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What is it like to perceive a feared object? According to a popular neo-Gibsonian theory in psychology, fear biases our perceptions of objects so as to encourage particular kinds of actions: when we are afraid, spiders may be perceived as physically closer than they are in order to promote fleeing. Firestone mounted severe criticisms against this view, arguing that these cases are better explained by non-perceptual biases that operate on accurate perceptions of the external environment. In this paper I will argue that fear might indeed distort our perceptions of the world, but not in the way neo-Gibsonians suppose. In the view I favor, perceptual distortions occur as by-products of fearful attention, a special mode of attention that is part of an orchestrated defensive response that prepares the organism to deal effectively with a threat. To argue for this view I will rely on empirical evidence that fearful attention narrows down the focus of attention and favors processing of local rather than global features of stimuli, which may jointly explain why perceptual distortions might occur in fearful object seeing. This view has consequences not only for empirical investigations in fearful perceptual distortions, but also for an explanation of the intentionality of fear and the phenomenal integration of bodily and intentional elements in fear episodes.

Studies suggest looming motion represents a special class of attentional capture stimulus due to behavioral urgency: the need to act upon objects moving toward us in an environment. In particular, one theory suggests that faster reaction times to targets cued by looming relative to receding motion are driven by post-attentional, motor-priming processes beyond the attentional capture effects seen with other stimulus qualities such as color pop-out. The present study tested this theory using a relative size judgment task where targets were pre-cued by looming and receding optic flow fields. Results show systematic increases in the perceived size of targets that were cued by looming flow fields, consistent with previous attentional capture studies using onset cues. These results challenge theories attributing behavioral changes from looming motion to motor-priming alone.

We live in a dynamic, distracting world. When distracting information captures attention, what are the consequences for perception? Previous literature has focused on effects such as reaction time (RT) slowing, accuracy decrements, and oculomotor capture by distractors. In the current study, we asked whether attentional capture by distractors can also more fundamentally alter target feature representations, and if so, whether participants are aware of such errors. Using a continuous report task and novel confidence range report paradigm, we discovered 2 types of feature-binding errors when a distractor was presented along with the target: First, when attention is strongly captured by the distractor, participants commit swapping errors (misreporting the color at the distractor location instead of the target color), which remarkably seem to occur without awareness. Second, when participants successfully resist capture, they tend to exhibit repulsion (perceptual distortion away from the color at the distractor location). Thus, we found that capture not only induces a spatial shift of attention, it also alters feature perception in striking ways. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Hallucinatory experiences (HEs) can be pronounced in psychosis, but similar experiences also occur in nonclinical populations. Cognitive mechanisms hypothesized to underpin HEs include dysfunctional source monitoring, heightened signal detection, and impaired attentional processes. Using data from an international multisite study on non-clinical participants (N = 419), we described the overlap between two sets of variables - one measuring cognition and the other HEs - at the level of individual items. We used a three-step method to extract and examine item-specific signal, which is typically obscured when summary scores are analyzed using traditional methodologies. The three-step method involved: (1) constraining variance in cognition variables to that which is predictable from HE variables, followed by dimension reduction, (2) determining reliable HE items using split-halves and permutation tests, and (3) selecting cognition items for interpretation using a leave-one-out procedure followed by repetition of Steps 1 and 2. The results showed that the overlap between HEs and cognition variables can be conceptualized as bi-dimensional, with two distinct mechanisms emerging as candidates for separate pathways to the development of HEs: HEs involving perceptual distortions on one hand (including voices), underpinned by a low threshold for signal detection in cognition, and HEs involving sensory overload on the other hand, underpinned by reduced laterality in cognition. We propose that these two dimensions of HEs involving distortions/liberal signal detection, and sensation overload/reduced laterality may map onto psychosis-spectrum and dissociation-spectrum anomalous experiences, respectively. publishedVersion

