Spatial summation of chemical irritation and itch produced by topical application of capsaicin

The effect of increasing the total area of stimulation on the sensations of irritation produced by topical application of capsaicin was studied in two experiments. In the first experiment, stimulus area was varied by changing the size of filter paper disks on which capsaicin was delivered to the skin of the forearm. Subjects rated the intensity and quality of the cutaneous sensations over a 15-min period. Increasing stimulus area by a factor of 15 resulted in a relatively modest increase in the peak perceived intensity of irritation, a shortening of the latency to the onset of irritation, and shifts in the frequency of reports of sensations of itching and stinging/pricking. However, itch was the most frequently reported sensation regardless of stimulus size. In Experiment 2, stimulus area was manipulated by varying the number of stimuli applied to the skin. Despite a smaller difference in total stimulus areas (9-fold vs. 15-fold), the difference in perceived irritation was more pronounced than it was in Experiment 1 and reached statistical significance. It is therefore concluded that spatial summation does occur in the afferent system or systems responsible for the perception of capsaicin on the skin. This result is consistent with previous reports of summation at the threshold for heat pain and constitutes new information about the spatial integration of pruritic stimulation.     

Expectations of sensations,discomfort and fear in dental treatment

A hundred dental patients and 40 dentists were asked to describe the sensations, discomfort and fear which they associated with a number of dental treatments. A number of patients were also asked to describe their experiences immediately after routine conservation procedures. It was concluded that although patients could accurately anticipate the pattern of sensations involved in treatment (even if they had not experienced some of the procedures), they expected more intense sensations and greater discomfort and apprehension than they were likely to experience. Dentists expressed more realistic ideas about the sensations produced by dental treatment. The discrepancy in patients' expectations appears to persist in spite of many discontinuing experiences, the fear of treatment being fostered by discomfort and the intensity of sensations expected, by lack of experience and, to a modest degree, by uncertainty about the sensations anticipated. Cognitive theories of fear do not appear to explain all these influences adequately. These observations support the need for information about sensations in treatment to help not so much with the experience of dentistry but rather with its anticipation.     

Health anxiety moderates the effects of distraction versus attention to pain

Little is known about the relationship between health anxiety and chronic pain. The present study explored whether individual differences in health anxiety would influence the response of chronic pain patients to physical therapy. Furthermore, the interaction of health anxiety with coping strategy usage (distraction versus attention) was studied. Participants were 81 chronic pain patients who were interviewed and completed measures of pain, anxiety and cognition following an active physiotherapy session in which they either: (1) attended to physical sensations; (2) distracted from physical sensations or (3) completed the session as usual. Health anxious, compared to non-health anxious, individuals worried more about their health and injury during the session and attended to and catastrophically misinterpreted sensations more frequently. A complex interaction between health anxiety and coping strategy emerged. Among health anxious patients, attention to sensations resulted in lower anxiety and pain than did distraction. It appears as though attention had a short-term anxiety reducing effect for health anxious patients. Among non-health anxious patients, attention resulted in greater worry about health than distraction. Clinical and theoretical implications are discussed.     

The effects of mental imagery on skin temperature and skin temperature sensation

In a series of six experimental sessions five subjects were instructed to imagine their hand in a hot and cold water stream. During the imagery period the subjects estimated with a psychophysical scale their subjective temperature sensations caused by the imagery. Skin temperature was measured from the thumb of the subjects' dominant hand. After each session the subjects were asked whether they had succeeded in producing an imagery. The skin temperature changes deviated significantly from the control level in the successful imagery experiments. Differences in the skin temperature changes between the successful and unsuccessful imagery experiments were significant. The skin temperature changes measured and the subjects' temperature sensations, produced by the imagery, were similar in the successful imagery experiments. The possible relationships between mental imagery and changes in skin temperature and skin temperature sensation are discussed.     

