Depth Inversion Illusion Research Articles

Resistance to depth inversion illusions: A biosignature of psychosis with potential utility for monitoring positive symptom emergence and remission in schizophrenia

The predictive coding theory of psychosis posits that individuals with schizophrenia demonstrate abnormalities in the strength of top-down modulation (based on prior experience) of sensory signals. Evidence suggests that difficulty perceiving depth inversion illusions (DIIs) (i.e., more accurate perception of stimuli under conditions in which control subjects perceive these illusions) may reflect this abnormality in people with schizophrenia. This review synthesizes findings from all studies that have investigated DII perception in schizophrenia, high-risk syndromes, and conditions associated with risk for psychosis outside of a psychotic disorder such as those involving cannabis use, alcohol intoxication and withdrawal, and sleep deprivation. Cognitive and biological mechanisms contributing to DII resistance, and strengths and confounds of using the DII task as a measure of predictive coding are also discussed. The available evidence indicates that psychosis is associated with resistance to DIIs, whereas schizophrenia in the absence of active psychosis is less strongly associated with this effect. This may be due to psychosis-related deficiencies in top-down signaling and a compensatory overreliance on bottom-up signaling. Overall, the evidence reviewed suggests that the DII task is a sensitive measure of predictive coding in schizophrenia that could be used as a visual biomarker to predict risk and impending changes in clinical state within the disorder. Additional studies that measure changes longitudinally are necessary to further explore the possibility of using the DII task as a visual biomarker for psychosis in clinical settings.

Using psiTurk to explore correlations between delusional ideation and perceiving depth-inversion illusions

Using psiTurk to explore correlations between delusional ideation and perceiving depth-inversion illusions

The role of binocular disparity in depth-inversion illusions studied with synopters and pseudoscopes

The role of binocular disparity in depth-inversion illusions studied with synopters and pseudoscopes

Face superiority - Cartoon 3-D faces produce a stronger depth-inversion illusion than geometric objects that share the same basic bounding contour.

Face superiority - Cartoon 3-D faces produce a stronger depth-inversion illusion than geometric objects that share the same basic bounding contour.

Neural correlates of binocular depth inversion illusion in antipsychotic-naïve first-episode schizophrenia patients.

Binocular depth inversion illusion (BDII), a visual, 'top-down'-driven information process, is impaired in schizophrenia and particularly in its early stages. BDII is a sensitive measure of impaired visual information processing and represents a valid diagnostic tool for schizophrenia and other psychotic disorders.However, neurobiological underpinnings of aberrant BDII in first-episode schizophrenia are largely unknown at present. In this study, 22 right-handed, first-episode, antipsychotic-naïve schizophrenia patients underwent BDII assessment and MRI scanning at 1.5T. The surface-based analysis via new version of Freesurfer (6.0) enabled calculation of cortical thickness and surface area. BDII total and faces scores were related to the two distinct cortical measurements. We found a significant correlation between BDII performance and cortical thickness in the inferior frontal gyrus and middle temporal gyrus (p < 0.003, Bonferroni corr.), as well as superior parietal gyrus, postcentral gyrus, supramarginal gyrus, and precentral gyrus (p < 0.05, CWP corr.), respectively. BDII performance was significantly correlated with surface area in the superior parietal gyrus and right postcentral gyrus (p < 0.003, Bonferroni corr.). BDII performance may be linked to cortical thickness and surface area variations in regions involved in "adaptive" or "top-down" modulation and stimulus processing, i.e., frontal and parietal lobes. Our results suggest that cortical features of distinct evolutionary and genetic origin differently contribute to BDII performance in first-episode, antipsychotic-naïve schizophrenia patients.

Seeing more clearly through psychosis: Depth inversion illusions are normal in bipolar disorder but reduced in schizophrenia

