Reduced P300 and P600 amplitude in the hollow-mask illusion in patients with schizophrenia

A neural model of modified excitation/inhibition and feedback levels in schizophrenia

Introduction

The strength of certain visual illusions, including contrast-contrast and apparent motion, is weakened in individuals with schizophrenia. Such phenomena have been interpreted as the impaired integration of inhibitory and excitatory neural responses, and impaired top-down feedback mechanisms.

Methods

To investigate whether and how these factors influence the perceived contrast-contrast and apparent motion illusions in individuals with schizophrenia, we propose a two-layer network, with top-down feedback from layer 2 to layer 1 that can model visual receptive fields (RFs) and their inhibitory and excitatory subfields.

Results

Our neural model suggests that illusion perception changes in individuals with schizophrenia can be influenced by altered top-down mechanisms and the organization of the on-center off-surround receptive fields. Alteration of the RF inhibitory surround and/or the excitatory center can replicate the difference of illusion precepts between individuals with schizophrenia within certain clinical states and normal controls. The results show that the simulated top-down feedback modulation enlarges the difference of the model illusion representations, replicating the difference between the two groups.

Discussion

We propose that the heterogeneity of visual and in general sensory processing in certain clinical states of schizophrenia can be largely explained by the degree of top-down feedback reduction, emphasizing the critical role of top-down feedback in illusion perception, and to a lesser extent on the imbalance of excitation/inhibition. Our neural model provides a mechanistic explanation for the modulated visual percepts of contrast-contrast and apparent motion in schizophrenia with findings that can explain a broad range of visual perceptual observations in previous studies. The two-layer motif of the current model provides a general framework that can be tailored to investigate subcortico-cortical (such as thalamocortical) and cortico-cortical networks, bridging neurobiological changes in schizophrenia and perceptual processing.

A neural model of modified excitation/inhibition and feedback levels in schizophrenia

The strength of certain visual illusions is weakened in individuals with schizophrenia. Such phenomena have been interpreted as the impaired integration of inhibitory and excitatory neural responses, and impaired top-down feedback mechanisms. To investigate whether and how these factors influence the perceived illusions in individuals with schizophrenia, we propose a two-layer network that can model visual receptive fields (RFs), their inhibitory and excitatory subfields, and the top-down feedback. Our neural model suggests that illusion perception changes in individuals with schizophrenia can be influenced by altered top-down mechanisms and the organization of the on-center off-surround receptive fields. Alteration of the RF inhibitory surround and/or the excitatory center can replicate the difference of illusion precepts between individuals with schizophrenia and normal controls. The results show that the simulated top-down feedback modulation enlarges the difference of the model illusion representations, replicating the difference between the two groups. We propose that the heterogeneity of visual and in general sensory processing in schizophrenia can be largely explained by the degree of top-down feedback reduction, emphasizing the critical role of top-down feedback in illusion perception, and to a lesser extent on the imbalance of excitation/inhibition. Our neural model provides a mechanistic explanation for the modulated visual percepts in schizophrenia with findings that can explain a broad range of visual perceptual observations in previous studies. The two-layer motif of the current model provides a general framework that can be tailored to investigate subcortico-cortical (such as thalamocortical) and cortico-cortical networks, bridging neurobiological changes in schizophrenia and perceptual processing.

The moderating role of early traumatic experiences on the association of schizotypal traits with visual perception

The findings on the association of schizotypal traits with the perception of visual illusions are scarce and inconsistent and have not taken into consideration potential effects of childhood traumatic experiences, a risk factor for schizophrenia-spectrum conditions. Thus, the present study addressed the question of potential moderating effects of early traumatic experiences on the association between different aspects of schizotypal traits with the perception of the Müller-Lyer and Navon's Hierarchical Letters (NHL) illusions. The study revealed that (a) increased suspiciousness was associated with increased liability to the Müller-Lyer illusion, when the exposure to traumatic events was high, whereas the opposite pattern was true when the exposure to traumatic events was low; (b) negative schizotypy was associated with more accurate global perception, and high disorganized schizotypy was associated with superior accuracy when target letters were present during the NHL illusion, when early traumatic experiences were at lower levels; and (c) high negative, disorganized, and total schizotypy were associated with lower accuracy when target letters were present in the NHL paradigm, when early traumatic experiences were at higher levels. The findings of the study suggest that early traumatic events differentially moderate the relationship between various aspects of schizotypal traits and visual perceptual processing.

