Influences of age and sex on a microencapsulated odor memory test

Olfactory function in psychotic disorders: Insights from neuroimaging studies

Olfactory deficits on measures of identification, familiarity, and memory are consistently noted in patients with psychotic disorders relative to age-matched controls. Olfactory intensity ratings, however, appear to remain intact while the data on hedonics and detection threshold are inconsistent. Despite the behavioral abnormalities noted, no specific regional brain hypoactivity has been identified in psychosis patients, for any of the olfactory domains. However, an intriguing finding emerged from this review in that the amygdala and pirifom cortices were not noted to be abnormal in hedonic processing (nor was the amygdala identified abnormal in any study) in psychotic disorders. This finding is in contrast to the literature in healthy individuals, in that this brain region is strongly implicated in olfactory processing (particularly for unpleasant odorants). Secondary olfactory cortex (orbitofrontal cortices, thalamus, and insula) was abnormally activated in the studies examined, particularly for hedonic processing. Further research, using consistent methodology, is required for better understanding the neurobiology of olfactory deficits. The authors suggest taking age and sex differences into consideration and further contrasting olfactory subgroups (impaired vs intact) to better our understanding of the heterogeneity of psychotic disorders.

Olfaction Modulates Early Neural Responses to Matching Visual Objects

Sensory information is initially registered within anatomically and functionally segregated brain networks but is also integrated across modalities in higher cortical areas. Although considerable research has focused on uncovering the neural correlates of multisensory integration for the modalities of vision, audition, and touch, much less attention has been devoted to understanding interactions between vision and olfaction in humans. In this study, we asked how odors affect neural activity evoked by images of familiar visual objects associated with characteristic smells. We employed scalp-recorded EEG to measure visual ERPs evoked by briefly presented pictures of familiar objects, such as an orange, mint leaves, or a rose. During presentation of each visual stimulus, participants inhaled either a matching odor, a nonmatching odor, or plain air. The N1 component of the visual ERP was significantly enhanced for matching odors in women, but not in men. This is consistent with evidence that women are superior in detecting, discriminating, and identifying odors and that they have a higher gray matter concentration in olfactory areas of the OFC. We conclude that early visual processing is influenced by olfactory cues because of associations between odors and the objects that emit them, and that these associations are stronger in women than in men.

Influences of hormone replacement therapy on olfactory and cognitive function in postmenopausal women

Olfactory dysfunction can be an early sign of Alzheimer's disease. Since hormone replacement therapy (HRT) may protect against Alzheimer's disease in postmenopausal women, the question arises as to whether it also protects against olfactory dysfunction in such women. A total of three olfactory and 12 neurocognitive tests were administered to 432 healthy postmenopausal women with varied HRT histories. Serum levels of reproductive hormones were obtained for all subjects; APOE-ε4 haplotype was determined for 77 women. National Adult Reading Test and Odor Memory/Discrimination Test scores were positively influenced by HRT. Odor Identification and Odor Memory/Discrimination Test scores were lower for women who scored poorly on a delayed recall test, a surrogate for mild cognitive impairment. The Wechsler Adult Intelligence Scale, Revised, as a Neuropsychological Instrument Spatial Span Backwards Test scores were higher in women receiving estrogen and progestin HRT and directly correlated with serum testosterone levels, the latter implying a positive effect of testosterone on spatial memory. APOE-ε4 was associated with poorer odor threshold test scores. These data suggest that HRT positively influences a limited number of olfactory and cognitive measures during menopause.

Long-term memory for odors: influences of familiarity and identification across 64 days

Few studies have investigated long-term odor recognition memory, although some early observations suggested that the forgetting rate of olfactory representations is slower than for other sensory modalities. This study investigated recognition memory across 64 days for high and low familiar odors and faces. Memory was assessed in 83 young participants at 4 occasions; immediate, 4, 16, and 64 days after encoding. The results indicated significant forgetting for odors and faces across the 64 days. The forgetting functions for the 2 modalities were not fundamentally different. Moreover, high familiar odors and faces were better remembered than low familiar ones, indicating an important role of semantic knowledge on recognition proficiency for both modalities. Although odor recognition was significantly better than chance at the 64 days testing, memory for the low familiar odors was relatively poor. Also, the results indicated that odor identification consistency across sessions, irrespective of accuracy, was positively related to successful recognition.

