Olfactory Perception: A Review of Cognitive Research Methods

Introduction. Olfaction, as one of the cognitive tools, participates in shaping our perception of the surrounding world together with other sensory modalities and has a direct impact on human behavior. This article is devoted to methods used to study olfactory perception and related cognitive functions. The evaluated methods were divided according to the criterion of the need for a conscious response from the participants, with further indication of their application characteristics in interdisciplinary research.

Objective. To analyze and classify methods to assess olfactory perception and related cognitive functions.

Subjective methods of olfactory assessment. Subjective methods for studying and evaluating olfactory perception included psychophysical methods, among which tests to determine thresholds for odor detection thresholds, discrimination, and odor identification. These include the single-staircase odor detection threshold test, the University of Pennsylvania Smell Identification Test (UPSIT), and others. Psychometric methods for assessing olfactory perception, also classified as subjective, are represented by the following instruments. Affective Impact of Odor Scale (AIO), Olfactory Awareness Scale (OAS), Importance of Olfaction Questionnaire (IOQ), Emotional Relational Olfactory Scale (EROL), Chemical Intolerance Index (CII), Chemical Sensitivity Scale (CSS), Chemical Odor Sensitivity Scale (COSS), Child's Olfactory Behavior in Everyday Life Questionnaire (COBEL) and Child Odor Influence on Parental Behavior Scale (COPs).

Objective methods of olfactory assessment. Objective methods of studying and assessing olfactory perception included psychophysiological, electrophysiological, and imaging techniques. Among the relationships established in psychophysiological experiments, changes in heart rate, respiratory rate, and amplitude and duration of skin electrical conductivity were recorded as a result of exposure to various olfactory stimuli. In neuroimaging and electrophysiological studies of the olfactory analyzer, magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), electroolfactography, and electroencephalography are commonly used.

Discussion. The literature analysis showed that subjective evaluation methods can reveal and evaluate both olfactory function disorders and perceptual responses to odors. In turn, objective methods can help determine the cause of olfactory dysfunction, investigate neural processing of odors, and correlate olfactory perception. Modern studies of olfactory perception use an interdisciplinary approach that combines psychophysics, neuroimaging, and behavioral experiments, which allows for a deeper understanding of how the brain processes odors and their influence on cognitive processes. The results of olfactory perception studies conducted using subjective methods serve as a useful complement to the results obtained from the research using the objective method.

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