The ego and the id revisited Freud and Damasio on the body ego/self

Freud's statement in The Ego and the Id (1923) that the ego is first and foremost a bodily ego is well known. This paper tempts to clarify the premises underlying Freud's thesis. Particular attention is paid to Freud's investigation of internal perceptions. Freud argued that internal perceptions are more primordial than perceptions arising externally. In Freud's opinion the roots of the ego, the id, are to be found in body sensations and feelings, but he had to admit that very little was known about these sensations and feelings. Only much later was neuroscience in a position to offer evidence that feelings can be the direct perception of the internal state of the body. Damasio (2010) has recently suggested that the core of the self might be found in what he, like Freud, terms primordial feelings. Not only was Freud able to conceive of the ego as the perception and feeling of our own body but also to conceive of knowing the mental life of another by means of recreating the bodily state of another through imitation.     

Quality of Life in Patients with Non-CAD Chest Pain: Associations to Fear of Pain and Psychiatric Disorder Severity

Chest pain in the absence of identified cardiac cause, or non-cardiac chest pain (NCCP), is a common condition that may result in impaired quality of life. Theories of NCCP put forward that patients who react to cardiopulmonary sensations with fear may avoid activities that elicit cardiac sensations. Co-morbid psychiatric disorders, which are prevalent in this population, may predispose individuals to be more vigilant to physiological sensations, including cardiac-related symptoms. The daily impact of avoiding cardiopulmonary cues may limit quality of life. This study examined psychiatric disorders, fear of pain, and quality of life in 30 non-coronary artery disease (CAD) chest pain patients. Psychiatric disorder severity was independently associated with mental health related quality of life and fear of pain was independently associated with physical health related quality of life. This research adds understanding to contributory factors to impaired quality of life among patients with non-CAD chest pain.     

Chronic pain relief after receiving affective touch: A single case report

Affective touch is gentle slow stroking of the skin, which can reduce experimentally induced pain. Our participant, suffering from Parkinson's Disease and chronic pain, received 1 week of non-affective touch and 1 week of affective touch as part of a larger study. Interestingly, after 2 days of receiving affective touch, the participant started to feel less pain. After 7 days, the burning painful sensations fully disappeared. This suggest that affective touch may reduce chronic pain in clinical populations.     

Conditioning,sensations, and the ergotropic-trophotropic balance

Analysis of Pschonik’s work on conditioning and sensation, in the light of Gellhorn’s studies on the tuning of the central nervous system through changes in the ergotropic-trophotropic balance, leads to the following results. Vasomotor and sensory reactions (VSR) induced by stimulation of cutaneous warmth and pain receptors (US), or by the conditional stimulus (CS) reinforced by the US, show parallel changes in a variety of circumstances: 1) anesthesia of the skin abolishes the effect of the US but not that of the CS; 2) various procedures lead to a reversal of VSR in the conditioned state in response to the US; 3) in a near-neurotic state VSR may be abolished while the plethysmogram gives evidence that ergotropic and trophotropic discharges occur at the same time. Changes in the ergotropic-trophotropic balance at the hypothalamic level alter VSR quantitatively and qualitatively. In an ergotropicallytuned state not only ergotropically-acting stimuli, but also trophotropically-acting stimuli lead to vasoconstriction and pain. Thus, stimulation of pain receptors, as well as stimulation of warmth receptors, produces vasoconstriction and pain. Similarly, these stimuli effect vasodilatation and warmth in the trophotropically-tuned state. It is concluded that the ergotropic-trophotropic balance has a profound influence on sensations and perceptions. It is of clinical significance that this balance can be altered through a conditional reflex mechanism,i.e., on the basis of individual experience.     

Relation of skin temperature to pain threshold

Two recent studies have established a very close relationship between environmentally-induced changes in skin temperature and the pain threshold for radiant heat stimuli. The present experiment was designed to verify the relationship by using as pain test area the skin surface of the back of the hand, as the skin temperature here is likely to vary from individual to individual much more than for the forehead.

