Involvement of the right piriform cortex in the familiarity judgment task of odors

Previous studies have shown activation of right orbitofrontal cortex during judgments of odor familiarity. In the present study, we sought to extend our knowledge about neural circuits involved in such a task. Fourteen right-handed male subjects were tested in fMRI in a single functional run of two olfactory conditions (detection and familiarity judgment). Within each condition, three epochs were performed. During the familiarity condition, subjects rated whether odors were familiar or unfamiliar, whereas during the detection condition, participants decided whether the odor was present or not. Contrasting familiarity with detection conditions, odor-activated areas were found mainly including the piriform cortex (PC), and hippocampus in the right hemisphere, and the inferior frontal gyrus and amygdala in the left hemisphere. Right PC activation was functionally connected with right hippocampus and left PC during that same task. By showing that PC was activated during a familiarity judgment task, the present study gives supports to the notion that PC participates in the processing of odor memory. It further showed preferential involvement of the right hemisphere in familiarity judgments. Key-words: Olfaction; Familiarity judgment; Recognition memory; Piriform cortex; fMRI