Systematic review of visual illusions in schizophrenia

Visual illusions have long been used as tools to investigate sensory-perceptual deficits in schizophrenia. Recent conflicting accounts have called into question the assumption of abnormal illusion perception in patients and, therefore, the validity of this approach. Here, we present a systematic review of the current evidence regarding visual illusion perception abnormalities in patients with schizophrenia. Relevant publications were identified by a systematic search of PubMed, Literatura LILACS, PsycINFO, Embase, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL), IBECS, BIOSIS, and Web of Science. Forty-five studies were selected which included illusions classified as 'Motion illusions', 'Geometric-optical illusions', 'Illusory contours', 'Depth inversion illusion', and 'Non-specific'. There is concordant evidence of abnormal processing of illusions in patients for most categories, especially in facial Depth Inversion and Müller-Lyer illusions. There were significant methodological disparities and shortcomings, but risk of bias was overall low for individual studies. The usefulness of visual illusions as tools in clinical settings as well as in basic research may be contingent on significant methodological refinements.

An active inference perspective on the negative symptoms of schizophrenia

Predictive coding has played a transformative role in the study of psychosis, casting delusions and hallucinations as statistical inference in a system with abnormal precision. However, the negative symptoms of schizophrenia, such as affective blunting, avolition, and asociality, remain poorly understood. We propose a computational framework for emotional expression based on active inference-namely that affective behaviours such as smiling are driven by predictions about the social consequences of smiling. Similarly to how delusions and hallucinations can be explained by predictive uncertainty in sensory circuits, negative symptoms naturally arise from uncertainty in social prediction circuits. This perspective draws on computational principles to explain blunted facial expressiveness and apathy-anhedonia in schizophrenia. Its phenomenological consequences also shed light on the content of paranoid delusions and indistinctness of self-other boundaries. Close links are highlighted between social prediction, facial affect mirroring, and the fledgling study of interoception. Advances in automated analysis of facial expressions and acoustic speech patterns will allow empirical testing of these computational models of the negative symptoms of schizophrenia.

State anxiety influences P300 and P600 event-related potentials over parietal regions in the hollow-mask illusion experiment

The hollow-mask illusion is an optical illusion where a concave face is perceived as convex. It has been demonstrated that individuals with schizophrenia and anxiety are less susceptible to the illusion than controls. Previous research has shown that the P300 and P600 event-related potentials (ERPs) are affected in individuals with schizophrenia. Here, we examined whether individual differences in neuroticism and anxiety scores, traits that have been suggested to be risk factors for schizophrenia and anxiety disorders, affect ERPs of healthy participants while they view concave faces. Our results confirm that the participants were susceptible to the illusion, misperceiving concave faces as convex. We additionally demonstrate significant interactions of the concave condition with state anxiety in central and parietal electrodes for P300 and parietal areas for P600, but not with neuroticism and trait anxiety. The state anxiety interactions were driven by low-state anxiety participants showing lower amplitudes for concave faces compared to convex. The P300 and P600 amplitudes were smaller when a concave face activated a convex face memory representation, since the stimulus did not match the active representation. The opposite pattern was evident in high-state anxiety participants in regard to state anxiety interaction and the hollow-mask illusion, demonstrating larger P300 and P600 amplitudes to concave faces suggesting impaired late information processing in this group. This could be explained by impaired allocation of attentional resources in high-state anxiety leading to hyperarousal to concave faces that are unexpected mismatches to standard memory representations, as opposed to expected convex faces.

