Abstract
Olfactory processing starts with the breath and elicits neuronal, metabolic and cortical responses. This process can be investigated centrally via the Olfactory Event-Related Potentials (OERPs) and peripherally via exhaled Volatile Organic Compounds (VOCs). Despite this, the relationship between OERPs (i.e., N1 and Late Positive Component LPC) and exhaled VOCs has not been investigated enough. The aim of this research is to study OERPs and VOCs connection to two different stimuli: phenylethyl alcohol (PEA) and Vaseline Oil (VO). Fifteen healthy subjects performed a perceptual olfactory task with PEA as a smell target stimulus and VO as a neutral stimulus. The results suggest that OERPs and VOCs distributions follow the same amplitude trend and that PEA is highly arousing in both psychophysiological measures. PEA shows ampler and faster N1, a component related to the sensorial aspect of the stimulus. The N1 topographic localization is different between PEA and VO: PEA stimulus evokes greater N1 in the left centroparietal site. LPC, a component elicited by the perceptual characteristic of the stimulus, shows faster latency in the Frontal lobe and decreased amplitude in the Central and Parietal lobe elicited by the PEA smell. Moreover, the delayed time between the onset of N1-LPC and the onset of VOCs seems to be about 3 s. This delay could be identified as the internal metabolic time in which the odorous stimulus, once perceived at the cortical level, is metabolized and subsequently exhaled. Furthermore, the VO stimulus does not allocate the attentive, perceptive and metabolic resource as with PEA.
Highlights
We investigated the trend between Olfactory Event-Related Potentials (OERPs) and the exhaled Volatile Organic Compounds (VOCs) during the phenylethyl alcohol (PEA) sensorial stimulation and the Vaseline Oil sensorial stimulation [48], focusing in particular on N1 and Late Positive Component (LPC) OERPs components, the main components elicited during an olfactory perceptive task [16,28]
N1 and LPC component; as the Within Factor we considered Smell (PEA, Vaseline Oil), and Electrodes
Our investigation is focused on how the olfactory system produces, through the receptor and cortical response, a perceptual variation induced by stimulation and how and when the metabolic system could be affected
Summary
The olfactory function, placed in a cortical localization connected to areas dedicated to emotional and mnestic activations (e.g., hippocampus, entorhinal cortex, amygdala), seems to be a borderline function between “perceptions”. The olfactive function strongly involves and modulates metabolic aspects [3,4], and this peculiarity is more clearly. Brain Sci. 2019, 9, 84 overt if compared to other sensory modalities. Different to olfactory animal models [5,6,7,8], the olfactory whole pathway, linked to human perceptions, has been largely unexplored and needs full investigation because it is a complex sense that has a sensorial/perceptive finality but guides internal chemical cues, such as metabolism [3].
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