Olfactive Event-Related Potentials and Volatile Organic Compound: from Physiological Response to Olfactory Perception

Several studies, analyzing the sensory components of olfactory stimuli, highlight laboriousness to estimate a precise stimulation interfaced in EEG and the consequent psychophysiological stimulus effect. Olfactory perception, starting with a breath, could elicit neuronal and cortical responses which could be investigated through Olfactory Event Related Potentials (OERPs). Nowadays no correlation has been examined between brain cortical response and physiological activation through respiratory markers. The purpose of this work is to investigate OERPs linked to breath physiology by using a new technological device dedicated to olfactory stimulation in EEG and a novel sensor able to detect biomarkers through the Volatile Organic Compound (VOCs). In order to record OERPs correlated to physiological effect on VOCs emission, we interfaced VOS EEG (MI2014A001344), a patent olfactometer connected to an electroencephalograph and an electronic sensor (e-nose iAQ-2000, Applied Sensor) for VOCs parallel recording. This condition allowed us to control olfactory stimulations and to relate them to psychophysiological responses. Consequently, we detected the olfactory response to record, for each given single step of stimulation, the EEG, the OERPs components and VOCs responses. The experimental settings allowed us to investigated, through OERPs and VOCs, the olfactory response to a neutral stimulus [Vaseline Oil CnH (2n+2)], and to a natural stimulus of rose characteristic odor (PEA, 2-phenyl ethanol C2H4O2). We recruited 15 safe adults (mean age 25 ±5 SD) non-smokers. Subjects performed a passive olfactory behavioral task during the experiment. Afterwards, the subjects filled the VAS on familiar and arousing stimuli dimensions. A general linear model repeated measure was performed on OERPs. Statistical analysis shows main OERPs results on slow potential components, in particular for P3b on Frontal right lobe (PEA p=.003) (PEA*arousing p=.023) in direction of a greater amplitude vs. control; N4 on right frontoparietal (PEA p=.037); and on right frontotemporal (p=.025) positions; N6 on right frontoparietal position (PEA p=.038) (PEA*arousing p=.009) both in direction of greater amplitude in PEA condition. The control exhaled VOCs frequencies are fitted by a normal distribution (single peak fit R2 = .8), PEA administration exhaled VOCs frequencies are fitted by a bimodal distribution (double peak fit R2 = .9). Exhaled VOCs are significantly different, according to the results of different cortical activation induced by olfactory stimulation. Our study suggests that in smell perception (both in odorous and neutral) we can observe the involvement of slow components, related to the breath of the subject, according to the time of perceptual processing. Furthermore, we connected in real time a given stimulus to olfactory cortical activation, analyzed through OERPs, and breath exhalation, as VOCs (physiological response), innovative connection never yet investigate.