Schizophrenia patients with more positive symptoms are less susceptible to depth inversion illusions (DIIs) in which concave objects appear as convex. It remains unclear, however, the extent to which this perceptual advantage uniquely characterizes the schizophrenia phenotype. To address the foregoing, we compared 30 bipolar disorder patients to a previously published sample of healthy controls (N=25) and schizophrenia patients (N=30). The task in all cases was to judge the apparent convexity of physically concave faces and scenes. Half of the concave objects were painted with realistic texture to enhance the convexity illusion and the remaining objects were untextured to reduce the illusion. Subjects viewed objects stereoscopically or via monocular motion parallax depth cues. For each group, DIIs were stronger with texture than without, and weaker with stereoscopic information than without, indicating a uniformly normal response to stimulus alterations across groups. Bipolar patients experienced DIIs more frequently than schizophrenia patients but as commonly as controls, irrespective of the face/scene category, texture, or viewing condition (motion/stereo). More severe positive and disorganized symptoms predicted reduced DIIs for schizophrenia patients and across all patients. These results suggest that people with schizophrenia, but not bipolar disorder, more accurately perceive object depth structure. Psychotic symptoms—or their accompanying neural dysfunction—may primarily drive the effect presumably through eroding the visual system's generalized tendency to construe unusual or ambiguous surfaces as convex. Because such symptoms are by definition more common in schizophrenia, DIIs are at once state-sensitive and diagnostically specific, offering a potential biomarker for the presence of acute psychosis.

Disruptions in neural connectivity associated with reduced susceptibility to a depth inversion illusion in youth at ultra high risk for psychosis.

Patients with psychosis exhibit a reduced susceptibility to depth inversion illusions (DII) in which a physically concave surface is perceived as convex (e.g., the hollow mask illusion). Here, we examined the extent to which lessened susceptibility to DII characterized youth at ultra high risk (UHR) for psychosis. In this study, 44 UHR participants and 29 healthy controls judged the apparent convexity of face-like human masks, two of which were concave and the other convex. One of the concave masks was painted with realistic texture to enhance the illusion; the other was shown without such texture. Networks involved with top-down and bottom-up processing were evaluated with resting state functional connectivity magnetic resonance imaging (fcMRI). We examined regions associated with the fronto-parietal network and the visual system and their relations with susceptibility to DII. Consistent with prior studies, the UHR group was less susceptible to DII (i.e., they were characterized by more veridical perception of the stimuli) than the healthy control group. Veridical responses were related to weaker connectivity within the fronto-parietal network, and this relationship was stronger in the UHR group, suggesting possible abnormalities of top-down modulation of sensory signals. This could serve as a vulnerability marker and a further clue to the pathogenesis of psychosis.

Convexity Bias and Perspective Cues in the Reverse-Perspective Illusion.

The present experiment was designed to examine the roles of painted linear perspective cues, and the convexity bias that are known to influence human observers’ perception of three-dimensional (3D) objects and scenes. Reverse-perspective stimuli were used to elicit a depth-inversion illusion, in which far points on the stimulus appear to be closer than near points and vice versa, with a 2 (Type of stimulus) × 2 (Fixation mark position) design. To study perspective, two types of stimuli were used: a version with painted linear perspective cues and a version with blank (unpainted) surfaces. To examine the role of convexity, two locations were used for the fixation mark: either in a locally convex or a locally concave part of each stimulus (painted and unpainted versions). Results indicated that the reverse-perspective illusion was stronger when the stimulus contained strong perspective cues and when observers fixated a locally concave region within the scene.

Automatically Characterizing Sensory-Motor Patterns Underlying Reach-to-Grasp Movements on a Physical Depth Inversion Illusion

Recently, movement variability has been of great interest to motor control physiologists as it constitutes a physical, quantifiable form of sensory feedback to aid in planning, updating, and executing complex actions. In marked contrast, the psychological and psychiatric arenas mainly rely on verbal descriptions and interpretations of behavior via observation. Consequently, a large gap exists between the body's manifestations of mental states and their descriptions, creating a disembodied approach in the psychological and neural sciences: contributions of the peripheral nervous system to central control, executive functions, and decision-making processes are poorly understood. How do we shift from a psychological, theorizing approach to characterize complex behaviors more objectively? We introduce a novel, objective, statistical framework, and visuomotor control paradigm to help characterize the stochastic signatures of minute fluctuations in overt movements during a visuomotor task. We also quantify a new class of covert movements that spontaneously occur without instruction. These are largely beneath awareness, but inevitably present in all behaviors. The inclusion of these motions in our analyses introduces a new paradigm in sensory-motor integration. As it turns out, these movements, often overlooked as motor noise, contain valuable information that contributes to the emergence of different kinesthetic percepts. We apply these new methods to help better understand perception-action loops. To investigate how perceptual inputs affect reach behavior, we use a depth inversion illusion (DII): the same physical stimulus produces two distinct depth percepts that are nearly orthogonal, enabling a robust comparison of competing percepts. We find that the moment-by-moment empirically estimated motor output variability can inform us of the participants' perceptual states, detecting physiologically relevant signals from the peripheral nervous system that reveal internal mental states evoked by the bi-stable illusion. Our work proposes a new statistical platform to objectively separate changes in visual perception by quantifying the unfolding of movement, emphasizing the importance of including in the motion analyses all overt and covert aspects of motor behavior.

