Abstract

Psychotic symptoms, i.e., hallucinations and delusions, involve gross departures from conscious apprehension of consensual reality; respectively, perceiving and believing things that, according to same culture peers, do not obtain. In schizophrenia, those experiences are often related to abnormal sense of control over one's own actions, often expressed as a distorted sense of agency (i.e., passivity symptoms). Cognitive and computational neuroscience have furnished an account of these experiences and beliefs in terms of the brain's generative model of the world, which underwrites inferences to the best explanation of current and future states, in order to behave adaptively. Inference then involves a reliability-based trade off of predictions and prediction errors, and psychotic symptoms may arise as departures from this inference process, either an over- or under-weighting of priors relative to prediction errors. Surprisingly, there is empirical evidence in favor of both positions. Relatedly, there is evidence for both an enhanced and a diminished sense of agency in schizophrenia. How can this be? We argue that there is more than one generative model in the brain, and that ego- and allo-centric models operate in tandem. In brief, ego-centric models implement corollary discharge signals that cancel out the effects of self-generated actions while allo-centric models compare several hypothesis regarding the causes of sensory inputs (including the self among the potential causes). The two parallel hierarchies give rise to different levels of agency, with ego-centric models subserving “feelings of agency” and allo-centric predictions giving rise to “judgements of agency.” Those two components are weighted according to their reliability and combined, generating a higher-level “sense of agency.” We suggest that in schizophrenia a failure of corollary discharges to suppress self-generated inputs results in the absence of a “feeling of agency” and in a compensatory enhancement of allo-centric priors, which might underlie hallucinations, delusions of control but also, under certain circumstances, the enhancement of “judgments of agency.” We discuss the consequences of such a model, and potential courses of action that could lead to its falsification.

Highlights

  • In this article we will outline a computational account of perception and its disruption in psychosis

  • Someone with psychosis may believe that another agent is controlling their thoughts or actions against their will and they may perceive agents alien to themselves talking inside their head [auditory verbal hallucinations (AVH)]

  • Ego-centric and allo-centric models operate in tandem, making up the machinery required for attaining self-other distinction and sense of agency (SoA)

Read more

Summary

INTRODUCTION

In this article we will outline a computational account of perception and its disruption in psychosis. A kernel of the present paper is how strong priors and aberrant prediction errors can co-exist in the same brain and how those computational departures give rise to perturbed sense of agency over thoughts and actions and hallucinations and delusions. One influential theory of psychotic symptoms, hallucinations and delusions, posits that they are verbal thoughts, subvocal speech (in the case of hallucinations) or movements (in the case of passivity delusions) that are misattributed to an outside source (another agent that is communicating or controlling) (Jones and Fernyhough, 2007) This arises from compromised efference copy signals—‘‘copies” of motor signals that are sent to sensory processing regions, rather than being sent to effectors, depositing a prediction of the expected sensory consequences of the action. In both cases there is evidence supporting strong and weak priors, weak corollary discharge, misattributed inner speech, exaggerated, and diminished agency (though typically not at the same time in the same people with psychosis)

SUMMARY AND CONCLUSIONS
DATA AVAILABILITY STATEMENT
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call