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Perceptual inferences in schizophrenia: A preliminary study on healthy participants

Published online by Cambridge University Press:  15 April 2020

P. Leptourgos*
Affiliation:
For Neural Theory, Laboratoire de Neurosciences Cognitives, DEC, ENS, Paris, France
C.E. Notredame
Affiliation:
Scalab, Lille University, Lille, France
R. Jardri
Affiliation:
For Neural Theory, Laboratoire de Neurosciences Cognitives, DEC, ENS, Paris, France Scalab, Lille University, Lille, France
S. Denève
Affiliation:
For Neural Theory, Laboratoire de Neurosciences Cognitives, DEC, ENS, Paris, France
*
*Auteur correspondant. Adresse e-mail :plepto12@gmail.com (P. Leptourgos)

Abstract

Recently, Jardri and Denève proposed that positive symptoms in schizophrenia could be generated by an imbalance between excitation and inhibition in brain networks, which leads to circular inference, an aberrant form of inference where messages (bottom up and/or top down) are counted more than once and thus, are overweighted [1]. Moreover, they postulated that psychotic symptoms are caused by a system that “expects what it senses” and as a result attributes extreme weight even to weak sensory evidences. Their hypothesis was then validated by a probabilistic inference task (in prep.). Here, we put forward a new experimental study that could validate the circular inference framework in the domain of visual perception. Initially, we restricted ourselves to healthy controls, whose tendencies for psychotic symptoms were measured using appropriate scales. We investigated the computations performed by perceptual systems when facing ambiguous sensory evidence. In those cases, perception is known to oscillate between two interpretations, a phenomenon known as bistable perception. More specifically, we asked how prior expectations and visual cues affect the dynamics of bistability. Participants looked at a Necker cube that was continuously displayed on the screen and reported their percept every time they heard a sound [2]. We manipulated sensory evidence by adding shades to the stimuli and prior expectations by giving different instructions concerning the presence of an implicit bias [3]. We showed that both prior expectations and visual cues significantly affect bistability, using both static and dynamic measures. We also found that the behavior could be well fitted by Bayesian models (“simple” Bayes, hierarchical Bayesian model with Markovian statistics). Preliminary results from patients will also be presented.

Type
Congrès français de psychiatrie: Rencontres avec l’expert
Copyright
Copyright © European Psychiatric Association 2015

Disclosure of interest

The authors declare that they have no competing interest.

References

Jardri, R.Denève, S.Circular inferences in schizophrenia. Brain 2013; 136: 32273241.CrossRefGoogle Scholar
Mamassian, P.Goutcher, R.Temporal dynamics in bistable perception. J Vision 2005;5(4):3613753.CrossRefGoogle ScholarPubMed
Schmack, , et al.Delusions and the role of beliefs in perceptual inference. J Neurosci 2013;33(34):1370113712.CrossRefGoogle ScholarPubMed
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