Development of normative data for the Brazilian adaptation of the University of Pennsylvania Smell Identification Test

It is well established that olfactory dysfunction has significant implications for safety, nutrition, and quality of life. The more reliable standardized tests of olfactory function, such as the University of Pennsylvania Smell Identification Test (UPSIT), assess odor identification ability. Unfortunately, cultural factors can influence such tests, as a number of odors are not universally recognized. In this study, a Portuguese language version of the UPSIT was administered to an age- and sex-stratified prospective sample of 1820 Brazilian subjects. Normative data were developed for a subset of 1578 subjects who reported having no difficulties smelling or tasting. Individuals with a history of head trauma or, in the case of those over the age of 64 years, Mini-Mental State Examination Scores <24, were excluded from analysis. As in other populations, the test scores were significantly influenced by age and sex. The median overall difference between the North American and Brazilian UPSIT scores was 2.2 points for men and 0.8 points for women, although subtle age-related differences were also apparent. This research represents that largest clinical study of olfaction ever performed in South America. Correction factors based upon age and sex are provided to allow for direct comparisons of Brazilian test scores to those based upon North American norms.

Anosmia and hypogeusia in Churg-Strauss syndrome

Churg-Strauss syndrome is a rare disorder that is often misdiagnosed. In this report we describe a 57-year-old man with Churg-Strauss syndrome who presented with symptoms of lessened smell and taste function that occurred approximately 3 months before the onset of his neurological symptoms. Psychophysical testing using a battery of well-validated smell and taste tests revealed that the patient had total anosmia and marked hypogeusia. While one anecdotal report exists in the Spanish literature that alludes to the presence of anosmia in a single case of this syndrome, no further confirmation of such dysfunction has appeared in the literature. These findings support the concept that smell and taste loss may be an early sign of this disorder.

Schizophrenia and co-occurring substance use disorder: reward, olfaction and clozapine

Co-occurring substance use disorders (SUD), including alcohol, are common in schizophrenia (SZ) and are associated with poor outcome. Emerging data suggest that individuals with SZ have a dysfunctional brain reward circuit that may underlie their frequent use of alcohol and other substances, and further, that the atypical antipsychotic, clozapine (CLOZ), limits alcohol/substance use in these individuals, potentially by ameliorating this brain reward circuit dysfunction. To explore this hypothesis, reward functioning in a SZ sample with a history of co-occurring SUD, treated with either CLOZ (n=13) or typical antipsychotic agents (TYP), haloperidol or fluphenazine (n=14), as well as healthy controls (n=16), was evaluated through ratings of pleasurable and aversive odors, stimuli that are processed by several neural structures thought to play a key role in processing rewarding stimuli. Results suggest that CLOZ treatment is associated with broadening and strengthening the hedonic experience of these rewarding olfactory stimuli, both of a pleasant and unpleasant nature. This hedonic appraisal of odors appeared to be independent of odor perception (intensity ratings) and clinical symptoms. These preliminary findings provide important new data in support of the hypothesis that CLOZ ameliorates some aspects of abnormal brain reward functioning in individuals with co-occurring SZ and SUD. Further research may have valuable treatment implications for this population including interventions for other reward-associated deficits in learning, social interactions and other aspects of behavior and cognition.

The influences of age on olfaction: a review

Decreased olfactory function is very common in the older population, being present in over half of those between the ages of 65 and 80 years and in over three quarters of those over the age of 80 years. Such dysfunction significantly influences physical well-being and quality of life, nutrition, the enjoyment of food, as well as everyday safety. Indeed a disproportionate number of the elderly die in accident gas poisonings each year. As described in this review, multiple factors contribute to such age-related loss, including altered nasal engorgement, increased propensity for nasal disease, cumulative damage to the olfactory epithelium from viral and other environmental insults, decrements in mucosal metabolizing enzymes, ossification of cribriform plate foramina, loss of selectivity of receptor cells to odorants, changes in neurotransmitter and neuromodulator systems, and neuronal expression of aberrant proteins associated with neurodegenerative disease. It is now well established that decreased smell loss can be an early sign of such neurodegenerative diseases as Alzheimer's disease and sporadic Parkinson's disease. In this review we provide an overview of the anatomy and physiology of the aging olfactory system, how this system is clinically evaluated, and the multiple pathophysiological factors that are associated with its dysfunction.

