Perceptual Distortion Research Articles

The potential mechanisms underlying the effect of acute alcohol use on duration perception.

Acute alcohol consumption has been found to cause duration perception distortions, but the directions of these distortions are not consistent. The mechanisms underlying this effect are also unclear. The present study seeks to elucidate the effect of acute alcohol consumption on duration perception and the mechanisms involved. Forty-one participants in the placebo group and 40 in the alcohol group completed time bisection tasks, attentional network tests, digit span backward tests and arousal reports to evaluate their duration perception, attentional network, working memory capacity and arousal. The results showed that the alcohol group overestimated duration compared to the placebo group. The alcohol group also showed increased arousal, impaired executive control of attention and reduced working memory capacity. Arousal mediated the effect of acute alcohol consumption on duration perception, whilst working memory capacity masked this effect. The findings are discussed based on the Scalar Timing Model and the Cognitive Resource Allocation Model.

“The mushroom was more alive and vibrant”: Patient reports of synthetic versus organic forms of psilocybin

AbstractInterest in psychedelic research in the West is surging, however, clinical trials have almost exclusively studied synthetic compounds such as MDMA, ketamine, DMT, LSD, ibogaine, and psilocybin. To date, few clinical trials have utilized whole mushroom/plant material like Psilocybe mushrooms, Iboga, or Ayahuasca. Individuals participating in the Roots To Thrive Psilocybin-Assisted Therapy for End of Life Distress program were administered synthetic psilocybin, whole Psilocybe cubensis, and mycological extract on separate occasions and post-treatment interview transcripts were qualitatively analyzed to discern themes and patterns. There was broad consensus that all three forms were helpful and similar, all generating visual and perceptual distortions, emotional and cognitive insight, and mystical experiences. However, synthetic psilocybin was said to feel less natural compared to organic forms, and the overall quality of experience of synthetic psilocybin was inferior to the organic forms. Research should be conducted with whole psychedelic mushrooms and extract in addition to synthetic psilocybin given this preliminary data, especially when considering that medicine keepers around the world have utilized whole mushrooms and plant material for millennia.

An Analysis Through to Congruence Between Real and Self-Perceived Body Mass Index in Nursing Students.

Overweight and obesity are growing concerns that also affect nursing staff, healthcare professionals that play a critical role in public health awareness and intervention. This study aimed to define the health parameters associated with body weight, analyze if there is an erroneous self-perception of overweight/obesity through the distortion of body weight perception, and determine the predictive factors of body weight distortion. A cross-sectional study of 224 nursing students gathered anthropometric and demographic data. Self-perceived body weight was assessed using Stunkard and Stellar's scale. Descriptive statistics and multinomial logistic regression identified significant predictors of weight distortion. The analysis found that men reported greater weight discrepancies than women. Specifically, 57% of the men (28 of 49 participants) underestimated their real BMI, while only 23% of the women (40 of 175 participants) did so. Age, sex, and weight classification emerged as significant explanatory variables for the distortion of body weight perception. The findings indicate a significant vulnerability among nursing students to the misperception of their own body weight status, highlighting the need for targeted training strategies. These strategies should focus on correcting misperceptions of obesity among health professionals throughout their working life to improve future obesity prevention efforts for society.

Hierarchical Degradation-aware Network for Full-Reference Image Quality Assessment

