Neuromagnetic brain responses evoked by pleasant and unpleasant olfactory stimuli

It is reported that there have been growing number of conflicts, especially in the urban area, caused by unpleasant smells. Since it is mostly a subjective issue whether the certain smell in the everyday life is perceived as comfortable or not, a procedure to quantitatively evaluate the pleasantness of the smell might draw broad public attention. In the present study, we investigated the difference in the brain responses evoked by pleasant and unpleasant olfactory stimuli; so that we will eventually be able to objectively evaluate how the certain smell is perceived in each subject. Specifically, MEG signals were increased in the frontal/prefrontal regions between the latencies of 250 and 550 ms after the onset of the stimuli in the pleasant condition compared to the control condition. It is conceivable that the differences in the MEG waveforms observed in the frontal/prefrontal regions reflect the differences in the subjective olfactory perception (pleasant vs. unpleasant).