Bistable Percepts in the Brain: fMRI Contrasts Monocular Pattern Rivalry and Binocular Rivalry

The neural correlates of binocular rivalry have been actively debated in recent years, and are of considerable interest as they may shed light on mechanisms of conscious awareness. In a related phenomenon, monocular rivalry, a composite image is shown to both eyes. The subject experiences perceptual alternations in which the two stimulus components alternate in clarity or salience. The experience is similar to perceptual alternations in binocular rivalry, although the reduction in visibility of the suppressed component is greater for binocular rivalry, especially at higher stimulus contrasts. We used fMRI at 3T to image activity in visual cortex while subjects perceived either monocular or binocular rivalry, or a matched non-rivalrous control condition. The stimulus patterns were left/right oblique gratings with the luminance contrast set at 9%, 18% or 36%. Compared to a blank screen, both binocular and monocular rivalry showed a U-shaped function of activation as a function of stimulus contrast, i.e. higher activity for most areas at 9% and 36%. The sites of cortical activation for monocular rivalry included occipital pole (V1, V2, V3), ventral temporal, and superior parietal cortex. The additional areas for binocular rivalry included lateral occipital regions, as well as inferior parietal cortex close to the temporoparietal junction (TPJ). In particular, higher-tier areas MT+ and V3A were more active for binocular than monocular rivalry for all contrasts. In comparison, activation in V2 and V3 was reduced for binocular compared to monocular rivalry at the higher contrasts that evoked stronger binocular perceptual suppression, indicating that the effects of suppression are not limited to interocular suppression in V1

Review article - health promotion at work place - health monitoring at work site - a logistic health appraisal

This article on health appraisals at the place of work discusses various work situations, exposures, parameters to be studied and the shortcomings of some of the parameters. Elaborate information is given on many work situations and interpretations of screening tests. Different organ system affections have been dealt with reference to offending chemicals. Practical studies have been cited about the implications of biological monitoring in real-time situations

Low-dimensional tracking of association structures in categorical data

In modern applications, such as text mining and signal processing, large amounts of categorical data are produced at a high rate and are characterized by association structures changing over time. Multiple correspondence analysis (MCA) is a well established dimension reduction method to explore the associations within a set of categorical variables. A critical step of the MCA algorithm is a singular value decomposition (SVD) or an eigenvalue decomposition (EVD) of a suitably transformed matrix. The high computational and memory requirements of ordinary SVD and EVD make their application impractical on massive or sequential data sets. Several enhanced SVD/EVD approaches have been recently introduced in an effort to overcome these issues. The aim of the present contribution is twofold: (1) to extend MCA to a split-apply-combine framework, that leads to an exact and parallel MCA implementation; (2) to allow for incremental updates (downdates) of existing MCA solutions, which lead to an approximate yet highly accurate solution. For this purpose, two incremental EVD and SVD approaches with desirable properties are revised and embedded in the context of MCA