Olfactory dysfunction in Parkinson disease

Olfactory dysfunction is among the earliest nonmotor features of Parkinson disease (PD). Such dysfunction is present in approximately 90% of early-stage PD cases and can precede the onset of motor symptoms by years. The mechanisms responsible for olfactory dysfunction are currently unknown. As equivalent deficits are observed in Alzheimer disease, Down syndrome, and the Parkinson-dementia complex of Guam, a common pathological substrate may be involved. Given that olfactory loss occurs to a lesser extent or is absent in disorders such as multiple system atrophy, corticobasal degeneration, and progressive supranuclear palsy, olfactory testing can be useful in differential diagnosis. The olfactory dysfunction in PD and a number of related diseases with smell loss correlates with decreased numbers of neurons in structures such as the locus coeruleus, the raphe nuclei, and the nucleus basalis of Meynart. These neuroanatomical findings, together with evidence for involvement of the autonomic nervous system in numerous PD-related symptoms, suggest that deficits in cholinergic, noradrenergic and serotonergic function may contribute to the olfactory loss. This Review discusses the current understanding of olfactory dysfunction in PD, including factors that may be related to its cause.

Genetic and environmental influences on odor identification ability in the very old

Odor identification ability and cognition were measured in a population-based cohort of 1,222 very old twins and singletons, including 91 centenarians. Heritability for identifying odors was low, in contrast to that for cognition. Common genes were found to contribute to both olfaction and cognition. In a multiple regression model, sex, age, cognitive function, and smoking, but not APOEε4 status, were significant predictors of the olfactory test scores (all ps < 0.001). This study, along with data from other studies, suggests that indices of heritability for odor identification decline with age, likely reflecting adverse environmental influences on the smell system.

Human olfaction: a constant state of change-blindness

Paradoxically, although humans have a superb sense of smell, they don’t trust their nose. Furthermore, although human odorant detection thresholds are very low, only unusually high odorant concentrations spontaneously shift our attention to olfaction. Here we suggest that this lack of olfactory awareness reflects the nature of olfactory attention that is shaped by the spatial and temporal envelopes of olfaction. Regarding the spatial envelope, selective attention is allocated in space. Humans direct an attentional spotlight within spatial coordinates in both vision and audition. Human olfactory spatial abilities are minimal. Thus, with no olfactory space, there is no arena for olfactory selective attention. Regarding the temporal envelope, whereas vision and audition consist of nearly continuous input, olfactory input is discreet, made of sniffs widely separated in time. If similar temporal breaks are artificially introduced to vision and audition, they induce “change blindness”, a loss of attentional capture that results in a lack of awareness to change. Whereas “change blindness” is an aberration of vision and audition, the long inter-sniff-interval renders “change anosmia” the norm in human olfaction. Therefore, attentional capture in olfaction is minimal, as is human olfactory awareness. All this, however, does not diminish the role of olfaction through sub-attentive mechanisms allowing subliminal smells a profound influence on human behavior and perception.

Preoperative prognostic factors for olfactory change after functional endoscopic sinus surgery

BACKGROUND

Functional endoscopic sinus surgery (FESS) has been considered to improve the olfactory function in patients with chronic rhinosinusitis. However, which factors might affect the olfactory outcome after FESS has not been well investigated.

METHODS

A total of 70 patients with chronic rhinosinusitis who underwent FESS were enrolled in the study. The potential prognostic factors for improvement in olfaction after FESS were evaluated in these patients. On the day before FESS, the olfactory function was evaluated by a symptom score, a phenyl ethyl alcohol odor detection threshold test, the University of Pennsylvania Smell Identification Test, and a short-term odor memory/discrimination test, and were reevaluated by the same methods 6 months after FESS.

RESULTS

The degree of nasal obstruction, the second minimal cross-sectional area measured by acoustic rhinometry, computed tomography scores before FESS, the degree of preoperative olfactory loss indicated by threshold and identification scores, and coexistence of nasal polyps or allergic rhinitis were not significantly reliable to influence the rates of olfactory improvement after FESS.

CONCLUSION

Degree of nasal obstruction, extent of rhinosinusitis disease, and coexistence of nasal polyps or allergic rhinitis did not predicate the overall possibility of any olfactory improvement after FESS.

