Brain activation during odor perception in males and females.

Several studies indicate that women outperform men in olfactory identification tasks. The psychophysical data are more divergent when it comes to gender differences at levels of odor processing which are cognitively less demanding. We therefore compared cerebral activation with H2(15)O PET in 12 females and 11 males during birhinal passive smelling of odors and odorless air. The odorous compounds (odorants) were pure olfactory, or mixed olfactory and weakly trigeminal. Using odorless air as the baseline condition, activations were found bilaterally in the amygdala, piriform and insular cortices in both sexes, irrespective of the odor. No gender difference was detected in the pattern of cerebral activation (random effect analysis SPM99, corrected p < 0.05) or in the subjective perception of odors. Males and females seem to use similar cerebral circuits during the passive perception of odors. The reported female superiority in assessing olfactory information including odor identification is probably an effect of a difference at a cognitive, rather than perceptive level of olfactory processing.