Odorant perception and active olfaction: a study of olfactory magnetic fields evoked by odorant pulse stimuli synchronized with respiratory cycle

This paper presents a study on the odorant perception and active olfaction for human olfactory senses and their active locations of estimated signal sources in the brain. In these experiments olfactory event-related potentials were measured by electroencephalography (EEG) and olfactory event-related magnetic fields were also measured by magnetoencephalography (MEG) using a 122 ch whole-head neuromagnetometer. Odorant stimuli were actively given into the right or left nose cavity through a thin silicon tube using a mask attached on the subject's face by an odorant pulse synchronized with the subject's respiratory cycle. MEG main response waves were sharply detected and these signal sources were estimated to exist as two dipoles bilaterally at the orbito-frontal lobe in the brain. In the authors' second experiments olfactory event-related magnetic fields were measured by an oddball paradigm using two odorants and these estimated signal sources were obtained in a few superior temporal regions. These active responses for odorants show one the capabilities of the role on the olfactory perception and active olfaction.