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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Available from: Donald A Wilson, Oct 09, 2015
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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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    • "Piriform pyramidal neuron feedback projections onto OB granule cells also exhibit spike timing-dependent LTP (Gao and Strowbridge, 2009), which may be a particularly powerful computational element given the importance of dynamical, timing-dependent interactions within OB circuitry. Contemporary models of OB-piriform computations have regarded these circuits as a pattern separation/completion network not unlike the dentate gyrus/CA1 circuit of hippocampus, in which piriform association fibers underlie pattern completion (Hasselmo et al., 1992; Barnes et al., 2008) and their feedback projections onto inhibitory granule cells within OB underlie pattern separation (Strowbridge, 2009), within a common recurrent circuit. This rich and structured plasticity requires further experimental and theoretical development, but exemplifies the capacities of the olfactory system as a model for understanding complex memory systems. "
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    ABSTRACT: Memories are dynamic physical phenomena with psychometric forms as well as characteristic timescales. Most of our understanding of the cellular mechanisms underlying the neurophysiology of memory, however, derives from one-trial learning paradigms that, while powerful, do not fully embody the gradual, representational, and statistical aspects of cumulative learning. The early olfactory system-particularly olfactory bulb-comprises a reasonably well-understood and experimentally accessible neuronal network with intrinsic plasticity that underlies both one-trial (adult aversive, neonatal) and cumulative (adult appetitive) odor learning. These olfactory circuits employ many of the same molecular and structural mechanisms of memory as, for example, hippocampal circuits following inhibitory avoidance conditioning, but the temporal sequences of post-conditioning molecular events are likely to differ owing to the need to incorporate new information from ongoing learning events into the evolving memory trace. Moreover, the shapes of acquired odor representations, and their gradual transformation over the course of cumulative learning, also can be directly measured, adding an additional representational dimension to the traditional metrics of memory strength and persistence. In this review, we describe some established molecular and structural mechanisms of memory with a focus on the timecourses of post-conditioning molecular processes. We describe the properties of odor learning intrinsic to the olfactory bulb and review the utility of the olfactory system of adult rodents as a memory system in which to study the cellular mechanisms of cumulative learning.
    Frontiers in Behavioral Neuroscience 07/2014; 8:238. DOI:10.3389/fnbeh.2014.00238 · 3.27 Impact Factor
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