Sex differences and reproductive hormone influences on human odor perception

The question of whether men and women differ in their ability to smell has been the topic of scientific investigation for over a hundred years. Although conflicting findings abound, most studies suggest that, for at least some odorants, women outperform men on tests of odor detection, identification, discrimination, and memory. Most functional imaging and electrophysiological studies similarly imply that, when sex differences are present, they favor women. In this review we examine what is known about sex-related alterations in human smell function, including influences of the menstrual cycle, pregnancy, gonadectomy, and hormone replacement therapy on a range of olfactory measures. We conclude that the relationship between reproductive hormones and human olfactory function is complex and that simple associations between circulating levels of gonadal hormones and measures of olfactory function are rarely present.

Olfactory function in patients with chronic rhinosinusitis before and after functional endoscopic sinus surgery

BACKGROUND

The olfactory loss in patients with chronic rhinosinusitis has been measured by different methods. However, the results have been variable and it is not clear whether functional endoscopic sinus surgery (FESS) significantly improves olfactory function. This study was performed to evaluate the influences of FESS on olfactory function in patients with chronic rhinosinusitis using three different types of olfactory tests.

METHODS

Seventy patients with chronic rhinosinusitis were administered the University of Pennsylvania Smell Identification Test (UPSIT), a single staircase phenyl ethyl alcohol odor detection threshold test (STT), and a short-term odor memory/discrimination test a day before and 6 months after FESS. A questionnaire inquiring about the patients' self-perception of olfactory function was administered also. Independent ratings of the severity of chronic rhinosinusitis before FESS were established from CT scans.

RESULTS

Fifty-two (74.3%) of the patients reported that their olfactory function was impaired before surgery, and 68.6% of the patients reported impaired olfactory function after surgery, a difference that was not significant. No meaningful changes in any of the olfactory test scores were noted 6 or more months after FESS. Preoperatively, small correlations between CT scores and the symptom scores (r = 0.278; p = 0.024), threshold scores (r = -0.27; p = 0.031), and UPSIT scores (r = -0.36; p = 0.003) were observed.

CONCLUSION

In patients with severe rhinosinusitis, FESS had little impact on the ability to smell, regardless of the method for assessing smell function. Subtle associations between olfactory function and the severity of chronic rhinosinusitis determined by CT were observed, however, preoperatively. The olfactory test measures were correlated with one another both pre- and postoperatively.

Estrogen replacement therapy induces functional asymmetry on an odor memory/discrimination test

The secondary afferents of the olfactory system largely project to the ipsilateral cortex without synapsing in the thalamus, making unilateral olfactory testing a useful probe of ipsilateral hemispheric activity. In light of evidence that lateralized performance on some perceptual tasks may be influenced by estrogen, we assessed left:right nostril differences in two measures of olfactory function in 14 post-menopausal women receiving estrogen replacement therapy (ERT) and 48 post-menopausal women receiving no such therapy. Relative to women not taking ERT, those receiving ERT exhibited better performance in the left nostril and poorer performance in the right nostril on an odor memory/discrimination test. Similar laterality effects were not observed for an odor detection threshold test employing phenyl ethyl alcohol. These results suggest that estrogen influences the lateralization of an odor memory/discrimination task and that hormone replacement therapy in the menopause may be an excellent paradigm for understanding lateralizing effects of hormones on some sensory processes.

Sex differences in olfactory function in young patients with psychotic disorders

Female superiority on many measures of olfactory function is well established, but debate remains as to whether this pattern extends to patients with psychotic disorders. The purpose of this large retrospective study was to re-examine whether male vs. female differences in olfactory identification exist in patients with psychotic disorders, and if so, whether any such differences were related to features of the psychotic disorder or could be explained by a generalized male-female difference. We examined 353 relatively young patients, recently diagnosed with a psychotic illness, (258 males and 95 females) and compared these with 89 healthy control subjects (45 males and 44 females). All individuals had been assessed birhinally using the University of Pennsylvania Smell Identification Test (UPSIT). Overall, females were superior to males, and patients underperformed healthy controls. No interaction was noted between these two variables, and there was no significant effect found as a result of age of the subjects. The data suggested that sex differences in olfactory identification ability exist in young patients with psychotic disorders. They do not appear to be related to exposure to antipsychotic medication or smoking habit. Therefore, it is likely that they represent basic male vs. female differences and not diagnosis-specific sex differences in olfactory performance-at least in those who are in the early stages of illness.

