Abstract
We used functional fMRI with healthy human volunteers to study how the processing of odor information is influenced by preceding notification of odors. Seventeen right-handed volunteers with normal olfactory function estimated by T&T olfactometry participated in the study. At 4l/min pressurized clean air was directed continuously to plastic tubings connected to the mask on the nose with an aspiration tubing. Seven odor exposures using 13.5% of isovaleric acid at the highest scale of olfactometer was delivered for 8 seconds each with 32 seconds interruption by sorenoid-operated valves. Images were acquired by 1.5-T MRI. The imaging data were analyzed using FEAT. Significant acitivation was found in the cingulated gyrus, hippocampus, thalamus, external orbito-frontal (eOFC) and entorhinal (Ecx) cortices well-known as the brain regions involved in olfactory processing, when subjects were stimulated without notification. Only 1 subject (1 male and 8 female; age mean = 24) recognized the odor unpleasant. Seven subjects (4 male and 3 female; age mean = 23) notified of unpleasant odor before scanning, however, showed significant activation in the insula, the globus pallidus, eOFC, and ECx. All subjects showed unpleasantness to the odor. These results suggest that notification facilitates olfactory processing by activation of the brain region involved in emotion. [Jpn J Physiol 55 Suppl:S169 (2005)]
