Proprioception in somatoform disorders

Is the rubber hand illusion associated with somatic symptom reporting?

Current approaches to somatic symptom perception conceptualize somatic symptoms partly as somato-visceral or body illusions evoked by an interaction between bottom-up (sensory) and top-down (expectations, attention) processes. Similar processes of multisensory integration are assumed to contribute to the rubber hand illusion (RHI). Findings concerning the strength and direction of associations between these two phenomena, symptom perception and the RHI, are equivocal. Individuals of a non-clinical sample (N = 63; 56% females; Mage = 20.4; SD = 1.6) completed the Patient Health Questionnaire Somatic Symptom Scale (PHQ-15) and participated in an experiment that evoked the RHI. In repeated measures analyses of variance with the PHQ-15 score as covariate, no significant interaction effects between the PHQ-15 score and indicators of the RHI, i.e., proprioceptive drift (F(1,61) < 0.001 p = 0.993, partial η2 < 0.001; BF10 = 0.307), felt body ownership(F(1,59) = 0.043, p = 0.836, partial η2 = 0,001; BF10 = 0.501), and felt body disownership (F(1,59) = 0.148, p = 0.702, partial η2 = 0.002; BF10 = 1.972) were found. Overall, frequentist and Bayesian analysis indicated that the support for a possible association between the PHQ-15 and indicators of the RHI remains inconclusive, i.e., neither the null nor the alternative hypotheses were sufficiently supported. At least in this non-clinical sample, the association between somatic symptom distress and the strength of the RHI appears so weak (perhaps non-existing), that both phenomena (somatic symptom distress and the RHI) appear distinct and largely unrelated.

[Interoceptive difficulties in children and adolescents with severe form of somatic symptom disorder: A pilot study with nineteen participants]

INTRODUCTION

Despite the high rate of somatic symptom disorder (TSS) in the pediatric population, etiological mechanisms remain poorly understood. Previous studies conducted in youths with anxiety, eating disorder, or autistic disorder support a relation between difficulties in the perception of sensory signals (i.e., interoception) and difficulties in identifying emotions.

METHOD

A cross-sectional study was carried out at the University Hospital of Amiens-Picardie in 19 young people aged 9 to 17 hospitalized in the pediatric ward for TSS. A mental heartbeat tracking task was used to assess interoceptive accuracy, awareness and sensibility. The Porges Body Perception Questionnaire (PBPQ) was used to assess interoceptive attention. Other questionnaires were used to assess associated clinical dimensions such as depression, anxiety, emotional dysregulation and alexithymia.

RESULTS

The mean interoceptive accuracy score was lower in TSS subjects compared to expected scores in the general population (33% error vs. 20%). A statistically significant correlation was found between, on the one hand, interoceptive sensibility and the "avoidance" subscore of the ECAP (r=0.51) and, on the other hand, between interoceptive awareness and the total score of the Child Depression Inventory (r=0.51). A significant relationship was found between the PBPQ scale total score and the Children-Toronto Alexithymia Scale total score (r=0.42), in particular with the "difficulty expressing emotions" subscore (r=0.62).

CONCLUSION

This study confirms that interoceptive difficulties occur in young patients with severe TSS. Our finding adds empirical evidence supporting the relations between interoceptive difficulties, alexithymia and somatic symptoms in children and adolescents.

Interoceptive accuracy and bias in somatic symptom disorder, illness anxiety disorder, and functional syndromes: A systematic review and meta-analysis

Somatic symptom disorder, illness anxiety disorder, and functional syndromes are characterized by burdensome preoccupation with somatic symptoms. Etiological models propose either increased interoceptive accuracy through hypervigilance to the body, or decreased and biased interoception through top-down predictions about sensory events. This systematic review and meta-analysis summarizes findings of 68 studies examining interoceptive accuracy and 8 studies examining response biases in clinical or non-clinical groups. Analyses yielded a medium population effect size for decreased interoceptive accuracy in functional syndromes, but no observable effect in somatic symptom disorder and illness anxiety disorder. The overall effect size was highly heterogeneous. Regarding response bias, there was a small significant effect in somatic symptom disorder and illness anxiety disorder. Our findings strengthen the notion of top-down factors that result in biased rather than accurate perception of body signals in somatic symptom disorder and illness anxiety disorder.

