The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Mark Desposito - One of the best experts on this subject based on the ideXlab platform.
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the effect of non visual working memory load on top down modulation of visual processing
Neuropsychologia, 2009Co-Authors: Jesse Rissman, Mark Desposito, Adam GazzaleyAbstract:Abstract While a core function of the working memory (WM) system is the Active Maintenance of behaviorally relevant sensory representations, it is also critical that distracting stimuli are appropriately ignored. We used functional magnetic resonance imaging to examine the role of domain-general WM resources in the top-down attentional modulation of task-relevant and irrelevant visual representations. In our dual-task paradigm, each trial began with the auditory presentation of six random (high load) or sequentially ordered (low load) digits. Next, two relevant visual stimuli (e.g., faces), presented amongst two temporally interspersed visual distractors (e.g., scenes), were to be encoded and maintained across a 7-s delay interval, after which memory for the relevant images and digits was probed. When taxed by high load digit Maintenance, participants exhibited impaired performance on the visual WM task and a selective failure to attenuate the neural processing of task-irrelevant scene stimuli. The over-processing of distractor scenes under high load was indexed by elevated encoding activity in a scene-selective region-of-interest relative to low load and passive viewing control conditions, as well as by improved long-term recognition memory for these items. In contrast, the load manipulation did not affect participants’ ability to upregulate activity in this region when scenes were task-relevant. These results highlight the critical role of domain-general WM resources in the goal-directed regulation of distractor processing. Moreover, the consequences of increased WM load in young adults closely resemble the effects of cognitive aging on distractor filtering [Gazzaley, A., Cooney, J. W., Rissman, J., & D’Esposito, M. (2005). Top-down suppression deficit underlies working memory impairment in normal aging. Nature Neuroscience 8, 1298–1300], suggesting the possibility of a common underlying mechanism.
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differential effects of distraction during working memory on delay period activity in the prefrontal cortex and the visual association cortex
NeuroImage, 2006Co-Authors: Jong H Yoon, Clayton E Curtis, Mark DespositoAbstract:Maintaining relevant information for later use is a critical aspect of working memory (WM). The lateral prefrontal cortex (PFC) and posterior sensory cortical areas appear to be important in supporting Maintenance. However, the relative and unique contributions of these areas remain unclear. We have designed a WM paradigm with distraction to probe the contents of Maintenance representations in these regions. During delayed recognition trials of faces, selective interference was evident behaviorally with face distraction leading to significantly worse performance than with scene distraction. Event-related fMRI of the human brain showed that Maintenance activity in the lateral PFC, but not in visual association cortex (VAC), was selectively disrupted by face distraction. Additionally, the functional connectivity between the lateral PFC and the VAC was perturbed during these trials. We propose a hierarchical and distributed model of Active Maintenance in which the lateral PFC codes for abstracted mnemonic information, while sensory areas represent specific features of the memoranda. Furthermore, persistent coactivation between the PFC and sensory areas may be a mechanism by which information is Actively maintained.
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inferior temporal prefrontal and hippocampal contributions to visual working memory Maintenance and associative memory retrieval
The Journal of Neuroscience, 2004Co-Authors: Charan Ranganath, Michael X Cohen, Cathrine Dam, Mark DespositoAbstract:Higher order cognition depends on the ability to recall information from memory and hold it in mind to guide future behavior. To specify the neural mechanisms underlying these processes, we used event-related functional magnetic resonance imaging to compare brain activity during the performance of a visual associative memory task and a visual working memory task. Activity within category-selective subregions of inferior temporal cortex reflected the type of information that was Actively maintained during both the associative memory and working memory tasks. In addition, activity in the anterior prefrontal cortex and hippocampus was specifically enhanced during associative memory retrieval. These data are consistent with the view that the Active Maintenance of visual information is supported by activation of object representations in inferior temporal cortex, but that goal-directed associative memory retrieval additionally depends on top-down signals from the anterior prefrontal cortex and medial temporal lobes.
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medial temporal lobe activity associated with Active Maintenance of novel information
Neuron, 2001Co-Authors: Charan Ranganath, Mark DespositoAbstract:Using event-related functional magnetic resonance imaging, we investigated the role of medial temporal regions during Active Maintenance of information over short delays or working memory. In experiment 1, we observed sustained bilateral hippocampal activation during Maintenance of novel faces across a short delay period but not during face encoding or recognition. In contrast, we observed transient right parahippocampal activation during encoding and recognition but not during Maintenance. We replicated these findings in experiment 2 and further determined that anterior hippocampal activation was greater during Maintenance of novel than familiar faces. Our results reveal the importance of medial temporal lobe regions for the Active Maintenance of novel information in the absence of perceptual stimulation.