Methods to explore the influence of top-down visual processes on motor behavior.

Kinesthetic awareness is important to successfully navigate the environment. When we interact with our daily surroundings, some aspects of movement are deliberately planned, while others spontaneously occur below conscious awareness. The deliberate component of this dichotomy has been studied extensively in several contexts, while the spontaneous component remains largely under-explored. Moreover, how perceptual processes modulate these movement classes is still unclear. In particular, a currently debated issue is whether the visuomotor system is governed by the spatial percept produced by a visual illusion or whether it is not affected by the illusion and is governed instead by the veridical percept. Bistable percepts such as 3D depth inversion illusions (DIIs) provide an excellent context to study such interactions and balance, particularly when used in combination with reach-to-grasp movements. In this study, a methodology is developed that uses a DII to clarify the role of top-down processes on motor action, particularly exploring how reaches toward a target on a DII are affected in both deliberate and spontaneous movement domains.

What's in a face? The role of depth undulations in three-dimensional depth-inversion illusions.

Upright hollow human faces produce among the strongest depth-inversion illusions (DIIs), but why? We considered the role of depth undulations by comparing four types of hollow objects: an ellipsoid, a human mask, and two symmetric 'Martian'masks, which wavered in depth like the human mask but which lacked face-like features. Illusion strength was quantified either as the critical viewing distance at which the 3-D percept switched between convex and concave (experiment 1) or as the proportion of time ('predominance') that observers experienced DII from a fixed intermediate viewing distance (experiment 2). Critical distances were smallest--and hence the illusion was strongest--for the upright human mask; the remaining objects produced undifferentiated critical distance values. The predominance results were more fine-grained: illusions were experienced most often for the upright human mask, least often for the hollow ellipsoid, and to an intermediate extent for the Martian and upside-down human masks. These results suggest: (1) an upside-down human mask and a surface with nonface features undulating in depth are equivalent for the purposes of generating DIIs; (2) depth undulations contribute to DII; and (3) such undulations are most effective when structured into an upright human face.

Performance Consistency in Depth-Inversion Illusions: Faces and Scenes

Performance Consistency in Depth-Inversion Illusions: Faces and Scenes

Performance consistency in depth-inversion illusions: faces and scenes

Performance consistency in depth-inversion illusions: faces and scenes

Reduced depth inversion illusions in schizophrenia are state-specific and occur for multiple object types and viewing conditions.

Schizophrenia patients are less susceptible to depth inversion illusions (DIIs) in which concave faces appear as convex, but what stimulus attributes generate this effect and how does it vary with clinical state? To address these issues, we had 30 schizophrenia patients and 25 well-matched healthy controls make convexity judgments on physically concave faces and scenes. Patients were selectively sampled from three levels of care to ensure symptom heterogeneity. Half of the concave objects were painted with realistic texture to enhance the convexity illusion; the remaining objects were painted uniform beige to reduce the illusion. Subjects viewed the objects with one eye while laterally moving in front of the stimulus (to see depth via motion parallax) or with two eyes while remaining motionless (to see depth stereoscopically). For each group, DIIs were stronger with texture than without, and weaker with stereoscopic information than without, indicating that patients responded normally to stimulus alterations. More importantly, patients experienced fewer illusions than controls irrespective of the face/scene category, texture, or viewing condition (parallax/stereo). Illusions became less frequent as patients experienced more positive symptoms and required more structured treatment. Taken together, these results indicate that people with schizophrenia experience fewer DIIs with a variety of object types and viewing conditions, perhaps because of a lessened tendency to construe any type of object as convex. Moreover, positive symptoms and the need for structured treatment are associated with more accurate 3-D perception, suggesting that DII may serve as a state marker for the illness.

