Neural Mechanisms of Visual Motion Anomalies in Autism: A Two-Decade Update and Novel Aetiology

The 21st century has seen dramatic changes in our understanding of the visual physio-perceptual anomalies of autism and also in the structure and development of the primate visual system. This review covers the past 20 years of research into motion perceptual/dorsal stream anomalies in autism, as well as new understanding of the development of primate vision. The convergence of this literature allows a novel developmental hypothesis to explain the physiological and perceptual differences of the broad autistic spectrum. Central to these observations is the development of motion areas MT+, the seat of the dorsal cortical stream, central area of pre-attentional processing as well as being an anchor of binocular vision for 3D action. Such development normally occurs via a transfer of thalamic drive from the inferior pulvinar → MT to the anatomically stronger but later-developing LGN → V1 → MT connection. We propose that autistic variation arises from a slowing in the normal developmental attenuation of the pulvinar → MT pathway. We suggest that this is caused by a hyperactive amygdala → thalamic reticular nucleus circuit increasing activity in the PIm → MT via response gain modulation of the pulvinar and hence altering synaptic competition in area MT. We explore the probable timing of transfer in dominance of human MT from pulvinar to LGN/V1 driving circuitry and discuss the implications of the main hypothesis.

The Community Assessment of Psychic Experiences-Positive scale (CAPE-P15) accurately classifies and differentiates psychotic experience levels in adolescents from the general population

Background There is increasing interest in studying psychotic symptoms in non-clinical populations, with the Community Assessment of Psychic Experiences-Positive scale (CAPE-P15) being one of the self-screening questionnaires used most commonly for this purpose. Further research is needed to evaluate the ability of the scale to accurately identify and classify positive psychotic experiences (PE) in the general population. Aim To provide psychometric evidence about the accuracy of the CAPE-P15 for detecting PE in a sample of Chilean adolescents from the general population and classifying them according to their PE severity levels. Method We administered the CAPE-P15 to a general sample of 1594 students aged 12 to 19. Based on Item Response Theory (IRT), we tested the accuracy of the instrument using two main parameters: difficulty and discrimination power of the 15 items. Results We found that the scale provides very accurate information about PE, particularly for high PE levels. The items with the highest capability to determine the presence of the latent trait were those assessing perceptual anomalies (auditory and visual hallucinations), bizarre experiences (a double has taken the place of others; being controlled by external forces), and persecutory ideation (conspiracy against me). Conclusions The CAPE-P15 is an accurate and suitable tool to screen PE and to accurately classify and differentiate PE levels in adolescents from the general population. Further research is needed to better understand how maladaptive psychological mechanisms influence relationships between PE and suicidal ideation (SI) in the general population.

Individuals with autism spectrum disorder have altered visual encoding capacity

Perceptual anomalies in individuals with autism spectrum disorder (ASD) have been attributed to an imbalance in weighting incoming sensory evidence with prior knowledge when interpreting sensory information. Here, we show that sensory encoding and how it adapts to changing stimulus statistics during feedback also characteristically differs between neurotypical and ASD groups. In a visual orientation estimation task, we extracted the accuracy of sensory encoding from psychophysical data by using an information theoretic measure. Initially, sensory representations in both groups reflected the statistics of visual orientations in natural scenes, but encoding capacity was overall lower in the ASD group. Exposure to an artificial (i.e., uniform) distribution of visual orientations coupled with performance feedback altered the sensory representations of the neurotypical group toward the novel experimental statistics, while also increasing their total encoding capacity. In contrast, neither total encoding capacity nor its allocation significantly changed in the ASD group. Across both groups, the degree of adaptation was correlated with participants’ initial encoding capacity. These findings highlight substantial deficits in sensory encoding—independent from and potentially in addition to deficits in decoding—in individuals with ASD.