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the neural substrate and temporal dynamics of interference effects in working memory as revealed by event related functional mri
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Mark Desposito, John Jonides, Bradley R Postle, Edward E SmithAbstract:Research on the prefrontal cortex (PFC) of monkeys and humans indicates that this region supports a heterogeneous repertoire of mental processes that contribute to many complex behaviors, such as working memory. Anatomical evidence for some of these processes derives from functional neuroimaging experiments using blocked experimental designs, which average signal across all components of many trials and therefore cannot dissociate distinct processes with different time courses. Using event-related functional MRI, we were able to isolate temporally the neural correlates of processes contributing to the target presentation, delay, and probe portions of an item-recognition task. Two types of trials were of greatest interest: those with Recent Negative probes that matched an item from the target set of the previous, but not the present, two trials, and those with Nonrecent Negative probes that did not match a target item from either the present or the two previous trials. There was no difference between the two trial types in target presentation (i.e., encoding) or delay-period (i.e., Active Maintenance) PFC activation, but there was significantly greater activation for Recent Negatives than Nonrecent Negative activation associated with the probe period within left ventrolateral PFC. These findings characterize spatially and temporally a proActive interference effect that may reflect the operation of a PFC-mediated response-inhibition mechanism that contributes to working memory performance.
Susan M Courtney - One of the best experts on this subject based on the ideXlab platform.
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neural system for updating object working memory from different sources sensory stimuli or long term memory
NeuroImage, 2007Co-Authors: Jennifer K Roth, Susan M CourtneyAbstract:Working memory (WM) is the Active Maintenance of currently relevant information so that it is available for use. A crucial component of WM is the ability to update the contents when new information becomes more relevant than previously maintained information. New information can come from different sources, including from sensory stimuli (SS) or from long-term memory (LTM). Updating WM may involve a single neural system regardless of source, distinct systems for each source, or a common network with additional regions involved specifically in sensory or LTM processes. The current series of experiments indicates that a single fronto-parietal network (including supplementary motor area, parietal, left inferior frontal junction, middle frontal gyrus) is Active in updating WM regardless of the source of information. Bilateral cuneus was more Active during updating WM from LTM than updating from SS, but the activity in this region was attributable to recalling information from LTM regardless of whether that information was to be entered into WM for future use or not. No regions were found to be more Active during updating from SS than updating from LTM. Functional connectivity analysis revealed that different regions within this common update network were differentially more correlated with visual processing regions when participants updated from SS, and more correlated with LTM processing regions when participants updated from the contents of LTM. These results suggest that a single neural mechanism is responsible for controlling the contents of WM regardless of whether that information originates from a sensory stimulus or from LTM. This network of regions involved in updating WM interacts with the rest of the brain differently depending on the source of newly relevant information.
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attention and cognitive control as emergent properties of information representation in working memory
Cognitive Affective & Behavioral Neuroscience, 2004Co-Authors: Susan M CourtneyAbstract:A hallmark of primate, and particularly human, behavior is cognitive control, the ability to integrate information from a multitude of sources and use that information to flexibly guide behavior in order to achieve an infinite number of goals. The neural mechanisms of cognitive control have yet to be fully elucidated, although the prefrontal cortex is known to play a critical role. Here, I review evidence suggesting that a unifying principle regarding the role of various portions of the prefrontal cortex in a wide range of cognitive tasks is the Active Maintenance in working memory of different types of currently relevant information—from specific stimulus features, to instructional cues, to motivational goals and contexts. I argue that the key to demonstrating the existence of this domain-dependent organization lies in a better understanding of the nature of the representation of this information and the ways in which this information itself controls cognition and behavior.
Christian J. Fiebach - One of the best experts on this subject based on the ideXlab platform.