Child sexual violence can cause serious damage to the psychosocial development of its victims. Assessments in this context require the use of several psychological tests with proven validity for this purpose. This study aimed to assess children victims of sexual violence using the Zulliger R-Optimized application. The sample consisted of 37 children of both sexes, aged from seven to 13 years old (M = 10.92), distributed in three groups: Sexual Violence Victims (SVV), Cancer Patients (CP) and the Non-Victim Group (NVG). The statistical analyses were performed using the Mann-Whiney and one-way ANOVA tests. The Zulliger variables concerning the clusters Interpersonal Relationship (GHR, PHR, GHR:PHR, p), Self-Image (MOR) and Processing (W:M) showed statistical differences when the SVV group was compared to the other groups. The Zulliger R-Optimized application shows promising results in assessing SVV children, indicating its usefulness for assessments in this context. Resumo A violência sexual infantil pode gerar graves prejuízos para o desenvolvimento psicossocial de suas vítimas. As avaliações nesse contexto requerem o uso de vários testes psicológicos que possuem evidências de validade para este fim. Este estudo teve como objetivo avaliar crianças vítimas de violência sexual com o Zulliger aplicação R-Otimizada. A amostra consistiu em 37 crianças com idade entre 7 e 13 anos (M = 10,92), de ambos os sexos, distribuídas em três grupos: Vítimas de Violência Sexual (VVS), Pacientes com Câncer (PC) e Grupo de Não-Vítimas (GNV). Realizou-se tratamento estatístico por meio dos testes Mann-Whiney e Anova de uma via. Variáveis do Zulliger concernentes aos agrupamentos de Relacionamento Interpessoal (GHR, PHR, GHR:PHR, p), Autoimagem (MOR) e Processamento (W:M) apresentaram diferenças estatísticas quando o grupo VVS foi comparado aos outros grupos. O Zulliger aplicação R-Otimizada apresenta resultados promissores na avaliação de crianças VVS, indicando sua utilidade em avaliações desse contexto. Resumen La violencia sexual infantil puede causar daños al desarrollo psicosocial de las víctimas. Evaluaciones en este contexto requieren uso de exámenes psicológicos que tienen evidencia de validez para este propósito. Este estudio tuvo como objetivo evaluar niños víctimas de violencia sexual con lo Zulliger aplicación R-Optimizada. La muestra consistió en 37 niños de 7 a 13 años (M = 10.92), ambos sexos, distribuidos en tres grupos: Víctimas de Violencia Sexual (VVS), Pacientes con Cáncer (PC) y Grupo de No-Víctimas (GNV). El tratamiento estadístico se realizó utilizando las pruebas de Mann-Whiney y Anova de una vía. Variables de Zulliger para las agrupaciones de Relaciones Interpersonales (GHR, PHR, GHR:PHR, p), Autoimagen (MOR) y Procesamiento (W:M) mostraron diferencias estadísticas cuando el grupo VVS se comparó con los otros grupos. Zulliger aplicación R-Optimizada muestra resultados prometedores en la evaluación de niños VVS que indican su usabilidad en las evaluaciones en este contexto.

Aim: Body awareness arises when attending to and maintaining awareness of visuospatial body representations. By the same token, focussing on representations transfers them to working memory. Body awareness and working memory seemingly rely on similar processes and recruit common parietal areas involved in perception. Therefore, we asked whether visuospatial working memory abilities would define individual differences in the perception of spontaneous sensations (SPS), i.e., bodily sensations perceived in the absence of triggers (e.g., tactile stimulation or movement), when attending to the body.Method: Participants completed two visuospatial working memory tasks to assess various mechanisms: (i) the decay of representations was assessed through a Brown-Peterson task in which the delay between the memorandum presentation and its recall was manipulated, and (ii) the impact of distractors' interference and cognitive load (i.e., complexity) on recall performances were assessed through a complex span task that required the processing of distractors while maintaining a memorandum. A standard SPS task involving localization and characterization of SPS perceived on the hands was completed afterwards.Results: Low performance due to decay, distractors' interference and cognitive load in visuospatial working memory was associated with a decrease in the frequency of SPS. Additionally, low performance due to distractors' cognitive load predicted a decrease in the perception of surface-type sensations, and high performance despite distractors' interference led to a better perception of SPS on less sensitive areas of the hand.Conclusion: We discuss how visuospatial working memory processes might contribute to body awareness and perceptual distortions of the body.

Of the perceptual distortions characteristic of Alice in Wonderland syndrome, substantial alterations in the immediate experience of time are probably the least known and the most fascinating. We reviewed original case reports to examine the phenomenology and associated pathology of these time distortions in this syndrome. A systematic search in PubMed, Ovid Medline, and the historical literature yielded 59 publications that described 168 people experiencing time distortions, including 84 detailed individual case reports. We distinguished five different types of time distortion. The most common category comprises slow-motion and quick-motion phenomena. In 39% of all cases, time distortions were unimodal in nature, while in 61% there was additional involvement of the visual (49%), kinaesthetic (18%), and auditory modalities (14%). In all, 40% of all time distortions described were bimodal in nature and 19% trimodal, with 1% involving four modalities. Underlying neurological mechanisms are varied and may be triggered by intoxications, infectious diseases, metabolic disorders, CNS lesions, paroxysmal neurological disorders, and psychiatric disorders. Bizarre sensations of time alteration—such as time going backwards or moving in circles—were mostly associated with psychosis. Pathophysiologically, mainly occipital areas appear to be involved, although the temporal network is widely disseminated, with separate component timing mechanisms not always functioning synchronously, thus occasionally creating temporal mismatches within and across sensory modalities (desynchronization). Based on our findings, we propose a classification of time distortions and formulate implications for research and clinical practice.

Amblyopia is a relatively common (incidence 3%) developmental disorder in which there is loss of vision as a consequence of a disruption to normal visual development. Although the deficit is monocular and known to be of cortical origin, the nature of the processing deficit is controversial. Human behavioral studies have identified two main deficits - a loss of contrast sensitivity and perceived spatial distortions. Here we use a multifocal fMRI approach to ascertain, in a group of anisometropic amblyopes, whether these two deficits have a single common cause or whether they are the result of two underlying independent cortical disorders. We found that fMRI magnitudes were attenuated in amblyopic eye stimulation, and that there was poor fidelity for co-localization of the activity clusters between the amblyopic and fellow-fixing eye stimulation. These effects varied across eccentricities and correlate with the degree of amblyopia but not with one another, suggesting two independent cortical deficits: a reduced responsiveness as well as reduced fidelity of spatial representation. These deficits are independent of eccentricity within the central field and consistent across early cortical visual areas.