Full-Reference Image Quality Assessment (FR-IQA) algorithms excel in evaluating perceptual distortions by comparing reference and distorted images. However, as the severity and quantity of distortions in datasets increase, existing FR-IQA methods struggle to capture complex nonlinear perceptual features. This limitation results in reduced adaptability and inaccurate assessments for images with more severe or multiple distortions. Recognizing the importance of understanding image degradation mechanisms, we propose a novel hierarchical degradation-aware network (HDaN) method. First, by exploring the degradation mechanisms from the reference image to the distorted image, our degradation network matches distortions that align more closely with the human visual system (HVS). Next, we design a convertor to project the matched features into multiple spaces, creating multidimensional feature representations that more comprehensively capture the complexity of image distortions rather than being confined to a single feature space. Then, we calculate a similarity matrix between the distorted and mapped features, selecting the most similar (top-k) features for merging. Finally, a regression network maps the merged features to quality scores, providing the final quality prediction. The experimental results demonstrate that our proposed HDaN method outperforms traditional deep learning-based FR-IQA methods. Specifically, the HDaN shows higher PLCC and SROCC metrics on benchmark datasets, significantly improving over existing methods. Moreover, the method exhibits better adaptability to images with varying degrees and types of distortions, thereby greatly enhancing the overall performance of IQA.

Mechanism of Duration Perception in Artificial Brains Suggests New Model of Attentional Entrainment.

While cognitive theory has advanced several candidate frameworks to explain attentional entrainment, the neural basis for the temporal allocation of attention is unknown. Here we present a new model of attentional entrainment guided by empirical evidence obtained using a cohort of 50 artificial brains. These brains were evolved in silico to perform a duration judgment task similar to one where human subjects perform duration judgments in auditory oddball paradigms. We found that the artificial brains display psychometric characteristics remarkably similar to those of human listeners and exhibit similar patterns of distortions of perception when presented with out-of-rhythm oddballs. A detailed analysis of mechanisms behind the duration distortion suggests that attention peaks at the end of the tone, which is inconsistent with previous attentional entrainment models. Instead, the new model of entrainment emphasizes increased attention to those aspects of the stimulus that the brain expects to be highly informative.

Less is more? A review of psilocybin microdosing.

The applications of psilocybin, derived from 'magic mushrooms,' are vast, including a burgeoning practice known as microdosing, which refers to the administration of sub-hallucinogenic doses of psychedelic substances to obtain benefits without experiencing significant cognitive and perceptual distortion. However, current research is fairly new with several limitations and gaps that hinder adequate conclusions on its efficacy. This semi-structured review aimed to identify and highlight research gaps in the field of psilocybin microdosing for future research. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses based strategy was employed, utilizing a chain of keywords and key phrases across multiple databases, augmented by a cross-sectional Google search for relevant grey literature in the form of the top 10 search results. A total of 40 studies and 8 unique websites were identified, summarized and tabulated into four distinct categories, namely non-clinical, clinical, observational and anecdotal evidence. The majority of available evidence originates from observational studies, while non-clinical and clinical study findings remain comparatively sparse and inconsistent. Web-based findings were consistent with current research findings. Key research gaps were highlighted: the imperative for more randomized placebo-controlled trials, exploration of dose-response ranges, psychological and personality testing of participants, utilization of active placebos, greater diversity in study populations, an increase in psilocybin-exclusive microdosing studies and the refinement of animal models. Definitive conclusions regarding the efficacy of psilocybin microdosing remain elusive, emphasizing the need for further study. Numerous research gaps necessitate consideration for future investigations.

The serotonergic psychedelic DOI impairs deviance detection in the auditory cortex.

Psychedelics are known to induce profound perceptual distortions, yet the neural mechanisms underlying these effects, particularly within the auditory system, remain poorly understood. In this study, we investigated the effects of the psychedelic compound 2,5-Dimethoxy-4-iodoamphetamine (DOI), a serotonin 2A receptor agonist, on the activity of neurons in the auditory cortex of awake mice. We examined whether DOI administration alters sound-frequency tuning, variability in neural responses, and deviance detection (a neural process reflecting the balance between top-down and bottom-up processing). Our results show that while DOI does not alter the frequency selectivity of auditory cortical neurons in a consistent manner, it increases trial-by-trial variability in responses and consistently diminishes the neural distinction between expected (standard) and unexpected (oddball) stimuli. This reduction in deviance detection was primarily driven by a decrease in the response to oddball sounds, suggesting that DOI dampens the auditory cortex's sensitivity to unexpected events. These findings provide insights into how psychedelics disrupt sensory processing and shed light on the neural mechanisms underlying the altered perception of auditory stimuli observed in the psychedelic state.

