Tactile perceptual processes and their relationship to medically unexplained symptoms and health anxiety

Association between psychological traits and occlusal tactile acuity of healthy individuals

OBJECTIVES

Tactile acuity is a somatosensory measure of the extent to which humans can discern tactile stimuli. It is influenced by how peripheral signals are processed centrally. In the oral cavity, Occlusal Tactile Acuity (OTA) is the ability to perceive minimal thicknesses between antagonist teeth. The aim of the current study was to assess the association between psychological traits and OTA of otherwise healthy individuals.

METHODS

Sixty-three volunteers (32 males; mean age ± SD: 24.6 ± 2.7 years) participated in this study. Somatosensory amplification, anxiety, depression, physical symptoms and pain catastrophizing were scored using questionnaires, and subgroups of severity were created per variable based on cut-offs. OTA was measured using 9 aluminium foils with thickness (ranging from 8 to 72 μm) and one sham test (without foil). Each thickness was tested 10 times in random order, the participants were instructed to report whether they felt the foil between their molars and the mean percentage of correct answers was computed. A linear mixed model was used with OTA as a dependent variable and psychological domain as an independent variable.

RESULTS

Significantly different OTA was observed among the anxiety subgroups (p = .003), supporting a decreased perception of thicknesses 24 and 32 μm (p = .018 and p < .001, respectively) in participants with moderate/severe anxiety compared to those with no/mild anxiety. Significantly different OTA was also observed among the pain catastrophizing subgroups (p = .008), showing decreased perception of thicknesses 32 and 40 μm (p < .001 and p = .007, respectively) in severe catastrophizing levels, compared to no/mild catastrophizing levels. No significant differences were observed for the other variables.

CONCLUSIONS

Healthy adults with increased anxiety or pain catastrophizing levels show decreased interdental acuity as compared to participants with minor or no psychological impairment.

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.

Vague sensations. About the background and consequences of discordance between actual and perceived physiological changes

Empirical evidence consistently shows that discordance, also called dissociation or discrepancy, between actual physiological (mainly visceral) events and their perceived counterparts is substantial. On the one hand, we typically do not perceive actual visceral events occurring in our bodies; on the other hand, sometimes we do perceive bodily changes that do not really take place. This narrative review presents the available empirical findings on the discordance, and summarizes possible explanations that approach the phenomenon from the viewpoint of evolution, cognitive development, and predictive processing. Also, the role of top-down factors, such as expectations and experiences is discussed. Finally, practically relevant consequences of the discordance are presented using the examples of mind-body practices, the placebo and nocebo phenomenon, and medically unexplained symptoms. It is concluded that the discordance between actual and perceived body changes can have a negative impact on health, mainly through issues with adherence and other behavioral factors. The existence of actual-perceived discordance should be taught and demonstrated in the elementary and high school, as well as in many areas of higher education.

Symptom Perception in Pathological Illness Anxiety: Tactile Sensitivity and Bias

OBJECTIVE

Symptom perception in pathological illness anxiety (PIA) might be biased so that somatic signals are overreported. In the somatic signal detection task (SSDT), performance in detecting weak tactile stimuli gives information on overreporting or underreporting of stimuli. This task has not yet been applied in PIA.

METHODS

Participants with PIA (n = 44) and healthy controls (n = 40) underwent two versions of the SSDT in randomized order. In the original version, tactile and auxiliary light-emitting diode (LED) stimuli were each presented in half of the trials. In the adapted version, illness or neutral words were presented alongside tactile stimuli. Participants also conducted a heartbeat mental tracking task.

RESULTS

We found significantly higher sensitivity and a more liberal response bias in LED versus no-LED trials, but no significant differences between word types. An interaction effect showed a more pronounced increase of sensitivity from no LED to LED trials in participants with PIA when compared with the adapted SSDT and control group (F(1,76) = 5.34, p = .024, η2 = 0.066). Heartbeat perception scores did not differ between groups (BF01 of 3.63).

CONCLUSIONS

The increase in sensitivity from no LED to LED trials in participants with PIA suggests stronger multisensory integration. Low sensitivity in the adapted SSDT indicates that attentional resources were exhausted by processing word stimuli. Word effects on response bias might have carried over to the original SSDT when the word version was presented first, compromising group effects regarding bias.

TRIAL REGISTRATION

The study was preregistered on OSF (https://osf.io/sna5v/).

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.

