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Latent Inhibition of Rotation Chair-Induced Nausea in Healthy Male and Female Volunteers

From the Institute of Medical Psychology, University Hospitals Düsseldorf, Düsseldorf, Germany (S. Klosterhalfen, S. Kellerman, U.S.); the Department of Psychoendocrinology, Technical University of Dresden, Dresden, Germany (J.W., C.K.); the Department of Psychology, University of York, York, United Kingdom (G.H.); and the Department of Psychosomatic Medicine and Psychotherapy, University Hospitals Tüebingen, Tüebingen, Germany (P.E.).

Address correspondence and reprint requests to Prof. Dr. Paul Enck, University Hospitals Tüebingen, Department of Internal Medicine VI: Psychosomatic Medicine and Psychotherapy, Schaffhausen Str 113, 72072 Tüebingen, Germany. E-mail: paul.enck{at}uni-tuebingen.de

Objectives: Pre-exposure to an environment in which a nausea-inducing body rotation will subsequently be given constitutes a latent inhibition procedure that might act to reduce anticipatory and postrotation nausea.

Methods: This was tested in 24 healthy subjects randomly assigned to receive no pre-exposure (group 0), a single pre-exposure (group 1), or three pre-exposures (group 3). Rotation was standardized as 5 x 1 minute rotation, but the subjects could terminate it on request. Nausea was determined on a 7-item symptom rating scale before, during, and after rotation on days 3 and 4, whereas anticipatory nausea was measured before presumed rotation on day 5. Saliva cortisol and tumor necrosis factor (TNF-) levels were determined at baseline before, directly, and 15 and 30 minutes after rotation every day, and before presumed rotation on day 5.

Results: Pre-exposure significantly reduced the degree of anticipatory nausea on day 5. Cortisol levels increased with rotation and were higher at baseline on days 4 and 5, but subjects habituated from day 3 to day 4; levels were lower in women than in men. In contrast, TNF- decreased with rotation but showed no habituation. For both cortisol and TNF-, no effects on postrotational nausea were found.

Conclusion: It is concluded that repetitive pre-exposure (latent inhibition) reduces anticipatory but not postrotation nausea; behavioral measures (rotation time) and measures of acute stress (cortisol, TNF-) do not respond to latent inhibition. Thus, Pavlovian conditioning rules are effective in healthy humans with anticipatory nausea but not with postrotation nausea. Hormonal responses—TNF- decrease with stress, compensatory cortisol increase—and gender-related effects on learning and habituation are discussed with regard to psychophysiological and psychoimmunological processes.

Key Words: latent inhibition • Pavlovian conditioning • nausea • motion sickness • gender

Abbreviations: AN = anticipatory nausea; CS = conditioned stimulus; US = unconditioned stimulus; CR = conditioned response; PN = posttreatment nausea; UR = unconditioned response; TNF- = tumor necrosis factor ; RT = rotation tolerance; MSSQ = motion sickness susceptibility questionnaire; SR = symptom rating; ANOVA = analysis of variance.