Thought Insertion as a Self-Disturbance: An Integration of Predictive Coding and Phenomenological Approaches

Abstract

Current theories in the framework of hierarchical predictive coding propose that positive symptoms of schizophrenia, such as delusions and hallucinations, arise from an alteration in Bayesian inference, the term inference referring to a process by which learned predictions are used to infer probable causes of sensory data. However, for one particularly striking and frequent symptom of schizophrenia, thought insertion, no plausible account has been proposed in terms of the predictive-coding framework. Here we propose that thought insertion is due to an altered experience of thoughts as coming from “nowhere”, as is already indicated by the early 20th century phenomenological accounts by the early Heidelberg School of psychiatry. These accounts identified thought insertion as one of the self-disturbances (from German: “Ichstörungen”) of schizophrenia and used mescaline as a model-psychosis in healthy individuals to explore the possible mechanisms. The early Heidelberg School (Gruhle, Mayer-Gross, Beringer) first named and defined the self-disturbances, and proposed that thought insertion involves a disruption of the inner connectedness of thoughts and experiences, and a “becoming sensory” of those thoughts experienced as inserted. This account offers a novel way to integrate the phenomenology of thought insertion with the predictive coding framework. We argue that the altered experience of thoughts may be caused by a reduced precision of context-dependent predictions, relative to sensory precision. According to the principles of Bayesian inference, this reduced precision leads to increased prediction-error signals evoked by the neural activity that encodes thoughts. Thus, in analogy with the prediction-error related aberrant salience of external events that has been proposed previously, “internal” events such as thoughts (including volitions, emotions and memories) can also be associated with increased prediction-error signaling and are thus imbued with aberrant salience. We suggest that the individual’s attempt to explain the aberrant salience of thoughts results in their interpretation as being inserted by an alien agent, similarly to the emergence of delusions in response to the aberrant salience of sensory stimuli.

Hallucinations and Strong Priors

“…For example, internal action cues (experience of an intention, sensory feedback) may be imprecise, while the external cues (outcome of action for example) may be precise. This would lead some thoughts and actions to be experienced as unintended and thus externally generated [71,72]. At the same time, the binding of action and outcome may be increased (due to the relative precision of outcome processing), as has been empirically demonstrated in psychosis, ketamine infusion, and psychosis proneness [73][74][75][76][77].…”

Is Schizophrenia a Disorder of Consciousness? Experimental and Phenomenological Support for Anomalous Unconscious Processing

“…In this contribution, however, we argue that on the basis of a series of recent experimental results and a long tradition in phenomenological psychopathology, the automatic, unconscious processing of sensory information may be more impaired than believed until now. We further argue that such impairments play a role in the way patients perceive their environment and themselves, an approach which in the phenomenological tradition of psychiatry has been called the “perceptual anomalies” approach ( Mayer-Gross and Stein, 1926 , 1928 ; Mayer-Gross, 1932 ; Uhlhaas and Mishara, 2007 ; Sterzer et al, 2016 ).…”

“…Finally, the results of several studies suggest impairments at the automatic and unconscious levels ( Laprévote et al, 2010 , 2013 ; Lalanne et al, 2012b , c ; Duval et al, 2016 ), which we in part review here. Perceptual and low-level sensory anomalies may thus have a stronger role in the pathophysiology and self disorders of schizophrenia than usually believed ( Mayer-Gross and Stein, 1928 ; Mayer-Gross, 1932 ; Sterzer et al, 2016 ).…”

“…If information stays the same, it is considered as non-pertinent and canceled, whereas a detection of a change is considered as pertinent and attracts attention. Many studies have suggested these mechanisms are impaired in schizophrenia ( Gray et al, 1991 ; Friston and Frith, 2015 ; Sterzer et al, 2016 ; Corlett, 2017 ; Griffin and Fletcher, 2017 ). This impairment results in a difficulty to detect changes in perceptual information.…”

Prerequisites for an Artificial Self

“…Topics such as body ownership and agency that have traditionally been investigated in philosophy have recently gained attention from other disciplines, such as brain, cognitive and behavioral sciences, and even robotics and artificial intelligence. Some neuroscientists, for example, interpret certain human mental disorders-such as schizophrenia-as the result of a disrupted sense of the self (Frith et al, 2000;Nelson et al, 2014;Klaver and Dijkerman, 2016;Sterzer et al, 2016). In robotics, intuitive human interaction in natural and dynamic environments becomes more and more important, and requires skills such as self-other distinction and an understanding of agency effects (Holthaus and Wachsmuth, 2012;Belpaeme et al, 2018).…”