Olfactory perceptual stability and discrimination

Neurobehavioral Institute, Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Norman, Oklahoma 73019, USA.
Nature Neuroscience (Impact Factor: 16.1). 01/2009; 11(12):1378-80. DOI: 10.1038/nn.2217
Source: PubMed


No two roses smell exactly alike, but our brain accurately bundles these variations into a single percept 'rose'. We found that ensembles of rat olfactory bulb neurons decorrelate complex mixtures that vary by as little as a single missing component, whereas olfactory (piriform) cortical neural ensembles perform pattern completion in response to an absent component, essentially filling in the missing information and allowing perceptual stability. This piriform cortical ensemble activity predicts olfactory perception.

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    • "In rodents, odor mixtures are processed differently by the olfactory bulb and primary olfactory (piriform) cortex (Wilson and Sullivan, 2011). For example, the activity of olfactory bulb mitral/tufted cell neural ensembles is strongly consistent with pattern separation processing– responding uniquely to even minor changes in mixture elements (Barnes et al., 2008; Chapuis and Wilson, 2011; Sahay et al., 2011). Thus, it has been hypothesized that olfactory bulb neural ensembles respond to odor mixture features or components, rather than to the mixture configuration. "
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    • "The animals were allowed to recover for at least 2 weeks, and then began training with odour mixture discrimination. For mixture discrimination training, animals were presented with two overlapping 10 component odorant mixtures, which have been described in detail elsewhere (Barnes et al. 2008; Chen et al. 2011; Chapuis & Wilson, 2012; Lovitz et al. 2012). The full 10 component mixture (10 c) included the monomolecular odorants: isoamyl acetate (100 p. "
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    ABSTRACT: Bilateral cortical circuits are not necessarily symmetrical. Asymmetry, or cerebral lateralization, allows functional specialization of bilateral brain regions and has been described in humans for such diverse functions as perception, memory and emotion. There is also evidence for asymmetry in the human olfactory system, though evidence in non-human animal models is lacking. Here, we took advantage of the known changes in olfactory cortical local field potentials that occur over the course of odor discrimination training to test for functional asymmetry in piriform cortical activity during learning. Both the right and left piriform cortex local field potential activities were recorded. The results demonstrate robust inter-hemispheric asymmetry in anterior piriform cortex activity that emerges during specific stages of odor discrimination learning, with a transient bias toward the left hemisphere. This asymmetry is not apparent during error trials. Furthermore, functional connectivity (coherence) between the bilateral anterior piriform cortices is learning- and context-dependent. Steady-state inter-hemispheric anterior piriform cortex coherence is reduced during initial stages of learning and then recovers as animals acquire competent performance. The decrease in coherence is seen relative to bilateral coherence expressed in the home cage, which remains stable across conditioning days. Similarly, transient, trial-related inter-hemispheric coherence increases with task competence. Together the results demonstrate transient asymmetry in piriform cortical function during odor discrimination learning until mastery, and suggests that each PCX may contribute something unique to odor memory.This article is protected by copyright. All rights reserved
    The Journal of Physiology 01/2015; 593(7). DOI:10.1113/jphysiol.2014.288381 · 5.04 Impact Factor
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    • "After successfully (>80% correct) mastering this task, they were switched to a mixture discrimination task. This task used odor mixtures described in Barnes et al., [29]. These mixtures were composed of 9–10 components, with concentration based on vapor pressure and dilution in mineral oil. "
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    ABSTRACT: Alzheimer's disease is a neurodegenerative disorder that is the most common cause of dementia in the elderly today. One of the earliest reported signs of Alzheimer's disease is olfactory dysfunction, which may manifest in a variety of ways. The present study sought to address this issue by investigating odor coding in the anterior piriform cortex, the primary cortical region involved in higher order olfactory function, and how it relates to performance on olfactory behavioral tasks. An olfactory habituation task was performed on cohorts of transgenic and age-matched wild-type mice at 3, 6 and 12 months of age. These animals were then anesthetized and acute, single-unit electrophysiology was performed in the anterior piriform cortex. In addition, in a separate group of animals, a longitudinal odor discrimination task was conducted from 3-12 months of age. Results showed that while odor habituation was impaired at all ages, Tg2576 performed comparably to age-matched wild-type mice on the olfactory discrimination task. The behavioral data mirrored intact anterior piriform cortex single-unit odor responses and receptive fields in Tg2576, which were comparable to wild-type at all age groups. The present results suggest that odor processing in the olfactory cortex and basic odor discrimination is especially robust in the face of amyloid β precursor protein (AβPP) over-expression and advancing amyloid β (Aβ) pathology. Odor identification deficits known to emerge early in Alzheimer's disease progression, therefore, may reflect impairments in linking the odor percept to associated labels in cortical regions upstream of the primary olfactory pathway, rather than in the basic odor processing itself.
    PLoS ONE 09/2014; 9(9):e106431. DOI:10.1371/journal.pone.0106431 · 3.23 Impact Factor
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