Clinical Manifestations of Body Memories: The Impact of Past Bodily Experiences on Mental Health

Bodily experiences such as the feeling of touch, pain or inner signals of the body are deeply emotional and activate brain networks that mediate their perception and higher-order processing. While the ad hoc perception of bodily signals and their influence on behavior is empirically well studied, there is a knowledge gap on how we store and retrieve bodily experiences that we perceived in the past, and how this influences our everyday life. Here, we explore the hypothesis that negative body memories, that is, negative bodily experiences of the past that are stored in memory and influence behavior, contribute to the development of somatic manifestations of mental health problems including somatic symptoms, traumatic re-experiences or dissociative symptoms. By combining knowledge from the areas of cognitive neuroscience and clinical neuroscience with insights from psychotherapy, we identify Clinical Body Memory (CBM) mechanisms that specify how mental health problems could be driven by corporeal experiences stored in memory. The major argument is that the investigation of the neuronal mechanisms that underlie the storage and retrieval of body memories provides us with empirical access to reduce the negative impact of body memories on mental health.

Somatosensory Illusions Elicited by Sham Electromagnetic Field Exposure: Experimental Evidence for a Predictive Processing Account of Somatic Symptom Perception

OBJECTIVE

According to the predictive processing theory of somatic symptom generation, body sensations are determined by somatosensory input and central nervous predictions about this input. We examined how expectations shape predictions and consequently bodily perceptions in a task eliciting illusory sensations as laboratory analogue of medically unexplained symptoms.

METHODS

Using the framework of signal detection theory, the influence of sham Wi-Fi on response bias (c) and somatosensory sensitivity (d') for tactile stimuli was examined using the somatic signal detection task (SSDT). A healthy student sample (n = 83) completed the SSDT twice (sham Wi-Fi on/off) in a randomized order after watching a film that promoted adverse health effects of electromagnetic fields.

RESULTS

When expecting a Wi-Fi signal to be present, participants showed a significantly more liberal response bias c (p = .010, ηp2 = 0.08) for tactile stimuli in the SSDT as evidence of a higher propensity to experience somatosensory illusions. No significant alteration of somatosensory sensitivity d' (p = .76, ηp2 < 0.002) was observed.

CONCLUSIONS

Negative expectations about the harmfulness of electromagnetic fields may foster the occurrence of illusory symptom perceptions via alterations in the somatosensory decision criterion. The findings are in line with central tenets of the predictive processing account of somatic symptom generation. This account proposes a decoupling of percept and somatosensory input so that perception becomes increasingly dependent on predictions. This biased perception is regarded as a risk factor for somatic symptom disorders.

Enhanced Connectivity of Thalamo-Cortical Networks in First-Episode, Treatment-Naive Somatization Disorder

BACKGROUND

Dysfunctions of the thalamus and its projections to cortical cortices have been implicated in patient with somatization disorder (SD). However, changes in the anatomical specificity of thalamo-cortical functional connectivity (FC) in SD remain unclear.

METHODS

Resting-state fMRI scans were collected in 25 first-episode, drug-naive patients with SD, as well as 28 sex-, age-, and education-matched healthy controls. We parcellated the thalamus with seven predefined regions of interest (ROIs) and used them as seeds to map whole-brain FC. Correlation analysis was conducted in the patients.

RESULTS

We found an increased pattern of thalamic ROI-cortex connectivity in patients with SD. Patients with SD demonstrated enhanced thalamic connectivity to the bilateral anterior/middle cingulum, motor/sensory cortex, visual cortex, and auditory cortex. A significantly negative correlation was found between the right occipital thalamic ROI to the anterior cingulum and EPQ extraversion scores (r=0.404, p=0.045) after the Benjamini-Hochberg correction.

CONCLUSIONS

This study demonstrates that anatomical specificity of enhanced thalamo-cortical FCs exists in first-episode, drug-naive patients with SD. These findings further highlight the importance of the thalamic subregions in the pathophysiology of SD.

Contingent biofeedback outperforms other methods to enhance the accuracy of cardiac interoception: A comparison of short interventions

BACKGROUND AND OBJECTIVES

Deviations in interoception might contribute to the development and maintenance of mental disorders. The improvement of interoceptive accuracy (IA) is desirable but assessment and training methods remain controversial. For instance, it was assumed that performance increases in heartbeat counting paradigms after cardiac feedback were due to an improvement of knowledge with regard to heart rate rather than due to an actual improvement in IA.

METHODS

Here, we examined effects of contingent cardiac feedback training, non-contingent cardiac feedback, mindfulness practice, and a waiting period with external attentional focus on IA. 100 healthy participants underwent a mental tracking paradigm before and after 20 min of training or waiting.