Perceptual Distortions in Cartography: Maps for Trickery

Perceptual Distortions in Cartography: Maps for Trickery

Übersichtsarbeiten / Review Articles. Voreingenommenheiten und Wahrnehmungsverzerrungen (Bias) in der psychiatrisch-psychotherapeutischen Versorgung von Kindern und Jugendlichen mit intellektueller Beeinträchtigung

Bias in Mental Health Care of Children and Adolescents with Intellectual Disabilities Implicit and explicit bias and distortions of perception are partly responsible for the unequal and significantly deficient psychotherapeutic and psychiatric care situation for children and adolescents with intellectual disabilities and additional behavioral problems. The extent to which these biases influence misdiagnoses and treatment errors, refusals and exclusions from professional care, and grossly hostile rejections of people with disabilities requires empirical evidence (Bartig et al., 2021). The fact that all forms occur - probably to a considerable extent - contradicts the ethical principles of the medical and psychotherapeutic profession. In order to avoid misdiagnosis and treatment as a result of bias, this must be openly addressed. Selfawareness, supervision and second views, the concept of working diagnosis and, above all, the full application of child and adolescent psychiatric standards help to reduce bias.

No-reference Bitstream-based Perceptual Quality Assessment of Octree-Lifting Encoded 3D Point Clouds.

No-reference point cloud quality assessment (PCQA) based on bitstreams uses information extracted from the bitstream for quality monitoring at network nodes. We develop a no-reference PCQA model based on bitstreams for the perceived quality assessment of Octree-Lifting coded point clouds. At first, our research explores the essential correlation between subjective visual quality degradation and the texture quantization parameter (TQP) when using lossless geometric coding. Then, we enhance the proposed model by incorporating texture complexity (TC) while taking into account the dependence of perceptual coding distortion on the texture characteristics of a point cloud. We estimate TC by utilizing TQP and calculating the average standard deviation of the Y-component of the attribute value ( Y_ std), both of which are extracted from the bitstream. Then, a texture distortion assessment model is constructed based on TQP and Y_ std. The integration of the texture distortion model with the position quantization scale (PQS) results in the derivation of an overall no-reference bitstream-based PCQA model, named streamPCQ-OL. The findings from the conducted experiments highlight a significant superiority of the proposed model over existing approaches in terms of performance. The dataset and source code will be publicly released and made available for access at https://github.com/qdushl/Waterloo-Point-Cloud-Database-4.0.

Using Immersive Environments in E-Mental Health Rehabilitation Programs Directed to Future Health Professionals to Promote Empathy and Health Literacy about Schizophrenia.

Rehabilitation involves all types of patients, including people with schizophrenia. Schizophrenia is considered a complex syndrome characterized in general by fundamental and characteristic distortions of thinking and perception. The quality of life of a person with schizophrenia can be compromised by difficulty in carrying out their daily tasks and by the social stigma of their condition. The importance of training and sensitizing students in rehabilitation areas to this type of problem to improve the rehabilitation processes in which they will participate as future professionals involves empathy and the ability to communicate with these populations. It is possible through virtual reality to create immersive environments to simulate some psychotic symptoms characteristic of people with schizophrenia, such as visual hallucinations and hearing voices. The aim of this study was to test the effect of exposure to experiences characteristic of schizophrenia through two different types of immersive environments, graphical computational virtual reality and 360° video, on students from areas of social rehabilitation regarding empathy, social distance, and attitudes towards people with schizophrenia. Although the results were positive for the three parameters under study, no significant differences were found for each of them between the environments to which the participants were exposed. This study concluded that the choice between the two types of immersive environments should be based on the project's objectives, the target audience's needs, and available resources, rather than the type of environment itself, as their impact was similar.

Neurobiochemical Disturbances in Psychosis and their Implications for Therapeutic Intervention.

