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Brain waves spectral analysis of human responses to odorous and non-odorous substances: a preliminary study

Chow XH, Ting CM, Wan Hamizan AK, Zahedi FD, Tan HJ, Remli R, et al.

J Laryngol Otol, 2024 Mar;138(3):301-309.
PMID: 37259908 DOI: 10.1017/S0022215123000919

OBJECTIVE: The aim of this study was to identify the potential electrophysiological biomarkers of human responses by comparing the electroencephalogram brain wave changes towards lavender versus normal saline in a healthy human population.
METHOD: This study included a total of 44 participants without subjective olfactory disturbances. Lavender and normal saline were used as the olfactory stimulant and control. Electroencephalogram was recorded and power spectra were analysed by the spectral analysis for each alpha, beta, delta, theta and gamma bandwidth frequency upon exposure to lavender and normal saline independently.
RESULTS: The oscillatory brain activities in response to the olfactory stimulant indicated that the lavender smell decreased the beta activity in the left frontal (F7 electrode) and central region (C3 electrode) with a reduction in the gamma activity in the right parietal region (P4 electrode) (p < 0.05).
CONCLUSION: Olfactory stimulants result in changes of electrical brain activities in different brain regions, as evidenced by the topographical brain map and spectra analysis of each brain wave.

Matched MeSH terms: Smell/physiology
Olfactory dysfunction in patients with idiopathic intracranial hypertension

Khoo KF, Kunte H

Neurology, 2014 Jan 14;82(2):189.
PMID: 24419980 DOI: 10.1212/01.wnl.0000442872.80558.6c
Matched MeSH terms: Smell/physiology*
Our sense of smell at the crossroads

Gross M

Curr Biol, 2015 Mar 02;25(5):R173-6.
PMID: 25897437
Matched MeSH terms: Smell/physiology*
Global Study of Social Odor Awareness

Sorokowska A, Groyecka A, Karwowski M, Frackowiak T, Lansford JE, Ahmadi K, et al.

Chem. Senses, 2018 08 24;43(7):503-513.
PMID: 29955865 DOI: 10.1093/chemse/bjy038

Olfaction plays an important role in human social communication, including multiple domains in which people often rely on their sense of smell in the social context. The importance of the sense of smell and its role can however vary inter-individually and culturally. Despite the growing body of literature on differences in olfactory performance or hedonic preferences across the globe, the aspects of a given culture as well as culturally universal individual differences affecting odor awareness in human social life remain unknown. Here, we conducted a large-scale analysis of data collected from 10 794 participants from 52 study sites from 44 countries all over the world. The aim of our research was to explore the potential individual and country-level correlates of odor awareness in the social context. The results show that the individual characteristics were more strongly related than country-level factors to self-reported odor awareness in different social contexts. A model including individual-level predictors (gender, age, material situation, education, and preferred social distance) provided a relatively good fit to the data, but adding country-level predictors (Human Development Index, population density, and average temperature) did not improve model parameters. Although there were some cross-cultural differences in social odor awareness, the main differentiating role was played by the individual differences. This suggests that people living in different cultures and different climate conditions may still share some similar patterns of odor awareness if they share other individual-level characteristics.

Matched MeSH terms: Smell/physiology*
Analysis of the Influence of Complexity and Entropy of Odorant on Fractal Dynamics and Entropy of EEG Signal

Namazi H, Akrami A, Nazeri S, Kulish VV

Biomed Res Int, 2016;2016:5469587.
PMID: 27699169

An important challenge in brain research is to make out the relation between the features of olfactory stimuli and the electroencephalogram (EEG) signal. Yet, no one has discovered any relation between the structures of olfactory stimuli and the EEG signal. This study investigates the relation between the structures of EEG signal and the olfactory stimulus (odorant). We show that the complexity of the EEG signal is coupled with the molecular complexity of the odorant, where more structurally complex odorant causes less fractal EEG signal. Also, odorant having higher entropy causes the EEG signal to have lower approximate entropy. The method discussed here can be applied and investigated in case of patients with brain diseases as the rehabilitation purpose.

