Good News for Elderly Persons: Olfactory Pleasure Increases at Later Stages of the Life Span

Abstract

Understanding of delirium pathogenesis remains limited despite improved diagnosis, and elucidation of risk factors and prognosis. Major advances in neuroimaging offer the possibility of probing the mechanisms and networks involved in delirium and hence improving understanding of this often devastating syndrome. This review describes the current literature of imaging studies in delirium and related conditions, introduces some of the newer capabilities of neuroimaging with magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography, and discusses how these techniques may be applied to the study of delirium. Despite considerable challenges in patient recruitment, study design, intersubject variability, and scanner and contrast agent availability, imaging offers great potential for the identification and clarification of pathogenic mechanisms of delirium and its long-term sequelae.T HE rapid advancement of neuroimaging methods over the last few decades has made available a wide array of tools for research and clinical management of brain disorders. Imaging can be used to quantify normal or pathologic physiology and to localize abnormalities to specific regions of the brain. In clinical studies, imaging results can also help to control for intersubject variation due to varying severity of related or comorbid pathologies. These capabilities of imaging could prove highly valuable in the study of delirium, an important and highly prevalent syndrome in elderly people, but one for which understanding of pathophysiology remains limited.In this review article, we discuss the shortcomings of our current understanding of delirium and distill from this a series of target questions about the pathophysiology of delirium that might be addressable by neuroimaging studies and whose answers would provide a major advance in the understanding of delirium. We survey the existing literature on imaging studies in delirium and highlight the gaps that remain. Subsequently, we introduce a number of newer neuroimaging techniques and describe how some of these methods might be used to answer our target questions about delirium. Finally, we consider the obstacles to performing such neuroimaging studies and discuss potential solutions. This article may provide a useful framework to guide future neuroimaging studies investigating the pathophysiology of delirium.

Effect of Aging on Hedonic Appreciation of Pleasant and Unpleasant Odors

“…This finding was replicated in two successive experiments and could not be explained by perceived intensity effects. Past studies have shown diverging results regarding this topic [17], [18], [19], [22], and our study using a large number of odorants in the same intensity range offers new insights into this non-consensual issue highlighting for the first time a modulation in odor hedonic valence specifically for pleasant odors in old adults.…”

“…Indeed, studies of the emotional perception of odors during aging are rare and not consensual: in one study, the smells of lavender and spearmint [17] were judged more pleasant by the older subjects, while another study [18] found such an age effect for certain smells (turpentine, garlic and fish became less unpleasant with age and cloves and rose more pleasant) but not for others (orange, leather, cinnamon, spearmint, banana, lemon, anise, coffee, apple, pineapple, licorice). In contrast, by taking into account the hedonic valence of the odor, another study suggested that older subjects exhibit decreased identification abilities of pleasant but not unpleasant odors [19].…”

The olfactory sense: a developmental and lifespan perspective

“…Pelletier (2007) reports that there is decreased chemosensation in older people and that it may be a primary influence to explain poor compliance to diets and emphasises the great need for further research in orophyaryngeal dysphagia rehabilitation. Though Markovic et al. (2007) studied smell intensity and hedonics (pleasant or unpleasant sensations) in patients with increasing age.…”

The Psychophysical Assessment of Odor Valence: Does an Anchor Stimulus Influence the Hedonic Evaluation of Odors?

“…The three anchor stimuli 1) orange, 2) liquorice, and 3) fish were chosen based on the results of prior studies in the database HeDoS-F (Markovic et al 2007;Thuerauf et al 2008), comprising olfactory data of more than 200 healthy subjects assessed in a nonanchor-measuring condition. Accordingly, the odor orange had received highest pleasantness ratings, fish lowest pleasantness ratings, and liquorice neutral ratings.…”

“…VAS are widely used in a broad range of scientific contexts (Arruda et al 1996;Di Benedetto et al 2005;Wibbenmeyer et al 2011) and have proven high validity and reliability (de Boer et al 2004;Di Benedetto et al 2005;Fähndrich and Linden 1982;Luria 1975). VAS are a common technique for the assessment of olfactory hedonic judgments (Hummel et al 1998;Leon et al 2007;Markovic et al 2007;Royet et al 2001;Thuerauf et al 1999;Thuerauf et al 2000).…”