RESULTS

Results revealed a significant increase of IA in the contingent feedback condition (d = 1.21, p ≤ .001) and no significant changes after non-contingent feedback, mindfulness practice or waiting (d ≤ 0.37; p ≥ .06). Furthermore, IA increase was significantly higher after the contingent feedback training compared to all other conditions, including non-contingent feedback.

LIMITATIONS

Future studies need to replicate these findings in clinical samples and examine time dependent effects.

CONCLUSIONS

The results provide evidence for the trainability of heartbeat perception. IA improvements may reduce the symptom burden in people suffering from mental disorders and psychophysiological conditions that have been linked to lower interoceptive accuracy such as depression, somatic symptom disorder, chronic pain, and functional somatic syndromes. Consequently, exploration of biofeedback training procedures shall be continued with the aim of identifying relevant mediators of beneficial effects and future implementation in clinical practice.

Hypoesthesia in generalised anxiety disorder and major depression disorder

Objective: The determination of soft signs can be a conducive practice to understand the differential etiology between depression and anxiety. This study aims at examining malleolar hypoesthesia role in distinguishing between patients with generalised anxiety disorder (GAD) and major depression disorder (MDD). Methods: This study examines the presence of malleolar hypoesthesia in patients with GAD (n = 47) compared to patients with MDD (n = 48) and healthy individuals (controls; n = 99). The Wartenberg wheel, a medical device for neurological use, was employed to determine the presence of hypoesthesia on both sides of the ankles. Results: The data revealed: i) MDD patients showed higher hypoesthesia than GAD patients (p = .008), ii) participants with hypoesthesia had higher anxiety and depression scores than participants without hypoesthesia (all p < .001) and iii) logistic regression model indicated that hypoesthesia can be a predictor of MDD relative to GAD diagnosis (Odds Ratio: 17.43 (1.40-217.09; p = .026)). Conclusions: Malleolar hypoesthesia was higher in MDD than GAD. The detection of hypoesthesia may help to investigate the differential etiology between MDD and GAD diagnosis.

Attending away from the body predicts increased physical symptom reports at six months in primary care patients

OBJECTIVE

High symptom reporting (HSR) and medically unexplained symptoms (MUS) are associated with considerable distress, disability, healthcare utilization and costs, but are poorly understood, and current treatments are of limited benefit. Most models of HSR and MUS implicate cognitive-perceptual factors, such as increased body-focused attention, reduced perceptual thresholds and a tendency to experience somatic misperception, but little is known about the causal role of these variables. We investigated this issue by studying whether there is a longitudinal relationship between perceptual-attentional variables and later clinical outcomes in primary care patients.

METHOD

Primary care patients (N = 102) completed clinical (physical symptom reporting, health anxiety and healthcare utilization) and perceptual-attentional (body-focused attention, perceptual threshold, somatic misperception) measures at baseline and then again six months later (N = 72). Hierarchical regression was used to examine cross-lagged relationships between baseline and follow-up scores.

RESULTS

Contrary to expectation, attending away from the body at baseline predicted increased not decreased symptom reporting six months later. Neither perceptual threshold nor somatic misperception predicted clinical outcomes at six months.

CONCLUSIONS

These findings suggest that body avoidance, rather than increased body focus, contribute to the development of HSR. Future studies should consider the potential clinical benefits of reducing bodily avoidance, via techniques that promote adaptive engagement with bodily sensations.

How do illness-anxious individuals process health-threatening information? A systematic review of evidence for the cognitive-behavioral model

According to the cognitive-behavioral model, illness anxiety is developed and maintained through biased processing of health-threatening information and maladaptive responses to such information.

OBJECTIVE

This study is a systematic review of research that attempted to validate central tenets of the cognitive-behavioral model regarding etiological and maintenance mechanisms in illness anxiety.

METHODS

Sixty-two studies, including correlational and experimental designs, were identified through a systematic search of databases and were evaluated for their quality.

RESULTS

Outcomes were synthesized following a qualitative thematic approach under categories of theoretically driven mechanisms derived from the cognitive-behavioral model: attention, memory and interpretation biases, perceived awareness and inaccuracy in perception of somatic sensations, negativity bias, emotion dysregulation, and behavioral avoidance.

CONCLUSIONS

Findings partly support the cognitive-behavioral model, but several of its hypothetical mechanisms only receive weak support due to the scarcity of relevant studies. Directions for future research are suggested based on identified gaps in the existing literature.

