Time-course of trigeminal versus olfactory stimulation: Evidence from chemosensory evoked potentials

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Habituation is a filter that optimizes the processing of information by our brain in all sensory modalities. It results in an unconscious reduced responsiveness to continuous or repetitive stimulation. In olfaction, the main question is whether habituation works the same way for any odorant or whether we habituate differently to each odorant? In particular, whether chemical, physical or perceptual cues can limit or increase habituation. To test this, the odour intensity of 32 odorants differing in physicochemical characteristics was rated by 58 participants continuously during 120s. Each odorant was delivered at a constant concentration. Results showed odorants differed significantly in habituation, highlighting the multifactoriality of habituation. Additionally habituation was predicted from 15 physico-chemical and perceptual characteristics of the odorants. The analysis highlighted the importance of trigeminality which is highly correlated to intensity and pleasantness. The vapour pressure, the molecular weight, the Odor Activity Value (OAV) and the number of double bonds mostly contributed to the modulation of habituation. Moreover, length of the carbon chain, number of conformers and hydrophobicity contributed to a lesser extent to the modulation of habituation. These results highlight new principles involved in the fundamental process of habituation, notably trigeminality and the physicochemical characteristics associated.

Section: Discussionmentioning

confidence: 99%

New determinants of olfactory habituation

Sinding

Valadier²,

Al-Hassani

et al. 2017

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“…The better lateralization performance in experiment 1 might be due to the aforementioned substance interaction where the alternating stimulation with EA may have enhanced the perception and thus the localizability of AcOH. Alternatively, it is possible that participants habituated to the stimulation of AcOH in experiment 2 due to repeated presentation of the same substance 60 . The decreased perception could have complicated the localization.…”

Section: Discussionmentioning

confidence: 99%

Somatosensory Response to Trigeminal Stimulation: A Functional Near-Infrared Spectroscopy (fNIRS) Study

Hucke

Pacharra

Reinders

et al. 2018

Functional near-infrared spectroscopy (fNIRS) is an optical imaging technique measuring relative hemodynamic changes in superficial cortical structures. It has successfully been applied to detect a hemodynamic response in the somatosensory cortex evoked by irritating mechanical, electrical, and heat stimulations of limbs or the face. The aim of the current study was to explore the feasibility of fNIRS to detect respective responses evoked by irritating chemical stimulations of the nasal divisions of the trigeminal nerve. In two experiments, healthy subjects were exposed to acetic acid and ethyl acetate presented using a respiration-synchronized olfactometer. Results demonstrated that fNIRS can detect a signal in both hemispheres after birhinal (experiment 1: n = 14) and monorhinal (experiment 2: n = 12) stimulations using acetic acid but not ethyl acetate. This is a first evidence that fNIRS might be a suitable imaging technique to assess chemosensory neuronal correlates in the somatosensory cortex thereby offering a new, portable method to evaluate the irritating properties of certain volatiles in an objective, nonverbal, easy, and comparably inexpensive manner.

“…NP and PP peaks were determined as the most negative and the most positive peaks, respectively, between (40 and 200) ms in the ERP data of each participant according to previous studies 16,17,29 . For the comparison with negative and positive peaks in the previous odor habituation study 23 , the most negative peak between (200 and 700) ms (N1) and the most positive peak between (300 and 800) ms (P2) were also selected.…”

Section: Methodsmentioning

confidence: 99%

“…An examination of ERP data could provide evidence of temporal changes in brain signals during odor habituation. In recent studies, ERP signals with negative potential at (200-700) ms (N1) and positive potential at (300-800) ms (P2) changed during odor habituation 22,23 . These studies in rodents and humans suggest that during odor habituation processing, temporal changes in the brain signals can exist.…”

mentioning

confidence: 99%

“…Some lines of evidence suggest that similar to animal studies, the time of odor signal processing in the human brain could be earlier than 200 ms. Previous odor habituation ERP studies in humans [22][23][24][25] mainly focused on odor signals in the brain after 200 ms, because they were partially based on previous studies of OSNs from the olfactory epithelium 26,27 . These studies observed that the time of odor signal processing by OSNs was about 300 ms.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Odor habituation can modulate very early olfactory event-related potential

Kim

Bae

Young-Sun

et al. 2020

Odor habituation is a phenomenon that after repeated exposure to an odor, is characterized by decreased responses to it. The central nervous system is involved in odor habituation. To study odor habituation in humans, measurement of event-related potentials (ERPs) has been widely used in the olfactory system and other sensory systems, because of their high temporal resolution. Most previous odor habituation studies have measured the olfactory ERPs of (200–800) ms. However, several studies have shown that the odor signal is processed in the central nervous system earlier than at 200 ms. For these reasons, we studied whether when odors were habituated, olfactory ERP within 200 ms of odors could change. To this end, we performed an odor habituation behavior test and electroencephalogram experiments. In the behavior test, under habituation conditions, odor intensity was significantly decreased. We found significant differences in the negative and positive potentials within 200 ms across the conditions, which correlated significantly with the results of the behavior test. We also observed that ERP latency depended on the conditions. Our study suggests that odor habituation can involve the olfactory ERP of odors within 200 ms in the brain.