The pilot study of weak changes in the spatial EEG activity of healthy test subjects in a passive wakefulness with odors impacts

Abstract

The search for changes in the brain activity of the subjects directly related to the odors effects has attracted considerable interest among researchers since the late 1980s [Lorig, Tyler S., and Gary E. Schwartz. "Brain and odor: I. Alteration of human EEG by odor administration." Psychobiology 16.3 (1988): 281-284; Klemm, W. R., et al. "Topographical EEG maps of human responses to odors." Chemical senses 17.3 (1992): 347-361; Ezzatdoost, Kiana, Hadi Hojjati, and Hamid Aghajan. "Decoding Olfactory Stimuli in EEG Data using Nonlinear Features: A Pilot Study." Journal of Neuroscience Methods (2020): 108780]. Among the existing techniques, electroencephalography (EEG) is widely used because of its low setup costs, easy implementation and noninvasive nature. However, basically, research of the odors perception are associated with the study of changes in the emotional states of people under their influence. In the present work, the subject feels the repeated weak effect of the aroma in a calm environment, without additional stimuli. The aim of this work is to search for a physiological response with the exception of changes in the emotional and/or perceived state of a person.
The data were obtained from a small homogeneous group of 10 subjects (practically healthy, men, 20 - 35 aged). An innovative scenario of a pilot psychophysiological experiment based on the use of a special engineering device has been implemented. This device was used to periodically deliver a neutral mint odor to the subjects using a fixed face mask. The scent was supplied for 5 breaths of the subject, after which normal air entered the mask again during 2 - 5 minutes. The duration of the pause was varied at random in order to avoid the occurrence of addiction. During the first 10 minutes of the experimental work, no odors were added to the face mask. The total duration of the experiment was about 40 minutes. During the entire experiment, the subjects were in a light room in a state of calm passive wakefulness. The experimental work was carried out for one week in the first half of the day (10 - 12 a.m.) in clear sunny weather without abrupt changes in weather conditions.
On the basis of a comprehensive analysis of oscillatory EEG - activity, statistically significant changes were found for the frontal and parietal projections of the cerebral cortex that occur when exposed to odor. We described changes of the same type within the group in the ratio of the powers of the observed vibrational activity in standard neurophysiological ranges.

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Kamila Samatova
Saratov State Medical University
Russia

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