Learned Fear of Gastrointestinal Sensations in Healthy Adults

in Clinical Gastroenterology and Hepatology (2016), 14(11), 155215582

Background & Aims Gastrointestinal symptom-specific fear and anxiety are important determinants of gastrointestinal symptom perception. We studied learning of fear toward innocuous gastrointestinal ... [more ▼]

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. [less ▲]

Startle responding in the context of visceral pain

in International Journal of Psychophysiology (2015), 98(1), 128-134

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 ... [more ▼]

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. [less ▲]