The Effects of a 3-Week Heartbeat Perception Training on Interoceptive Abilities

Recent studies showed promising short-term effects of heartbeat perception training on interoceptive abilities. Research on the effects of heartbeat perception training on interoceptive abilities over time is sparse. Therefore, the aim of this study was to examine the short-term effects and the effects of a 3-week heartbeat perception training over time on interoceptive abilities, namely, cardiac interoceptive accuracy (IAc) and interoceptive sensibility (IS). A total of 40 healthy participants were randomized to the intervention group (n = 20) or the control group (n = 20). The intervention group conducted three cardiac biofeedback sessions (one per week) at the laboratory, whereas the control group watched a documentary instead. Interoceptive abilities were assessed via the heartbeat perception task (IAc) and confidence ratings (IS) at baseline, after each laboratory session, and 1 week after the last session (post-measurement). IAc was significantly increased in the intervention group compared to the control group after the first training session (short-term effect). There were no significant improvements in IS due to the first session, and neither on IAc nor IS over time. Descriptive trends of improved interoceptive abilities over time were found in both groups. Single session of heartbeat perception training seems to be a promising approach to improve IAc. Future research should further investigate the long-term effects of diverse heartbeat perception training varying in frequency and intensity of the training sessions in diverse samples aiming to improve interoceptive abilities.

Interoception in preschoolers: New insights into its assessment and relations to emotion regulation and stress

Interoception may play an important role for emotion regulation and stress, thereby affecting mental health in children and adults. Yet, little is known on interoception in preschool children. Therefore, we investigated interoceptive accuracy using the adapted Jumping Jack Paradigm (JJP) and its relationship with emotion regulation and stress. In Study I, 40 preschoolers completed the JJP and an emotion regulation task, demonstrating a positive relationship between interoceptive accuracy and emotion regulation at trend level (R² = 0.231, p = .023; β = .278, p = .073). In Study II, 31 preschoolers completed the adapted JJP before and after an acute laboratory stress test. Higher total cortisol output following acute stress induction was associated with reduced interoceptive accuracy (r = -0.670, p = .017). Extending earlier findings in adults and school-children, the relationship of interoceptive accuracy with emotion regulation and stress highlights the importance to investigate interoception in early childhood.

Cardiac and Proprioceptive Accuracy Are Not Related to Body Awareness, Perceived Body Competence, and Affect

Interoception in the broader sense refers to the perception of internal states, including the perception of the actual state of the internal organs (visceroception) and the motor system (proprioception). Dimensions of interoception include (1) interoceptive accuracy, i.e., the ability to sense internal changes assessed with behavioral tests, (2) confidence rating with respect to perceived performance in an actual behavioral test, and (3) interoceptive sensibility, i.e., the self-reported generalized ability to perceive body changes. The relationship between dimension of cardioceptive and proprioceptive modalities and their association with affect are scarcely studied. In the present study, undergraduate students (N = 105, 53 males, age: 21.0 ± 1.87 years) filled out questionnaires assessing positive and negative affect (Positive and Negative Affect Schedule), interoceptive sensibility (Body Awareness Questionnaire), and body competence (Body Competence Scale of the Body Consciousness Questionnaire). Following this, they completed a behavioral task assessing cardioceptive accuracy (the mental heartbeat tracking task by Schandry) and two tasks assessing proprioceptive accuracy with respect to the tension of arm flexor muscles (weight discrimination task) and the angular position of the elbow joint (joint position reproduction task). Confidence ratings were measured with visual analog scales after the tasks. With the exception of a weak association between cardioceptive accuracy and the respective confidence rating, no associations between and within modalities were found with respect to various dimensions of interoception. Further, the interoceptive dimensions were not associated with state and trait positive and negative affect and perceived body competence. In summary, interoceptive accuracy scores do not substantially contribute to conscious representations of cardioceptive and proprioceptive ability. Within our data, non-pathological affective states (PANAS) are not associated with the major dimensions of interoception for the cardiac and proprioceptive modalities.

Proprioception but not cardiac interoception is related to the rubber hand illusion

The rubber hand illusion (RHI) is a widely used tool in the study of multisensory integration. It develops as the interaction of temporally consistent visual and tactile input, which can overwrite proprioceptive information. Theoretically, the accuracy of proprioception may influence the proneness to the RHI but this has received little research attention to date. Concerning the role of cardioceptive information, the available empirical evidence is equivocal. The current study aimed to test the impact of proprioceptive and cardioceptive input on the RHI. 60 undergraduate students (32 females) completed sensory tasks assessing proprioceptive accuracy with respect to the angle of the elbow joint, a heartbeat tracking task assessing cardioceptive accuracy (the Schandry-task) and the RHI. We found that those with more consistent joint position judgements (i.e., less variable error) in the proprioceptive task were less prone to the illusion, particularly with respect to disembodiment ratings in the asynchronous condition. Systematic error, indicating a systematic distortion in position judgements influenced the illusion in the synchronous condition. Participants with more proprioceptive bias toward the direction of the rubber hand in the proprioceptive test reported a stronger felt embodiment. The results are in accordance with Bayesian causal inference models of multisensory integration. Cardioceptive accuracy, however, was not associated with the strength of the illusion. We concluded that individual differences in proprioceptive processing impact the RHI, while cardioceptive accuracy is unrelated to it. Theoretical and practical relevance of the findings are discussed.

