Irritancy expectancy alters odor perception : 3 Evidence from Olfactory Event Related Potential

22 The aim of the present research was to investigate the influences of cognition on temporal 23 processing of olfactory information in a health-relevant context. We investigated whether 24 expecting an odor to cause adverse health effects alters perception of that odor. An irritation25 free odor (Study 1: H2S; Study 2: PEA) was presented after which participants expected to 26 experience either adverse sensory irritation (caused by intra-nasal CO2 presentation) in one 27 condition, or no adverse effects in another condition, depending on a previously presented 28 visual cue. Olfactory Event Related Potentials (OERPs) were measured to assess effects of 29 expectations on the temporal course of olfactory processing. When participants expected 30 irritancy after perceiving the odor of H2S, N1 and P3 peak amplitude, and N1 latency, were 31 increased and shortened, respectively, suggesting more intense and faster processing of the 32 odor as well as effects on salience and anticipation of sensory irritation. When the odor was 33 PEA, only the N1 amplitude was increased. These results, obtained with OERP, provide 34 converging evidence for comparable conclusions regarding the influence of cognition on odor 35 perception reached with fMRI. Furthermore, the results suggest that a-priori hedonic valence 36 of an odor affects how susceptible the olfactory percept is to modulation via expectations. 37