Critérios de decisão na ilusão da máscara côncava na esquizofrenia

RESUMO Objetivo Alguns estudos têm mostrado que indivíduos com esquizofrenia não experimentam a ilusão da máscara côncava. Nesse fenômeno, uma máscara apresentada em seu lado côncavo é percebida como convexa. A ocorrência dessa ilusão, de acordo com uma hipótese, dar-se-ia pela inibição dos processos top-down sobre os processos bottom-up. Neste estudo, foi investigado se havia uma diferença estatisticamente significativa entre os indivíduos com esquizofrenia comparados aos indivíduos saudáveis na distinção do lado côncavo do convexo de uma máscara, bem como qual hipótese melhor explicava o fenômeno, a inibição top-down ou critérios de decisão diferentes. Métodos Adotando a teoria da detecção do sinal e o método de coleta de dados, Confidence Rating , procurou-se verificar o desempenho nos julgamentos dos indivíduos com esquizofrenia comparados aos indivíduos saudáveis frente a uma máscara que ora foi apresentada em seu lado côncavo ora em seu lado convexo. Resultados Neste estudo, os indivíduos com esquizofrenia foram suscetíveis à ilusão e mais liberais em seus julgamentos diante do estímulo máscara. Conclusões A hipótese de inibição top-down sobre os processos bottom-up parece não ser uma explicação plausível. Talvez, a tomada de decisão ou critérios de decisão explique melhor os resultados encontrados neste estudo. Mais estudos são necessários para esclarecer melhor o fenômeno da ilusão da máscara côncava em indivíduos com esquizofrenia.

A review of abnormalities in the perception of visual illusions in schizophrenia

Specific abnormalities of vision in schizophrenia have been observed to affect high-level and some low-level integration mechanisms, suggesting that people with schizophrenia may experience anomalies across different stages in the visual system affecting either early or late processing or both. Here, we review the research into visual illusion perception in schizophrenia and the issues which previous research has faced. One general finding that emerged from the literature is that those with schizophrenia are mostly immune to the effects of high-level illusory displays, but this effect is not consistent across all low-level illusions. The present review suggests that this resistance is due to the weakening of top-down perceptual mechanisms and may be relevant to the understanding of symptoms of visual distortion rather than hallucinations as previously thought.

The neural correlates of vertical disparity gradient and cue conflict in Panum's limiting case

Although Panum's limiting case has been extensively researched, only recently has it been discovered that in addition to horizontal disparity, the final perception of depth is influenced by (i) the vertical disparity gradient and (ii) the degree of cue conflict between 2D and 3D shapes. The present study examines the neural correlates of the two factors, using EEG while observers viewed several versions of stereoscopic stimuli, which depicted Panum's limiting case. In these patterns the vertical disparity gradient was varied from 0.1 to 0.6, while the degree of cue conflict was manipulated from low to high. The ERP data showed that the amplitude of the N170 component (exogenous) was modulated by the vertical disparity gradient and cue conflict. In contrast, the N270 component (endogenous) was modulated by cue conflict only. Such findings demonstrate that both factors affect the perception of depth in Panum's limiting case, but at different stages: the vertical disparity gradient at an early stage of processing (N170) and cue conflict at two stages (N170 and N270). Hence, vertical disparity gradient is related to low-level visual stimulus parameters and can modulate exogenous component, while cue conflict is related to both exogenous and endogenous components.

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.

Event-related potentials elicited by the Deutsch "high-low" word illusion in the patients with first-episode schizophrenia with auditory hallucinations

BACKGROUND

The exact cerebral structural and functional mechanisms under the auditory verbal hallucinations (AVHs) in schizophrenia are still unclear. The Deutsch "high-low" word illusion might trigger attentional responses mimicking those under AVHs.

METHODS

We therefore have invited 16 patients with first-episode, paranoid schizophrenia, and 16 age- and gender-matched healthy volunteers to undergo the "oddball" event-related potentials elicited by the illusion. The clinical characteristics of patients were measured with the positive and negative symptom scale.

