Olfactory activity in the human brain identified by fMRI

Modern imaging methods such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET) enable us to map brain activities associated with stimulation of various functional systems in the human brain. Data concerning the localization and lateralization of secondary olfactory areas are not in agreement.

localization of secondary olfactory brain areas activated by a pleasant stimulus--vanillin.

Our fMRI method was based on the blood-oxygen-level dependent effect. All measurements were carried out on a 1.5 T scanner (Siemens-Vision), using gradient-echo EPI technic. The basic block-like scheme included no odour/and odour was repeated 8 times. In the definitive phase of the study, experiments were performed on 12 healthy volunteers aged from 20 to 68 (9 men and 3 women) stimulated birhinally by vanillin odour.

Bilateral activations of the inferior frontal gyrus, anterior insular-periinsular area, hippocampus, amygdala, caudate nucleus and cerebellum were seen. A greater extent of activation was evident in the right hemisphere and in the right half of the cerebellum.

The anterior insular-periinsular area and hippocampus can be considered as secondary olfactory areas in human brain. Strong activation of the right inferior frontal gyrus demonstrated in our study may be related to effort to name the presented odour. Activation of the cerebellum may be evaluated as a consequent phenomenon due to extensive activation of the frontal lobe.