Apraxia and Alzheimer’s Disease: Review and Perspectives

Apraxia is one of the cognitive deficits that characterizes Alzheimer\u27s disease. Despite its prevalence and relevance to diagnosing Alzheimer\u27s disease, this topic has received little attention and is without comprehensive review. The review herein is aimed to fill this gap by first presenting an overview of the impairment caused in different clinical situations: pantomime of tool use, single tool use, real tool use, mechanical problem solving, function and manipulation knowledge tasks, and symbolic/meaningless gestures. On the basis of these results, we then propose alternative interpretations regarding the nature of the underlying mechanisms impaired by the disease. Also presented are principal methodological issues precluding firm conclusions from being drawn

Apraxie et maladie d’Alzheimer : revue et perspectives

Alzheimer’s disease is characterized by the progressive impairment of cognitive functions. Whereas the study of amnesia, aphasia, agnosia and dysexecutive impairments to a lesser extent has been well documented, apraxia has received little attention [1]. The aim of this review is to fill this gap by presenting an overview of the praxis impairment, which typically appears in the course of the disease. This review focuses on transitive gestures (i.e., tool use tasks) and intransitive gestures (i.e., symbolic and meaningless). On the basis of these results, we propose interpretations as to the nature of the underlying mechanisms impaired by the disease. Finally, we provide some answers to help clinicians to better understand and assess the apraxic disorders in Alzheimer’s disease

Tool use in left brain damage and Alzheimer's disease: What about function and manipulation knowledge?

Tool use disorders are usually associated with difficulties in retrieving function and manipulation knowledge. Here, we investigate tool use (Real Tool Use, RTU), function (Functional Association, FA) and manipulation knowledge (Gesture Recognition, GR) in 17 left-brain-damaged (LBD) patients and 14 AD patients (Alzheimer disease). LBD group exhibited predicted deficit on RTU but not on FA and GR while AD patients showed deficits on GR and FA with preserved tool use skills. These findings question the role played by function and manipulation knowledge in actual tool use

Bostonia: The Boston University Alumni Magazine. Volume 10

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Rethinking the Cognitive Mechanisms Underlying Pantomime of Tool Use: Evidence from Alzheimer's Disease and Semantic Dementia

OBJECTIVES: Pantomiming the use of familiar tools is a central test in the assessment of apraxia. However, surprisingly, the nature of the underlying cognitive mechanisms remains an unresolved issue. The aim of this study is to shed a new light on this issue by exploring the role of functional, mechanical, and manipulation knowledge in patients with Alzheimer\u27s disease and semantic dementia and apraxia of tool use. METHODS: We performed multiple regression analyses with the global performance and the nature of errors (i.e., production and conception) made during a pantomime of tool use task in patients and control participants as dependent variables and tasks investigating functional, mechanical, and manipulation knowledge as predictors. RESULTS: We found that mechanical problem solving, assessing mechanical knowledge, was a good predictor of the global performance of pantomime of tool use. We also found that occurrence of conception errors was robustly predicted by the task assessing functional knowledge whereas that of production errors was not explained by only one predictor. CONCLUSIONS: Our results suggest that both functional and mechanical knowledge are important to pantomime the use of tools. To our knowledge, this is the first demonstration that mechanical knowledge plays a role in pantomime of tool use. Although impairment in pantomime of tool use tasks (i.e., apraxia) is widely explained by the disruption of manipulation knowledge, we propose that pantomime of tool use is a complex problem-solving task. (JINS, 2017, 23, 128-138)

Direct constraint on the distance of y2 Velorum from AMBER/VLTI observations

In this work, we present the first AMBER observations, of the Wolf-Rayet and O (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the telescopes UT2, UT3, and UT4 on baselines ranging from 46m to 85m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R = 1500 in the spectral band 1.95-2.17 micron. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. We show that the AMBER observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. The expected absolute separation and position angle at the time of observations were 5.1±0.9mas and 66±15° respectively. However, we infer a separation of 3.62+0.11-0.30 mas and a position angle of 73+9-11°. Our analysis thus implies that the binary system lies at a distance of 368+38-13 pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258+41-31 pc

Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument

We present the first NIR spectro-interferometry of the LBV Eta Carinae. The K band observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer using three 8.2m Unit Telescopes with baselines from 42 to 89m. The aim of this work is to study the wavelength dependence of Eta Car's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution. The medium spectral resolution observations (R=1,500) were performed in the wavelength range around both the HeI 2.059 micron and the Br gamma 2.166 micron emission lines, the high spectral resolution observations (R=12,000) only in the Br gamma line region. In the K-band continuum, a diameter of 4.0 +/-0.2 mas (Gaussian FWHM, fit range 28-89m) was measured for Eta Car's optically thick wind region. If we fit Hillier et al. (2001) model visibilities to the observed AMBER visibilities, we obtain 50 % encircled-energy diameters of 4.2, 6.5 and 9.6mas in the 2.17 micron continuum, the HeI, and the Br gamma emission lines, respectively. In the continuum near the Br gamma line, an elongation along a position angle of 120+/-15 degrees was found, consistent with previous VLTI/VINCI measurements by van Boekel et al. (2003). We compare the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. Furthermore, we discuss the detectability of the hypothetical hot binary companion. For the interpretation of the non-zero differential and closure phases measured within the Br gamma line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.Comment: 22 pages, 14 figures, 2 tables; A&A in pres

