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

Abstract

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.

The Perceptual Prediction Paradox

“…For example, concave faces are frequently misperceived to have the more typical convex structure ( [12]; see Figure 1) and we may perceive ambiguously-coloured fruit in line with its typical colour [13, but see 14]. Aberrations in these illusions are observed across certain clinical conditionse.g., schizophrenia and autismand interpreted as evidence for atypical sensory prediction [12,[15][16][17]. At the neural level, concurring evidence demonstrates higher fidelity representations of expected sensory events [5,18] and sensory representations biased towards expected inputs [19] with neural biases predicting the perceptual biases [13].…”

A inversão visual da profundidade na esquizofrenia

“…Na maioria dos estudos levantados nesta revisão, os indivíduos com esquizofrenia não realizaram a inversão visual da profundidade [7][8][9][10][11][12][13][14]16,18,19 . Por outro lado, no estudo de Alves et al 15 , os indivíduos com esquizofrenia realizaram a inversão visual da profundidade.…”

“…Dessa forma, as diferenças nos resultados poderiam ser explicadas pelas variações metodológicas. No entanto, os estudos de Keane et al 13 , Wang et al 14 , Keane et al 16 e Alves et al 15 poderiam ser considerados como tendo metodologias próximas, observação monocular e máscara côncava física, se não fosse a adoção da paralaxe de movimento nos três primeiros estudos e luz e sombra, no último. Isso, talvez justifique os resultados diferentes encontrados nessas pesquisas.…”

“…Keane et al 16 realizaram um estudo com o objetivo de aprofundar o estudo de Keane et al 13 sobre a ilusão de profundidade visual. Participaram do estudo 30 indivíduos com transtorno bipolar, sendo 26 do tipo I, 3 do tipo II e 2 não especificados.…”

“…Tal busca ocorreu em SciELO, Lilacs, IndexPsi, Medline, Psycinfo, ISI Web of Knowledge e ScienceDirect, com os descritores esquizofrenia, ilusão da máscara côncava, inversão visual da profundidade, schizophrenia, hollow-face illusion, visual depth inversion. Foram encontrados 12 estudos que abordaram a inversão visual da profundidade em indivíduos com esquizofrenia [7][8][9][10][11][12][13][14][15][16]18,19 . Conforme pode ser verificado na Tabela 1, notam-se estudos com uma variedade de métodos e um estudo com resultados não alinhados.…”