Ilse Van Diest

Inaccurate perception of asthma symptoms: a cognitive-affective framework and implications for asthma treatment.

Inaccurate perception of respiratory symptoms is often found in asthma patients. Typically, patients who inaccurately perceive asthma symptoms are divided into underperceivers and overperceivers. In this paper we point out that this division is problematic. We argue that little evidence exists for a trait-like stability of under- and overperception and that accuracy of respiratory symptom perception is highly variable within persons and strongly influenced by contextual information. Particularly, expectancy and affective cues appear to have a powerful influence on symptom accuracy. Based on these findings and incorporating recent work on associative learning, attention and mental representations in anxiety and symptom perception, we propose a cognitive-affective model of symptom perception in asthma. The model can act as a framework to understand both normal perception as well as under- and overperception of asthma symptoms and can guide the development of affect-related interventions to improve perceptual accuracy, asthma control and quality of life in asthma patients.

Media warnings about environmental pollution facilitate the acquisition of symptoms in response to chemical substances.

Objective Previous studies showed that somatic symptoms can be acquired in response to chemical substances using an associative learning paradigm, but only when the substance was foul smelling and not when it smelled pleasant. In this study, we investigated whether warnings about environmental pollution would facilitate acquiring symptoms, regardless of the pleasantness of the smell. Method One group received prior information framing the study in the context of the rapidly increasing chemical pollution of our environment. Another group received no prior information. Conditional odor stimuli (CS) were diluted ammonia (foul-smelling) and niaouli (neutral-positive smelling); the unconditional stimulus (UCS) was 10% CO2-enriched air. Each subject breathed one odor mixed with CO2 and a control odor mixed with air in 80-sec breathing trials. The type of odor mixed with CO2 was counterbalanced across participants. Next, the same breathing trials were administered without CO2. Breathing behavior was measured during each trial; subjective symptoms were assessed after each trial. Results Only participants who had been given warnings about environmental pollution reported more symptoms to the odor that had previously been associated with CO2, compared with the control odor. This was so for both the foul- and the pleasant-smelling odor. Symptom learning did not occur in the group that did not receive warnings. The elevated symptom level could not be accounted for by altered respiratory behavior, nor by experimental demand effects. Conclusions Raising environmental awareness through warnings about chemical pollution facilitates learning of subjective health symptoms in response to chemical substances.

Generalization of acquired somatic symptoms in response to odors: a pavlovian perspective on multiple chemical sensitivity.

Objective Somatic symptoms that occur in response to odors can be acquired in a pavlovian conditioning paradigm. The present study investigated 1) whether learned symptoms can generalize to new odors, 2) whether the generalization gradient is linked to the affective or irritant quality of the new odors, and 3) whether the delay between acquisition and testing modulates generalization. Methods Conditional odor stimuli (CS) were (diluted) ammonia and niaouli. One odor was mixed with 7.4% CO2-enriched air (unconditional stimulus) during 2-minute breathing trials (CS+ trial), and the other odor was presented with air (CS− trial). Three CS+ and three CS− trials were conducted in a semirandomized order (acquisition phase). The test phase involved one CS+-only (CS+ without CO2) and one CS− test trial, followed by three trials using new odors (butyric acid, acetic acid, and citric aroma). Half of the subjects (N = 28) were tested immediately, and the other half were tested after 1 week. Ventilatory responses were measured during and somatic symptoms were measured after each trial. Results Participants had more symptoms in response to CS+-only exposures, but only when ammonia was used as the CS+. Also, generalization occurred: More symptoms were reported in response to butyric and acetic acid than to citric aroma and only in participants who had been conditioned. Both the selective conditioning and the generalization effect were mediated by negative affectivity of the participants. The delay between the acquisition and test phases had no effect. Conclusions Symptoms that occur in response to odorous substances can be learned and generalize to new substances, especially in persons with high negative affectivity. The findings further support the plausibility of a pavlovian perspective of multiple chemical sensitivity.

Hyperventilation beyond fight/flight: respiratory responses during emotional imagery

Hyperventilation (HV) is often considered part of a defense response, implying an unpleasant emotion (negative valence) combined with a strong action tendency (high arousal). In this study, we investigated the importance of arousal and valence as triggers for HV responses. Forty women imagined eight different scripts varying along the arousal and valence dimensions. The scripts depicted relaxation, fear, depressive, action, and desire situations. After each trial, the imagery was rated for valence, arousal, and vividness. FetCO2, inspiratory and expiratory time, tidal volume, and pulse rate were measured in a nonintrusive way. FetCO2 drops and decreases in inspiratory and expiratory time occurred in all but the depressive and the relaxation scripts, suggesting that a defense conceptualization of hyperventilation is not always appropriate.

Sigh rate and respiratory variability during mental load and sustained attention

Spontaneous breathing consists of substantial correlated variability: Parameters characterizing a breath are correlated with parameters characterizing previous and future breaths. On the basis of dynamic system theory, negative emotion states are predicted to reduce correlated variability whereas sustained attention is expected to reduce total respiratory variability. Both are predicted to evoke sighing. To test this, respiratory variability and sighing were assessed during a baseline, stressful mental arithmetic task, nonstressful sustained attention task, and recovery in between tasks. For respiration rate (excluding sighs), reduced total variability was found during the attention task, whereas correlated variation was reduced during mental load. Sigh rate increased during mental load and during recovery from the attention task. It is concluded that mental load and task-related attention show specific patterns in respiratory variability and sigh rate.