Constraining the wind launching region in Herbig Ae stars: AMBER/VLTI spectroscopy of HD 104237

This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Aims. We investigate the origin of the Brγ emission of the Herbig Ae star HD 104237 on Astronomical Unit (AU) scales. Methods. Using AMBER/VLTI at a spectral resolution R = 1500 we spatially resolve the emission in both the Brγ line and the adjacent continuum. Results. The visibility does not vary between the continuum and the Brγ line, even though the line is strongly detected in the spectrum, with a peak intensity 35% above the continuum. This demonstrates that the line and continuum emission have similar size scales. We assume that the K-band continuum excess originates in a “puffed-up” inner rim of the circumstellar disk, and discuss the likely origin of Brγ. Conclusions. We conclude that this emission most likely arises from a compact disk wind, launched from a region 0.2–0.5 AU from the star, with a spatial extent similar to that of the near infrared continuum emission region, i.e., very close to the inner rim location.This work has been partly supported by the MIUR COFIN grant 2003/027003-001 and 025227/2004 to the INAFOsservatorio Astrofisico di Arcetri. This project has benefited from funding from the French Centre National de la Recherche Scientifique (CNRS) through the Institut National des Sciences de l’Univers (INSU) and its Programmes Nationaux (ASHRA, PNPS). The authors from the French laboratories would like to thank the successive directors of the INSU/CNRS directors. C. Gil work was supported in part by the Fundac¸˜ao para a Ciˆencia e a Tecnologia through project POCTI/CTE-AST/55691/2004 from POCTI,with funds from the European program FEDER

Interferometric data reduction with AMBER/VLTI. Principle, estimators, and illustration

This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Aims. In this paper, we present an innovative data reduction method for single-mode interferometry. It has been specifically developed for the AMBER instrument, the three-beam combiner of the Very Large Telescope Interferometer, but it can be derived for any single-mode interferometer. Methods. The algorithm is based on a direct modelling of the fringes in the detector plane. As such, it requires a preliminary calibration of the instrument in order to obtain the calibration matrix that builds the linear relationship between the interferogram and the interferometric observable, which is the complex visibility. Once the calibration procedure has been performed, the signal processing appears to be a classical least-square determination of a linear inverse problem. From the estimated complex visibility, we derive the squared visibility, the closure phase, and the spectral differential phase. Results. The data reduction procedures have been gathered into the so-called amdlib software, now available for the community, and are presented in this paper. Furthermore, each step in this original algorithm is illustrated and discussed from various on-sky observations conducted with the VLTI, with a focus on the control of the data quality and the effective execution of the data reduction procedures. We point out the present limited performances of the instrument due to VLTI instrumental vibrations which are difficult to calibrate.The AMBER project4 was founded by the French Centre National de la Recherche Scientifique (CNRS), the Max Planck Institute für Radioastronomie (MPIfR) in Bonn, the Osservatorio Astrofisico di Arcetri (OAA) in Firenze, the French Region “Provence Alpes Côte D’Azur” and the European Southern Observatory (ESO). The CNRS funding has been made through the Institut National des Sciences de l’Univers (INSU) and its Programmes Nationaux (ASHRA, PNPS, PNP). The OAA co-authors acknowledge partial support from MIUR grants to the Arcetri Observatory: A LBT interferometric arm, and analysis of VLTI interferometric data and From Stars to Planets: accretion, disk evolution and planet formation and from INAF grants to the Arcetri Observatory Stellar and Extragalactic Astrophysics with Optical Interferometry. C. Gil work was supported in part by the Fundação para a Ciência e a Tecnologia through project POCTI/CTE-AST/55691/2004 from POCTI, with funds from the European program FEDER

Fyn Mediates Leptin Actions in the Thymus of Rodents

BACKGROUND:Several effects of leptin in the immune system rely on its capacity to modulate cytokine expression and apoptosis in the thymus. Surprisingly, some of these effects are dependent on signal transduction through the IRS1/PI3-kinase, but not on the activation of JAK2. Since all the well known effects of leptin in different cell types and tissues seem to be dependent on JAK2 activation, we hypothesized that, at least for the control of thymic function, another, unknown kinase could mediate the transduction of the leptin signal from the ObR towards the IRS1/PI3-kinase signaling cascade. METHODOLOGY/PRINCIPAL FINDINGS:Here, by employing immunoblot, real-time PCR and flow citometry we show that the tyrosine kinase, Fyn, is constitutively associated with the ObR in thymic cells. Following a leptin stimulus, Fyn undergoes an activating tyrosine phosphorylation and a transient association with IRS1. All these effects are independent of JAK2 activation and, upon Fyn inhibition, the signal transduction towards IRS1/PI3-kinase is abolished. In addition, the inhibition of Fyn significantly modifies the effects of leptin on thymic cytokine expression. CONCLUSION/SIGNIFICANCE:Therefore, in the thymus, Fyn acts as a tyrosine kinase that transduces the leptin signal independently of JAK2 activation, and mediates some of the immunomodulatory effects of leptin in this tissue