Self-monitoring in schizophrenia : weighting exteroceptive visual signals against self-generated vestibular cues

Disturbances in self-monitoring are core symptoms of schizophrenia. Some research suggests an over-reliance on exteroceptive cues and a reduced weighting of self-generated interoceptive signals to guide perception. The vestibular sense provides important self-generated information about the body in space. Alterations of vestibular function are reported in schizophrenia, but it is unknown whether internally generated vestibular information is discounted in favour of exteroceptive input. In this study, we test for evidence of an over-reliance on exteroceptive visual cues and a reduced weighting of vestibular signals in guiding perception. In a group of individuals with schizophrenia and healthy controls, we used a well-studied visual illusion – the Tilt Illusion – to probe the respective weight given to visual and vestibular cues in judging line orientation. The Tilt Illusion reveals that perceived orientation of a vertical grating is biased by the orientation in its surround. This illusion increases when the head is tilted, due to the reduced reliability of vestibular information that would otherwise provide an internally generated reference for vertical. We predicted that an over-reliance on exteroceptive cues in schizophrenia would lead to a reduced susceptibility to the effects of head position on Tilt Illusion strength. We find no difference between patients and controls. Both groups show comparable Tilt Illusion magnitudes that increase when the head is tilted. Thus, our findings suggest that chronic patients with schizophrenia adequately combine self-generated vestibular cues and exteroceptive visual input to judge line verticality. A stronger reliance on exteroceptive information over internally generated signals in guiding perception is not evident in our data. Deficits in self-monitoring might therefore be modality specific or state dependant

Examining motion speed processing in schizophrenia using the flash lag illusion

Research on visual perception in schizophrenia suggests a deficit in motion processing. Specifically, difficulties with discriminating motion speed are commonly reported. However, speed discrimination tasks typically require participants to make judgments about the difference between two stimuli in a two-interval forced choice (2IFC) task. Such tasks not only tap into speed processing mechanisms, but also rely on higher executive functioning including working memory and attention which has been shown to be compromised in schizophrenia. We used the Flash Lag illusion to examine speed processing in patients with schizophrenia. Based on previous research showing a strong dependence between motion speed and the illusion magnitude, we expected a deficit in speed processing to alter this relationship. A motion processing deficit in patients would also predict overall reductions in perceived lag. We found the magnitude and speed dependence of the Flash Lag illusion to be similar in patients and controls. Together, the findings suggest no general abnormality in motion speed processing in schizophrenia

Belief Revision and Delusions: How Do Patients with Schizophrenia Take Advice?

The dominant cognitive model that accounts for the persistence of delusional beliefs in schizophrenia postulates that patients suffer from a general deficit in belief revision. It is generally assumed that this deficit is a consequence of impaired reasoning skills. However, the possibility that such inflexibility affects the entire system of a patient's beliefs has rarely been empirically tested. Using delusion-neutral material in a well-documented advice-taking task, the present study reports that patients with schizophrenia: 1) revise their beliefs, 2) take into account socially provided information to do so, 3) are not overconfident about their judgments, and 4) show less egocentric advice-discounting than controls. This study thus shows that delusional patients' difficulty in revising beliefs is more selective than had been previously assumed. The specificities of the task and the implications for a theory of delusion formation are discussed

Waste blast furnace slags as raw materials for the production of binders

Problem. Industrial waste accumulating in dumps, in many cases, have valuable technical properties, so they can be considered as secondary resources. Тhe study of the properties and modification of slags under various conditions requires an integrated approach, including different analysis. Goal. Based on the selected experimental methods to justify the resource value of Zaporizhstal waste blast furnace slag.  Methodology. The methods of the study were X-ray diffraction, gamma-spectrometry, spectrographic analysis and electron-probe microanalysis. Results. X-ray phase analysis revealed the minerals of the blast-furnace slags in the crystalline state: rankinite 3CaO∙2SiO2, quartz SiO2, gehlenite 2CaO∙Al2O3∙SiO2, bredigit α-2CaO∙SiO2, okermanit 2CaO∙MgO∙2SiO2, pseudowollastonite α-CaO∙SiO2. The mass fraction of the glassy component is calculated, which is half the mass of Zaporizhstal blast furnace slag. The elemental composition of the slag, determined by electron probe microanalysis, made it possible to characterize its fractions from the standpoint of toxicity. The elements potassium, sodium, sulfur, chlorine, copper and titanium, which are not included in the composition of minerals, were recorded using a scanning electron microscope, which gives grounds for assuming that they are sorbed by the surface of mineral particles. Micrographs of the surface of the particles of blast furnace slag indicate a high degree of loosening with the presence of needle-like and plate-like crystals, which determines the sorption properties of the slag. The maximum content of potassium, sodium and titanium is characteristic of the 2.5–5 mm fraction. Slag contains an insignificant amount (<1 %) of compounds of metals Fe, Ti and Cu belonging to the 3rd hazard class of substances, which does not interfere with the further disposal of slag. The III hazard class of waste slag blast furnace slag has been determined. Gamma-spectrometric method determined the specific radioactivity and the effective specific activity of slag fractions. Natural radionuclides 40K, 226Ra and 232Th were detected. It is proved that slag and its separate fractions belong to the first class of radiation hazard and can be used in building industry without restriction. Originality. The minerals okermanit, bredigit, pseudovollastonite are technically valuable in the production of binding materials, since they have hydraulic activity. The presence of amorphous phases indicates increased sorption and chemical activity of slag, which is important from the standpoint of the use of slag in the production of binders. In the large slag fraction, the mass contribution of the amorphous state of the substance is slightly higher. Practical value. Zaporizhstal waste blast furnace slag can be recommended in the production of binders – Portland cement and slag Portland cement, according to a combination of chemical indicators: a high concentration of hydraulically active minerals and amorphous phase, highly developed surface of slag particles, the presence of sorption surface activity, attitude to moderately hazardous production waste and class I radiation danger