Distinctive body perception mechanisms in high versus low symptom reporters: A neurophysiological model for medically-unexplained symptoms

OBJECTIVE

The neurophysiological processes involved in the generation of medically-unexplained symptoms (MUS) remain unclear. This study tested three assumptions of the perception-filter model contributing to MUS: (I.) increased bodily signal strength (II.) decreased filter function, (III.) increased perception.

METHODS

In this cross-sectional, observational study, trait MUS were assessed by a web-based survey (N = 486). The upper and lower decile were identified as extreme groups of high (HSR; n = 29; 26 women; Mage = 26.0 years) and low symptom reporters (LSR; n = 29; 21 women; Mage = 28.4 years). Mean heart rate (HR) and heart rate variability (HRV), and cortisol awakening response (CAR) were assessed as indicators of bodily signal strength (I.). Heartbeat-evoked potentials (HEPs) were assessed during rest and a heartbeat perception task. HEPs reflect attentional resources allocated towards heartbeats and served as index of filter function (II.). Interoceptive accuracy (IAc) in heartbeat perception was assessed as an indicator of perception (III.).

RESULTS

HSR showed higher HR and lower HRV (RMSSD) than LSR (I.), but no differences in CAR. HSR exhibited a stronger increase of HEPs when attention was focused on heartbeats than LSR (II.); there were no group differences in IAc (III.).

CONCLUSIONS

The perception-filter model was partially confirmed in that HSR showed altered bodily signals suggesting higher sympathetic activity (I.); higher HEP increases indicated increased filter function for bodily signals (II.). As more attentional resources are mobilized to process heartbeats, but perception accuracy remains unchanged (III.), this overflow could be responsible for detecting minor bodily changes associated with MUS.

Proprioceptive accuracy is not associated with self-reported body awareness, body competence, and affect

PURPOSE

Proprioception plays an essential role in motor control and in psychological functioning: it is the basis of body schema and the feeling of body ownership. There are individual differences in the processing accuracy of proprioceptive stimuli. Although proprioceptive acuity plays an important role in physical competence, there are contradictory findings concerning the role it plays in healthy psychological functioning. This study aims to shed more light on this association.

MATERIAL AND METHODS

Sixty-eight young adults participated in this study. We estimated proprioceptive acuity by the reposition accuracy of elbow joint positions. We tested both dominant and non-dominant hands with two different versions of Joint Position Reproduction Test. Perceived physical competence, body awareness, and affectivity were assessed using questionnaires (Physical Competence scale of Body Consciousness Questionnaire, Somatic Absorption Scale, and Positive and Negative Affectivity Schedule, respectively).

RESULTS

No significant association between proprioceptive acuity and body awareness, perceived body competence, and positive and negative affect was found.

CONCLUSION

Proprioceptive acuity, measured in the elbow joint, does not play a substantial role in body awareness, perceived body competence, and affect.

Multisensory mechanisms of body perception in somatoform disorders

OBJECTIVE

According to one of the hypotheses, somatoform disorders (SD) are related to disturbed perception of bodily signals. We suspect that the disturbances and abnormalities of multisensory integration dynamics may be an additional SD mechanism. The objective of the research was to investigate multisensory bodily illusion dynamics in SD patients.

METHODS

A clinical group of SD patients (n = 16) and a control group (n = 17) participated in experiments aimed at eliciting a visual-tactile rubber hand illusion (RHI) and a visual-kinesthetic virtual hand illusion (VHI).

RESULTS

For both illusions studied, the illusion dynamics in SD patients differed from those of healthy subjects. The visual-tactile illusion on the subjective level appeared to be less strong in SD patients, and no proprioceptive drift (PD) was detected. The subjective dynamics of the visual-kinesthetic illusion in patients were similar to those of the control group, but the PD dynamics were different: after the termination of stimuli from the artificial limb, the proprioceptive system did not return to its initial state; on the contrary, PD continued to increase.

CONCLUSION

In comparison with the norm, patients with somatoform disorders display differences in multisensory mechanisms underlying the development of body perception. The results suggest that the disturbance of visual-tactile integration of the stimuli represents one of the mechanisms of body perception distortion in somatoform disorders. It may be assumed that one of the reasons for persistent symptom perception in SD patients is the rigidity of multisensory stimuli perception, at least in the visual-motor domain.

