Topographical EEG Maps of Human Responses to Odorants — A Preliminary Report

Abstract

EEG recordings from 19 scalp loci from 10 young adult females were used to assess the physiological response to seven odorants (birch tar, galbanum, heliotropine, jasmine, lavender, lemon, and peppermint). The odorants were randomly delivered to a face mask via valve-selectable tubing pathways that diverted air flow through one of seven sample vials or through an empty vial to serve as a control. Subjects first scored the odors on a scale of 1–9 along continua for sleep-arousal, intensity, and pleasantness. Topographic maps were constructed from the amplitude spectra in the frequency bands of delta (1–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), and beta (13–30 Hz). Eight seconds of representative and artifact-free EEG were selected for FFT analysis before onset of stimulus delivery, and at three times after stimulus onset. EEG was also quantified at 30 seconds after stimulus termination.

Subjects differed in their subjective responses to the various odor­ants, with the most consistently arousing and strong odors being galbanum, lavender, and lemon. Heliotropine was notably weak. The most pleasant odors were lemon and peppermint, while Lavender was consistently unpleas­ant. All subjects showed EEG map changas for several odorants, although the odorants giving the most pronounced EEG map changes differed across subjects. EEG map responses typically involved several-to-many scalp loci in one or more frequency bands. EEG map changes were seen even to weak odors and even in some cases when the subject was not consciously aware of stimulus presentation. These methods seem appropriate for evaluating odors. They have the potential for testing many hypotheses.