Article

Characteristic component odors emerge from mixtures after selective adaptation.

Department of Psychology, Cornell University, Ithaca, NY, USA.
Brain Research Bulletin (Impact Factor: 2.97). 05/2007; 72(1):1-9. DOI: 10.1016/j.brainresbull.2006.12.010
Source: PubMed

ABSTRACT Humans cannot reliably identify the distinctive characteristic odors of components in mixtures containing more than three compounds. In the present study, we demonstrate that selective adaptation can improve component identification. Characteristic component odors, lost in mixtures, were identifiable after presenting other mixture constituents for a few seconds. In mixtures of vanillin, isopropyl alcohol, l-menthol and phenethyl alcohol, this rapid selective adaptation unmasked each component. We suggest that these findings relate directly to how olfactory qualities are coded: olfactory receptors do not act as detectors of isolated molecular features, but likely recognize entire molecules closely associated with perceived olfactory qualities or "notes". Rapid and focused activation of a few distinct receptor types may dominate most odor percepts, emphasizing the importance of many dynamic and specific neural signals. An interaction between two fundamental coding strategies, mixture suppression and selective adaptation, with hundreds of potential olfactory notes, explains humans experiencing the appearance and disappearance of identifiable odors against ambient mixture backgrounds.

0 Followers
 · 
62 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Smelling monomolecular odors hardly ever occurs in everyday life, and the daily functioning of the sense of smell relies primarily on the processing of complex mixtures of volatiles that are present in the environment (e.g., emanating from food or conspecifics). Such processing allows for the instantaneous recognition and categorization of smells and also for the discrimination of odors among others to extract relevant information and to adapt efficiently in different contexts. The neurophysiological mechanisms underpinning this highly efficient analysis of complex mixtures of odorants is beginning to be unraveled and support the idea that olfaction, as vision and audition, relies on odor-objects encoding. This configural processing of odor mixtures, which is empirically subject to important applications in our societies (e.g., the art of perfumers, flavorists, and wine makers), has been scientifically studied only during the last decades. This processing depends on many individual factors, among which are the developmental stage, lifestyle, physiological and mood state, and cognitive skills; this processing also presents striking similarities between species. The present review gathers the recent findings, as observed in animals, healthy subjects, and/or individuals with affective disorders, supporting the perception of complex odor stimuli as odor objects. It also discusses peripheral to central processing, and cognitive and behavioral significance. Finally, this review highlights that the study of odor mixtures is an original window allowing for the investigation of daily olfaction and emphasizes the need for knowledge about the underlying biological processes, which appear to be crucial for our representation and adaptation to the chemical environment.
    Frontiers in Psychology 06/2014; 5:504. DOI:10.3389/fpsyg.2014.00504 · 2.80 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ethylphenols are micro-organism-derived compounds that contribute to the Brett character in wine. These chemicals give off characteristic odors, associated with descriptors such as phenolic, pharmaceutical, stable, leather, and horse. Their organoleptic impact on wine is a recurring debate among wine professionals. However, links between these compounds and an attenuation of fruity and varietal aromas in wine have been demonstrated, while several studies have highlighted the poor correlation between ethylphenol concentrations and the perception of Brett character. These variations in assessment may be explained by several perceptual factors. This article presents an investigation of perceptual skills and socio-professional parameters that affect ethylphenol assessment. As tasting performance relies on both perceptual skills and a decision-making process, several psychophysical tests (detection threshold, description task, and the Signal Detection Theory methodology) were used to assess the impact of socio-professional parameters on olfactory capacities and strategic/decisional factors. The hypothesis that expertise, in terms of age and qualifications, had an impact on the assessment of Brett character was confirmed.
    Food Quality and Preference 06/2014; 34:29–36. DOI:10.1016/j.foodqual.2013.12.007 · 2.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: By attenuating neural and perceptual responses to sustained stimulation, adaptation enhances the detection of new, transient stimuli. Disadaptation serves a similarly important role as a temporal filter for chemoreceptor cells, producing rapid recovery of sensitivity upon termination of the adapting odorant. Previous research from our laboratory indicated that a rapid form of odor adaptation can be measured using a novel, simultaneous-odorant paradigm. In the present study, we extended the earlier method by measuring recovery from adaptation. Perceptual odor adaptation was measured by estimating psychophysical detection thresholds in a group of college-aged student volunteers (N = 20; 12 females, eight males) for a self-adapting odorant, vanilla extract. To induce adaptation, the time between the onset of the adapting odorant and the onset of the target odorant was systematically varied. By first quantifying adaptation, recovery of sensitivity could therefore be investigated by using different time points following the termination of the adapting odorant. Consistent with our previous work, thresholds estimated in the presence of the simultaneous adapting odorant were significantly increased, reflecting a decrease in sensitivity due to adaptation. Conversely, approximately 100 ms following termination of the adapting stimulus (the briefest delay tested), sensitivity began to rapidly recover. Nevertheless, some residual adaptation was evident at the longest offset delay of 500 ms. These findings suggest that the recovery from adaptation proceeds at least as rapidly as the onset of adaptation, a finding that is consistent with physiological evidence from olfactory receptors. These data also suggest the effectiveness of this new odorant paradigm in characterizing the temporal characteristics underlying these critical olfactory mechanisms.
    Attention Perception & Psychophysics 02/2014; 76(4). DOI:10.3758/s13414-013-0620-0 · 2.15 Impact Factor

Full-text (2 Sources)

Download
6 Downloads
Available from
Sep 15, 2014