BackgroundIn individuals with body dysmorphic disorder (BDD), selective attention biases and aberrant visual scanning patterns may cause imbalances in global vs. detailed visual processing, contributing to perceptual distortions for appearance. The mechanistic effects of modifying visual attention on brain function in BDD, which may be critical to developing perceptual-based treatments, have not been explored. This study tested the effects of visual-attention modulation on dorsal and ventral visual stream activation and connectivity, and eye behaviors.MethodsWe acquired functional magnetic resonance imaging data in 37 unmedicated adults with BDD and 30 controls. Participants viewed their faces under two conditions: a) unconstrained (naturalistically), and b) holding their gaze on the center of the image (visual-attention modulation), monitored with an eye-tracking camera. We analyzed activation and dynamic effective connectivity in dorsal and ventral visual streams and visual fixation duration.ResultsVisual-attention modulation resulted in longer fixation duration and reduced activation in dorsal and ventral visual streams in both groups compared with naturalistic viewing. Longer fixation duration was associated with greater effective connectivity from V1 to early dorsal visual stream during the second naturalistic viewing, across groups. During naturalistic viewing, there was greater V1 to early dorsal visual stream connectivity after, compared with before, visual-attention modulation.ConclusionsWhen viewing one’s face, longer visual fixation may confer greater communication in dorsal visual system, facilitating global/holistic visual processing. The finding that reduction in visual scanning while viewing one’s face results in persistent effects during unconstrained viewing has implications for perceptual retraining treatment design for BDD.

Concurrent body movements have been shown to enhance the accuracy of spatial judgment, but it remains unclear whether they also contribute to perceptual estimates of gravitational space not involving body movements. To address this, we evaluated the effects of static or dynamic arm movements during prolonged whole-body tilt on the subsequent perceptual estimates of visual or postural vertical. In Experiment 1, participants were asked to continuously perform static or dynamic arm movements during prolonged tilt, and we assessed their effects on the prolonged tilt-induced shifts of subjective visual vertical (SVV) at a tilted position (during-tiltsession) or near upright (post-tiltsession). In Experiment 2, we evaluated how static or dynamic arm movements during prolonged tilt subsequently affected the subjective postural vertical (SPV). In Experiment 1, we observed that the SVV was significantly shifted toward the direction of prolonged tilt in both sessions. The SVV shifts decreased when performing dynamic arm movements in theduring-tiltsession, but not in thepost-tiltsession. In Experiment 2, as well as SVV, the SPV was shifted toward the direction of prolonged tilt, but it was not significantly attenuated by the performance of static or dynamic arm movements. The results of theduring-tiltsession suggest that the central nervous system utilizes additional information generated by dynamic body movements for perceptual estimates of visual vertical.

The sources and consequences of a sensorineural hearing loss are diverse. While several approaches have aimed at disentangling the physiological and perceptual consequences of different etiologies, hearing deficit characterization and rehabilitation have been dominated by the results from pure-tone audiometry. Here, we present a novel approach based on data-driven profiling of perceptual auditory deficits that attempts to represent auditory phenomena that are usually hidden by, or entangled with, audibility loss. We hypothesize that the hearing deficits of a given listener, both at hearing threshold and at supra-threshold sound levels, result from two independent types of “auditory distortions”. In this two-dimensional space, four distinct “auditory profiles” can be identified. To test this hypothesis we gathered a dataset consisting of a heterogeneous group of listeners that were evaluated using measures of speech intelligibility, loudness perception, binaural processing abilities and spectro-temporal resolution. The subsequent analysis revealed that distortion type-I was associated with elevated hearing thresholds at high frequencies and reduced temporal masking release and was significantly correlated with elevated speech reception thresholds in noise. Distortion type-II was associated with low-frequency hearing loss and abnormally steep loudness functions. The auditory profiles represent four robust subpopulations of hearing-impaired listeners that exhibit different degrees of perceptual distortions. The four auditory profiles may provide a valuable basis for improved hearing rehabilitation, e.g. through profile-based hearing-aid fitting

Anorexia nervosa (AN) and body dysmorphic disorder (BDD) are characterized by distorted perception of appearance, yet no studies have directly compared the neurobiology associated with body perception. We compared AN and BDD in brain activation and connectivity in relevant networks when viewing images of others' bodies and tested their relationships with clinical symptoms and subjective appearance evaluations. We acquired fMRI data from 64 unmedicated females (20 weight-restored AN, 23 BDD, 21 controls) during a matching task using unaltered or spatial-frequency filtered photos of others' bodies. Using general linear model and independent components analyses we compared brain activation and connectivity in visual, striatal, and parietal networks and performed univariate and partial least squares multivariate analyses to investigate relationships with clinical symptoms and appearance evaluations. AN and BDD showed partially overlapping patterns of hyperconnectivity in the dorsal visual network and hypoconnectivity in parietal network compared with controls. BDD, but not AN, demonstrated hypoactivity in dorsal visual and parietal networks compared to controls. Further, there were significant activity and connectivity differences between AN and BDD in both networks. In both groups, activity and/or connectivity were associated with symptom severity and appearance ratings of others' bodies. Thus, AN and BDD demonstrate both distinct and partially-overlapping aberrant neural phenotypes involved in body processing and visually encoding global features. Nevertheless, in each disorder, aberrant activity and connectivity show relationships to clinically relevant symptoms and subjective perception. These results have implications for understanding distinct and shared pathophysiology underlying perceptual distortions of appearance and may inform future novel treatment strategies.

