Differential effects of the hiba odor on CNV and MMN

The aim of this study was to objectively measure some psychophysiological effects of odors, particularly the effects of odors on the contingent negative variation (CNV) and the mismatch negativity (MMN). It is generally believed that CNV reflects arousal processes and MMN reflects activity in an automatic detection system. Sixteen females were exposed to the odor of Thujopsis dolabrata (hiba), a conifer. CNV was obtained with a foreperiod of 2 s in a traditional click-flash reaction-time (RT) paradigm. Auditory MMN was measured while the subject was reading a book with SOA fixed at 500 ms. The amplitude of the early and late CNV components were significantly larger and RT to the imperative stimulus (IS) was shorter in the aroma condition than in the absence-of-odor condition, but there was no significant difference in the amplitude of MMN obtained in the two conditions. Our results indicate that the odor generates a high level of arousal within the nervous system but does not have a significant effect on automatic information processing.