether subjectively 'free' decisions are determined by brain activity ahead of time. We found that the outcome of a decision can be encoded in brain activity of prefrontal and parietal cortex up to 10 s before it enters awareness. This delay presumably reflects the operation of a network of high-level control areas that begin to prepare an upcoming decision long before it enters awareness.
    • 2001
    • Stefan Pollmann
    • Switching between Dimensions, Locations, and Responses: The Role of the Left Frontopolar Cortex
    • We review event-related fMRI data regarding the role of the left lateral frontopolar cortex (LFPC) in attentional switching processes. We found LFPC activation when subjects had to reallocate attentional resources, either between visual dimensions (color and motion) or between locations. However, LFPC activation during these dimension or location switches was observed only when subjects had to counteract stimulus-driven attention to an invalid dimension or location. LFPC was not activated following changes of stimulus–response associations. Further experiments will have to show whether LFPC is actively involved in the reallocation of attentional resources or whether it rather has a monitoring function.
    • 1996
    • Adrian M. Owen et al
    • Evidence for a Two-Stage Model of Spatial Working Memory Processing within the Lateral Frontal Cortex: A Positron Emission Tomography Study
    • Previous work in nonhuman primates and in patients with frontal lobe damage has suggested that the frontal cortex plays a critical rolein the performance of both spatial and nonspatial working memory tasks. The present study used positron emission tomography with magnetic resonance imaging to demonstrate the existence, within the human brain, of two functionally distinct subdivisions of the lateral frontal cortex, which may subserve different aspects of spatial working memory. Five spatial memory tasks were used, which varied in terms of the extent to which they required different executive processes. When the task required the organization and execution of a sequence of spatial moves retained in working memory, significant changes in blood flow were observed in ventrolateral frontal cortex (area 41) bilaterally. By contrast, when the task required active monitoring and manipulation of spatial information within working memory, additional activation foci were observed in mid-dorsolat..

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