Visual awareness is thought to result from integration of low- and high-level processing; instances of integration failure provide a crucial window into the cognitive and neural bases of awareness. We present neurophysiological evidence of complex cognitive processing in the absence of awareness, raising questions about the conditions necessary for visual awareness. We describe an individual with a neurodegenerative disease who exhibits impaired visual awareness for the digits 2 to 9, and stimuli presented in close proximity to these digits, due to perceptual distortion. We identified robust event-related potential responses indicating 1) face detection with the N170 component and 2) task-dependent target-word detection with the P3b component, despite no awareness of the presence of faces or target words. These data force us to reconsider the relationship between neural processing and visual awareness; even stimuli processed by a workspace-like cognitive system can remain inaccessible to awareness. We discuss how this finding challenges and constrains theories of visual awareness.

Tactile perception is referenced to, and modulated by, body parts and their boundaries. For example, tactile distances presented over the wrist are perceptually elongated relative to those presented within the hand or arm. This phenomenon is argued to result from a segmentation of tactile space according to body parts and their boundaries, i.e., touches presented within a body part are perceived as being more similar, and therefore closer together, whereas those that straddle a body part boundary (e.g. presented across two body parts) are perceived as more distinct and thus further apart. We tested the hypothesis that language shapes this effect by providing consolidatory labels for categories and boundaries, as it does in other perceptual domains. We examined the perceptual elongation of distance over the wrist in a group of Croatian adults (n = 37) whose first language does not differentiate between hand and arm at the wrist in common noun terms (instead, the Croatian word “ruka” encompasses the entire limb). Croatian adults, like UK adults reported in a previous study (Le Cornu Knight, Longo, & Bremner, 2014), perceived distances presented proximodistally over the wrist boundary as longer than those presented mediolaterally, whereas the reverse was found for both the hand and the arm. This pattern of results was remained when Croatian participants were split into two groups of inexperienced or proficient English-language speakers. This is striking evidence that body part boundaries consistently modulate tactile perception, despite differences in the linguistic distinctions of such body parts made by one's first language.

Additional gravitational cues generated by active body movements may play a role in the perception of gravitational space, but no experimental evidence has been shown on this. To investigate this possibility, we evaluated how arm movements made against gravity influenced the perceptual distortion of visual and postural vertical induced by prolonged whole-body tilt. In Experiment 1, participants were asked to perform static or dynamic arm movements during prolonged whole-body tilt and we assessed their effects on subjective visual vertical (SVV) at the tilt position (during-tiltsession) and after tilting back to the upright position (post-tiltsession). In Experiment 2, we evaluated how static or dynamic arm movements during prolonged tilt subsequently affected the subjective postural vertical (SPV). In Experiment 1, we observed that prolonged tilt induced the SVV shifts toward the side of body tilts in both sessions. The prolonged tilt-induced SVV shifts effectively decreased when performing dynamic arm movements in theduring-tiltsession, but not in thepost-tiltsession. In Experiment 2, the SPV shifted toward the side of prolonged body tilt, which was not significantly influenced by the performance of static or dynamic arm movements. Results of theduring-tiltsession suggest that the central nervous system utilizes additional cues generated by dynamic body movements for the perception of the visual vertical.

Hand size perceptual distortions characterize adult human cognition. Notwithstanding the importance of uncovering how hand size representation develops in humans, studies in this field are still at a preliminary stage. Indeed, it is yet to be understood whether hand size distortions are present and reliable in early childhood and whether they differ from adults’ distortions, offering a more in-depth insight into the emergence and development of such representations. We addressed this issue by comparing 4- to 6- year-old children and adults’ representation of their own hand size, as assessed with a 2-forced choice visual perceptual task. To test participants’ ability to estimate their own hand size, children and adults judged whether pictures of their own hand, resized to appear smaller or bigger than their own hand, matched or not its actual dimension. Results show that children aged 4 to 6 years tend to underestimate their own hand size, while adults underestimate their own hand more weakly. This evidence suggests that body-parts perceptual distortions are already in place in early childhood, and thus represent a characteristic of the human body representation.

An object appears smaller in the periphery than in the center of the visual field. In two experiments ( N = 24), we demonstrated that visuospatial attention contributes substantially to this perceptual distortion. Participants judged the size of central and peripheral target objects after a transient, exogenous cue directed their attention to either the central or the peripheral location. Peripheral target objects were judged to be smaller following a central cue, whereas this effect disappeared completely when the peripheral target was cued. This outcome suggests that objects appear smaller in the visual periphery not only because of the structural properties of the visual system but also because of a lack of spatial attention.