Psychosis, marked by the emergence of psychotic symptoms, delves into the intricate dance of neurotransmitter dynamics, prominently featuring dopamine as a key orchestrator. In individuals living with psychotic conditions, the finely tuned balance of dopamine becomes disrupted, setting off a cascade of perceptual distortions and the manifestation of psychotic symptoms. A lot of factors can impact dopamine metabolism, further complicating its effects. From genetic predispositions to environmental stressors and inflammation, the delicate equilibrium is susceptible to various influences. The sensorium, the origin of incoming information, loses its intrinsic valence in this complex interplay. The concept of the "signal-to-noise ratio" encapsulates dopamine's role as a molecular switch in neural networks, influencing the flow of information serving the basic biological functions. This nuanced modulation acts as a cognitive prism, shaping how the world is perceived. However, in psychosis, this balance is disrupted, steering individuals away from a shared reality. Understanding dopamine's centrality requires acknowledging its unique status among neurotransmitters. Unlike strictly excitatory or inhibitory counterparts, dopamine's versatility allows it to toggle between roles and act as a cognitive director in the neural orchestra. Disruptions in dopamine synthesis, exchange, and receptor representation set off a chain reaction, impacting the delivery of biologically crucial information. The essence of psychosis is intricately woven into the delicate biochemical ballet choreographed by dopamine. The disruption of this neurotransmitter not only distorts reality but fundamentally reshapes the cognitive and behavioral field of our experience. Recognizing dopamine's role as a cognitive prism provides vital insights into the multifaceted nature of psychotic conditions, offering avenues for targeted therapeutic interventions aimed at restoring this delicate neurotransmitter balance.

Associations of Cognitive Expectancies With Auditory Hallucinations and Hallucinatory-Like Experiences in Patients With Schizophrenia.

Various neurocognitive models explore perceptual distortions and hallucinations in schizophrenia and the general population. A variant of predictive coding account suggests that strong priors, like cognitive expectancy, may influence perception. This study examines if stronger cognitive expectancies result in more auditory false percepts in clinical and healthy control groups, investigates group differences, and explores the association between false percepts and hallucinations. Patients diagnosed with schizophrenia with current auditory hallucinations (n = 51) and without hallucinations (n = 66) and healthy controls (n = 51) underwent the False Perception Task under various expectancy conditions. All groups were examined for the presence and severity of hallucinations or hallucinatory-like experiences. We observed a main effect of condition across all groups, ie, the stronger the cognitive expectancy, the greater the ratio of auditory false percepts. However, there was no group effect for the ratio of auditory false percepts. Despite modest pairwise correlations in the hallucinating group, the ratio of auditory false percepts was not predicted by levels of hallucinations and hallucinatory-like experiences in a linear mixed model. The current study demonstrates that strong priors in the form of cognitive expectancies affect perception and play a role in perceptual disturbances. There is also a tentative possibility that overreliance on strong priors may be associated with hallucinations in currently hallucinating subjects. Possible, avoidable confounding factors are discussed in detail.

Lesions Causing Alice in Wonderland Syndrome Map to a Common Brain Network Linking Body and Size Perception.

Alice in Wonderland syndrome (AIWS) profoundly affects human perception of size and scale, particularly regarding one's own body and the environment. Its neuroanatomical basis has remained elusive, partly because brain lesions causing AIWS can occur in different brain regions. Here, we aimed to determine if brain lesions causing AIWS map to a distributed brain network. A retrospective case-control study analyzing 37 cases of lesion-induced AIWS identified through systematic literature review was conducted. Using resting-state functional connectome data from 1,000 healthy individuals, the whole-brain connections of each lesion were estimated and contrasted with those from a control dataset comprising 1,073 lesions associated with 25 other neuropsychiatric syndromes. Additionally, connectivity findings from lesion-induced AIWS cases were compared with functional neuroimaging results from 5 non-lesional AIWS cases. AIWS-associated lesions were located in various brain regions with minimal overlap (≤33%). However, the majority of lesions (≥85%) demonstrated shared connectivity to the right extrastriate body area, known to be selectively activated by viewing body part images, and the inferior parietal cortex, involved in size and scale judgements. This pattern was uniquely characteristic of AIWS when compared with other neuropsychiatric disorders (family-wise error-corrected p < 0.05) and consistent with functional neuroimaging observations in AIWS due to nonlesional causes (median correlation r = 0.56, interquartile range 0.24). AIWS-related perceptual distortions map to one common brain network, encompassing regions critical for body representation and size-scale processing. These findings lend insight into the neuroanatomical localization of higher-order perceptual functions, and may inform future therapeutic strategies for perceptual disorders. ANN NEUROL 2024;96:662-674.

