In this study we recorded the electroencephalograms (EEGs) of humans during exposure to the odorant stimuli. The EEGs were divided into superficial components and deep components by a source derivation (SD) method, and each superficial and deep component of the EEGs was divided into an inspiratory phases and an expiratory phase.
The subjects were 13 euosmic adults. Strawberry ice syrup (strawberry smell), β-phenylethyl alcohol (rose smell), and prosultiamine (Alinamin smell) were used as odorant stimuli. We analyzed the power spectrum of each EEG by fast Fourier transform (FFT) and calculated the spectrum density (power value) for each frequency band (δ, θ, α 1, α 2, β 1, β 2).
Stimulation with each of the three odorants decreased the power value of the θband. Division of the EEGs into an inspiratory phase and an expiratory phase showed that all three olfactory stimuli decreased the power value of the θband. A decreased power value of the θband in the expiratory phase was found in a deep component in response to the strawberry and rose odors, and appeared to be a response to an agreeable smell. The change in the θband appeared to be related to recognition of the smell in the inspiratory phase. The decreased power value of the α1 band was concentrated in the right region on the scalp in the breathing phase, the inspiratory phase, and the expiratory phase. It showed a significant response only to the strawberry smell. The decreased β1 power value occurred in response to the strawberry in the deep component of the breathing phase.
Division of the EEGs into an inspiratory phase and an expiratory phase showed that there is a difference of EEG responses in kinds of odor stimuli. And also division of the EEGs by SD method there is a difference between superficial and deep components in EEGs.