Do body-related sensations make feel us better? Subjective well-being is associated only with the subjective aspect of interoception

According to the proposition of several theoretical accounts, the perception of the bodily cues, interoceptive accuracy and interoceptive sensibility, has a significant positive impact on subjective well-being. Others assume a negative association; however, empirical evidence is scarce. In this study, 142 young adults completed questionnaires assessing subjective well-being, interoceptive sensibility, and subjective somatic symptoms and participated in measurements of proprioceptive accuracy (reproduction of the angle of the elbow joint), gastric sensitivity (water load test), and heartbeat tracking ability (Schandry task). Subjective well-being showed weak to medium positive associations with interoceptive sensibility and weak negative associations with symptom reports. No associations with measures of interoceptive accuracy were found. Gastric sensitivity as opposed to heartbeat perception and proprioceptive accuracy moderated the association between interoceptive sensibility and well-being. Thus, subjective well-being is associated only with the self-reported (perceived) aspect of interoception but not related to the sensory measures of interoceptive accuracy.

Evidence that subclinical somatoform dissociation is not characterised by heightened awareness of proprioceptive signals

INTRODUCTION

It has been suggested that abnormal perceptual processing and somatosensory amplification may be contributory factors to somatoform symptom reporting. A key source of somatosensory information is proprioception, yet the perception and integration of this sense has not been sufficiently investigated in those prone to somatoform disorders.

METHODS

Subclinical groups of high- and low-scorers on the Somatoform Dissociation Questionnaire made judgements about the location of their unseen hand following congruent or incongruent visuo-proprioceptive feedback, which was manipulated using a MIRAGE-mediated reality system.

RESULTS

No differences were found between groups, with both groups displaying normal proprioceptive accuracy under congruent conditions and equivalent visuo-proprioceptive integration under incongruent conditions.

CONCLUSIONS

The results suggest that amplification of, or abnormal weighting for, proprioceptive signals is not a contributing factor to somatoform symptom reporting.

Perspectives on the clinical significance of functional pain syndromes in children

Functional pain syndromes (FPS) characterize a subset of individuals who experience pain and related symptoms and disability without clear structural or disease etiology. In the pediatric population, FPS hold high clinical importance due to significant prevalence rates and potential to persist into adulthood. Although extensive research has been executed to disambiguate FPS, the syndromes that fall within its spectrum remain conceptually complex and sometimes ill-defined. This paper provides an overview of available research on the classification and multifaceted etiology of FPS in youth and their effects on interpersonal, psychological, and familial function. Vital aspects of a successful multidisciplinary approach to treating this population are described; however, it is evident that future research requires more longitudinal studies.

Illusory touch and tactile perception in somatoform dissociators

OBJECTIVE

The psychological mechanisms of somatoform dissociation (i.e., pseudoneurological symptoms) are poorly understood. This study evaluated recent theoretical predictions regarding the role of tactile perception in the development of somatoform dissociative symptoms.

METHODS

Eighty nonclinical participants scoring either high or low on the Somatoform Dissociation Questionnaire (SDQ-20) completed the Somatic Signal Detection Task (SSDT), a novel perceptual paradigm designed to simulate the occurrence of somatoform symptoms in the laboratory. Prior to the SSDT, participants completed a memory task designed to produce either minimal or maximal activation of tactile representations in memory.

RESULTS

The high SDQ-20 group exhibited a more liberal response criterion (c) on the SSDT than the low SDQ-20 group after controlling for negative affectivity, somatosensory amplification and depression. This effect was mainly attributable to an increased number of false alarms (i.e., illusory experiences of touch) in the high SDQ-20 group rather than an increased hit rate. General perceptual ability (i.e., tactile sensitivity) was comparable between the two groups. The memory manipulation had no effect on SSDT performance.

CONCLUSIONS

Somatoform dissociators appear more likely to experience illusory perceptual events under conditions of sensory ambiguity than nondissociators, despite comparable perceptual abilities more generally. These findings support theories that identify distorted perceptual processing as a feature of somatoform dissociation. The SSDT has potential as a tool for further research in this area.

