Abstract
EEGs of twelve normal subjects were recorded during pleasant (β-Phenyl ethyl alcohol: odor A) and unpleasant (Iso-valeric acid: odor C) odor stimulations using Olfactometer <Takasuna, Co. LTD). Each odor was tested and divided into individual threshold and recognition levels. Respiratory volume and flow, and EEG were simultaneously recorded to determine the onset of inspirations for averaging EEG. Respiratory frequency decreased significantly in odor A recognition (A-R) (P<0.01) and increased in odor C threshold (C-T) and odor C recognition (C-R)(P<0.001, respectively). There were no changes in O2 consumption and CO2 production in all tests. Averaged potentials triggered by onset of inspiration found that there were three positive waves observed during 500ms after inspiring. According to power spectra of these waves, there were significant increases of alpha power on the electrodes except in parietal-occipital areas in A-R and C-R compared with others. The dipole tracing method estimated that dipoles were located in the entorhinal (ENT), centro posterior orbitofrontal (OFC) in A threshold (A-T), and also in the amygdala in C-T. In odor recognition, dipoles were estimated in the ENT and rostmedial OFC, and in the hippocampus in C-R. In general, alpha waves generate from the thalamus. We suggest that there is a link between alpha rhythm generator and brain areas related to odor perception. [Jpn J Physiol 54 Suppl:S193 (2004)]