Immersive scene representation in human visual cortex with ultra-wide-angle neuroimaging

While human vision spans 220°, traditional functional MRI setups display images only up to central 10-15°. Thus, it remains unknown how the brain represents a scene perceived across the full visual field. Here, we introduce a method for ultra-wide angle display and probe signatures of immersive scene representation. An unobstructed view of 175° is achieved by bouncing the projected image off angled-mirrors onto a custom-built curved screen. To avoid perceptual distortion, scenes are created with wide field-of-view from custom virtual environments. We find that immersive scene representation drives medial cortex with far-peripheral preferences, but shows minimal modulation in classic scene regions. Further, scene and face-selective regions maintain their content preferences even with extreme far-periphery stimulation, highlighting that not all far-peripheral information is automatically integrated into scene regions computations. This work provides clarifying evidence on content vs. peripheral preferences in scene representation and opens new avenues to research immersive vision.

Visuo-motor updating in individuals with heightened autistic traits

Autism spectrum disorder (ASD) presents a range of challenges, including heightened sensory sensitivities. Here, we examine the idea that sensory overload in ASD may be linked to issues with efference copy mechanisms, which predict the sensory outcomes of self-generated actions, such as eye movements. Efference copies play a vital role in maintaining visual and motor stability. Disrupted efference copies hinder precise predictions, leading to increased reliance on actual feedback and potential distortions in perceptions across eye movements. In our first experiment, we tested how well healthy individuals with varying levels of autistic traits updated their mental map after making eye movements. We found that those with more autistic traits had difficulty using information from their eye movements to update the spatial representation of their mental map, resulting in significant errors in object localization. In the second experiment, we looked at how participants perceived an object displacement after making eye movements. Using a trans-saccadic spatial updating task, we found that those with higher autism scores exhibited a greater bias, indicating under-compensation of eye movements and a failure to maintain spatial stability during saccades. Overall, our study underscores efference copy’s vital role in visuo-motor stability, aligning with Bayesian theories of autism, potentially informing interventions for improved action–perception integration in autism.

Visuo-motor updating in individuals with heightened autistic traits.

Autism spectrum disorder (ASD) presents a range of challenges, including heightened sensory sensitivities. Here, we examine the idea that sensory overload in ASD may be linked to issues with efference copy mechanisms, which predict the sensory outcomes of self-generated actions, such as eye movements. Efference copies play a vital role in maintaining visual and motor stability. Disrupted efference copies hinder precise predictions, leading to increased reliance on actual feedback and potential distortions in perceptions across eye movements. In our first experiment, we tested how well healthy individuals with varying levels of autistic traits updated their mental map after making eye movements. We found that those with more autistic traits had difficulty using information from their eye movements to update the spatial representation of their mental map, resulting in significant errors in object localization. In the second experiment, we looked at how participants perceived an object displacement after making eye movements. Using a trans-saccadic spatial updating task, we found that those with higher autism scores exhibited a greater bias, indicating under-compensation of eye movements and a failure to maintain spatial stability during saccades. Overall, our study underscores efference copy's vital role in visuo-motor stability, aligning with Bayesian theories of autism, potentially informing interventions for improved action-perception integration in autism.

