Sex-specific hemispheric differences in cortical activation to a bimodal odor.

Most odorants we experience in every day life are bimodal in that they activate both the main olfactory and the intranasal trigeminal system. Few studies have investigated whether true bimodal odorants are processed differently than unimodal odorants. The aim of the study was to address sex-dependent hemispheric differences in olfactory event-related potentials. Event-related potentials (ERP) of the bimodal stimulant peppermint oil were recorded in 34 healthy subjects (17 women). No sex-related differences in olfactory sensitivity, trigeminal sensitivity or hedonic ratings of the stimuli were found. Although perceived similarly by men and women, results indicated a sex-differentiated hemispheric response to bimodal odors. Women generally expressed larger amplitudes and longer latencies over their left hemisphere, whereas men demonstrated a similar pattern over their right hemisphere. This effect was most evident for the early sensory derived ERP components indicating a sex-dependent difference in the sensory processing of bimodal odors.