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distractor resistant short term memory is supported by transient changes in neural stimulus representations
Journal of Cognitive Neuroscience, 2017Co-Authors: Christian J. Fiebach, Jan Derrfuss, Matthias Ekman, Michael Hanke, Marc TittgemeyerAbstract:Goal-directed behavior in a complex world requires the Maintenance of goal-relevant information despite multiple sources of distraction. However, the brain mechanisms underlying distractor-resistant working or short-term memory (STM) are not fully understood. While early single-unit recordings in monkeys and fMRI studies in humans pointed to an involvement of lateral prefrontal cortices, more recent studies highlighted the importance of posterior cortices for the Active Maintenance of visual information also in the presence of distraction. Here, we used a delayed match-to-sample task and multivariate searchlight analyses of fMRI data to investigate STM Maintenance across three extended delay phases. Participants maintained two samples (either faces or houses) across an unfilled pre-distractor delay, a distractor-filled delay, and an unfilled post-distractor delay. STM contents (faces vs. houses) could be decoded above-chance in all three delay phases from occipital, temporal, and posterior parietal areas. Classifiers trained to distinguish face vs. house Maintenance successfully generalized from preto post-distraction delays and vice versa, but not to the distractor delay period. Furthermore, classifier performance in all delay phases was correlated with behavioral performance in house, but not face trials. Our results demonstrate the involvement of distributed posterior, but not lateral prefrontal, cortices in Active Maintenance during and after distraction. They also show that the neural code underlying STM Maintenance is transiently changed in the presence of distractors, and re instated after distraction. The correlation with behavior suggests that Active STM Maintenance is particularly relevant in house trials, whereas face trials might rely more strongly on contributions from long-term memory.
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Modulation of inferotemporal cortex activation during verbal working memory Maintenance.
Neuron, 2006Co-Authors: Christian J. Fiebach, Jesse Rissman, Mark D'espositoAbstract:Regions of the left inferotemporal cortex are involved in visual word recognition and semantics. We utilized functional magnetic resonance imaging to localize an inferotemporal language area and to demonstrate that this area is involved in the Active Maintenance of visually presented words in working memory. Maintenance activity in this inferotemporal area showed an effect of memory load for words, but not pseudowords. In the absence of visual input, the selective modulation of this language-related inferotemporal area for the Maintenance of words is accompanied by an increased functional connectivity with left prefrontal cortex. These results demonstrate an involvement of inferotemporal cortex in verbal working memory and provide neurophysiological support for the notion that nonphonological language representations can be recruited in the service of verbal working memory. More generally, they suggest that verbal working memory should be conceptualized as the frontally guided, sustained activation of pre-existing cortical language representations.
Jonathan D. Cohen - One of the best experts on this subject based on the ideXlab platform.
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an integrative theory of prefrontal cortex function
Annual Review of Neuroscience, 2001Co-Authors: Earl K Miller, Jonathan D. CohenAbstract:▪ Abstract The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we propose that cognitive control stems from the Active Maintenance of patterns of activity in the prefrontal cortex that represent goals and the means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task. We review neurophysiological, neurobiological, neuroimaging, and computational studies that support this theory and discuss its implications as well as further issues to be addressed
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a biologically based computational model of working memory
1999Co-Authors: Randall C Oreilly, Todd S. Braver, Jonathan D. CohenAbstract:FIVE CENTRAL FEATURES OF THE MODEL We define working memory as controlled processing involving Active Maintenance and/or rapid learning, where controlled processing is an emergent property of the dynamic interactions of multiple brain systems, but the prefrontal cortex (PFC) and hippocampus (HCMP) are especially influential owing to their specialized processing abilities and their privileged locations within the processing hierarchy (both the PFC and HCMP are well connected with a wide range of brain areas, allowing them to influence behavior at a global level). The specific features of our model include: (1) A PFC specialized for Active Maintenance of internal contextual information that is dynamically updated and self-regulated, allowing it to bias (control) ongoing processing according to maintained information (e.g., goals, instructions, partial products). (2) An HCMP specialized for rapid learning of arbitrary information, which can be recalled in the service of controlled processing, whereas the posterior perceptual and motor cortex (PMC) exhibits slow, long-term learning that can efficiently represent accumulated knowledge and skills. (3) Control that emerges from interacting systems (PFC, HCMP, and PMC). (4) Dimensions that define continua of specialization in different brain systems: for example, robust Active Maintenance, fast versus slow learning. (5) Integration of biological and computational principles. Working memory is an intuitively appealing theoretical construct – perhaps deceptively so.
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temporal dynamics of brain activation during a working memory task
Nature, 1997Co-Authors: Todd S. Braver, Leigh E. Nystrom, Douglas C. Noll, Jonathan D. Cohen, William M Perlstein, John Jonides, Edward E SmithAbstract:Working memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving. Traditionally, working memory has been divided into two types of processes: executive control (governing the encoding manipulation and retrieval of information in working memory) and Active Maintenance (keeping information available 'online'). It has also been proposed that these two types of processes may be subserved by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for Active Maintenance. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in Active Maintenance. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a working memory task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in Active Maintenance.