The Relationship Between Pain Perception and Interoception

The question of whether the perception of externally applied pain stimuli and the perception of interoceptive stimuli are based upon similar neuronal or behavioral processes is still open to debate. If such a similarity exists, one would expect that persons who are highly sensitive to visceral stimuli would also exhibit a higher sensitivity to pain stimuli. The present study investigated the sensitivity to heat pain of individuals with high vs. low cardiac interoceptive sensitivity. Pain threshold and pain tolerance were assessed using a testing-the-limits procedure. Furthermore, participants rated the subjective intensity and unpleasantness of tonic heat stimuli on visual analog scales and in a questionnaire. The results show that pain experience did not differ between participants with high and low interoceptive sensitivity, nor did correlation analyses reveal significant relationships between pain experience and cardiac interoceptive sensitivity. These findings suggest that the pathway of peripheral pain processing is at least partially independent of the pathway of interoceptive sensations.

Explaining medically unexplained symptoms-models and mechanisms

We summarize the psychological mechanisms that have been linked to the development and maintenance of medically unexplained symptoms (MUS). Many models postulate that patients with MUS misinterpret physical sensations and show other cognitive abnormalities (e.g., an over-exclusive concept of health) that play a major role in symptom development. While there is strong evidence for the role of cognitive aspects, there is less evidence for their interaction with perceptual features (e.g., perceptual sensitivity, lowered perceptual threshold). Modern neuroimaging techniques show that the expectation of symptoms leads to the activation of brain areas corresponding to symptom perception, while distraction from symptoms reduces brain activity in perception areas. The frequently postulated monocausal organic attribution for physical sensations by patients with MUS needs to be modified, as many patients report multiple symptom attributions, including psychological. Symptom attributions and causal models depend on memorized concepts, and so memory processes need to be investigated in more detail. Aberrations in memory processes not only offer a link to understanding perceptual processes, but are also involved in doctor-patient interaction. This encounter is characterized by unsuccessful medical reassurance, which again involves memory processes. We conclude that psychological mechanisms such as expectation, distraction, and memory processes need to be integrated with biological models to aid understanding of MUS.

Somatoform dissociation and somatosensory amplification are differentially associated with attention to the tactile modality following exposure to body-related stimuli

OBJECTIVE

Body-focused attention is regarded as an important maintaining factor for somatoform illness, although there is limited empirical evidence pertaining to this hypothesis. This study was conducted to assess whether individual differences in somatoform dissociation and somatosensory amplification were associated with biased attention towards the tactile modality, particularly following exposure to threatening body-related stimuli.

METHODS

Forty-eight nonclinical participants completed the Somatoform Dissociation Questionnaire (SDQ-20; a proxy measure of somatoform symptomatology), the Somatosensory Amplification Scale (SSAS), and a modality bias task. The task consisted of a series of body-relevant or body-irrelevant (scene) picture stimuli, half of which were threatening and half were neutral, followed by target stimuli in either the visual or the tactile modality. Participants judged the location of each target stimulus, and performance data were used to calculate the degree to which participants were biased towards the tactile modality following each of the picture types.

RESULTS

Participants in the high SDQ-20 group (defined by median split) showed a significant increase in tactile bias when responding to targets occurring 250 ms after the presentation of threatening body-relevant stimuli only. This effect was not observed for the low SDQ-20 group. Scores on the SSAS correlated negatively with tactile bias for both threatening and neutral body-relevant stimuli at 250 ms.

CONCLUSIONS

Individuals with a tendency to experience somatoform symptoms focus more on stimuli in the tactile modality immediately following exposure to threatening body-relevant information. In contrast, self-reported somatosensory amplification appears to be associated with attention away from the tactile modality rather than with increased tactile focus.

A cognitive-behavioral/psychophysiological model of tic disorders

This article discusses current cognitive behavioral, as well as neurophysiological, accounts of the development and maintenance of tic behavior in chronic (simple or complex) tic disorders. A cognitive psychophysiological model is further elaborated, highlighting the reciprocal interplay of background cognitive and physiological factors preceding tic onset. According to the model, cognitive factors such as perfectionist concerns and heightened sensory awareness and self-attention, as well as physiological factors such as a high level of motor activation and accompanying elevated muscle tension, play a role in tic habits. Negative appraisals of tics and counter-productive coping strategies developed by clients as a means to suppress or to disguise the tic behavior may also locally reinforce tic onset. Neurochemical factors are viewed largely as concomitants of behavioral adaptations or compensations to the tic problem rather than as independent markers or precursors of tic onset. Clinically, the model emphasizes the role of cognitive-behavioral factors in tic onset, and suggests that tic management is best accomplished through cognitive behavioral interventions designed to prevent build up of both tension and pre-monitory urge in tic-affected muscles, rather than reverse the tic at the onset of the premonitory urge. The clinical validity of parts of the model is supported by recent experimental, psychometric and clinical studies. Other parts of the model remain speculative but at least yield testable predictions. A strength of the model is its ability to account for findings over diverse psychological and biological domains.