Search results for " processing"

An Information-Theoretic Framework to Map the Spatiotemporal Dynamics of the Scalp Electroencephalogram

2016

We present the first application of the emerging framework of information dynamics to the characterization of the electroencephalography (EEG) activity. The framework provides entropy-based measures of information storage (self entropy, SE) and information transfer (joint transfer entropy (TE) and partial TE), which are applied here to detect complex dynamics of individual EEG sensors and causal interactions between different sensors. The measures are implemented according to a model-free and fully multivariate formulation of the framework, allowing the detection of nonlinear dynamics and direct links. Moreover, to deal with the issue of volume conduction, a compensation for instantaneous e…

Instantaneous Transfer Entropy for the Study of Cardiovascular and Cardio-Respiratory Nonstationary Dynamics

2017

Objective: Measures of transfer entropy (TE) quantify the direction and strength of coupling between two complex systems. Standard approaches assume stationarity of the observations, and therefore are unable to track time-varying changes in nonlinear information transfer with high temporal resolution. In this study, we aim to define and validate novel instantaneous measures of TE to provide an improved assessment of complex nonstationary cardiorespiratory interactions. Methods: We here propose a novel instantaneous point-process TE (ipTE) and validate its assessment as applied to cardiovascular and cardiorespiratory dynamics. In particular, heartbeat and respiratory dynamics are characteriz…

Perceived collective burnout: a multilevel explanation of burnout

2011

Building up on the socially induced model of burnout and the job demands-resources model, we examine how burnout can transfer without direct contagion or close contact among employees. Based on the social information processing approach and the conservation of resources theory, we propose that perceived collective burnout emerges as an organizational-level construct (employees' shared perceptions about how burned out are their colleagues) and that it predicts individual burnout over and above indicators of demands and resources. Data were gathered during the first term and again during the last term of the academic year among 555 teachers from 100 schools. The core dimensions of burnout, ex…

Improved T2* assessment in liver iron overload by magnetic resonance imaging.

2009

In the clinical MRI practice, it is common to assess liver iron overload by T2* multi-echo gradient-echo images. However, there is no full consensus about the best image analysis approach for the T2* measurements. The currently used methods involve manual drawing of a region of interest (ROI) within MR images of the liver. Evaluation of a representative liver T2* value is done by fitting an appropriate model to the signal decay within the ROIs vs. the echo time. The resulting T2* value may depend on both ROI placement and choice of the signal decay model. The aim of this study was to understand how the choice of the analysis methodology may affect the accuracy of T2* measurements. A softwar…

Volumetry of Ventilated Airspaces by 3He MRI

2001

To develop a validated post-processing routine for volumetry of the ventilated airspaces by 3He MRI.3Helium MRI and pulmonary function tests were performed in seven healthy volunteers. After segmentation of ventilated airspaces, their volumes were calculated. Functional residual capacity (FRC) was used as a reference. For comparison of absolute volumes, correction factors were evaluated.Mean lung volume (+/- standard deviation) calculated from 3He MRI was 4,082 +/- 908 mL and mean FRC was 3,696 +/- 1166 mL, with a mean difference of 386 mL (r = 0.88). After correction for the relative pulmonary air content (factor 0.82), posture (0.72), and the individual tidal volume, 3He MRI volume was 3,…

Three-dimensional (3D) versus two-dimensional (2D) laparoscopic adrenalectomy: A case-control study

2016

Abstract Introduction Laparoscopic adrenalectomy is today considered the gold standard of treatment for adrenal tumors. The development of high definition cameras does not eliminate the major limitation of two-dimensional (2D) laparoscopy: lack of depth perception and loss of spatial orientation. Tree-dimensional (3D) HD laparoscopy was developed as an alternative to conventional 2D laparoscopy. Methods We report our experience with use of 3D vision system for laparoscopic adrenalectomy. Between January 2009 and March 2015 we performed a total of 52 laparoscopic adrenalectomies. In this case-control study we considered 13 laparoscopic adrenalectomies performed with three-dimensional (3D) vi…

Effects of a 21 days space flight on the mechanical performance and the EMG power spectrum of the leg muscles

2002

The effect of associative strength on semantic priming in schizophrenia

2017

The present research was designed to investigate the pattern of semantic priming in schizophrenia as a function of strength of association (or semantic distance between concepts in the semantic network). Thirty schizophrenia patients, without formal thought disorder, and twenty-nine healthy controls participated in a lexical decision task in which prime-target associative strength (strong, weak and not related) and stimulus-onset asynchrony (SOA: 250 ms and 750 ms) were manipulated. Patients and controls showed the same associative strength effect on RTs. In the short SOA condition priming effects were obtained for both strong and weak prime-target associative conditions. However in the lon…

Objective measurement of intraocular forward light scatter using Hartmann-Shack spot patterns from clinical aberrometers. Model-eye and human-eye stu…

2007

Purpose To apply software-based image-analysis tools to objectively determine intraocular scatter determined from clinically derived Hartmann-Shack patterns. Setting Aston Academy of Life Sciences, Aston University, Birmingham, United Kingdom, and Department of Optics, University of Valencia, Valencia, Spain. Methods Purpose-designed image-analysis software was used to quantify scatter from centroid patterns obtained using a clinical Hartmann-Shack analyzer (WASCA, Zeiss/Meditec). Three scatter values, as the maximum standard deviation within a lenslet for all lenslets in the pattern, were obtained in 6 model eyes and 10 human eyes. In the model-eye sample, patterns were obtained in 4 sessi…

Associative and semantic priming effects occur at very short stimulus-onset asynchronies in lexical decision and naming

1997

Abstract Prior research has found significant associative/semantic priming effects at very short stimulus-onset asynchronies (SOAs) in experimental tasks such as lexical decision, but not in naming tasks (however, see Lukatela and Turvey, 1994 ). In this paper, the time course of associative priming effects was analyzed at several very short SOAs (33, 50, and 67 ms), using the masked priming paradigm ( Forster and Davis, 1984 ), both in lexical decision (Experiment 1) and naming (Experiment 2). The results show small—but significant—associative priming effects in both tasks. Additionally, using the masked priming procedure at the 67 ms SOA, Experiments 3 and 4, shows facilitatory priming ef…