Fannes Stien, Van Diest Ilse, Meulders Ann, De Peuter Steven, Vansteenwegen Debora, Van den Bergh Omer
Department of Psychology, University of Leuven, Tiensestraat 102, 3000 Leuven, Belgium.
Biol Psychol. 2008 Apr;78(1):87-92. doi: 10.1016/j.biopsycho.2008.01.003. Epub 2008 Jan 31.
This study investigated breathing behavior in an odor-CO2-inhalation fear conditioning paradigm. A differential conditioning paradigm was applied in 55 participants. Both acquisition and extinction consisted of three CS+ and three CS- trials. Diluted ammonia and butyric acid served as conditional odor cues (CSs); inhalation of 20% CO2-enriched as US. The US was presented 10s after CS+ onset and both stimuli co-terminated 30s later. Subjective anxiety and US-expectancy were measured online upon presentation of the CSs. Respiratory behavior showed a biphasic pattern during CS+ acquisition trials. Participants paradoxically lowered their ventilation first; an increased ventilation was observed only towards the end of the trial. Extinction of this breathing inhibition was found. Participants avoiding the CO2 during acquisition did not show a reduction in fear from acquisition to extinction, whereas Non-avoiders did. We conclude that paradoxical decreases in ventilation constitute a relevant behavioral index of fear in CO2-inhalation paradigms.
