Pavlovian aversive and appetitive odor conditioning in humans: subjective, peripheral, and electrocortical changes |
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Authors: | Christiane Hermann Silvio Ziegler Niels Birbaumer Herta Flor |
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Institution: | (1) Department of Psychology, Humboldt-University, Section Clinical Psychology and Behavioral Neuroscience, Hausvogteiplatz 5–7, 10117 Berlin, Germany,;(2) Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany,;(3) Dipartimento di Psicologica Generale, Padua, Italy, |
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Abstract: | Differential Pavlovian conditioning of aversive and appetitive odors was examined in 30 male healthy subjects. The appetitive
conditioning group (n=15) received a pleasant odor (vanilla), the aversive conditioning group (n=15) an unpleasant odor (fermented yeast) as unconditioned stimulus. Slides of two different neutral faces that were easy
to discriminate served as conditioned stimuli (CS). An EEG was recorded from nine electrodes. Electromyographic activity was
measured bilaterally from the m. corrugator supercilii and m. zygomaticus. The startle response was obtained from the m. orbicularis
oculi. Finally, heart rate and skin conductance response were assessed. The subjective data and the skin conductance response
revealed successful differential aversive conditioning. By contrast, the pleasant odor failed to produce appetitive odor conditioning.
The conditioned and unconditioned response of the corrugator muscles confirm previous reports on the m. corrugator being strongly
involved in the expression of negative affect. Contrary to previous findings, magnitude of the startle reflex was not found
to be modulated depending on the valence of the CS. Central psychophysiological parameters showed little change during differential
conditioning. The presence of subjective–evaluative conditioning and contingency awareness without significant changes in
cortical and cardiovascular correlates might be due to extremely localized cortical processing of conditioned olfactory cues
or primarily subcortical processing. The latter interpretation is strengthened by the presence of differential conditioning
in non-voluntary responses such as the corrugator muscles.
Electronic Publication |
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Keywords: | Odor conditioning Aversive learning Appetitive learning Human Psychophysiological correlates |
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