Many studies have argued for distinct but complementary contributions from each hemisphere in the control of movements to visual targets. Investigators have attempted to extend observations from patients with unilateral left- and right-hemisphere damage, to those using neurologically-intact participants, by assuming that each hand has privileged access to the contralateral hemisphere. Previous attempts to illustrate right hemispheric contributions to the control of aiming have focussed on increasing the spatial demands of an aiming task, to attenuate the typical right hand advantages, (...) to try to enhance a left hand reaction time advantage in right-handed participants. These early attempts have not been successful. The present study circumnavigates some of the theoretical and methodological difficulties of some of the earlier experiments, by using three different tasks linked directly to specialized functions of the right hemisphere: bisecting, the gap effect, and visuospatial localization. None of these tasks were effective in reducing the magnitude of left hand reaction time advantages in right handers. Results are discussed in terms of alternatives to right hemispheric functional explanations of the effect, the one-dimensional nature of our target arrays, power and precision given the size of the left hand RT effect, and the utility of examining the proportions of participants who show these effects, rather than exclusive reliance on measures of central tendency and their associated null hypothesis significance tests. (shrink)

We assessed how synchronous speech listening and lipreading affects speech recognition in acoustic noise. In simple audiovisual perceptual tasks, inverse effectiveness is often observed, which holds that the weaker the unimodal stimuli, or the poorer their signal-to-noise ratio, the stronger the audiovisual benefit. So far, however, inverse effectiveness has not been demonstrated for complex audiovisual speech stimuli. Here we assess whether this multisensory integration effect can also be observed for the recognizability of spoken words. To that end, we presented audiovisual (...) sentences to 18 native-Dutch normal-hearing participants, who had to identify the spoken words from a finite list. Speech-recognition performance was determined for auditory-only, visual-only (lipreading) and auditory-visual conditions. To modulate acoustic task difficulty, we systematically varied the auditory signal-to-noise ratio. In line with a commonly-observed multisensory enhancement on speech recognition, audiovisual words were more easily recognized than auditory-only words (recognition thresholds of -15 dB and -12 dB, respectively). We here show that the difficulty of recognizing a particular word, either acoustically or visually, determines the occurrence of inverse effectiveness in audiovisual word integration. Thus, words that are better heard or recognized through lipreading, benefit less from bimodal presentation. Audiovisual performance at the lowest acoustic signal-to-noise ratios (45%) fell below the visual recognition rates (60%), reflecting an actual deterioration of lipreading in the presence of excessive acoustic noise. This suggests that the brain may adopt a strategy in which attention has to be divided between listening and lipreading. (shrink)

Background Speech understanding may rely not only on auditory, but also on visual information. Non-invasive functional neuroimaging techniques can expose the neural processes underlying the integration of multisensory processes required for speech understanding in humans. Nevertheless, noise (from fMRI) limits the usefulness in auditory experiments, and electromagnetic artefacts caused by electronic implants worn by subjects can severely distort the scans (EEG, fMRI). Therefore, we assessed audio-visual activation of temporal cortex with a silent, optical neuroimaging technique: functional near-infrared spectroscopy (fNIRS). Methods (...) We studied temporal cortical activation as represented by concentration changes of oxy- and deoxy-hemoglobin in four, easy-to-apply fNIRS optical channels of 33 normal-hearing adult subjects and 5 post-lingually deaf cochlear implant (CI) users in response to supra-threshold unisensory auditory and visual, as well as to congruent auditory-visual speech stimuli. Results Activation effects were not visible from single fNIRS channels. However, by discounting physiological noise through reference channel subtraction, auditory, visual and audiovisual speech stimuli evoked concentration changes for all sensory modalities in both cohorts (p<0.001). Auditory stimulation evoked larger concentration changes than visual stimuli (p<0.001). A saturation effect was observed for the audiovisual condition. Conclusions Physiological, systemic noise can be removed from fNIRS signals by reference channel subtraction. The observed multisensory enhancement of an auditory cortical channel can be plausibly described by a simple addition of the auditory and visual signals with saturation. (shrink)

This collection of 11 studies provides a new discussion of Lucretius' History of the Human Mankind and of other topics (Lucretius' explanation of sleep, dreams and optical illusions) in relationship to other philosophical and scientific doctrines of Antiquity.

This collection of 11 studies provides a new discussion of Lucretius' History of the Human Mankind and of other topics (Lucretius' explanation of sleep, dreams and optical illusions) in relationship to other philosophical and scientific doctrines of Antiquity.