Purpose: The Enright phenomenon describes the distortion in speed perception experienced by an observer looking sideways from a moving vehicle when viewing with interocular differences in retinal image brightness, usually induced by neutral density filters. We investigated whether the Enright phenomenon could be induced with monocular pupil dilation using tropicamide. Methods: We tested 17 visually normal young adults on a closed road driving circuit. Participants were asked to travel at Goal Speeds of 40 km/h and 60 km/h while looking sideways from the vehicle with: (i) both eyes with undilated pupils; (ii) both eyes with dilated pupils; (iii) with the leading eye only dilated; and (iv) the trailing eye only dilated. For each condition we recorded actual driving speed. Results: With the pupil of the leading eye dilated participants drove significantly faster (by an average of 3.8 km/h) than with both eyes dilated (p = 0.02); with the trailing eye dilated participants drove significantly slower (by an average of 3.2 km/h) than with both eyes dilated (p

Parkinson's disease (PD) is a movement disorder caused by deterioration of the dopaminergic system. Previous studies have demonstrated temporal as well as emotional facial recognition impairment in PD patients. Moreover, it has been demonstrated that emotional facial expressions alter temporal judgments. In the present study, we investigate the magnitude of temporal distortions caused by the presentation of emotional facial expressions (happiness, sadness, and neutral) in PD patients with mild cognitive impairment (PD-MCI) and controls.Seventeen older adults with PD-MCI and 22 healthy older adults took part in the present study. Participants were tested with a time bisection task with standard intervals lasting 400 ms and 1600 ms. Moreover, a complete neuropsychological evaluation was conducted to characterize the sample.Differences between groups were observed indicating a general underestimation of time in PD-MCI patients. Temporal impairments in PD-MCI patients seem to be caused mainly by a dysfunction at the level of reference memory. The effect of emotional facial expressions on time perception was evident in both PD patients and controls, with an overestimation of perceived duration when happiness was presented and an underestimation when sadness was presented.Overall, our results indicate that reduced cognitive abilities might be responsible for the lower temporal ability observed in PD-MCI patients. Moreover, similar effects of emotional stimuli were observed in both PD-MCI patients and controls.

The feeling of hunger is an inseparable part of people's daily lives. It has been established that hunger, caused by food deprivation, influences people's physiological and emotional state and their everyday behavior. Yet, it remains unclear whether and in which manner food deprivation affects the way people perceive their environment. In two experiments, we examined the effects of food deprivation on the perceptual resolution of food portion size. We calculated Just Noticeable Differences (JNDs) to measure sensitivity to detect the smallest difference between two stimuli of different sizes. Participants' resolution in both experiments was higher to detect changes in food size compared with baseline when they were hungry due to a short period of food deprivation. Food deprivation did not lead to any biases in the average perception of food size. The results show that food deprivation changes the way people perceive their environment. We discuss the possible role of attention in mediating the effect of food deprivation on the visual resolution of food size.

Abstract: The aim of this literature review is to integrate the results of various studies regarding body image and body image distortion into a unified framework. The concept of body image is complex and can be interpreted from multiple points of view. The first part of the study touches upon different age characteristics, attentional focus on the body, the early and important role of the body in identity formation, specific features in adolescence, gender differences, and the often-observed stability of body image (distortion), which may be present as a (trait) marker throughout the lifespan. The second part focuses on the organization of body image. The results of different studies on cognitive information processing are reviewed, the question of perceptual accuracy is addressed and the concepts of embodiment are examined. The third topic is body image distortion. First, the concept is contextualized along different continua, then discussed in a clinical sense along with the complexity of diagnostic methods, as well as the state and trait aspects of body image distortion. Orv Hetil. 2017; 158(19): 723–730.

Background: Phenomenological psychopathology, through theoretical and idiographic studies, conceptualizes major depressive disorder (MDD) as a disorder of time experience. Investigations on abnormal time experience (ATE) in MDD adopting methodologies requested by the standards of empirical sciences are still lacking. Our study aimed to provide a qualitative analysis, on an empirical ground and on a large scale, of narratives of temporal experiences of persons affected by MDD. Methods: We interviewed 550 consecutive patients affected by affective and schizophrenic disorders. Clinical files were analysed by means of consensual qualitative research. Results: Out of 100 MDD patients, 96 reported at least 1 ATE. The principal categories of ATE are vital retardation - the experience of a stagnation of endogenous vital processes (37 patients), the experience of present and future dominated by the past (29 patients), and the experience of the slackening of the flow oftime (25 patients). A comparison with ATE in schizophrenia patients showed that in MDD, unlike in schizophrenia, there is no disarticulation of time experience (disorder of temporal synthesis) but rather a disorder of conation or inhibition of becoming. Limitations: The interview style was not meant to make a quantitative assessment (“false negatives” cannot be excluded). Conclusions: Our findings confirm the relevance of distinctive features of ATE in MDD, support the hypothesis of an intrinsic disordered temporal structure in depressive symptoms, and may have direct implications in clinical practice, especially in relation to differential diagnosis, setting the boundaries between “true” and milder forms of depression, and neurobiological research.

