When moving faces activate the house area: an fMRI study of object-file retrieval

<p>Abstract</p> <p>Background</p> <p>The visual cortex of the human brain contains specialized modules for processing different visual features of an object. Confronted with multiple objects, the system needs to attribute the correct features to each object (often referred to as 'the binding problem'). The brain is assumed to integrate the features of perceived objects into object files – pointers to the neural representations of these features, which outlive the event they represent in order to maintain stable percepts of objects over time. It has been hypothesized that a new encounter with one of the previously bound features will reactivate the other features in the associated object file according to a kind of pattern-completion process.</p> <p>Methods</p> <p>Fourteen healthy volunteers participated in an fMRI experiment and performed a task designed to measure the aftereffects of binding visual features (houses, faces, motion direction). On each trial, participants viewed a particular combination of features (S1) before carrying out a speeded choice response to a second combination of features (S2). Repetition and alternation of all three features was varied orthogonally.</p> <p>Results</p> <p>The behavioral results showed the standard partial repetition costs: a reaction time increase when one feature was repeated and the other feature alternated between S1 and S2, as compared to complete repetitions or alternations of these features. Importantly, the fMRI results provided evidence that repeating motion direction reactivated the object that previously moved in the same direction. More specifically, perceiving a face moving in the same direction as a just-perceived house increased activation in the parahippocampal place area (PPA). A similar reactivation effect was not observed for faces in the fusiform face area (FFA). Individual differences in the size of the reactivation effects in the PPA and FFA showed a positive correlation with the corresponding partial repetition costs.</p> <p>Conclusion</p> <p>Our study provides the first neural evidence that features are bound together on a single presentation and that reviewing one feature automatically reactivates the features that previously accompanied it.</p

Characterization of displacement forces and image artifacts in the presence of passive medical implants in low-field (< 100 mT) permanent magnet-based MRI systems, and comparisons with clinical MRI systems

Purpose: To investigate the displacement forces and image artifacts associated with passive medical implants for recently-developed low-field (128) turbo spin echo sequences can be run with short inter-pulse times (5-10 ms) within SAR limits.Conclusions: This work presents the first evaluation of the effects of passive implants at field strengths less than 100 mT in terms of displacement forces, image artifacts and SAR. The results support previous claims that such systems can be used safely and usefully in challenging enviroments such as the intensive care unit.Radiolog

The Application and Implications of Novel Deterministic Sensitivity Analysis Methods

Deterministic sensitivity analyses (DSA) remain important to interpret the effect of uncertainties in individual parameters on results of cost-effectiveness analyses. Classic DSA methodologies may lead to wrong conclusions due to a lack of or misleading information regarding marginal effects, non-linearity, likelihood and correlations. In addition, tornado diagrams are misleading in some situations. Recent advances in DSA methods have the potential to provide decision makers with more reliable information regarding the effects of uncertainties in individual parameters. This practical application discusses advances to classic DSA methods and their implications. Three methods are discussed: stepwise DSA, distributional DSA and probabilistic DSA. For each method, the technical specifications, options for presenting results, and its implications for decision making are discussed. Options for visualizing DSA results in incremental cost-effectiveness ratios and in incremental net benefits are presented. The use of stepwise DSA increases interpretability of marginal effects and non-linearities in the model, which is especially relevant when arbitrary ranges are implemented. Using the probability distribution of each parameter in distributional DSA provides insight on the likelihood of model outcomes while probabilistic DSA also includes the effects of correlations between parameters. Probabilistic DSA, preferably expressed in incremental net benefit, is the most appropriate method for providing insight on the effect of uncertainty in individual parameters on the estimate of cost effectiveness. However, the opportunities provided by probabilistic DSA may not always be needed for decision making. Other DSA methods, in particular distributional DSA, can sometimes be sufficient depending on model features. Decision makers must determine to which extent they will accept and implement these new and improved DSA methodologies and adjust guidelines accordingly

Feasibility of pseudocontinuous arterial spin labeling at 7 T with whole-brain coverage

Neuro Imaging Researc

Evidence-based cardiovascular care in the community: A population-based cross-sectional study

BACKGROUND: Ischaemic heart disease and congestive heart failure are common and important conditions in family practice. Effective treatments may be underutilized, particularly in women and the elderly. The objective of the study was to determine the rate of prescribing of evidence-based cardiovascular medications and determine if these differed by patient age or sex. METHODS: We conducted a two-year cross-sectional study involving all hospitals in the province of Nova Scotia, Canada. Subjects were all patients admitted with ischaemic heart disease with or without congestive heart failure between 15 October 1997 and 14 October 1999. The main measure was the previous outpatient use of recommended medications. Chi-square analyses followed by multivariate logistic regression analyses were used to examine age-sex differences. RESULTS: Usage of recommended medications varied from approximately 60% for beta-blockers and angiotensin converting enzyme (ACE) inhibitors to 90% for antihypertensive agents. Patients aged 75 and over were significantly less likely than younger patients to be taking any of the medication classes. Following adjustment for age, there were no significant differences in medication use by sex except among women aged 75 and older who were more likely to be taking beta-blockers than men in the same age group. CONCLUSIONS: The use of evidence-based cardiovascular medications is rising and perhaps approaching reasonable levels for some drug classes. Family physicians should ensure that all eligible patients (prior myocardial infarction, congestive failure) are offered beta-blockers or ACE inhibitors

Quadrature Operation of Segmented Dielectric Resonators Facilitated With Metallic Connectors

Radiolog