[The application of functional magnetic resonance imaging for the assessment of localisation and activation of cortex smell centers depending on stimulus used in normal volunteers].

PURPOSE: To determine the location and activation of brain smell centres in response to olfactory nerve-mediated and combined olfactory and trigeminal nerve-mediated stimulation using functional MRI.

SUBJECTS AND METHODS: MRI brain scans were performed in 10 healthy volunteers, aged 22-36 years, right handed, non-smokers, without any CNS diseases, not taking any medication to determine and compare the activated cortex regions during stimulation by patchouli and geraniol. fMRI was performed on Siemens Magnetom Vision 1,5 T imager with a head-neck coil using SE and EPI sequences. Functional MR imaging studies were obteined in the same plane as T11 eighted images in an axial plane by using echo planar imaging. In each of 14 contiguous planes parallel to anterior-posterior commisure line images that depicted blood-oxygen-level-dependent (BOLD) effect were acquired. The subject inhaled odorized air through both nares for 30 seconds. During 30-second off period the subject received room air at the same flow rate. For each of activated cortical zones the number of pixels activated was calculated. Image reconstruction and analysis were performed using standard imager software installed in MR imager.

RESULTS: The exposure to the olfactory and trigeminal nerve-mediated stimuli showed more activated regions than to the olfactory nerve-mediated stimuli. Geraniol evoked the biggest activation in orbitofrontal region, cingulate gyrus and insula. Patchouli activated orbitofrontal cortex, insula, parahippocampal gyrus, occipital cortex, and corpus callosum.

CONCLUSIONS: The results of present study confirm the ability to localize patterns of cortical activity with fMRI during olfactory tasks.