Our body is a volumetric, three-dimensional (3-D) object in the world, and we experience it as such. Existing methods for measuring the perceptual body image, however, have been based on judgments of one-dimensional (1-D) length or two-dimensional images. We developed a new approach to the 3-D perceptual body image of the fingers by asking people to judge whether each finger would fit through rings of varying diameter. This task requires participants to conceptualize their finger as a volumetric object entering the ring. In two experiments, we used an adaptive staircase procedure to estimate the perceived size of each finger. There were systematic distortions of perceived 3-D finger size, with the size of index finger and (to a lesser extent) the middle finger underestimated. These distortions were unaffected by changes in hand posture. Notably, the pattern of distortions is qualitatively different from that found in previous research investigating 1-D finger length, suggesting that 3-D judgments of the body may differ in fundamental ways from 1-D judgments of individual body dimensions.

The knowledge of the size of our own body parts is essential for accurately moving in space and efficiently interact with objects. A distorted perceptual representation of the body size often represents a core diagnostic criterion for some psychopathological conditions. The metric representation of the body was shown to depend on somatosensory afferences: local deafferentation indeed causes a perceptual distortion of the size of the anesthetized body part. A specular effect can be induced by altering the cortical map of body parts in the primary somatosensory cortex. Indeed, the present study demonstrates, in healthy adult participants, that repetitive Transcranial Magnetic Stimulation to the somatosensory cortical map of the hand in both hemispheres causes a perceptual distortion (i.e., an overestimation) of the size of the participants' own hand (Experiments 1-3), which does not involve other body parts (i.e., the foot, Experiment 2). Instead, the stimulation of the inferior parietal lobule of both hemispheres does not affect the perception of the own body size (Experiment 4). These results highlight the role of the primary somatosensory cortex in the building up and updating of the metric of body parts: somatosensory cortical activity not only shapes our somatosensation, it also affects how we perceive the dimension of our body.

Recent studies have demonstrated that mental representations of the hand dorsum are distorted even for healthy participants. Perceptual hand maps estimated by pointing to specific landmarks (e.g., knuckles and tips of fingers) is stretched and shrunk along the medio-lateral and the proximo-distal axes, respectively. Similarly, tactile distance perception between two touches is longer along the medio-lateral axis than the proximo-distal axis. The congruency of the two types of distortions suggests that common perceptual and neural representations may be involved in these processes. Prolonged stimulation by two simultaneous touches having a particular distance can bias subsequent perception of tactile distances (e.g., adaptation to a long distance induces shorter stimuli to be perceived even shorter). This tactile distance adaptation aftereffect has been suggested to occur based on the modulations of perceptual and neural responses at low somatosensory processing stages. The current study investigated whether tactile distance adaptation aftereffects affect also the pattern of distortions on the perceptual hand maps. Participants localized locations on the hand dorsum cued by tactile stimulations (Experiment 1) or visually presented landmarks on a hand silhouette (Experiment 2). Each trial was preceded by adaptation to either a small (2 cm) or large (4 cm) tactile distance. We found clear tactile distance aftereffects. However, no changes were observed for the distorted pattern of the perceptual hand maps following adaptation to a tactile distance. Our results showed that internal body representations involved in perceptual distortions may be distinct between tactile distance perception and the perceptual hand maps underlying position sense.

Humans display a very good understanding of the content in briefly presented photographs. To achieve this understanding, humans rely on information from both high-acuity central vision and peripheral vision. Previous studies have investigated the relative contribution of central/peripheral vision. However, the role of attention in this task remains unclear. In this study, we presented composite images with a scene in the center and another scene in the periphery. The two channels conveyed different information, and the participants were asked to focus on one channel while ignoring the other. In two experiments, we showed that (1) people are better at recognizing the central part, (2) the conflicting signal in the ignored part hinders performance, and (3) this effect is true for both parts (focusing on the central or peripheral part). We conclude that scene recognition is based on both central and peripheral information, even when participants are instructed to focus only on one part of the image and ignore the other. In contrast to the zoom-out hypothesis, we propose that the gist recognition process should be interpreted in terms of the evidence accumulation model in which information from the to-be-ignored parts is also included.

We experience our body as a 3D, volumetric object in the world. Measures of our conscious body image, in contrast, have investigated the perception of body size along one or two dimensions at a time. There is, thus, a discrepancy between existing methods for measuring body image and our subjective experience of having 3D body. Here we assessed in a sample of healthy adults the perception of body size in terms of its 1D length and 3D volume. Participants were randomly assigned to two groups using different measuring units (other body part and non-body object). They estimated how many units would fit in a perceived size of body segments and the whole body. The patterns of length and volume misperception across judged segments were determined as their perceived size proportional to their actual size. The pattern of volume misperception paints the representation of 3D body proportions resembling those of a somatosensory homunculus. The body parts with a smaller actual surface area relative to their volume were underestimated more. There was a tendency for body parts underestimated in volume to be overestimated in length. Perceived body proportions thus changed as a function of judgement type while showing a similarity in magnitude of the absolute estimation error, be it an underestimation of volume or overestimation of length. The main contribution of this study is assessing the body image as a 3D body representation, and thus extending beyond the conventional 'allocentric' focus to include the body on the inside. Our findings highlight the value of studying the perceptual distortions "at the baseline", i.e., in healthy population, so as to advance the understanding of the nature of perceptual distortions in clinical conditions.