Rationale, aims and objectives Given the increasing prevalence of cataract and demand for cataract extraction surgery, patients must often wait to undergo this procedure. We validated a previously developed priority scoring system in terms of clinical variables, pre-intervention health status, appropriateness of surgery and gain in visual acuity (VA) and health-related quality of life (HRQoL).Methods Explicit prioritization criteria for cataract extraction created by a variation of the Research and Development (RAND) and University of California Los Angeles appropriateness methodology were retrospectively (...) applied to a prospective cohort of 5257 patients on waiting lists to undergo cataract by phacoemulsification at 17 hospitals in Spain. Demographic data, clinical data and data related to surgical technique were collected by trained ophthalmologists. Patients were evaluated by their ophthalmologist before the intervention and 6 weeks afterward. They also completed, by mail, the Visual Function Index (VF-14) before the intervention and 3 months afterward.Results High-priority patients experienced greater improvement in VA and HRQoL than those classified as intermediate or low-priority (P < 0.0001), even after adjusting by VA and the VF-14 score at baseline. The time to intervention was the same for high-priority patients as it was for intermediate and low-priority patients.Conclusions The priority score we developed identified patients most likely to experience the greatest improvements from cataract extraction. Use of this tool could provide a fairer and more rational way to prioritize patients for cataract extraction. (shrink)

Background: Dementia care at home often involves decisions in which the caregiver must weigh safety concerns with respect for autonomy. These dilemmas can lead to situations where caregivers provide care against the will of persons living with dementia, referred to as involuntary treatment. To prevent this, insight is needed into how family caregivers of persons living with dementia deal with care situations that can lead to involuntary treatment. Objective: To identify and describe family caregivers’ experiences regarding care decisions for situations (...) that can lead to involuntary treatment use in persons living with dementia at home. Research design: A qualitative descriptive interview design. Data were analysed using the Qualitative Analysis Guide of Leuven. Participants and research context: A total of 10 family caregivers providing care for 13 persons living with dementia participated in in-depth semi-structured interviews. Participants were recruited by registered nurses via purposive sampling. Ethical consideration: The study protocol was approved by the Ethics Committee of the University Hospitals Leuven and the Medical Ethical Test Committee Zuyderland. Findings: Family caregivers experience the decision-making process concerning care dilemmas that can lead to involuntary treatment as complicated, stressful and exhausting. Although they consider safety and autonomy as important values, they struggle with finding the right balance between them. Due to the progressive and unpredictable nature of dementia, they are constantly seeking solutions while they adapt to new situations. Family caregivers feel responsible and experience social pressure for the safety of persons living with dementia. They may be blamed if something adverse happens to the persons living with dementia, which increases an already stressful situation. Their experience is influenced by characteristics of the care triad such as practical and emotional support, knowledge, and previous experiences. Discussion and conclusion: To prevent involuntary treatment, professionals need to proactively inform family caregivers, and they need to support each other in dealing with complex care situations. (shrink)

Originally published in 1962. A clear and simple account of the growth and structure of Mathematical Logic, no earlier knowledge of logic being required. After outlining the four lines of thought that have been its roots - the logic of Aristotle, the idea of all the parts of mathematics as systems to be designed on the same sort of plan as that used by Euclid and his Elements, and the discoveries in algebra and geometry in 1800-1860 - the book goes (...) on to give some of the main ideas and theories of the chief writers on Mathematical Logic: De Morgan, Boole, Jevons, Pierce, Frege, Peano, Whitehead, Russell, Post, Hilbert and Goebel. Written to assist readers who require a general picture of current logic, it will also be a guide for those who will later be going more deeply into the expert details of this field. (shrink)

A theory of the joint measurement of quantum mechanical observables is generalized in order to make it applicable to the measurement of the local observables of field theory. Subsequently, the property of local commutativity, which is usually introduced as a postulate, is derived by means of the theory of measurement from a requirement of mutual nondisturbance, which, for local observables performed at a spacelike distance from each other, is interpreted as a requirement of macrocausality. Alternative attempts at establishing a deductive (...) relationship between relativistic causality and local commutativity are reviewed, but found wanting, either because of the assumption of an unwarranted objectivity of the object system (algebraic approach) or because of the use of a projection postulate (operational approach). Finally, the quantum mechanical nonobjectivity is related to certain features of nonlocality which are present in the formalism of quantum mechanics. (shrink)