Learning to integrate contradictory multisensory self-motion cue pairings

Humans integrate multisensory information to reduce perceptual uncertainty when perceiving the world and self. Integration fails, however, if a common causality is not attributed to the sensory signals, as would occur in conditions of spatiotemporal discrepancies. In the case of passive self-motion, visual and vestibular cues are integrated according to statistical optimality, yet the extent of cue conflicts that do not compromise this optimality is currently underexplored. Here, we investigate whether human subjects can learn to integrate two arbitrary, but co-occurring, visual and vestibular cues of self-motion. Participants made size comparisons between two successive whole-body rotations using only visual, only vestibular, and both modalities together. The vestibular stimulus provided a yaw self-rotation cue, the visual a roll (Experiment 1) or pitch (Experiment 2) rotation cue. Experimentally measured thresholds in the bimodal condition were compared with theoretical predictions derived from the single-cue thresholds. Our results show that human subjects combine and optimally integrate vestibular and visual information, each signaling self-motion around a different rotation axis (yaw vs. roll and yaw vs. pitch). This finding suggests that the experience of two temporally co-occurring but spatially unrelated self-motion cues leads to inferring a common cause for these two initially unrelated sources of information about self-motion. We discuss our results in terms of specific task demands, cross-modal adaptation, and spatial compatibility. The importance of these results for the understanding of bodily illusions is also discussed

No evidence for abnormal priors in early vision in schizophrenia

The predictive coding account of psychosis postulates the abnormal formation of prior beliefs in schizophrenia, resulting in psychotic symptoms. One domain in which priors play a crucial role is visual perception. For instance, our perception of brightness, line length, and motion direction are not merely based on a veridical extraction of sensory input but are also determined by expectation (or prior) of the stimulus. Formation of such priors is thought to be governed by the statistical regularities within natural scenes. Recently, the use of such priors has been attributed to a specific set of well-documented visual illusions, supporting the idea that perception is biased toward what is statistically more probable within the environment. The Predictive Coding account of psychosis proposes that patients form abnormal representations of statistical regularities in natural scenes, leading to altered perceptual experiences. Here we use classical vision experiments involving a specific set of visual illusions to directly test this hypothesis. We find that perceptual judgments for both patients and control participants are biased in accordance with reported probability distributions of natural scenes. Thus, despite there being a suggested link between visual abnormalities and psychotic symptoms in schizophrenia, our results provide no support for the notion that altered formation of priors is a general feature of the disorder. These data call for a refinement in the predictions of quantitative models of psychosis

Using co-occurrence to evaluate belief coherence in a large non clinical sample.

Much of the recent neuropsychological literature on false beliefs (delusions) has tended to focus on individual or single beliefs, with few studies actually investigating the relationship or co-occurrence between different types of co-existing beliefs. Quine and Ullian proposed the hypothesis that our beliefs form an interconnected web in which the beliefs that make up that system must somehow "cohere" with one another and avoid cognitive dissonance. As such beliefs are unlikely to be encapsulated (i.e., exist in isolation from other beliefs). The aim of this preliminary study was to empirically evaluate the probability of belief co-occurrence as one indicator of coherence in a large sample of subjects involving three different thematic sets of beliefs (delusion-like, paranormal & religious, and societal/cultural). Results showed that the degree of belief co-endorsement between beliefs within thematic groupings was greater than random occurrence, lending support to Quine and Ullian's coherentist account. Some associations, however, were relatively weak, providing for well-established examples of cognitive dissonance