Experimentally induced strange-face illusions can be perceived when two individuals look at each other in the eyes under low illumination for about 10 minutes. This task of subject-other eye-to-eye gazing produces the following perceptions by the subject: (i) mild to huge deformations and color/shape changes of face and facial features; (ii) lifeless, unmoving faces and immaterial presences akin to out-of-body experiences; (iii) pseudo-hallucinations, enlightened 'idealized' faces and personalities - rather than the other's actual face. Dissociative phenomena seem to be involved, whereas the effects of non-pathological dissociation on strange-face illusions have not yet been directly investigated. In the present study, dissociative perceptions and strange-face illusions were measured through self-report questionnaires on a large sample (N = 90) of healthy young individuals. Results of correlation and factor analyses suggest that strange-face illusions can involve, respectively: (i) strange-face illusions correlated to derealization; (ii) strange-face illusions correlated to depersonalization; and (iii) strange-face illusions of identity, which are supposedly correlated to identity dissociation. The findings support the separation between detachment and compartmentalization in dissociative processes. Effects of gender show that strange-face illusions are more frequent in men with respect to women if dyads are composed of individuals of different-gender. Furthermore, drawings of strange-faces, which were perceived by portrait artists in place the others' faces, allowed a direct illustration of examples of dissociative identities. Findings are discussed in relation to the three-level model of self-referential processing.

usc Perception is not simply a carbon copy of the real world, but is subject to distortions that may reflect protective drive. This study aimed to investigate whether people with chronic shoulder pain show perceptual distortions of space and body that may promote protective behavior. Eighty-four people with shoulder pain and 51 healthy controls participated. Participants estimated (1) distances to points on a cork-board within and outside reaching distance, and (2) the perceived length of their own arms. A novel measure of movement-related pain was also used to determine whether movement-related pain relates to perceptual distortion. Overall, distance and arm length estimates did not differ between groups, nor did participants perceive their arms to be of different length. However, a moderate correlation between movement-related pain and the index of distance perception was found within the pain group, specifically for distance estimates to points within reach. Our results suggest that distorted perception is not a typical consequence of chronic shoulder pain; however, that it may occur in cases where pain is strongly linked to movement. Our findings have implications for understanding avoidance of movement in people with persistent pain. Refereed/Peer-reviewed

BackgroundStudies investigating the underlying mechanisms of hallucinations in patients with schizophrenia suggest that an imbalance in top-down expectations v. bottom-up processing underlies these errors in perception. This study evaluates this hypothesis by testing if individuals drawn from the general population who have had auditory hallucinations (AH) have more misperceptions in auditory language perception than those who have never hallucinated.MethodsWe used an online survey to determine the presence of hallucinations. Participants filled out the Questionnaire for Psychotic Experiences and participated in an auditory verbal recognition task to assess both correct perceptions (hits) and misperceptions (false alarms). A hearing test was performed to screen for hearing problems.ResultsA total of 5115 individuals from the general Dutch population participated in this study. Participants who reported AH in the week preceding the test had a higher false alarm rate in their auditory perception compared with those without such (recent) experiences. The more recent the AH were experienced, the more mistakes participants made. While the presence of verbal AH (AVH) was predictive for false alarm rate in auditory language perception, the presence of non-verbal or visual hallucinations were not.ConclusionsThe presence of AVH predicted false alarm rate in auditory language perception, whereas the presence of non-verbal auditory or visual hallucinations was not, suggesting that enhanced top-down processing does not transfer across modalities. More false alarms were observed in participants who reported more recent AVHs. This is in line with models of enhanced influence of top-down expectations in persons who hallucinate.

Previous research has found that the perception of our hands is inaccurate. This distorted representation has several constant characteristics including an overestimation of hand width and an underestimation of finger length. In this study, we further investigate this phenomenon by exploring the boundaries of hand representation. Participants placed one hand underneath a table top so it was occluded from view. Using their free hand, participants were instructed to point to the location where they believed the tips and bases of each of their fingers were. These ten landmarks were recorded using a motion capture system. One group of participants pointed to the landmarks in a random order (as done in previous studies) while another group pointed to them in a systematic fashion (from the tip of the thumb sequentially through to the pinky). Furthermore, to explore if having a frame of reference facilitates hand perception, some participants initiated each of their estimations directly from the previous landmark while others initiated them from a home spot located outside the span of the hand. Results showed that the participants who pointed in the systematic order made numerous accurate judgments of hand size and were overall more precise than participants who pointed in a random order. Including a frame of reference however, had no effect on the judgments. The results also showed asymmetries in hand perception. These findings are discussed in relation to different possible internal body representations and hemispheric asymmetries in body perception.