Supplemental Material for Reduced Depth Inversion Illusions in Schizophrenia Are State-Specific and Occur for Multiple Object Types and Viewing Conditions

Supplemental Material for Reduced Depth Inversion Illusions in Schizophrenia Are State-Specific and Occur for Multiple Object Types and Viewing Conditions

Binocular depth inversion as a paradigm of reduced visual information processing in prodromal state, antipsychotic-naïve and treated schizophrenia

The binocular depth inversion illusion test (BDII) represents a sensitive measure of impaired visual information processing that manifests in various experimental and naturally occurring psychotic states. This study explores impairment of visual processing in different major psychiatric diseases investigating 313 subjects, suffering of either an initial prodromal state of psychosis (IPS) or a first-episode, antipsychotic-naïve paranoid schizophrenia (SZ-N) as well as short-term antipsychotically treated schizophrenia (SZ-T), major depression (MDD), bipolar disorder (BD), dementia (D), and healthy controls (HC). Patients suffering from either IPS, SZ-N or a SZ-T showed significantly higher scores of BDII compared to HC, indicating that visual processing is already disturbed at an early state of the disease. For MDD, BD and D no statistically significant difference was found compared to HC. As the identification of individuals at high risk for developing schizophrenia relies on rating scales assessing subtle, pre-psychotic psychopathology, it would be of interest to have more diagnostic criteria available, testing, e.g. cognitive and perceptual impairment. We therefore analysed the receiver operating characteristic (ROC) curve, testing prodromal cases versus a clinically relevant sample of non-psychotic patients and controls, which included HC as well as the groups of patients suffering from MDD, BD or D revealing a AUC of 0.70. Thus, the BDII may be useful as an additional neuropsychological test for assessment of patients at high risk for developing schizophrenia.

Binocular depth inversion illusion for early assessment of altered visual information processing in the course of schizophrenia

Binocular depth inversion illusion for early assessment of altered visual information processing in the course of schizophrenia

Disturbances of visual information processing in early states of psychosis and experimental delta-9-tetrahydrocannabinol altered states of consciousness

Recent data on alterations of the endogenous cannabinoid system in schizophrenia have raised the question of its functional role in this disease. The psychoactive compound of Cannabis sativa, delta-9-tetrahydrocannabinol (Δ 9-THC), has been shown to induce psychotic symptoms, but it is unknown to what extend prodromal states of psychoses are reflected by these experimental approaches. This study compares four groups of subjects: antipsychotic-naïve patients suffering from acute paranoid schizophrenic or schizophreniform psychosis (SZ), patients in the prodromal state (IPS), healthy controls without any pharmacological intervention (HC) and a second group of healthy volunteers who were orally administered synthetic Δ 9-THC (Dronabinol) (HC-THC). Neither SZ and IPS nor HC received the experimental drug. All subjects were assessed using the Brief Psychiatric Rating Scale (BPRS) and the Binocular Depth Inversion Illusion Test (BDII). The latter represents a sensitive measure of impaired visual information processing that manifests in various experimental and naturally occurring psychotic states. BDII values were well comparable in SZ, IPS and HC-THC, and all groups differed significantly to HC. The BPRS revealed no significant difference between HC-THC and IPS while both were significantly different from SZ and HC, respectively. Our results suggest that Δ 9-THC-induced altered states of consciousness may serve as a useful tool for modeling psychotic disorders, particularly their prodromal states. Furthermore, they provide insight into the perceptual and psychopathological alterations induced by Δ 9-THC, which is essential for the understanding of the pro-psychotic effects of herbal cannabis preparations with highly enriched Δ 9-THC content.

Reduced binocular depth inversion in regular cannabis users

The binocular depth inversion illusion (BDII) has been shown to be a sensitive measure of impaired visual information processing under conditions including cannabinoid-intoxicated states, alcohol withdrawal, sleep deprivation, and in patients with positive symptoms of schizophrenia. This study assessed whether the BDII could detect subtle cognitive impairment due to regular cannabis use by comparing 10 regular cannabis users and 10 healthy controls from the same community sources, matched for age, sex, and premorbid IQ. Subjects were also compared on measures of executive functioning, memory, and personality. Regular cannabis users were found to have significantly higher BDII scores for inverted images. This was not due to a problem in the primary processing of visual information, as there was no significant difference between the groups for depth perception of normal images. There was no relationship between BDII scores for inverted images and time since last dose, suggesting that the measured impairment of BDII more closely reflected chronic than acute effects of regular cannabis use. There were no significant differences between the groups for other neuropsychological measures of memory or executive function. A positive relationship was found between EPQ-R-psychoticism and cannabis, tobacco, and alcohol use. Cannabis users also used significantly larger amounts of alcohol. However, no relationship was found between BDII scores and drug use other than cannabis or psychoticism. Compared to the other neuropsychological tests used, the BDII appears to be a more sensitive tool for the detection of subtle impairments in visual information processing related to chronic cannabis use.