•Excess brain iron is associated with neurodegeneration.•Even in the absence of disease, brain iron increases with adult age.•QSM is a recent MRI method for estimating brain iron from magnetic ...susceptibility.•QSM studies suggest a potential role of brain iron in age-related cognitive decline.
Quantitative susceptibility mapping (QSM) is a magnetic resonance imaging (MRI) technique that can assess the magnetic properties of cerebral iron in vivo. Although brain iron is necessary for basic neurobiological functions, excess iron content disrupts homeostasis, leads to oxidative stress, and ultimately contributes to neurodegenerative disease. However, some degree of elevated brain iron is present even among healthy older adults. To better understand the topographical pattern of iron accumulation and its relation to cognitive aging, we conducted an integrative review of 47 QSM studies of healthy aging, with a focus on five distinct themes. The first two themes focused on age-related increases in iron accumulation in deep gray matter nuclei versus the cortex. The overall level of iron is higher in deep gray matter nuclei than in cortical regions. Deep gray matter nuclei vary with regard to age-related effects, which are most prominent in the putamen, and age-related deposition of iron is also observed in frontal, temporal, and parietal cortical regions during healthy aging. The third theme focused on the behavioral relevance of iron content and indicated that higher iron in both deep gray matter and cortical regions was related to decline in fluid (speed-dependent) cognition. A handful of multimodal studies, reviewed in the fourth theme, suggest that iron interacts with imaging measures of brain function, white matter degradation, and the accumulation of neuropathologies. The final theme concerning modifiers of brain iron pointed to potential roles of cardiovascular, dietary, and genetic factors. Although QSM is a relatively recent tool for assessing cerebral iron accumulation, it has significant promise for contributing new insights into healthy neurocognitive aging.
Pushed off the map Madden, David J
Urban studies,
06/2018, Volume:
55, Issue:
8
Journal Article
Peer reviewed
Open access
This article examines conflicts over neighbourhood renaming and the politics of place. Toponymy, or the practice of place naming, is central to the constitution of place, and neighbourhood renaming ...is a pervasive urban strategy. But despite its prevalence, the role of neighbourhood toponymic conflict in processes of urban restructuring has not been given sustained engagement from urban scholars. This article uses archival and ethnographic data from an area in Brooklyn, New York to argue that contemporary neighbourhood renaming facilitates uneven local development. Real estate developers and residents of expensive private housing use toponymy to legitimise their privileged positions, while public housing residents experience the same toponymic change as a form of symbolic displacement. Conflicts surrounding neighbourhood renaming should therefore be seen as elements of struggles over resources, property, identity, and belonging in urban space.
本文探讨了街区重命名和地方政治之间的矛盾。地名学（也就是给一个地方命名的行为）是地方建制的核心，街区重命名是一种普遍的城市战略。但是，尽管其普遍存在，城市学者并未对城市结构调整过程中街区命名冲突的影响进行持续的研究。本文采用纽约布鲁克林一个地区的档案和民族志资料，证明当代街区重命名会促进当地发展的不平衡。房地产开发商和昂贵的私人住宅的住户往往通过地名的命名来使他们的特权地位合法化，公共住房居民也经历了同样的地名变化，这是拆迁的一个象征符号。因此，应当将围绕街区重命名的矛盾视为争夺城市资源、财产、身份和归属的重要因素。
BLAST is a commonly-used software package for comparing a query sequence to a database of known sequences; in this study, we focus on protein sequences. Position-specific-iterated BLAST (PSI-BLAST) ...iteratively searches a protein sequence database, using the matches in round i to construct a position-specific score matrix (PSSM) for searching the database in round i + 1. Biegert and Söding developed Context-sensitive BLAST (CS-BLAST), which combines information from searching the sequence database with information derived from a library of short protein profiles to achieve better homology detection than PSI-BLAST, which builds its PSSMs from scratch.
We describe a new method, called domain enhanced lookup time accelerated BLAST (DELTA-BLAST), which searches a database of pre-constructed PSSMs before searching a protein-sequence database, to yield better homology detection. For its PSSMs, DELTA-BLAST employs a subset of NCBI's Conserved Domain Database (CDD). On a test set derived from ASTRAL, with one round of searching, DELTA-BLAST achieves a ROC5000 of 0.270 vs. 0.116 for CS-BLAST. The performance advantage diminishes in iterated searches, but DELTA-BLAST continues to achieve better ROC scores than CS-BLAST.
DELTA-BLAST is a useful program for the detection of remote protein homologs. It is available under the "Protein BLAST" link at http://blast.ncbi.nlm.nih.gov.
Aging and Visual Attention Madden, David J.
Current directions in psychological science,
04/2007, Volume:
16, Issue:
2
Journal Article
Peer reviewed
Open access
Older adults are often slower and less accurate than are younger adults in performing visual-search tasks, suggesting an age-related decline in attentional functioning. Age-related decline in ...attention, however, is not entirely pervasive. Visual search that is based on the observer's expectations (i.e., top-down attention) is relatively preserved as a function of adult age. Neuroimaging research suggests that age-realted decline occurs in the structure and function of brain regions mediating the visual sensory input, whereas activation of regions in the frontal and parietal lobes is often greater for older adults than for younger adults. This increased activation may represent an age-related increase in the role of top-down attention during visual tasks. To obtain a more complete account of age-related decline and preservation of visual attention, current research is beginning to explore the relation of neuroimaging measures of brain structure and function to behavioral measures of visual attention.
