Taste identification used as a potential discriminative test among depression and Alzheimer׳s disease in elderly: A pilot study.

Major Depression and Alzheimer׳s disease (AD) are two diseases in the elderly characterized by an overlap of early symptoms including memory and emotional disorders. The identification of specific markers would facilitate their diagnosis. The aim of this study was to identify such markers by investigating gustatory function in depressed and AD patients. We included 20 patients with unipolar major depressive episodes (MDE), 20 patients with mild to moderate AD and 24 healthy individuals. We investigated the cognitive profile (depression, global cognitive efficiency and social/physical anhedonia) and gustatory function (ability to identify four basic tastes and to judge their intensity and hedonic value) in all participants. We found that AD patients performed worse than healthy participants in the taste identification test (for the analysis of all tastants together); however, this was not the case for depressed patients. We found no significant differences among the three groups in their ability to evaluate the intensity and hedonic value of the four tastes. Overall, our findings suggest that a taste identification test may be useful to distinguish AD and healthy controls but further investigation is required to conclude whether such a test can differentiate AD and depressed patients.

An odor identification approach based on event-related pupil dilation and gaze focus.

Olfactory disorders constitute a potential marker of many diseases and are considered valuable clues to the diagnosis and evaluation of progression for many disorders. The most commonly used test for the evaluation of impairments of olfactory identification requires the active participation of the subject, who must select the correct name of the perceived odor from a list. An alternative method is required because speech may be impaired or not yet learned in many patients. As odor identification is known to be facilitated by searching for visual clues, we aimed to develop an objective, vision-based approach for the evaluation of odor identification. We used an eye tracking method to quantify pupillary and ocular responses during the simultaneous presentation of olfactory and visual stimuli, in 39 healthy participants aged from 19 to 77years. Odor presentation triggered an increase in pupil dilation and gaze focus on the picture corresponding to the odor presented. These results suggest that odorant stimuli increase recruitment of the sympathetic system (as demonstrated by the reactivity of the pupil) and draw attention to the visual clue. These results validate the objectivity of this method.

[Perception of taste and smell in normal and pathological aging: an update]. / Perception du goût et des odeurs au cours du vieillissement normal et pathologique : mise au point.

The physiological and pathological aging on sense organs is widely studied in the visual and hearing modalities. By contrast, taste and smell changes are widely overlooked. These symptoms are rarely evoked in the elderly and often neglected in clinical practice. Studies in this population are rare and show contradictory results. In this update, we describe the perception of taste and smell in aging. In a first part, we present studies about the aging of smell and taste senses. While taste is remarkably spared during aging, olfaction decreases dramatically since 5th decade of life, frequently resulting in anosmia after 90 years. Numerous causes are evoked: acute conditions (mouth health, medications…) and chronic diseases frequently observed during aging (Alzheimer or Parkinson's diseases) may be responsible of such decline. In the last part, we approach the consequences on geriatric practice, as regards the nutrition of old subjects, including a cognitive approach regarding to perceptual functions and environmental determinants of nutrition. Taste and olfaction disorders should be considered as a geriatric syndrome that geriatricians have to be aware in clinical practice.

Long-term odor recognition memory in unipolar major depression and Alzheimer׳s disease.

Major depression and Alzheimer׳s disease (AD) are often observed in the elderly. The identification of specific markers for these diseases could improve their screening. The aim of this study was to investigate long-term odor recognition memory in depressed and AD patients, with a view to identifying olfactory markers of these diseases. We included 20 patients with unipolar major depressive episodes (MDE), 20 patients with mild to moderate AD and 24 healthy subjects. We investigated the cognitive profile and olfactory memory capacities (ability to recognize familiar and unfamiliar odors) of these subjects. Olfactory memory test results showed that AD and depressed patients were characterized by significantly less correct responses and more wrong responses than healthy controls. Detection index did not differ significantly between patients with major depression and those with AD when the results were analyzed for all odors. However, MDE patients displayed an impairment of olfactory memory for both familiar and unfamiliar odors, whereas AD subjects were impaired only in the recognition of unfamiliar odors, with respect to healthy subjects. If preservation of olfactory memory for familiar stimuli in patients with mild to moderate AD is confirmed, this test could be used in clinical practice as a complementary tool for diagnosis.

