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  • Fibrin(ogen) and neurodegeneration in the progressive multiple sclerosis cortex.

    3 July 2018

    OBJECTIVE: Neuronal loss, a key substrate of irreversible disability in multiple sclerosis (MS), is a recognized feature of MS cortical pathology of which the cause remains unknown. Fibrin(ogen) deposition is neurotoxic in animal models of MS, but has not been evaluated in human progressive MS cortex. The aim of this study was to investigate the extent and distribution of fibrin(ogen) in progressive MS cortex and elucidate its relationship with neurodegeneration. METHODS: A postmortem cohort of pathologically confirmed MS (n = 47) and control (n = 10) cases was used. The extent and distribution of fibrin(ogen) was assessed and related to measures of demyelination, inflammation, and neuronal density. In a subset of cases (MS, n = 20; control, n = 10), expression of plasminogen activator inhibitor 1 (PAI-1), a key enzyme in the fibrinolytic cascade, was assessed and related to the extent of fibrin(ogen). RESULTS: Motor cortical fibrin(ogen) deposition was significantly over-represented in MS compared to control cases in all compartments studied (ie, extracellular [p = 0.001], cell body [p = 0.003], and neuritic/glial-processes [p = 0.004]). MS cases with high levels of extracellular fibrin(ogen) had significantly upregulated PAI-1 expression in all cortical layers assessed (p < 0.05) and reduced neuronal density (p = 0.017), including in the functionally-relevant layer 5 (p = 0.001). INTERPRETATION: For the first time, we provide unequivocal evidence that fibrin(ogen) is extensively deposited in progressive MS motor cortex, where regulation of fibrinolysis appears perturbed. Progressive MS cases with severe fibrin(ogen) deposition have significantly reduced neuronal density. Future studies are needed to elucidate the provenance and putative neurotoxicity of fibrin(ogen), and its potential impact on clinical disability. Ann Neurol 2017;82:259-270.

  • Cultivating the multiple sclerosis workforce of the future

    3 July 2018

    © 2017 Consortium of Multiple Sclerosis Centers. Multiple sclerosis (MS) is a complex neurologic disorder that affects people with ever-changing needs. The MS health-care field has entered an era of exponential knowledge growth in which better understanding of the immunologic dysregulation of the disease has translated into an expanding array of treatment options. It is estimated that, if it has not already, within the next decade the demands of a growing MS patient population will outstrip the number of professionals dedicated to the management of this chronic, lifelong disease. Therefore, there is a pressing need to attract and retain clinicians in this dynamic field. In response to this need, the Foundation of the Consortium of Multiple Sclerosis Centers organized a 2-day colloquium, a Mentorship Forum, on January 23-24, 2015, bringing together talented internal medicine and neurology trainees from across North America with an interest in MS and neuroimmunology. This article highlights the rationale for the MS Mentorship Forum, its structure and content, and its outcomes. We believe that the stage has been set to interest young, promising clinicians in learning more about MS and to encourage them to consider a career in this field. In so doing, we hope to contribute to the development of the next generation of MS experts to make a palpable difference in the lives of those affected by MS.

  • Effects of dopamine on reinforcement learning and consolidation in Parkinson's disease.

    3 July 2018

    Emerging evidence suggests that dopamine may modulate learning and memory with important implications for understanding the neurobiology of memory and future therapeutic targeting. An influential hypothesis posits that dopamine biases reinforcement learning. More recent data also suggest an influence during both consolidation and retrieval. Eighteen Parkinson's disease patients learned through feedback ON or OFF medication, with memory tested 24 hr later ON or OFF medication (4 conditions, within-subjects design with matched healthy control group). Patients OFF medication during learning decreased in memory accuracy over the following 24 hr. In contrast to previous studies, however, dopaminergic medication during learning and testing did not affect expression of positive or negative reinforcement. Two further experiments were run without the 24 hr delay, but they too failed to reproduce effects of dopaminergic medication on reinforcement learning. While supportive of a dopaminergic role in consolidation, this study failed to replicate previous findings on reinforcement learning.

