Gender effects on odor-stimulated functional magnetic resonance imaging

On standardized tests of odor identification and odor detection. women tend to score better than men at nearly all age groups. We sought to determine if these findings would translate to differences between the sexes in the v olume of activated bl ain when odors Lire presented to subjects as the stim ulants for functional magnetic resonance imaging (FMRI) experiments. The ac tivation maps of eight right-handed women (mean age 25.3 years old, range 2 0-44, S.D. 8.3 years) were compared with those of 8 right-handed men (mean age 30.5, range 18-37, S.D. 6.5 years) given the same olfactory nerve stimu li in an FMRI experiment at 1.5 T, Olfactory stimuli were delivered to the patients in a passive fashion using a Burghart OM4-B olfactometer with a no se piece inserted into the patients' nostrils. We used agents (eugenol, phe nyl ethyl alcohol, or phenyl ethyl alcohol alternating with hydrogen sulfid e) that were selective for olfactory nerve stimulation in the nose. The odo rants were delivered to both nostrils for 1 s every 4 s during a 30 s 'on-p eriod'. During the 30 s 'off-period', the patient received room air at the same flow rate. The women's group-averaged activation maps showed up to eig ht times more activated voxels than men for specific regions of the brain ( frontal and perisylvian regions). The left and right inferior frontal regio ns showed a statistically significant increase in activation in women at p < 0.01. In general, more women showed activation than men. The results sugg est that (1) FMRI activation maps in subject group; can demonstrate correla tes to psychophysical tests of olfaction, and (2) one must control for gend er when performing odor-stimulated FMRI experiments. (C) 1999 Elsevier Scie nce B.V. All rights reserved.