Subjects were 50 neurotic and depressed patients of both sexes, age range 20-79. Skin temperatures were recorded on the right hand until a steady level was reached, then radiant heat stimuli were applied to a blackened area of the left hand. Results showed a highly significant negative correlation between pain threshold and skin temperature level, while differences due to age and sex were negligible. Drops in skin temperature were a common reaction during pain testing.

The significance of this finding is discussed in terms of the adaptive function of skin temperature changes and their relation to tissue damage. The results are consistent with the view that the pain experience, although having its distinctive sensory components, is intimately related to, and affected by, central factors of autonomic regulation. Some implications for general experimental and clinical research on pain are briefly outlined.     

Anesthesia Awareness: Narrative Review of Psychological Sequelae,Treatment, and Incidence

Awareness during general anesthesia occurs when patients recall events or sensations during their surgeries, although the patients should have been unconscious at the time. Anesthesiologists are cognizant of this phenomenon, but few discussions occur outside the discipline. This narrative review summarizes the patient recollections, psychological sequelae, treatment and follow-up of psychological consequences, as well as incidence and etiology of awareness during general anesthesia. Recalled memories include noises, conversations, images, mental processes, feelings of pain and/or paralysis. Psychological consequences include anxiety, flashbacks, and posttraumatic stress disorder diagnosis. Limited discussion for therapeutic treatment after an anesthesia awareness experience exists. The incidence of anesthesia awareness ranges from 0.1 to 0.2% (e.g., 1–2/1000 patients). Increased recognition of awareness during general anesthesia within the psychological/counseling community, with additional research focusing on optimal therapeutic treatment, will improve the care of these patients.     

Anxiety and hypervigilance to cardiopulmonary sensations in non-cardiac chest pain patients with and without psychiatric disorders

We investigated body vigilance, cardiac anxiety, and the mediating role of interoceptive fear on pain in patients with non-cardiac chest pain (NCCP; a syndrome of chest pain in the absence of identifiable organic etiology). Patients were more attentive to cardiac-congruent sensations than cardiac-incongruent sensations (e.g., gastrointestinal, cognitive dyscontrol; p's < .001). Patients with a DSM-IV Axis I anxiety or mood disorder were more body vigilant compared to patients who did not have a disorder (p's < .05). Patients with anxiety disorders were particularly vigilant to and fearful of cardiac sensations relative to patients without anxiety disorders. Latent variable path models examined the extent that interoceptive fear mediated the association between body vigilance and cardiac anxiety on chest pain. Within each model, diagnostic status, body vigilance, and cardiac anxiety were exogenous and predicted interoceptive fear that in turn predicted pain. Separate models examined body vigilance and cardiac anxiety, and both models fit the data well. Findings showed partial mediation for the body vigilance factor, and full mediation for the cardiac anxiety factor. Interoceptive fear played a mediating role in both models. The syndrome of NCCP may persist partly due to conscious hypervigilance to and fear of cardiac-congruent body sensations, particularly among anxious patients.     

Effects of preparatory information about sensations, threat of pain, and attention on cold pressor distress.

Pain experience is conceptualized as a combination of stimulus sensations (e.g., aching) and emotional distress. In Experiment 1, less distress was reported to cold pressor stimulation by subjects first told about stimulus sensations than by subjects who were uninformed or were told about symptoms of bodily arousal (e.g., tension). Adding a pain warning to sensation information blocked distress reduction, presumably by eliciting an emotional interpretation of the stimulus. In Experiment 2, subjects attending only to hand sensations reported less distress than subjects attending to their bodies. This decrease in the power of the stimulus to provoke emotion is presumably mediated by a schema of hand sensations formed by attention. In Experiment 3, subjects attending to hand sensations early in the immersion and distracting themselves later reported the same low levels of distress as did subjects who attended to hand sensations throughout. Subjects distracted throughout and subjects attending to hand sensations later showed no distress reduction. Therefore, stimulus schematization must precede distress reduction. Implications for distress control are discussed.     

