Habituation is one of the oldest forms of learning, broadly expressed across sensory systems and taxa. Here, we demonstrate that olfactory habituation induced at different timescales (comprising different odor exposure and intertrial interval durations) is mediated by different neural mechanisms. First, the persistence of habituation memory is greater when mice are habituated on longer timescales. Second, the specificity of the memory (degree of cross-habituation to similar stimuli) also depends on induction timescale. Third, we demonstrate a pharmacological double dissociation between the glutamatergic mechanisms underlying short-and long-timescale odor habituation. LY341495, a class II/III metabotropic glutamate receptor antagonist, blocked habituation only when the induction timescale was short. Conversely, MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist, prevented habituation only when the timescale was long. Finally, whereas short-timescale odor habituation is mediated within the anterior piriform cortex, infusion of MK-801 into the olfactory bulbs prevented odor habituation only at longer timescales. Thus, we demonstrate two neural mechanisms underlying simple olfactory learning, distinguished by their persistence and specificity, mediated by different olfactory structures and pharmacological effectors, and differentially utilized based solely on the timescale of odor presentation.Habituation, or the progressive reduction in behavioral responsiveness to repeated similar stimuli, is a simple form of learning that underlies animals' capacity to perceptually deemphasize static conditions or inconsequential stimuli in favor of novel, potentially more relevant environmental features or events (Thompson and Spencer 1966;Rose and Rankin 2001). In the laboratory, experimental paradigms based on habituation have been employed to study the properties of nonassociative perceptual learning, to measure the persistence of memory traces, and even to assess the stringency of spontaneous discrimination among similar stimuli. In studies of olfactory spontaneous discrimination using rats or mice, animals habituated to an odorant stimulus demonstrate a cross-habituation response to novel odorant stimuli that are structurally and perceptually similar to the habituated odorant. The degree of cross-habituation declines progressively as test odorants become more dissimilar, and habituation to both the original and cross-habituated odorant stimuli persists for at least several minutes (Cleland et al. 2002;Linster et al. 2002; Mandairon et al. 2006b,c).Olfactory habituation has also been observed in studies in which it is attributed to rapid synaptic adaptation of the mitrapyramidal synapse in the rat anterior piriform cortex (aPC) (Best and Wilson 2004;Yadon and Wilson 2005). Odor-evoked activity in piriform pyramidal neurons adapts within tens of seconds, and this adaptation persists for up to 2 min (Wilson 1998a,b), a substantially faster timescale than that exhibited in the behavioral studies discussed above. Further...

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Some controversy still exists as to how binary odorant mixtures are behaviorally perceived, despite many studies aimed at understanding this phenomenon. Binary mixture perception by rodents is a first step in elucidating how more complex odor blends may be perceived. Research thus far has examined how the degree of component similarity, olfactory receptor overlap, relative concentration of components, and even olfactory enrichment affect the behavioral perception of binary mixtures. These studies have aimed to categorize binary mixtures into 1 of 3 rigid categories, but often the results conflict as to which category a particular mixture belongs. In the present article, the authors used a habituation/discrimination paradigm to determine whether rats' perception of one component of a binary mixture of either perceptually similar or dissimilar components changed when the concentration of both components was varied together. The authors found that perception of a binary mixture changed with changing component concentration, such that one binary mixture could be categorized differently depending on component intensity.

The traditional model of emergency care no longer fits the growing needs of the over 20 million older adults annually seeking emergency department care. In 2007 a tailored “geriatric emergency department” model was introduced and rapidly replicated among hospitals, rising steeply over the past 5 years. This survey examined all U.S. emergency departments self-identifying themselves as Geriatric Emergency Departments (GEDs) and providing enhanced geriatric emergency care services. It was guided by the recently adopted Geriatric Emergency Department Guidelines and examined domains including, GED identity, staffing, and administration; education, equipment, and supplies; policies, procedures, and protocols; follow-up and transitions of care; and quality improvement. Results reveal a heterogeneous mix of GED staffing, procedures, physical environments and that GEDs’ familiarity with the GED Guidelines is low. Findings will inform emergency departments and gerontologists nationwide about key GED model elements and will help hospitals to improve ED services for their older adult patients.

Introduction: Older adults present unique challenges to both emergency clinicians and health systems. These challenges are especially evident with respect to discharge after an emergency department (ED) visit as older adults are at risk for short-term, negative outcomes including repeat ED visits. The aim of this study was to evaluate characteristics and risk factors associated with repeat ED utilization by older adults. Methods: ED visits among participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study between 2003-2016 were examined using linked Medicare claims data to identify such visits and resulting disposition. Multilevel proportional hazards models examined associations of age, comorbidity status, race, gender, Medicaid dual eligibility status, social support characteristics (living alone or caregiver support), and use of ambulatory primary and subspecialty care with repeat ED utilization. Results: Older adults discharged from the ED seen by a primary care provider (hazard ratio [HR] = 0.93, confidence interval [CI], 0.87-0.98, p = 0.01) or subspecialist (HR = 0.91, CI 0.86-0.97, P <0.01) after the ED visit were less likely to return to the ED within 30 days compared to those who did not have such postED ambulatory visits.