What visual illusions teach us about schizophrenia

Abstract

Illusion, namely a mismatch between the objective and perceived properties of an object present in the environment, is a common feature of visual perception, both in normal and pathological conditions. This makes illusion a valuable tool with which to explore normal perception and its impairments. Although still debated, the hypothesis of a modified, and typically diminished, susceptibility to illusions in schizophrenia patients is supported by a growing number of studies. The current paper aimed to review how illusions have been used to explore and reveal the core features of visual perception in schizophrenia from a psychophysical, neurophysiological and functional point of view. We propose an integration of these findings into a common hierarchical Bayesian inference framework. The Bayesian formalism considers perception as the optimal combination between sensory evidence and prior knowledge, thereby highlighting the interweaving of perceptions and beliefs. Notably, it offers a holistic and convincing explanation for the perceptual changes observed in schizophrenia that might be ideally tested using illusory paradigms, as well as potential paths to explore neural mechanisms. Implications for psychopathology (in terms of positive symptoms, subjective experience or behavior disruptions) are critically discussed.

Abnormal Resting State fMRI Activity Predicts Processing Speed Deficits in First-Episode Psychosis

“…Moreover, consistent with our prior study in chronic patients (Argyelan et al, 2014) we also observed significant abnormalities in first-episode patients compared with healthy volunteers in sensory networks (both visual, auditory, and somatosensory). This may be particularly noteworthy because both prior empirical and theoretical work implicate a disruption in perceptual processes in schizophrenia (Butler et al, 2001;Grillon et al, 1992;Javitt et al, 1996;Notredame et al, 2014;Patterson et al, 2008;Umbricht and Krljes, 2005). Consistent with the global connectivity analysis, we identified lower expression scores in first-episode patients overall compared with healthy volunteers using ICA.…”

Error detection and surprise in stochastic robot actions

“…We argue that mid-level perceptual features may be strongly influenced by top down expectations so that only a subset of detectors must be active at a time. This is consistent with a hypothesis introduced by Notredame et al that explains how visual illusions could be caused by prior expectations overtaking the actual stimulus [18]. A lot of research in computer vision has also been done on building models that perform top down inference [26] [25].…”

Translational Perspectives for Computational Neuroimaging

“…Two separate fMRI and EEG studies examined potential mechanisms for this phenomenon: applying structurally analogous DCMs to fMRI and EEG data, these two studies consistently found a strengthening of bottom-up connections and diminished top-down connectivity in patients, consistent with the notion of reduced precision of predictions about facial stimuli (Dima et al, 2009(Dima et al, , 2010. Notably, weakening of top-down predictions may explain a range of perceptual alterations in schizophrenia (Notredame et al, 2014) and may also play a role in the initial formation of delusions (Schmack et al, 2013).…”