Fear of hypoglycemia in patients with type 2 diabetes: The role of interoceptive accuracy and prior episodes of hypoglycemia

OBJECTIVE

Fear of hypoglycemia (FoH) is a limiting factor for diabetes self-management and can have detrimental effects on quality of life. However, relatively little is known about its underlying mechanisms. In line with findings on patients with anxiety disorders, we hypothesized that interoceptive accuracy (IA) might be positively linked to FoH in patients with type 2 diabetes (T2DM).

METHODS

133 patients with T2DM were screened according to the extreme quartiles of the Hypoglycemia Fear Survey worry subscale (HFS-W). Overall, 66 participants (HFS-W<4; HFS-W>17) were included in the present study. Participants completed questionnaires on sociodemographic and diabetes-related measures. Accuracy of heartbeat perception was assessed using the mental tracking task.

RESULTS

Contrary to expectations, IA did not differ significantly between patients with low and high FoH. A linear regression analysis demonstrated that the experience of mild hypoglycemia (β=0.32, p≤0.01) and its interaction with IA (β=-0.26, p=0.040) were significant predictors of FoH, indicating that low IA and a history of experiencing mild hypoglycemia are positively associated with FoH.

CONCLUSION

Our findings suggest a positive association of low IA in combination with prior episodes of hypoglycemia and FoH in patients with T2DM. The results are in line with recent findings on IA in patients with chronic somatic symptom distress more generally and contribute to our understanding of the relations between interoception, body related fears, and physical symptom perception.

The neuropsychophysiology of tingling

Tingling is a bodily sensation experienced under a variety of conditions from everyday experiences to experimental and therapeutic situations. It can be induced by both peripheral or afferent (external stimulation, peripheral pathology) and higher cognitive (expectation) processes. The paper summarizes the current scientific knowledge on the neurophysiological and psychological concomitants of the tingling sensation. Four possible models are identified and presented: the afferent, the attention-disclosed, the attention-evoked, and the efferent model. Of these, only the attention-disclosed model, i.e., attention discloses the sensation by opening the gate for suppressed sensory information, appears to be able to explain every aspect of the tingling phenomenon. Terminological issues and the possible role of the tingling phenomenon in medically unexplained symptoms, nocebo and placebo reactions, and body-oriented therapeutic interventions are also discussed.

Are media reports able to cause somatic symptoms attributed to WiFi radiation? An experimental test of the negative expectation hypothesis

People suffering from idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) experience numerous non-specific symptoms that they attribute to EMF. The cause of this condition remains vague and evidence shows that psychological rather than bioelectromagnetic mechanisms are at work. We hypothesized a role of media reports in the etiology of IEI-EMF and investigated how somatosensory perception is affected. 65 healthy participants were instructed that EMF exposure can lead to enhanced somatosensory perception. Participants were randomly assigned to watch either a television report on adverse health effects of EMF or a neutral report. During the following experiment, participants rated stimulus intensities of tactile (electric) stimuli while being exposed to a sham WiFi signal in 50% of the trials. Sham WiFi exposure led to increased intensity ratings of tactile stimuli in the WiFi film group, especially in participants with higher levels of somatosensory amplification. Participants of the WiFi group reported more anxiety concerning WiFi exposure than the Control group and tended to perceive themselves as being more sensitive to EMF after the experiment compared to before. Sensational media reports can facilitate enhanced perception of tactile stimuli in healthy participants. People tending to perceive bodily symptoms as intense, disturbing, and noxious seem most vulnerable. Receiving sensational media reports might sensitize people to develop a nocebo effect and thereby contribute to the development of IEI-EMF. By promoting catastrophizing thoughts and increasing symptom-focused attention, perception might more readily be enhanced and misattributed to EMF.

Symptoms and the body: Taking the inferential leap

The relationship between the conscious experience of physical symptoms and indicators of objective physiological dysfunction is highly variable and depends on characteristics of the person, the context and their interaction. This relationship often breaks down entirely in the case of "medically unexplained" or functional somatic symptoms, violating the basic assumption in medicine that physical symptoms have physiological causes. In this paper, we describe the prevailing theoretical approach to this problem and review the evidence pertaining to it. We then use the framework of predictive coding to propose a new and more comprehensive model of the body-symptom relationship that integrates existing concepts within a unifying framework that addresses many of the shortcomings of current theory. We describe the conditions under which a close correspondence between the experience of symptoms and objective physiology might be expected, and when they are likely to diverge. We conclude by exploring some theoretical and clinical implications of this new account.