  • Changes in health-related quality of life (HRQoL) after discharge from intensive care unit: a protocol for a systematic review.

    2 July 2018

    INTRODUCTION: Treatment on an intensive care unit (ICU) imposes a high treatment burden on patients, as well as an economic burden for the healthcare provider. Many studies have recorded health-related quality of life (HRQoL) in patients after treatment on an ICU. We propose a systematic review of these studies. METHODS: We will search the National Library of Medicine's PubMed electronic database (PubMed), the Cochrane database, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science and Open Grey to identify papers reporting quality of life after discharge from ICU. We will include papers including validated quality of life measures. We will examine three categories: populations of patients treated on general ICUs, patients with severe infections and patients with respiratory dysfunction. We will extract HRQoL data. We will assess papers for risk of bias using the QUADAS-2 tool. The strength of our conclusions will depend on the quality and number of papers showing uniform results. ETHICS AND DISSEMINATION: This review will use published literature and contains no primary data; so we do not need ethical approval. We will submit the outcome of the systematic review to a peer-reviewed journal. TRIAL REGISTRATION NUMBER: PROSPERO CRD42015024700.

  • Benefits of flexible prioritization in working memory can arise without costs.

    3 July 2018

    Most recent models conceptualize working memory (WM) as a continuous resource, divided up according to task demands. When an increasing number of items need to be remembered, each item receives a smaller chunk of the memory resource. These models predict that the allocation of attention to high-priority WM items during the retention interval should be a zero-sum game: improvements in remembering cued items come at the expense of uncued items because resources are dynamically transferred from uncued to cued representations. The current study provides empirical data challenging this model. Four precision retrocueing WM experiments assessed cued and uncued items on every trial. This permitted a test for trade-off of the memory resource. We found no evidence for trade-offs in memory across trials. Moreover, robust improvements in WM performance for cued items came at little or no cost to uncued items that were probed afterward, thereby increasing the net capacity of WM relative to neutral cueing conditions. An alternative mechanism of prioritization proposes that cued items are transferred into a privileged state within a response-gating bottleneck, in which an item uniquely controls upcoming behavior. We found evidence consistent with this alternative. When an uncued item was probed first, report of its orientation was biased away from the cued orientation to be subsequently reported. We interpret this bias as competition for behavioral control in the output-driving bottleneck. Other items in WM did not bias each other, making this result difficult to explain with a shared resource model. (PsycINFO Database Record

  • Prioritizing Information during Working Memory: Beyond Sustained Internal Attention.

    3 July 2018

    Working memory (WM) has limited capacity. This leaves attention with the important role of allowing into storage only the most relevant information. It is increasingly evident that attention is equally crucial for prioritizing representations within WM as the importance of individual items changes. Retrospective prioritization has been proposed to result from a focus of internal attention highlighting one of several representations. Here, we suggest an updated model, in which prioritization acts in multiple steps: first orienting towards and selecting a memory, and then reconfiguring its representational state in the service of upcoming task demands. Reconfiguration sets up an optimized perception-action mapping, obviating the need for sustained attention. This view is consistent with recent literature, makes testable predictions, and links WM with task switching and action preparation.

  • Feature-based attentional weighting and spreading in visual working memory.

    3 July 2018

    Attention can be directed at features and feature dimensions to facilitate perception. Here, we investigated whether feature-based-attention (FBA) can also dynamically weight feature-specific representations within multi-feature objects held in visual working memory (VWM). Across three experiments, participants retained coloured arrows in working memory and, during the delay, were cued to either the colour or the orientation dimension. We show that directing attention towards a feature dimension (1) improves the performance in the cued feature dimension at the expense of the uncued dimension, (2) is more efficient if directed to the same rather than to different dimensions for different objects, and (3) at least for colour, automatically spreads to the colour representation of non-attended objects in VWM. We conclude that FBA also continues to operate on VWM representations (with similar principles that govern FBA in the perceptual domain) and challenge the classical view that VWM representations are stored solely as integrated objects.