Certain visual disturbances make it difficult to read text and have been attributed to visual stress, also called "pattern-related visual stress". 12 Children with ASD, 12 children with Tourette's syndrome and without ASD and 12 controls, all matched on age and non verbal ability, participated in an experiment exploring sensory behaviours and visual stress. Reading rate and accuracy were assessed with the Wilkins Rate of Reading test with and without the Intuitive Overlays. Both the children with Tourette's and the children with ASD showed a higher prevalence of atypical sensory behaviours and symptoms of visual stress than the typically developing control children. Six out of twelve children with Tourette's syndrome (50%) read more accurately and over 15% more quickly with a coloured overlay. Four of the 12 children with ASD and none of the control children read over 15% more quickly with an overlay. The findings are discussed in relation to problems in sensory modulation.

Individuals with schizophrenia, particularly those with passivity symptoms, often feel that their actions and thoughts are controlled by an external agent. Recent evidence has elucidated the role of body representations in the aetiology of passivity symptoms, yet one representation - body structural description - has not yet been examined. Additionally, body image has rarely been examined outside of bodily illusions (e.g., rubber hand experiments) and external validation is required.Body structural description was assessed with an in-between task and a matching body parts by location task, and body image with a questionnaire examining body distortion experiences (containing subscales assessing boundary loss, depersonalisation and body size distortions). Individuals with schizophrenia (20 with current, 12 with past and 21 with no history of passivity symptoms) and 48 healthy controls participated in the study.People with schizophrenia (as a group) made more errors on the in-between task, but not on the matching body parts by location task. Individuals with current passivity symptoms reported greater distortions on all subscales relative to the other clinical samples, except for experiences of boundary loss which were common to both passivity symptom groups.The results indicate that body structural description may be altered in schizophrenia generally and body image alterations are worsened in passivity symptoms, and these alterations likely contribute to the emergence of passivity symptoms.

Anorexia nervosa (AN) is a severe mental illness characterized by problems with self-perception. Whole-brain neural activations in healthy women, women with AN and women in long-term weight recovery following AN were compared using two functional magnetic resonance imaging tasks probing different aspects of self-perception. The Social Identity-V2 task involved consideration about oneself and others using socially descriptive adjectives. Both the ill and weight-recovered women with AN engaged medial prefrontal cortex less than healthy women for self-relevant cognitions, a potential biological trait difference. Weight-recovered women also activated the inferior frontal gyri and dorsal anterior cingulate more for direct self-evaluations than for reflected self-evaluations, unlike both other groups, suggesting that recovery may include compensatory neural changes related to social perspectives. The Faces task compared viewing oneself to a stranger. Participants with AN showed elevated activity in the bilateral fusiform gyri for self-images, unlike the weight-recovered and healthy women, suggesting cognitive distortions about physical appearance are a state rather than trait problem in this disease. Because both ill and recovered women showed neural differences related to social self-perception, but only recovered women differed when considering social perspectives, these neurocognitive targets may be particularly important for treatment.

Several lines of evidence suggest that motoric brain structures may form the core amodal component of a neural network supporting a wide range of timed behaviours. Here, we review recent findings which elucidate the neural computations that occur within motor regions, and in particular the supplementary motor area, in order to support precisely timed actions. Although motor activity may help us represent time, it is also clear that action both enriches and complicates the interpretation of sensory inputs. Hence, in the second half of this review, we consider the latest findings regarding the perceptual distortions that our actions can impose upon our subjective perception of time.

Different processes are involved during visuomotor learning, including an error-based procedural and a strategy based cognitive mechanism. Our objective was to analyze if the changes in the adaptation or the aftereffect components of visuomotor learning measured across development, reflected different maturation rates of the aforementioned mechanisms. Ninety-five healthy children aged 4-12years and a group of young adults participated in a wedge prism and a dove prism throwing task, which laterally displace or horizontally reverse the visual field respectively. The results show that despite the age-related differences in motor control, all children groups adapted in the error-based wedge prisms condition. However, when removing the prism, small children showed a slower aftereffects extinction rate. On the strategy-based visual reversing task only the older children group reached adult-like levels. These results are consistent with the idea of different mechanisms with asynchronous maturation rates participating during visuomotor learning.

The paper describes how standard psychotherapy techniques need to be modified to suit the specialized needs of patients diagnosed with schizophrenia. Patients with psychosis often have lost their ability to use words to describe their inner states. As a result, traditional forms of psychotherapy which depend so crucially on the use of language are compromised. The goal of treatment at the start is to help the patient recover his ability to use language to describe his inner life. Eventually, this enables the patient to make use of more traditional forms of psychodynamic treatment.

The objective of this study was to determine vulnerability to pattern-related visual stress in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). A total of 20 ME/CFS patients and 20 matched (age, gender) controls were recruited to the study. Pattern-related visual stress was determined using the Pattern Glare Test. Participants viewed three patterns, the spatial frequencies (SF) of which were 0.3 (low-SF), 2.3 (mid-SF), and 9.4 (high-SF) cycles per degree (c/deg). They reported the number of distortions they experienced when viewing each pattern. ME/CFS patients exhibited significantly higher pattern glare scores than controls for the mid-SF pattern. Mid-high SF differences were also significantly higher in patients than controls. These findings provide evidence of altered visual perception in ME/CFS. Pattern-related visual stress may represent an identifiable clinical feature of ME/CFS that will prove useful in its diagnosis. However, further research is required to establish if these symptoms reflect ME/CFS-related changes in the functioning of sensory neural pathways.