This article argues for a reconceptualization of one of the most basic concepts in urban studies: the neighborhood. Traditionally neighborhoods have been understood as clearly bounded, ...quasi‐Westphalian containers or as ‘natural areas’ of urban community. But this approach is widely acknowledged to be under‐theorized. And it fails to account for the ways in which the production of neighborhood is inherently political and often conflictual. After reviewing the ways in which neighborhood has been used in urban sociology and urban planning, this article offers a critical conception of neighborhoods as ‘spatial projects’ on the submetropolitan scale. This approach captures the ways in which neighborhoods are not spaces on a city map, but the uneven, unequal products of complex, ongoing struggles between various groups and institutions. This approach is developed through an ethnographic and historical case study of neighborhood formation in one part of Brooklyn, New York. The article concludes with a discussion of how the language of spatial projects refocuses urban research on the political and economic forces that produce neighborhood in the contemporary city.
There is a strong and growing need in the biology research community for accurate, automated image analysis. Here, we describe CellProfiler 2.0, which has been engineered to meet the needs of its ...growing user base. It is more robust and user friendly, with new algorithms and features to facilitate high-throughput work. ImageJ plugins can now be run within a CellProfiler pipeline.
CellProfiler 2.0 is free and open source, available at http://www.cellprofiler.org under the GPL v. 2 license. It is available as a packaged application for Macintosh OS X and Microsoft Windows and can be compiled for Linux.
anne@broadinstitute.org
Supplementary data are available at Bioinformatics online.
•Across age, moderate-to-strong correlations between standard and high-resolution DWI.•Higher gray matter FA/MD in high-resolution DWI, and stronger age correlation.•Higher white matter connectivity ...in high-resolution DWI, but weaker age correlation.•Only high-resolution MD/connectivity strength mediated age-related cognitive decline.
Healthy neurocognitive aging has been associated with the microstructural degradation of white matter pathways that connect distributed gray matter regions, assessed by diffusion-weighted imaging (DWI). However, the relatively low spatial resolution of standard DWI has limited the examination of age-related differences in the properties of smaller, tightly curved white matter fibers, as well as the relatively more complex microstructure of gray matter. Here, we capitalize on high-resolution multi-shot DWI, which allows spatial resolutions < 1 mm3 to be achieved on clinical 3T MRI scanners. We assessed whether traditional diffusion tensor-based measures of gray matter microstructure and graph theoretical measures of white matter structural connectivity assessed by standard (1.5 mm3 voxels, 3.375 μl volume) and high-resolution (1 mm3 voxels, 1μl volume) DWI were differentially related to age and cognitive performance in 61 healthy adults 18–78 years of age. Cognitive performance was assessed using an extensive battery comprising 12 separate tests of fluid (speed-dependent) cognition. Results indicated that the high-resolution data had larger correlations between age and gray matter mean diffusivity, but smaller correlations between age and structural connectivity. Moreover, parallel mediation models including both standard and high-resolution measures revealed that only the high-resolution measures mediated age-related differences in fluid cognition. These results lay the groundwork for future studies planning to apply high-resolution DWI methodology to further assess the mechanisms of both healthy aging and cognitive impairment.
Against the background of contemporary worldwide transformations of urbanizing spaces, this paper evaluates recent efforts to mobilize the concept of 'assemblage' as the foundation for contemporary ...critical urban theory, with particular attention to a recent paper by McFarlane (
2011a
) in this journal. We argue that there is no single 'assemblage urbanism', and therefore no coherence to arguing for or against the concept in general. Instead, we distinguish between three articulations between urban political economy and assemblage thought. While empirical and methodological applications of assemblage analysis have generated productive insights in various strands of urban studies by building on political economy, we suggest that the ontological application favored by McFarlane and several other assemblage urbanists contains significant drawbacks. In explicitly rejecting concepts of structure in favor of a 'naïve objectivism', it deprives itself of a key explanatory tool for understanding the sociospatial 'context of contexts' in which urban spaces and locally embedded social forces are positioned. Relatedly, such approaches do not adequately grasp the ways in which contemporary urbanization continues to be shaped and contested through the contradictory, hierarchical social relations and institutional forms of capitalism. Finally, the normative foundations of such approaches are based upon a decontextualized standpoint rather than an immanent, reflexive critique of actually existing social relations and institutional arrangements. These considerations suggest that assemblage-based approaches can most effectively contribute to critical urban theory when they are linked to theories, concepts, methods and research agendas derived from a reinvigorated geopolitical economy.
•The relation between cognitive and perceptual decline in aging is unclear.•Correlational analyses do not allow for this relation to be thoroughly examined.•Interventions or experimental ...manipulations of perception are needed.•Studies show that perceptual signal strength modification affects cognition.•We proposed future directions for the field.
Several hypotheses attempt to explain the relation between cognitive and perceptual decline in aging (e.g., common-cause, sensory deprivation, cognitive load on perception, information degradation). Unfortunately, the majority of past studies examining this association have used correlational analyses, not allowing for these hypotheses to be tested sufficiently. This correlational issue is especially relevant for the information degradation hypothesis, which states that degraded perceptual signal inputs, resulting from either age-related neurobiological processes (e.g., retinal degeneration) or experimental manipulations (e.g., reduced visual contrast), lead to errors in perceptual processing, which in turn may affect non-perceptual, higher-order cognitive processes. Even though the majority of studies examining the relation between age-related cognitive and perceptual decline have been correlational, we reviewed several studies demonstrating that visual manipulations affect both younger and older adults’ cognitive performance, supporting the information degradation hypothesis and contradicting implications of other hypotheses (e.g., common-cause, sensory deprivation, cognitive load on perception). The reviewed evidence indicates the necessity to further examine the information degradation hypothesis in order to identify mechanisms underlying age-related cognitive decline.
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