Distorted Symptom Perception in Patients With Medically Unexplained Symptoms

The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing). Breathing behavior was continuously monitored, and dyspnea was rated every 10 s. The within-subject correlations between dyspnea on the one hand and end-tidal CO2 and minute ventilation on the other were used to index the degree to which perceived dyspnea was related to specific relevant respiratory changes. The results showed that perceived symptoms were less strongly related to relevant physiological parameters in MUS patients than in healthy persons, specifically when afferent physiological input was relatively weak. This suggests a stronger role for top-down psychological processes in the symptom perception of patients with MUS.

Can subjective asthma symptoms be learned

Objective: We investigated whether perception of subjective asthma symptoms can be brought under control of biomedically irrelevant cues in the environment, i.e., whether subjective asthma symptoms can be learned in response to harmless stimuli. Methods: Twenty patients with asthma and 20 healthy participants were presented with two placebo-inhalers presented as new chemicals for diagnosing asthma. One inhaler was coupled three times with rebreathing 5% CO2 in oxygen, the other inhaler was coupled three times with rebreathing oxygen. In the subsequent test phase, both inhalers were coupled once with oxygen. We assessed airway resistance and subjective symptoms throughout the study. Results: Both groups expected and reported more symptoms with the inhaler that was previously associated with the CO2 trials compared with trials with the inhaler that was used on trials without CO2 without concomitant effects on respiratory resistance. The learning effects were most pronounced in a subgroup of patients reporting symptoms of hyperventilation during asthma exacerbations in daily life. Conclusions: Subjective respiratory symptoms can be learned in response to harmless stimuli and a substantial proportion of patients with asthma might be especially vulnerable to this phenomenon. Because asthma patients rely mainly on perceived symptoms for their medication use, it is likely that they will take reliever medication based on expected symptoms instead of real exacerbations of respiratory dysfunction. ASC = Asthma Symptom Checklist; ANX = ASC anxiety subscale; DYS = ASC dyspnea subscale; FAT = ASC fatigue subscale; FOT = forced oscillation technique; HYP = ASC hyperventilation subscale; IRR = ASC irritability subscale; NA = negative affectivity; OBS = ASC obstruction subscale; VAS = visual analog scale.

Illness-Specific Catastrophic Thinking and Overperception in Asthma

OBJECTIVE This study investigated the role of illness-specific catastrophic thinking in symptom perception in asthma. DESIGN AND MAIN OUTCOME MEASURES A total sample of 72 patients with intermittent to moderate persistent asthma completed the Catastrophizing about Asthma Scale and completed the Asthma Symptom Checklist to measure retrospective symptom reporting. In addition, symptoms were concurrently assessed during different respiratory challenges eliciting mild and ambiguous versus salient and pronounced symptoms. RESULTS Catastrophic thinking in general, when patients are not having an exacerbation, is related to an increase in emotional symptoms, especially in ambiguous situations where respiratory difficulties could occur. Catastrophic thinking during exacerbations is related to an increase in emotional symptoms as well as in respiratory symptoms during respiratory challenges. CONCLUSION These strong relationships between catastrophic thinking and increased perception of asthma symptoms suggest a link between illness-specific catastrophic thinking and overperception. Consequently, catastrophic thoughts are an important target for psychological interventions in support of drug treatment.

Associative fear learning and perceptual discrimination: a perceptual pathway in the development of chronic pain.

Recent neuropsychological theories emphasize the influence of maladaptive learning and memory processes on pain perception. However, the precise relationship between these processes as well as the underlying mechanisms remain poorly understood; especially the role of perceptual discrimination and its modulation by associative fear learning has received little attention so far. Experimental work with exteroceptive stimuli consistently points to effects of fear learning on perceptual discrimination acuity. In addition, clinical observations have revealed that in individuals with chronic pain perceptual discrimination is impaired, and that tactile discrimination training reduces pain. Based on these findings, we present a theoretical model of which the central tenet is that associative fear learning contributes to the development of chronic pain through impaired interoceptive and proprioceptive discrimination acuity.

Accuracy and awareness of perception: related, yet distinct (commentary on Herbert et al., 2012).

3 The finding of Herbert and colleagues (2012) in the January 4 issue of Biological Psychology sheds interesting new perspectives 5 on the correspondence between homeostatic challenges and accu6 racy of heartbeat perception. One of their conclusions is that 7 changes in autonomic activity, which in their study were induced 8 by short-term fasting, intensify overall Interoceptive Awareness 9 (IAw). Below, it is argued that this conclusion can be somewhat 10 misleading; a more nuanced conclusion and additional directions 11 for future research based on this revised conclusion are proposed. 12 In the article of Herbert and colleagues as well as in numer13 ous other articles, heartbeat perception tasks are considered to 14 be a proxy of IAw. To say that “cardiac IAw [. . .] reflects the sen15 sory accuracy of perceiving one’s own cardiac signals” (p.77, Herbert 16 et al., 2012) is to say that IAw and Interoceptive Accuracy (IAc) are 17 synonymous, whereas in fact they are not. IAc specifically refers 18 to the capability of accurately perceiving changes in homeostatic 19 function. To be aware, means to be cognizant, to be mindful. Thus 20 IAw should be taken to mean the cognizant, mindful perception of 21 bodily signals (given the definition of interoception proposed by 22 Herbert and colleagues). Although IAw can be accompanied by an 23 accurate perception of bodily sensations, such accuracy is not nec24 essarily implied. This distinction between awareness and accuracy 25 is highlighted by a study of Khalsa and colleagues (2008) who found 26 that IAw is increased in meditative practices, but IAc is not. 27 Nevertheless, the idea that IAw and IAc can be used inter28 changeably is widespread, and most prevalent in the heartbeat 29 perception literature (e.g., Stewart et al., 2001; Sturges and Goetsch, 3