On the Origin of Interoception.

Over the course of a century, the meaning of interoception has changed from the restrictive to the inclusive. In its inclusive sense, it bears relevance to every individual via its link to emotion, decision making, time-perception, health, pain, and various other areas of life. While the label for the perception of the body state changes over time, the need for an overarching concept remains. Many aspects can make any particular interoceptive sensation unique and distinct from any other interoceptive sensation. This can range from the sense of agency, to the physical cause of a sensation, the ontogenetic origin, the efferent innervation, and afferent pathways of the tissue involved amongst others. In its overarching meaning, interoception primarily is a product of the central nervous system, a construct based on an integration of various sources, not per se including afferent information. This paper proposes a definition of interoception as based on subjective experience, and pleas for the use of specific vocabulary in addressing the many aspects that contribute to it.

Learned Fear of Gastrointestinal Sensations in Healthy Adults.

BACKGROUND & AIMS: Gastrointestinal symptom-specific fear and anxiety are important determinants of gastrointestinal symptom perception. We studied learning of fear toward innocuous gastrointestinal sensations as a putative mechanism in the development of gastrointestinal symptom-specific fear and anxiety. METHODS: Fifty-two healthy subjects (26 women) received 2 types of esophageal balloon distention at a perceptible but nonpainful intensity (conditioned stimulus [CS], the innocuous sensation) and at a painful intensity (unconditioned stimulus [US]). Subjects were assigned randomly to 1 of 2 groups. During the learning phase, the innocuous CS preceded the painful US in the experimental group (n = 26). In the control group (n = 26), on the contrary, the US never followed the CS directly. During a subsequent extinction phase, both groups received only CS distention-the painful US was no longer administered. Indexes of fear learning toward the innocuous CS distention included the skin conductance response, fear-potentiated startle (measured by the eye-blink electromyogram), and self-reported expectancy of the US. RESULTS: During the learning phase, only the experimental group learned to fear the innocuous gastrointestinal CS, based on the increase in US expectancy (compared with the control group, P = .04), increased skin conductance response (compared with the control group, P = .03), and potentiated startle reflex (compared with the control group, P = .001) in response to the CS. The differences between the experimental and control groups in US expectancy and skin conductance, but not fear-potentiated startle, disappeared during the extinction phase. CONCLUSIONS: Fear toward innocuous gastrointestinal sensations can be established through associative learning in healthy human beings. This may be an important mechanism in the development of fear of gastrointestinal symptoms, implicated in the pathophysiology of functional gastrointestinal disorders.

Startle responding in the context of visceral pain.

This study aimed to investigate affective modulation of eye blink startle by aversive visceral stimulation. Startle blink EMG responses were measured in 31 healthy participants receiving painful, intermittent balloon distentions in the distal esophagus during 4 blocks (positive, negative, neutral or no pictures), and compared with startles during 3 'safe' blocks without esophageal stimulations (positive, negative or neutral emotional pictures). Women showed enhanced startle during blocks with distentions (as compared with 'safe' blocks), both when the balloon was in inflated and deflated states, suggesting that fear and/or expectations may have played a role. Men's startle did not differ between distention and non-distention blocks. In this particular study context affective picture viewing did not further impose any effect on startle eye blink responses. The current results may contribute to a better understanding of emotional reactions to aversive interoceptive stimulation.

Effect of seated trunk posture on eye blink startle and subjective experience: comparing flexion, neutral upright posture, and extension of spine.

Postures are known to be able to affect emotion and motivation. Much less is known about whether (affective) modulation of eye blink startle occurs following specific postures. The objective of the current study was to explore this. Participants in the present study were requested to assume three different sitting postures: with the spine flexed (slouched), neutral upright, and extended. Each posture was assumed for four minutes, and was followed by the administration of brief self-report questionnaires before proceeding to the next posture. The same series of postures and measures were repeated prior to ending the experiment. Results indicate that, relative to the other postures, the extended sitting posture was associated with an increased startle, was more unpleasant, arousing, had smaller levels of dominance, induced more discomfort, and was perceived as more difficult. The upright and flexed sitting postures differed in the level of self-reported positive affect, but not in eye blink startle amplitudes.

Atypical modulation of startle in women in face of aversive bodily sensations.

Eye blink startle magnitude is assumed to be higher in threatening contexts. A scarce amount of studies suggest that this does not hold true when startle is measured during perceived threats to homeostatic integrity. The present study was set up to describe the startle response pattern to a selection of interoceptive stimuli. Female subjects (N=36) were exposed once to 90 s of continued (1) cold pain, (2) inhalation of a gas mixture of 7.5% CO2, and (3) breathing against an inspiratory and expiratory resistive load. Each stimulus was preceded and followed by a 90 second period of rest, respectively labeled baseline and recovery. Even after correcting eye blink startle responses for habituation, a decreased startle amplitude was evident during these stimuli. Results suggest that startle amplitude during aversive stimulation is inversely correlated with perceived fearfulness for women, although further studies are necessary to corroborate this interpretation.

Learning to fear obstructed breathing: comparing interoceptive and exteroceptive cues.

The present study investigated interoceptive fear conditioning (IFC) to an interoceptive and exteroceptive conditional stimulus (CS) with a severe respiratory load applied for 30s as the unconditional stimulus (US). CSs were another, weak respiratory load in the intero-IFC study (N=74), and a neutral picture in the extero-IFC study (N=42). CSs preceded the US in the paired groups, whereas the unpaired groups received the same number of unpaired CSs and USs. We measured startle blink EMG, self-reported fear and respiration. In the intero-IFC study, the CS-load was associated with larger startle blinks and a smaller decrease in respiratory rate and tidal volume in the paired compared to the unpaired group. In the extero-IFC study, the CS-picture evoked an increase in tidal volume and self-reported fear only in the paired group. In addition, startle potentiation during the CS-picture was greater for the paired than for the unpaired group.

Detecting coached feigning using the Test of Memory Malingering (TOMM) and the Structured Inventory of Malingered Symptomatology (SIMS).

Undergraduate students were administered the Test of Memory Malingering (TOMM) and the Structured Inventory of the Malingered Symptomatology (SIMS) and asked to respond honestly, or instructed to feign cognitive dysfunction due to head injury. Before both instruments were administered, symptom-coached feigners were provided with some information about brain injury, while feigners who received a mix of symptom-coaching and test-coaching were given the same information plus advice on how to defeat symptom validity tests. Results show that, although the accuracy of both instruments appears to be somewhat reduced by a mix of symptom coaching and test coaching, the TOMM and SIMS are relatively resistant to different kinds of coaching.