Skin-transmitted pathogens and the heebie jeebies: evidence for a subclass of disgust stimuli that evoke a qualitatively unique emotional response

Skin-transmitted pathogens have threatened humans since ancient times. We investigated whether skin-transmitted pathogens were a subclass of disgust stimuli that evoked an emotional response that was related to, but distinct from, disgust and fear. We labelled this response “the heebie jeebies”. In Study 1, coding of 76 participants’ experiences of disgust, fear, and the heebie jeebies showed that the heebie jeebies was elicited by unique stimuli which produced skin-crawling sensations and an urge to protect the skin. In Experiment 2,350 participants’ responses to skin-transmitted pathogen, fear-inducing, and disgust-inducing vignettes showed that the vignettes elicited sensations and urges which loaded onto heebie jeebies, fear, and disgust factors, respectively. Experiment 3 largely replicated findings from Experiment 2 using video stimuli (178 participants). Results are consistent with the notion that skin-transmitted pathogens are a subclass of disgust stimuli which motivate behaviours that are functionally consistent with disgust yet qualitatively distinct.     

Reappraisal mitigates overestimation of remembered pain in anxious individuals

Anxiety sensitivity, a trait characterised by fear of anxiety-related body sensations, has been linked to heightened attention to pain, appraising body sensations as threatening, and remembering threat-related information. We assessed whether individuals with greater anxiety sensitivity overestimate in remembering pain. We also assessed whether emotion regulation strategies that direct attention away from pain (distraction), or alter appraisals of pain (reappraisal), alleviate memory bias. Participants (N = 137) were randomly assigned to one of two emotion regulation conditions or to a control condition before taking part in a cold pressor task. Greater anxiety sensitivity was associated with overestimation in remembering pain. Engaging in reappraisal mitigated this memory bias but engaging in distraction did not. This is the first study to examine the relations among anxiety sensitivity, emotion regulation and memory for pain. The findings suggest that health-care practitioners can encourage reappraisal to promote more positive memories of procedural pain, particularly in patients high in anxiety sensitivity.     

Cognition and self-control: Cognitive control of painful sensory input

Eighty Ss were first tested for base-level response to a pain-producing stimulus and then were re-tested on the same pain stimulus after receiving 1 of 8 experimental treatments. The 8 treatments were arranged in a 2×2×2 factorial design: presence or absence of hypnotic induction procedure; presence or absence of instructions for anesthesia; and presence or absence of demands for honest reports. Neither the hypnotic-induction procedure nor the demands for honesty affected the Ss’ reports of the degree of pain experienced. The anesthesia instructions—“think of the hand as numb and insensitive as if it were a piece of rubber...”— produced an equal degree of pain reduction in hypnotic and non-hypnotic Ss and in Ss who were and those who were not exposed to demands for honesty. The results indicate that (a) Ss’ reports of pain are less affected by demands for honesty and are more closely related to their actual experiences than has been previously assumed and (b) instructions which direct Ss to exercise cognitive control over painful sensory input are effective (with or without ‘hypnosis’) in reducing the experience of pain.     

Expectancy, redefinition and reported pain

Three groups of subjects were administered a redefinition strategy which asked them to focus on sensations during noxious stimulation. Those in one group were informed that the strategy would reduce pain (positive expectancy), those in a second were informed that it would augment pain (negative expectancy), and those in a third were given no information on expectancy. Subjects in a fourth group received neither redefinition nor instructions on expectancy. The four groups did not differ either in expectancy of pain reduction or in reduction of reported pain. Subjects in all groups expected more pain than they reported, and expectations for pain reduction showed only a small correlation with degree of reported pain reduction. In all groups, men reported less pain than women.     

Interoception and gender: What aspects should we pay attention to?

