Positive relationship between odor identification and affective responses of negatively valenced odors

Hedonic ratings of odors and olfactory preferences are influenced by a number of modulating factors, such as prior experience and knowledge about an odor's identity. The present study addresses the relationship between knowledge about an odor's identity due to prior experience, assessed by means of a test of cued odor identification, and odor pleasantness ratings in children who exhibit ongoing olfactory learning. Ninetyone children aged 8-11 years rated the pleasantness of odors in the Sniffin' Sticks test and, subsequently, took the odor identification test. A positive association between odor identification and pleasantness was found for two unpleasant food odors (garlic and fish): higher pleasantness ratings were exhibited by those participants who correctly identified these odors compared to those who failed to correctly identify them. However, we did not find a similar effect for any of the more pleasant odors. The results of this study suggest that pleasantness ratings of some odors may be modulated by the knowledge of their identity due to prior experience and that this relationship might be more evident in unpleasant odors

Time frequency analysis of olfactory induced EEG-power change

Objectives The objective of the present study was to investigate the usefulness of time-frequency analysis (TFA) of olfactory-induced EEG change with a low-cost, portable olfactometer in the clinical investigation of smell function. Materials & methods A total of 78 volunteers participated. The study was composed of three parts where olfactory stimuli were presented using a custom-built olfactometer. Part I was designed to optimize the stimulus as well as the recording conditions. In part II EEG-power changes after olfactory/trigeminal stimulation were compared between healthy participants and patients with olfactory impairment. In Part III the test-retest reliability of the method was evaluated in healthy subjects. Results Part I indicated that the most effective paradigm for stimulus presentation was cued stimulus, with an interstimulus interval of 18-20s at a stimulus duration of 1000ms with each stimulus quality presented 60 times in blocks of 20 stimuli each. In Part II we found that central processing of olfactory stimuli analyzed by TFA differed significantly between healthy controls and patients even when controlling for age. It was possible to reliably distinguish patients with olfactory impairment from healthy individuals at a high degree of accuracy (healthy controls vs anosmic patients: sensitivity 75%; specificity 89%). In addition we could show a good test-retest reliability of TFA of chemosensory induced EEG-power changes in Part III. Conclusions Central processing of olfactory stimuli analyzed by TFA reliably distinguishes patients with olfactory impairment from healthy individuals at a high degree of accuracy. Importantly this can be achieved with a simple olfactometer

EEG-power in response to olfactory stimulation.

<p>EEG-power in response to olfactory stimulation.</p

Stimulus conditions used in part I.

<p>Stimulus conditions used in part I.</p

Distinguishing between patients and normosmic participants by means of time-frequency analysis.

<p>Displayed are the AUC calculated by ROC analysis to distinguish between normosmic participants and dysosmic (hyposmic/anosmic) patients. The analysis revealed an AUC of 0.78 for the separation of normosmic participants and dysosmic patients. The analysis between normosmic participants and anosmic patients was even greater with an AUC of 0.91.</p

EEG-power change after olfactory, trigeminal and control stimulation (condition D).

<p>Displayed are the Cz EEG-power changes (group average including the 10 participants) after control (a), olfactory (b) and trigeminal (c) stimulation. The dashed black line marks the stimulus onset. An increase in low frequency within the ROI (red square) can be observed in b and c but not in a. The scale displays EEG-power change in percent compared to the pre-stimulus interval.</p

AUC in relation to different stimulus conditions.

<p>Displayed are the AUC calculated by ROC, a-d for olfactory and e-h for trigeminal stimulation for the four stimulus conditions. The largest AUC and therefore the highest sensitivity and specificity to distinguish between control and olfactory stimulation in terms of EEG-power change was obtained in condition D. The AUC analysis revealed only a significant AUC for trigeminal stimulation in condition B.</p

EEG-power change in response to trigeminal stimulation.

<p>EEG-power change in response to trigeminal stimulation.</p

Ethyl alcohol threshold test: a fast, reliable and affordable olfactory Assessment tool for COVID-19 patients

International audienceObjective: COVID-19 patients may present mild symptoms. The identification of paucisymptomatic patients is paramount in order to interrupt the transmission chain of the virus. Olfactory loss could be one of those early symptoms which might help in the diagnosis of COVID-19 patients. In this study, we aim to develop and validate a fast, inexpensive, reliable and easy-to-perform olfactory test for the screening of suspected COVID-19 patients. Study design: Phase I was a case–control study and Phase II a transversal descriptive study. Subjects and methods: Olfaction was assessed with the ethyl alcohol threshold test and symptoms with visual analogue scales. The study was designed in two phases: In Phase I, we compared confirmed COVID-19 patients and healthy controls. In Phase II, patients with suspected COVID-19 infection referred for testing were studied. Results: 275 participants were included in Phase I, 135 in Phase II. The ROC curve showed an AUC of 0.749 in Phase I, 0.737 in Phase II. The cutoff value which offered the highest amount of correctly classified patients was ≥ 2 (10% alcohol) for all age intervals. The odds ratio was 8.19 in Phase I, 6.56 in Phase II with a 75% sensitivity. When cases report normal sense of smell (VAS < 4), it misdiagnoses 57.89% of patients detected by the alcohol threshold test. Conclusion: The olfactory loss assessed with the alcohol threshold test has shown high sensitivity and odds ratio in both patients with confirmed COVID-19 illness and participants with suspected SARS-CoV-2 infection