Perceptive biases in major depressive episode.

INTRODUCTION: Alterations in emotional processing occur during a major depressive episode (MDE), and olfaction and facial expressions have implications in emotional and social interactions. To gain a better understanding of these processes, we characterized the perceptive sensorial biases, potential links, and potential remission after antidepressant treatment of MDE. METHODS: We recruited 22 patients with acute MDE, both before and after three months of antidepressant treatment, and 41 healthy volunteers matched by age and smoking status. The participants underwent a clinical assessment (Mini International Neuropsychiatry Interview, Montgomery-Åsberg Depression Rating Scale, State-Trait Anxiety Inventory, Physical and Social Anhedonia scales, Pleasure-Displeasure Scale), an olfactory evaluation (hedonic aspect, familiarity and emotional impact of odors), and a computerized Facial Affect Recognition task. RESULTS: MDE was associated with an olfactory bias concerning hedonic and emotional aspects, including negative olfactory alliesthesia (unpleasant odorants perceived as more unpleasant), facial emotion expression recognition (happy facial expressions), and in part olfactory anhedonia (pleasant odorants perceived as less pleasant). In addition, the results revealed that these impairments represent state markers of MDE, suggesting that the patients recovered the same sensory processing as healthy subjects after antidepressant treatment. DISCUSSION: This study demonstrated that MDE is associated with negative biases toward olfactory perception and the recognition of facial emotional expressions. The link between these two sensory parameters suggests common underlying processes.

[Alzheimer's disease and olfaction]. / Maladie d'Alzheimer et olfaction.

Although olfactory disorders are not at the forefront of the clinical description of Alzheimer's disease (AD), they are common and often overlooked by clinicians and by patients who are largely unaware of their deficits. The past 30 years, the literature has shown early olfactory deficits in AD that is spreading across the olfactory spectrum with disease worsening. Partial overlap between brain areas implies both in olfaction and AD - especially limbic system - motivating these researches. This study describes olfactory parameters and tests using to investigate peripheral (odor threshold) and central (hedonicity, familiarity, intensity, discrimination, identification, olfactory memory) levels. Besides, this article takes an inventory of olfactory disorders in AD including odor threshold, discrimination, identification and olfactory memory capacities with controversial results observed in literature. At last, we discuss which type of olfactory dysfunction could have a clinical interest.

State and trait olfactory markers of major depression.

Nowadays, depression is a major issue in public health. Because of the partial overlap between the brain structures involved in depression, olfaction and emotion, the study of olfactory function could be a relevant way to find specific cognitive markers of depression. This study aims at determining whether the olfactory impairments are state or trait markers of major depressive episode (MDE) through the study of the olfactory parameters involving the central olfactory pathway. In a pilot study, we evaluated prospectively 18 depressed patients during acute episodes of depression and 6 weeks after antidepressant treatment (escitalopram) against 54 healthy volunteers, matched by age, gender and smoking status. We investigated the participants' abilities to identify odors (single odors and in binary mixture), to evaluate and discriminate the odors' intensity, and determine the hedonic valence of odors. The results revealed an "olfactory anhedonia" expressed by decrease of hedonic score for high emotional odorant as potential state marker of MDE. Moreover, these patients experienced an "olfactory negative alliesthesia", during the odor intensity evaluation, and failed to identify correctly two odorants with opposite valences in a binary iso-mixture, which constitute potential trait markers of the disease. This study provides preliminary evidence for olfactory impairments associated with MDE (state marker) that are persistent after the clinical improvement of depressive symptoms (trait marker). These results could be explained by the chronicity of depression and/or by the impact of therapeutic means used (antidepressant treatment). They need to be confirmed particularly the ones obtained in complex olfactory environment which corresponds a more objective daily life situation.