Interoception is involved in both somatic and mental disorders with different prevalence between genders; however, gender differences are often neglected. To examine the potential gender differences in interoceptive awareness, we recruited 376 healthy subjects (51% males, aged 17–30 years), to fill in the Multidimensional Assessment of Interoceptive Awareness (MAIA). Of that sample, in a subgroup of 40 subjects (50% males), interoceptive accuracy was assessed by heartbeat counting task (HCT).The results on interroceptive awareness suggest that females tend to notice bodily sensations more often, better understand relations between bodily sensations and emotional states, worry or experience more emotional distress with sensations of pain or discomfort and see body as less safe. The results of interoceptive accuracy further suggest that females are less efficient in consciously detecting heartbeats. Therefore, gender should be considered when interoceptive evaluation is performed in disorders associated to bodily sensations and to the emotional/mood states.     

Chromatic information processing: Rate depends on stimulus location in the category and psychological complexity

Summary Colors are typically categorized, and color sensations can be conceived to lie on a continuum of psychological complexity from simple, sensations provoked by colors that fall near the centers of color categories and that convey predominately a single percept (like blue), to complex, sensations provoked by colors that fall near boundaries between color categories and that convey two percepts (like blue-green). In three experiments we assessed the effect of the location of colors in a category (their psychological complexity) on the rate at which observers identified and classified them. In Experiment 1, observers named category center colors faster than boundary colors. A subsidiary experiment with range-shifted stimuli showed that observers were not merely bisecting a stimulus continuum. In Experiment 2, observers classified a variety of category centers more rapidly than a variety of boundaries. In Experiment 3, observers who first practiced classifying color centers or boundaries as such later classified category centers faster than boundaries. A subsidiary experiment showed that this differential was not selective to particular response category labels. Neither Experiment 2 nor Experiment 3 showed any differential effect of visual field of presentation. The advantage of category center or simple over boundary or complex sensations in chromatic information processing is discussed in terms of the physiological sensitivity of the visual system to color.     

Interpretation of bodily symptoms in hypochondriasis.

Although it has been suggested that hypochondriasis is caused by the misinterpretation of innocuous bodily sensations, support for this hypothesis rests largely upon uncontrolled self-report. We investigated the interpretation of ambiguous bodily sensations in three experiments using separate samples of non-clinical subjects differing in level of hypochondriacal concern. Results confirmed that subjects with high hypochondriacal concern endorse more thoughts about illness interpretations of bodily sensations, but reported thought content resembled 'catastrophic' rather than the 'non-emergency' thoughts suggested by Warwick and Salkovskis (Hypochondriasis. Behavior Research and Therapy, 28, 105-117, 1990). Presence of an interpretive bias was further supported in a study of recognition bias for disambiguated versions of ambiguously threatening sentences, although this applied as much to social as to illness threats. A final experiment failed to support the hypothesis of an automatic inference bias, but did show that subjects with high hypochondriacal concern were quicker to correctly identify previously exposed illness words. Thus, reported thoughts are consistent with catastrophic interpretations of common bodily sensations, but interpretive bias may not be limited to illness threat. However, high hypochondriacal subjects do show a more specific enhanced perceptual sensitivity to illness cues, which may play a role in maintaining their concern with bodily symptoms.     

Unconscious sensations

D. M. Armstrong proposes to explain the possibility of unconscious sensations by means of a distinction between the perceptual consciousness, which is essentially involved in sensations, and our introspective consciousness of sensations. He holds that unconscious sensations are instances of perceptual consciousness of which we are not introspectively conscious. I contend that, although Armstrong's distinction is plausible and significant, it fails to explain his own examples of unconscious sensation. I argue that the puzzle of how unconscious sensations are possible arises at the level of perceptual consciousness and does not concern our introspective awareness of mental states.This paper grew out of research supported by the National Endowment for the Humanities at Cornell University in 1985. I would like to express my gratitude to the National Endowment, to Cornell, and to Sydney Shoemaker.