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Dissociating working memory from task difficulty in human prefrontal cortex
Neuropsychologia, 1997Co-Authors: M Deanna, Todd S. Braver, Leigh E. Nystrom, Steven D. Forman, Douglas C. Noll, Jonathan D. CohenAbstract:A functional magnetic resonance imaging (fMRI) study was conducted to determine whether prefrontal cortex (PFC) increases activity in working memory (WM) tasks as a specific result of the demands placed on WM, or to other processes affected by the greater difficulty of such tasks. Increased activity in dorsolateral PFC (DLPFC) was observed during task conditions that placed demands on Active Maintenance (long retention interval) relative to control conditions matched for difficulty. Furthermore, the activity was sustained over the entire retention interval and did not increase when task difficulty was manipulated independently of WM requirements. This contrasted with the transient increases in activity observed in the anterior cingulate, and other regions of frontal cortex, in response to increased task difficulty but not WM demands. Thus, this study established a double-dissociation between regions responsive to WM versus task difficulty, indicating a specific involvement of DLPFC and related structures in WM function.
Nash Unsworth - One of the best experts on this subject based on the ideXlab platform.
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variation in working memory capacity and cognitive control goal Maintenance and microadjustments of control
Quarterly Journal of Experimental Psychology, 2012Co-Authors: Nash Unsworth, Thomas S. Redick, Gregory J Spillers, Gene A BrewerAbstract:Variation in working memory capacity (WMC) and cognitive control was examined in four experiments. In the experiments high- and low-WMC individuals performed a choice reaction time task (Experiment 1), a version of the antisaccade task (Experiment 2), a version of the Stroop task (Experiment 3), and an arrow version of the flanker task (Experiment 4). An examination of response time distributions suggested that high- and low-WMC individuals primarily differed in the slowest responses in each experiment, consistent with the notion that WMC is related to Active Maintenance abilities. Examination of two indicators of microadjustments of control (posterror slowing and conflict adaptation effects) suggested no differences between high- and low-WMC individuals. Collectively these results suggest that variation in WMC is related to some, but not all, cognitive control operations. The results are interpreted within the executive attention theory of WMC.
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speed and accuracy of accessing information in working memory an individual differences investigation of focus switching
Journal of Experimental Psychology: Learning Memory and Cognition, 2008Co-Authors: Nash Unsworth, Randall W EngleAbstract:Working memory (WM) can be defined as a system responsible for the Active Maintenance, manipulation, and retrieval of task relevant information. Given these varied functions, it is not surprising that measures of WM have been found to be related to many higher-order cognitive functions, including reading comprehension and learning, and more broadly to fluid intelligence (see Engle & Kane, 2004). It is important, therefore, to examine aspects of each construct in detail and to examine the relations among these constructs to gain a better understanding of these important relations. In the present article we explore aspects of a dynamic WM system that combines Maintenance of information in the focus of attention with the retrieval of information from outside the focus. To place these two functions in a real-world context, consider the simple example of trying to multiply 2 two-digit numbers in your head (e.g., 47 23). To solve this problem, one must typically break the problem up into smaller problems, solve each of the smaller problems, and then combine the results. This process of breaking up the problem into more manageable subcomponents likely requires the use of efficient attention switching and updating mechanisms. The ability to quickly and accurately switch attention to recent representations is also likely required in other higherorder cognitive operations, including reasoning and language comprehension.
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The nature of individual differences in working memory capacity: Active Maintenance in primary memory and controlled search from secondary memory.
Psychological review, 2007Co-Authors: Nash UnsworthAbstract:Studies examining individual differences in working memory capacity have suggested that individuals with low working memory capacities demonstrate impaired performance on a variety of attention and memory tasks compared with individuals with high working memory capacities. This working memory limitation can be conceived of as arising from 2 components: a dynamic attention component (primary memory) and a probabilistic cue-dependent search component (secondary memory). This framework is used to examine previous individual differences studies of working memory capacity, and new evidence is examined on the basis of predictions of the framework to performance on immediate free recall. It is suggested that individual differences in working memory capacity are partially due to the ability to maintain information accessible in primary memory and the ability to search for information from secondary memory.