Evidence for Specific Associations Between Depressive Symptoms, Psychotic Experiences, and Suicidal Ideation in Chilean Adolescents From the General Population

Associations between psychotic experiences and suicidal ideation are not yet fully understood, and the potential role of depressive symptoms in this relationship remains unclear. The current study examined relationships between depressive symptoms (DS), psychotic experiences (PE) and suicidal ideation (SI) using two complementary approaches on cross-sectional data from a community sample of adolescents aged 13–19 years (N = 1,591). First, we investigated the association between the three domains using mediation analysis, showing that depressive symptoms partly mediate the relationship between psychotic experiences and suicidal ideation. Second, we looked at associations between the three domains at item level using network analysis. Specific associations between symptoms of the three domains were found, indicating depressive symptoms of sadness, avolition, pessimism, and self-criticalness/worthlessness as the most central symptoms in the network. Suicidal ideation was associated with the depressive symptoms pessimism and worthlessness, to social anxiety, and to perceptual anomalies. Our results show that the mediating effect of depressive symptoms between psychotic experiences and suicidal ideation may be due to associations between specific aspects of SI, depressive symptoms and psychotic experiences. These findings can contribute to the planning of health services and programs aimed at the timely detection of psychopathology and suicidal risk in young people.

Adaptação de uma Escala de Avaliação de Anomalias Perceptuais para o Brasil

Resumo O objetivo desta pesquisa foi adaptar a Structured Interview for Assessing Perceptual Anomalies (SIAPA) para o Brasil para ser utilizada como instrumento de autorrelato. Utilizou-se uma amostra não probabilística de 854 universitários, a maioria do sexo masculino (51,4 %) e com idades entre 16 e 65 anos (M = 23,7; DP = 6,8). Após a tradução e validação semântica da SIAPA, testaram-se os parâmetros de validade e precisão por meio de análises fatoriais, coeficientes alfa de Cronbach e análises via Teoria de Resposta ao Item (TRI). Os resultados confirmaram a adequação psicométrica da medida, apontando uma solução unidimensional com altas cargas no fator geral e alta consistência interna (α = 0,88; Ω = 0,88). Acredita-se que o objetivo proposto tenha sido satisfeito, de modo que, ao final da pesquisa, contou-se com uma medida válida e fidedigna que pode ser utilizada, tanto para rastreio quanto para pesquisa, para compreender e diagnosticar anomalias perceptuais.

Individual Differences in the Tendency to See the Expected

Prior knowledge has been shown to facilitate the incorporation of visual stimuli into awareness. We adopted an individual differences approach to explore whether a tendency to ‘see the expected’ is general or method-specific. We administered a binocular rivalry task and manipulated selective attention, as well as induced expectations via predictive context, self-generated imagery, expectancy cues, and perceptual priming. Most prior manipulations led to a facilitated awareness of the biased percept in binocular rivalry, whereas strong signal primes led to a suppressed awareness, i.e., adaptation. Correlations and factor analysis revealed that the facilitatory effect of priors on visual awareness is closely related to attentional control. We also investigated whether expectation-based biases predict perceptual abilities. Adaptation to strong primes predicted improved naturalistic change detection and the facilitatory effect of weak primes predicted the experience of perceptual anomalies. Taken together, our results indicate that the facilitatory effect of priors may be underpinned by an attentional mechanism but the tendency to ‘see the expected’ is method-specific.

O3.3. DO DEPRESSIVE SYMPTOMS MEDIATE THE RELATIONSHIPS BETWEEN SUICIDAL IDEATION AND PSYCHOTIC EXPERIENCES IN ADOLESCENTS?