RESULTS

Besides the longer reaction time to the illusion, the standard P2 latency was shortened, the N2 latency was prolonged, and both N1 and P3 amplitudes were reduced in patients. The P3 source analyses showed the activated bilateral temporal lobes, parietal lobe and cingulate cortex in both groups, left inferior temporal gyrus in controls, and left postcentral gyrus in schizophrenia. Moreover, the N1 amplitude was positively correlated with the paranoid score in patients.

CONCLUSIONS

Our results were in line with previous neurophysiological and neuroimaging reports of hallucination or auditory processing in schizophrenia, and illustrated a whole process of cerebral information processing from N1 to P3, indicating this illusion had triggered a dynamic cerebral response similar to that of the AVHs had engaged.

Faces of Intersubjectivity

Here we consider interpersonal experience in schizophrenia, melancholia, and mania. Our goal is to improve understanding of similarities and differences in how other people can be experienced in these disorders, through a review of first-person accounts and case examples and of contemporary and classic literature on the phenomenology of these disorders. We adopt a tripartite/dialectical structure: first we explore main differences as traditionally described; next we consider how the disorders may resemble each other; finally we discuss more subtle but perhaps foundational ways in which the phenomenology of these disorders may nonetheless be differentiated. These involve disruptions of common sense and conventionality, abnormalities of empathy, distinct forms of paranoia and the sense of personal centrality, and altered perceptions of intentionality, deadness, and artificiality. We end by considering some neurocognitive research relevant to these abnormal forms of subjectivity, including work on theory of mind, experience of human movement, and perception of faces.

Schizophrenia and the eye

Although visual processing impairments are common in schizophrenia, it is not clear to what extent these originate in the eye vs. the brain. This review highlights potential contributions, from the retina and other structures of the eye, to visual processing impairments in schizophrenia and high-risk states. A second goal is to evaluate the status of retinal abnormalities as biomarkers for schizophrenia. The review was motivated by known retinal changes in other disorders (e.g., Parkinson’s disease, multiple sclerosis), and their relationships to perceptual and cognitive impairments, and disease progression therein. The evidence reviewed suggests two major conclusions. One is that there are multiple structural and functional disturbances of the eye in schizophrenia, all of which could be factors in the visual disturbances of patients. These include retinal venule widening, retinal nerve fiber layer thinning, dopaminergic abnormalities, abnormal ouput of retinal cells as measured by electroretinography (ERG), maculopathies and retinopathies, cataracts, poor acuity, and strabismus. Some of these are likely to be illness-related, whereas others may be due to medication or comorbid conditions. The second conclusion is that certain retinal findings can serve as biomarkers of neural pathology, and disease progression, in schizophrenia. The strongest evidence for this to date involves findings of widened retinal venules, thinning of the retinal nerve fiber layer, and abnormal ERG amplitudes. These data suggest that a greater understanding of the contribution of retinal and other ocular pathology to the visual and cognitive disturbances of schizophrenia is warranted, and that retinal changes have untapped clinical utility.

The hollow-face illusion monocularly observed in a box

Under monocular conditions, 40 students observed the reverse of polychrome and monochrome masks and judged them to be concave, convex or flat. The mask was presented upright and illuminated from above, below, right and left and in the upside down position illuminated from below. The magnitude of the perceived depth or relief was estimated using a retractable tape measure. Regardless of color, lighting and orientation, the majority of responses indicated that the hollow masks were perceived to be convex. No significant differences were observed between the depth or convexity of the metric magnitudes and scalar magnitudes of the concave masks in relation to variations in the light source direction, color, and position. The illusory depth, seeing the concave mask as convex, is a robust phenomenon that suggests the predominant role of higher-order processes over the low-order processes in visual face perception.

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.