Matched MeSH terms: Smell/physiology*
Is the perception of odour pleasantness shared across cultures and ecological conditions? Evidence from Amazonia, East Africa, New Guinea, Malaysia and Poland

Sorokowski P, Misiak M, Roberts SC, Kowal M, Butovskaya M, Omar-Fauzee MS, et al.

Biol Lett, 2024 Jun;20(6):20240120.
PMID: 38863390 DOI: 10.1098/rsbl.2024.0120

What makes an odour pleasant or unpleasant? The inherent properties of the constituent chemical compounds, or the nose of the beholder, driven by idiosyncratic differences and culture-specific learning? Here, 582 individuals, including Tanzanian Hadza hunter-gatherers, Amazonian Tsimane' horticulturalists, Yali from the Papuan highlands and two industrialized populations (Poles, Malaysians), rated the pleasantness of 15 odour samples. We find considerable similarities in odour assessments across cultures, but our data do not fully support a claim regarding the universality of smell preferences. Despite cross-cultural similarities in olfactory assessments, probably driven by odour properties, we suggest that odour availability in ecological and cultural niches bears an undeniable effect on human odour preferences.

Matched MeSH terms: Smell/physiology
Fulltext Taste, smell and food-related nausea and vomiting responses in hyperemesis gravidarum: A case-controlled study

Tan PC, Kartik B, Thanendran P, Zakaria R, Win ST, Omar SZ

Sci Rep, 2020 03 10;10(1):4445.
PMID: 32157169 DOI: 10.1038/s41598-020-61114-y

A case-controlled study was performed to evaluate taste and smell impairment, nausea or vomiting (NV) response to taste and smell and toleration to food texture, item and cooking method in hyperemesis gravidarum patients (HG) compared to gestation-matched controls from a university hospital and primary care clinic in Malaysia. Taste strips (4 base tastes), sniff sticks (16 selected smells) and a food-related questionnaire were used. 124 participants were recruited. Taste impairment was found in 13%(8/62) vs. 0%(0/62) P = 0.003 and the median for correct smell identification was 5[4-6] vs. 9[7-9] P smell was most likely to provoke NV, 77% vs. 32% P smell least likely 10% vs. 0% P = 0.012; NV response was significantly more likely for HG arm in 10/16 smells. In HG, worst and best NV responses to food-texture were pasty 69% and crunchy 26%; food-item, plain rice 71% and apple 16% and cooking-style, deep-frying 71% and steaming 55%. HG demonstrated taste and smell impairment and increased NV responses to many tastes and smells. Crunchy sweet uncooked food (apple or watermelon) maybe best tolerated in HG.

Matched MeSH terms: Smell/physiology*
Mimicking the biological olfactory system: a Portable electronic Mucosa

Che Harun FK, Covington JA, Gardner JW

IET Nanobiotechnol, 2012 Jun;6(2):45-51.
PMID: 22559706 DOI: 10.1049/iet-nbt.2010.0032

In this study the authors report on the development of a new type of electronic nose (e-nose) instrument, which the authors refer to as the Portable electronic Mucosa (PeM) as a continuation of previous research. It is designed to mimic the human nose by taking significant biological features and replicating them electronically. The term electronic mucosa or simply e-mucosa was used because our e-nose emulates the nasal chromatographic effect discovered in the olfactory epithelium, located within the upper turbinate. The e-mucosa generates spatio-temporal information that the authors believe could lead to improved odour discrimination. The PeM comprises three large sensor arrays each containing a total of 576 sensors, with 24 different coatings, to increase the odour selectivity. The nasal chromatographic effect provides temporal information in the human olfactory system, and is mimicked here using two-coated retentive channels. These channels are coated with polar and non-polar compounds to enhance the selectivity of the instrument. Thus, for an unknown sample, the authors have both the spatial information (as with a traditional e-nose) and the temporal information. The authors believe that this PeM may offer a way forward in developing a new range of low-cost e-noses with superior odour specificity.

Matched MeSH terms: Smell/physiology