Background Youth mental health is a global challenge, with onset of mental illness peaking in adolescence. In this population, depressive symptoms (DS), psychotic experiences (PE) and suicidal ideation (SI) are prevalent and risk factors for future mental disorders. DS could mediate relationships between psychotic experiences (PE) and suicidal ideation (SI); however, its precise role in this association remains uncertain. We examined whether depressive symptoms mediate the association between psychotic experiences and suicidal ideation using two complementary approaches to cross-sectional data from a community sample of adolescents. We hypothesized that DS mediate relationships between PE and SI. Additionally, we expected to find that specific DS would play a central role in this association and that this would show via higher centrality values for affective symptoms reflecting low energy, hopelessness and self-depreciating feelings in the network analyses. Methods We examined cross-sectional relationships between PE, SI and DS in a community sample of adolescents (N= 1715; 13–19 years old) recruited from Chilean secondary schools between April and August 2015. We addressed depressive symptoms (DS) using the Depression and Anxiety Scale (DASS-21). We assessed suicidal ideation using 6 items of the Columbia Suicide Severity Rating Scale (C-SSRS), adapted for being used as a self-report questionnaire. We addressed psychotic experiences (PE) by items of two pre-existing scales we adapted in prior studies with adolescents: the Community Assessment of Psychic Experiences - Positive scale (CAPE-P15), and the Brief Self-report Questionnaire for Screening Putative Pre-psychotic States (BQSPS). We first conducted a mediation analysis, where PE was the predictor, SI was the outcome, and DS were the mediator variables. Next, we performed a network analysis and estimated the strength centrality index for each symptom, and the network robustness through accuracy and stability test. Results Pearson’s correlations showed significant associations between all the variables in (SI-DS: r= .491, p<.001; PE-SI: r= .436, p<.001; PE-DS: r= .617, p<.001). No demographic variables (i.e gender, age) had to be controlled for in the mediation. The mediation analysis yielded that depression mediates the relationship between PE and SI (b= .2206, 95% BCa CI [.1783, .2644]). Additionally, network analysis showed the following strength centrality values (SV): depression (mean= 5.92, σ2=1.72; median= 6.08); bizarre experiences (mean= 3.94, σ2=0.35; median= 4.02); perceptual anomalies (mean= 3.75, σ2=2.21; median= 3.75); social anxiety (mean= 3.49, σ2=0.79; median= 3.23); negative symptoms (mean= 3.32, σ2=.23; median= 3.49). SI was strongly connected to pessimism (SV= .69); social anxiety (SV= .41); and self-criticalness/worthlessness (SV= .39). The correlation stability coefficient for the strength was (cor = 0.7) = 0.672, suggesting robustness of the findings. Discussion Our findings support prior research showing that DS mediate relationship between PE and SI and adds to this literature by showing which symptoms in particular are important. Some specific depressive symptoms having a central role in this process (pessimism and worthlessness) and also psychotic experiences (social anxiety: being distant to people) and perceptual anomalies (seeing things other cannot) are connected in a meaningful way to suicidal ideation in a community sample of adolescents. These findings should be considered when planning early detection/intervention programs.

Aberrant Sensory Encoding in Patients with Autism

Perceptual anomalies in patients with Autism Spectrum Disorder (ASD) have been attributed to irregularities in the Bayesian interpretation (i.e., decoding) of sensory information. Here we show that how sensory information is encoded and adapts to changing stimulus statistics also characteristically differs between healthy and ASD groups. In a visual estimation task, we extracted the accuracy of sensory encoding directly from psychophysical data, bypassing the decoding stage by using information theoretic measures. Initially, sensory representations in both groups reflected the statistics of visual orientations in natural scenes, but encoding capacity was overall lower in the ASD group. Exposure to an artificial statistical distribution of visual orientations altered the sensory representations of the control group toward the novel experimental statistics, while also increasing their total encoding resources. Neither total encoding resources nor their allocation changed significantly in the ASD group. Most interestingly, across both groups the adaptive re-allocation of encoding resources was correlated with subjects’ initial encoding capacity. These findings suggest that neural encoding resources are limited in ASD, and this limitation may explain their reduced perceptual flexibility.

Psychotic Experiences in Schizophrenia and Sensitivity to Sensory Evidence

Perceptual inference depends on an optimal integration of current sensory evidence with prior beliefs about the environment. Alterations of this process have been related to the emergence of positive symptoms in schizophrenia. However, it has remained unclear whether delusions and hallucinations arise from an increased or decreased weighting of prior beliefs relative to sensory evidence. To investigate the relation of this prior-to-likelihood ratio to positive symptoms in schizophrenia, we devised a novel experimental paradigm which gradually manipulates perceptually ambiguous visual stimuli by disambiguating stimulus information. As a proxy for likelihood precision, we assessed the sensitivity of individual participants to sensory evidence. As a surrogate for the precision of prior beliefs in perceptual stability, we measured phase duration in ambiguity. Relative to healthy controls, patients with schizophrenia showed a stronger increment in congruent perceptual states for increasing levels of disambiguating stimulus evidence. Sensitivity to sensory evidence correlated positively with the individual patients’ severity of perceptual anomalies and hallucinations. Moreover, the severity of such experiences correlated negatively with phase duration. Our results indicate that perceptual anomalies and hallucinations are associated with a shift of perceptual inference toward sensory evidence and away from prior beliefs. This reduced prior-to-likelihood ratio in sensory processing may contribute to the phenomenon of aberrant salience, which has been suggested to give rise to the false inferences underlying psychotic experiences.