Reviewing the ketamine model for schizophrenia

The observation that antagonists of the N-methyl-D-aspartate receptor (NMDAR), such as phencyclidine (PCP) and ketamine, transiently induce symptoms of acute schizophrenia had led to a paradigm shift from dopaminergic to glutamatergic dysfunction in pharmacological models of schizophrenia. The glutamate hypothesis can explain negative and cognitive symptoms of schizophrenia better than the dopamine hypothesis, and has the potential to explain dopamine dysfunction itself. The pharmacological and psychomimetic effects of ketamine, which is safer for human subjects than phencyclidine, are herein reviewed. Ketamine binds to a variety of receptors, but principally acts at the NMDAR, and convergent genetic and molecular evidence point to NMDAR hypofunction in schizophrenia. Furthermore, NMDAR hypofunction can explain connectional and oscillatory abnormalities in schizophrenia in terms of both weakened excitation of inhibitory γ-aminobutyric acidergic (GABAergic) interneurons that synchronize cortical networks and disinhibition of principal cells. Individuals with prenatal NMDAR aberrations might experience the onset of schizophrenia towards the completion of synaptic pruning in adolescence, when network connectivity drops below a critical value. We conclude that ketamine challenge is useful for studying the positive, negative, and cognitive symptoms, dopaminergic and GABAergic dysfunction, age of onset, functional dysconnectivity, and abnormal cortical oscillations observed in acute schizophrenia.

Percepção monocular da profundidade ou relevo na ilusão da máscara côncava na esquizofrenia

Este trabalho foi desenvolvido com o propósito de investigar a percepção monocular da profundidade ou relevo da máscara côncava por 29 indivíduos saudáveis, sete indivíduos com esquizofrenia sob uso de antipsicótico por um período inferior ou igual a quatro semanas e 29 sob uso de antipsicótico por um período superior a quatro semanas. Os três grupos classificaram o reverso de uma máscara policromada em duas situações de iluminação, por cima e por baixo. Os resultados indicaram que a maioria dos indivíduos com esquizofrenia inverteu a profundidade da máscara côncava na condição de observação monocular e perceberam-na como convexa, sendo, portanto, suscetíveis à ilusão da máscara côncava. Os indivíduos com esquizofrenia sob uso de medicação antipsicótica pelo período superior a quatro semanas estimaram a convexidade da máscara côncava iluminada por cima em menor comprimento comparados aos indivíduos saudáveis.

Apparent motion perception in patients with paranoid schizophrenia

Impaired perceptual inference has been suggested to be at the core of positive symptoms in schizophrenia. Apparent motion (AM) is a visual illusion in which perceptual inference gives rise to the experience of a single object moving back and forth when two spatially separated objects are flashed in alternation. Here, we investigated the strength of AM perception in patients with paranoid schizophrenia. Patients were less susceptible to the illusion as indicated by a lower probability of motion perception at the individual's optimal presentation frequency for AM. In addition, the probability of AM perception was inversely related to delusional conviction in the patient group. These results suggest that schizophrenia may be associated with a reduced susceptibility to visual phenomena that commonly rely on perceptual inference.

Detection of visual events along the apparent motion trace in patients with paranoid schizophrenia

Dysfunctional prediction in sensory processing has been suggested as a possible causal mechanism in the development of delusions in patients with schizophrenia. Previous studies in healthy subjects have shown that while the perception of apparent motion can mask visual events along the illusory motion trace, such motion masking is reduced when events are spatio-temporally compatible with the illusion, and, therefore, predictable. Here we tested the hypothesis that this specific detection advantage for predictable target stimuli on the apparent motion trace is reduced in patients with paranoid schizophrenia. Our data show that, although target detection along the illusory motion trace is generally impaired, both patients and healthy control participants detect predictable targets more often than unpredictable targets. Patients had a stronger motion masking effect when compared to controls. However, patients showed the same advantage in the detection of predictable targets as healthy control subjects. Our findings reveal stronger motion masking but intact prediction of visual events along the apparent motion trace in patients with paranoid schizophrenia and suggest that the sensory prediction mechanism underlying apparent motion is not impaired in paranoid schizophrenia.