Time Course of Perceptual Adaptation Differs among Odorants

Abstract

Perceptual adaptation, a fundamental property of all sensory systems, functions to attenuate neural and perceptual responses to sustained or redundant stimulation as a means of limiting neural saturation and of enhancing the detection of new transient stimuli. While our understanding of the complex physiological mechanisms underlying adaptation has grown in recent years, how these processes are affected by individual odorant properties remains unclear. Recent data from our laboratory demonstrate that the onset time course of perceptual odor adaptation can be estimated by use of a simultaneous‐odorant‐stimulus paradigm, where the delay from the onset of a relatively long‐duration adapting odorant to the onset of a brief target odorant is varied. Adaptation was observed as an increase in threshold with increasing adapting‐to‐target‐odorant onset delay. Using this technique, we compared the estimated onset time course for four common odorants (vanilla extract, coconut extract, vinegar and propanol). Thresholds were estimated for a brief target odorant presented during a simultaneous adapting odorant in a group of college‐aged student volunteers (n = 124; 88 females). Onset of adaptation for the vanilla and coconut mixtures was more rapid than for vinegar and propanol, though the asymptotic levels (approximately 400 ms) of adaptation were similar for coconut extract, vanilla extract and vinegar. In contrast, propanol did not reach asymptotic levels within the 1,000‐ms timeframe. Considering propanol is a pure alcohol, relative differences in trigeminal reactivity may partially explain this variance in adaptation contours. Practical Applications A method for capturing rapid changes in response to odor adaptation is described. The automated method can be reliably used to compare both the magnitude and time course for a wide range of stimuli. The technique may be reproduced to evaluate how individual olfactory sensitivity changes in response to prolonged stimulation. Importantly, this procedure can be used to assess shifts in odor perception on rapid timescales – in the 50–100‐ms range, rather than seconds or minutes.

Changes in olfactory function after immersive exposure to odorants

“…In terms of the number and category of odorants, most previous studies (Birte-Antina et al, 2018;Haehner et al, 2013) used only four odorants from four different categories (i.e., flowery, fruity, spicy, and resinous; Oleszkiewicz, Hanf, et al, 2018;Oleszkiewicz, Würfel, et al, 2018). Given previous studies have demonstrated using molecularly diverse odorants may promote threshold sensitivity (Oleszkiewicz, Würfel, et al, 2018) and using a small sample of odorants may reduce sensitivity due to adaptation effects (Yoder et al, 2013), having a large variety of olfactory stimuli to train with is important. In the current study, 72 different odorants from 10 categories were presented to patients.…”

The vulnerability of human sensory evaluation and the promising senses instrumentation

“…Human sensory evaluation is vulnerable to individual variability, which is derived from birth-given sensitivity and declining sensitivity due to continuous exposure of a particular substance, i.e., brain adaptation mechanism or sensory fatigue. A research done by Yoder et al (2013) has successfully incorporated threshold measurement to analyze not only birth-given sensitivity, but also adaptation mechanism. The adaptation mechanism was observed as an increase in threshold with increasing adapting-to-target-odorant onset delay.…”

“…The sensory evaluation that is integrated to daily quality control process is vulnerable to the sensory fatigue, resulting in an unreliable sensory interpretation. O’Mahony and Wong (1989) observed the fatigue effect on taste evaluation of NaCl and MSG, while Yoder et al (2013) specifically observed the fatigue effect on odor evaluation of vanilla extract, coconut extract, vinegar, and propanol. Due to its high dependency on products characteristics and panelists endurance, there is no rigid rule to avoid the fatigue effect during the sensory evaluation.…”

Effects of Scent and Scent Emission Methods: Implications on Workers’ Alertness, Vigilance, and Memory under Fatigue Conditions

“…Dalton and Wysocki (1996) suggested that scent should be emitted intermittently to maintain the intensity as long-term continuous exposure to a scent may cause sensory adaptation (i.e., one becomes less sensitive to that scent). Sensory adaptation involves reduced synaptic activity to avoid neural saturation, enabling adaptive detection of new and different stimuli (Yoder et al, 2013). People habituate to repeatedly experienced stimuli such that the same stimuli no longer elicit the initial response (Wilson, 2008).…”