Het Alice in Wonderland-syndroom en psychotische ervaringen: een differentiaaldiagnostische uitdaging

Alice in Wonderland syndrome and psychotic experiences: a challenging differential diagnosis Alice in Wonderland syndrome (AIWS) is an understudied condition associated with a variety of symptoms, from visual and somesthetic perceptual distortions to disturbances in time perception and symptoms in the psychotic spectrum. The syndrome is pathophysiologically associated with cortical dysfunction in sensory brain areas. When AIWS symptoms occur, possible underlying neurological conditions should be investigated as they may be amenable to treatment. From a psychiatric perspective, distinguishing it from disorders within the psychotic spectrum poses a challenge. This article aims to clearly describe the phenomenology and definition of AIWS and to explore whether a strict differential diagnosis with psychotic experiences is possible. To the best of the authors’ knowledge, psychiatric disorders have to this date only been associated with AIWS in adults. A case of a 14-year-old girl with depression and subclinical psychotic symptoms with an unclear origin of AIWS is presented. Presumably, there was a looping effect and the subclinical psychotic symptoms were mistakenly identified as AIWS symptoms. Due to substantial differences in prognosis and treatment, the authors want to emphasize the importance of differentiating AIWS from a (subclinical) psychotic syndrome. It is crucial to thoroughly examine each individual AIWS symptom phenomenologically in all its facets. Additionally, clinicians should be aware of the influence of the looping effect.

Alice in Wonderland Syndrome (AIWS): prevalence and characteristics in adults with migraine

ObjectiveAlice in Wonderland Syndrome (AIWS) is a sensory disorder characterized by a distorted somatosensory and/or visual perception. Additionally, distortion of time perception and symptoms of derealization/depersonalization may occur. AIWS is frequently associated with migraine. However, its prevalence, and clinical characteristics remain poorly understood. Here, we investigated the prevalence and features of AIWS in individuals with migraine. We hypothesized AIWS is more frequent in migraine patients with aura than in those without aura.MethodsThis was a prospective cross-sectional cohort study, conducted at a tertiary headache center. Participants with migraine filled out questionnaires, providing details on demographics, headache, AIWS characteristics and the occurrence of transient visual phenomena such as fragmented vision.ResultsOf 808 migraine patients, 133 individuals (16.5%, mean age 44.4 ± 13.3 years, 87% women) reported AIWS symptoms throughout their lives. Micro- and/or telopsia (72.9%) were most frequent, followed by micro- and/or macrosomatognosia (49.6%), and macro- and/or pelopsia (38.3%), lasting on average half an hour. AIWS symptoms occurred in association with headache in 65.1% of individuals, and 53.7% had their first AIWS episode at the age of 18 years or earlier. Migraine patients with aura were more likely to report AIWS symptoms than those without aura (19.5% vs. 14.1%, p = 0.04). Participants with AIWS reported a higher incidence of 17 out of the 22 investigated visual phenomena.ConclusionAIWS symptoms appear to be a common lifetime phenomenon in migraine patients. The correlation and clinical parallels between AIWS and migraine aura could indicate shared underlying pathomechanisms.

Review of Image Quality Assessment Methods for Compressed Images.

The compression of images for efficient storage and transmission is crucial in handling large data volumes. Lossy image compression reduces storage needs but introduces perceptible distortions affected by content, compression levels, and display environments. Each compression method generates specific visual anomalies like blocking, blurring, or color shifts. Standardizing efficient lossy compression necessitates evaluating perceptual quality. Objective measurements offer speed and cost efficiency, while subjective assessments, despite their cost and time implications, remain the gold standard. This paper delves into essential research queries to achieve visually lossless images. The paper describes the influence of compression on image quality, appropriate objective image quality metrics (IQMs), and the effectiveness of subjective assessment methods. It also provides an overview of the existing literature, surveys, and subjective and objective image quality assessment (IQA) methods. Our aim is to offer insights, identify challenges in existing methodologies, and assist researchers in selecting the most effective assessment approach for their needs.