Somatic Symptom Perception From a Predictive Processing Perspective: An Empirical Test Using the Thermal Grill Illusion

Abstract

Objective: In a predictive coding perspective, symptom perceptions result from an integration of pre-existing information in memory with sensory input. Physical symptoms can therefore reflect the relative predominance of either sensory input or pre-existing information. In this study, we used the thermal grill illusion (TGI), which applies interlaced warm and cool temperatures to the skin to create a paradoxical heat-pain experience. Assuming that the TGI compared to single temperature stimulation relies more importantly on an active integration process of the brain to create this paradoxical sensation, we tested the hypothesis whether a manipulation of the expectations during TGI would have more impact than during single temperature stimulation. Methods: Sixty-four participants received different temperature combinations (16/16 °C, 40/40 °C, 16/40 °C) with neutral, positive ("placebo"), and negative ("nocebo") instructions. Subjective stimulus intensity was rated and neuroticism and absorption (openness to absorbing and self-altering experiences) served as potential moderating traits. Results: The TGI condition was rated highest. Overall, negative instructions increased (p < .001, d = 0.58), whereas positive instructions did not significantly change the TGI intensity perception (vs. neutral; p = .144, d = 0.19). In the TGI condition, increased modulation of pain was observed with higher neuroticism (β = .33, p = .005) and absorption (β = 0.30, p = .010). Conclusions: Whereas negative instructions induced a nocebo effect, no placebo effect emerged after positive instructions. The findings are in line with the predictive coding model of symptom perception for participants with higher levels of neuroticism and absorption.

Responsiveness to Direct Verbal Suggestions and Dissociation Independently Predict Symptoms Associated with Environmental Factors

“…SAEF are typically conceptualized as psychogenic in origin, and multiple models have proposed that suggestions (communications for involuntary changes in behavior and perception) contribute to the manifestation or expression of these symptoms [6]. Previous research has shown that individuals experiencing SAEF are more prone to symptoms in response to suggestions that specific (benign) stimuli will trigger symptoms [7][8][9], in a similar manner to functional neurological disorder, which is characterized by elevated direct verbal suggestibility including in response to suggestive symptom induction protocols [10,11]. The reporting of SAEF, and germane nocebo responses, such as hypochondrial concerns, is also associated with absorption [2,6], a form of dissociation that is frequently associated with suggestibility [9].…”

“…Previous research has shown that individuals experiencing SAEF are more prone to symptoms in response to suggestions that specific (benign) stimuli will trigger symptoms [7][8][9], in a similar manner to functional neurological disorder, which is characterized by elevated direct verbal suggestibility including in response to suggestive symptom induction protocols [10,11]. The reporting of SAEF, and germane nocebo responses, such as hypochondrial concerns, is also associated with absorption [2,6], a form of dissociation that is frequently associated with suggestibility [9]. A role for suggestion in this condition similarly aligns with predictive processing models of SAEF, which attribute symptoms to the overweighting of precise symptom priors relative to sensory evidence, such as relying more on expectations pertaining to a specific environmental context or a specific cue [2].…”

Unstable Gaze in Functional Dizziness: A Contribution to Understanding the Pathophysiology of Functional Disorders

“…Within the framework of predictive coding, central processing of incoming sensory information is biased by a mismatch resulting from incorrect internal expectations leading to symptom perception ( Figure 1 ). Providing empirical validation of this hypothesis has been a current effort: several studies report “symptom-like” somatic illusions that could be evoked in healthy participants by experimentally altering internal expectations (e.g., Iodice et al, 2019 ; Bräscher et al, 2020 ; Wolters et al, 2020 ). Moreover, experimentally induced symptoms are more persistent in patients with functional disorders, uncoupled from corresponding sensory input ( Bogaerts et al, 2010 ; Van Den Houte et al, 2018 ).…”

Psychomotor Predictive Processing

“…Apropos, findings from empirical research by others indicate that pain experience can be predicted in Bayesian terms [ 7 ]. Furthermore, findings from empirical research by others have indicated that symptoms can reflect the relative predominance of either prior beliefs or sensory inputs with predictive processing being influenced by personal characteristics [ 8 ].…”