[Olfactory disturbance screening with the odor stick identification test (OSIT-J) in executive checkups]

The odor stick identification test for Japanese (OSIT-J) has been shown to be useful for detecting and evaluating olfactory disturbances in Japanese people. We studied the usefulness of OSIT-J in screening for olfactory disturbances in 83 Japanese participants (49 male, 34 female) participating in an executive checkup at NTT West Kanazawa Hospital in Japan. The olfactory ability was self-reported on a grade scale. Olfactory function was then evaluated with a three-odors OSIT-J (rose, curry and sweaty socks). Participants with low self-reported olfactory ability or less-than-full scores in the three-odor test were evaluated with an additional 10 odors of OSIT-J. Eight or less points are considered to be lower than average in the 13-odor test of OSIT-J (Saito S, et al.). Eleven of the 83 participants had low self-reported olfactory ability. Four participants with a full score in the three odors test with low self-reported olfactory ability scored more than eight points in the 13-odor test. Thirty-eight participants scored less than three points in the three-odor test. Seven of 29 participants with two points in the three-odor test scored eight or less in the 13-odor test. In the 29 participants, subjects with low self-reported olfactory ability scored significantly lower scores than those without a low self-reported olfactory ability in the 13-odor test. The self-reported olfactory ability was not related to the score in the 13-odor test in the nine participants with one point or less in the three-odor test. Males scored significantly lower scores than females in the three-odor test. However, gender was not significantly related to the rate of olfactory disability estimated based on the 13-odor test. Use of a three-odor OSIT-J along with a self-administered questionnaire pertaining to olfactory disability is useful for olfactory disturbance screening during executive health checkups.

Olfactory Ability in the Healthy Population: Reassessing Presbyosmia

Age-associated loss of olfactory function, or presbyosmia, has been described in many studies of olfactory ability. Presbyosmia has been ascribed to idiopathic causes despite recognition that many neurodegenerative diseases also induce loss of olfactory function and increase in incidence in the aged population. Often this olfactory loss is unnoticed or unreported by affected individuals. More effective olfactory function in women compared with men is another common feature of many studies of olfactory function. Here we report on normative data from an Australian population study (n = 942) that has been divided into 2 subpopulations and reassessed as (included) a population of healthy, nonmedicated, nonsmokers with no history of nasal problems (n = 485) and (excluded) a population of participants who were either medicated, smokers or had a history of nasal problems (n = 457). The "included" data set shows a strong relationship between self-reporting of olfactory sensitivity and olfactory function score. The included data set shows a small but significant decline in olfactory ability after 65 years of age and better olfactory function in females compared with males. Data from the excluded population show a marked decline in olfactory ability after 65 years of age, no difference between males and females, and a weak relationship between self-reporting of olfactory function and actual olfactory function. The power of this approach is that it provides a normative data set against which many factors such as medication schedules and pathological conditions can be compared.

Cross-Modal Interactions Between Olfaction and Touch

We report two experiments designed to investigate the nature of any cross-modal interactions between olfactory and tactile information processing. In Experiment 1, we assessed the influence of olfactory cues on the tactile perception of fabric softness using computer-controlled stimulus presentation. The results showed that participants rated fabric swatches as feeling significantly softer when presented with a lemon odor than when presented with an animal-like odor, demonstrating that olfactory cues can modulate tactile perception. In Experiment 2, we assessed whether this modulatory effect varied as a function of the particular odors being used and/or of the spatial coincidence between the olfactory and tactile stimuli. The results replicated those reported in Experiment 1 thus further supporting the claim that people's rating of tactile stimuli can be modulated by the presence of an odor. Taken together, the results of the two experiments reported here support the existence of a cross-modal interaction between olfaction and touch.

Olfactory dysfunction and its measurement in the clinic and workplace

OBJECTIVES

To provide an overview of practical means for quantitatively assessing the sense of smell in both the clinic and workplace. To address basic measurement issues, including those of test sensitivity, specificity, and reliability. To describe and discuss factors that influence olfactory function, including airborne toxins commonly found in industrial settings.

METHODS

Selective review and discussion.

RESULTS

A number of well-validated practical threshold and suprathreshold tests are available for assessing smell function. The reliability, sensitivity, and specificity of such techniques vary, being influenced by such factors as test length and type. Numerous subject factors, including age, sex, health, medications, and exposure to environmental toxins, particularly heavy metals, influence the ability to smell.

CONCLUSIONS

Modern advances in technology, in conjunction with better occupational medicine practices, now make it possible to reliably monitor and limit occupational exposures to hazardous chemicals and their potential adverse influences on the sense of smell. Quantitative olfactory testing is critical to establish the presence or absence of such adverse influences, as well as to (a) detect malingering, (b) establish disability compensation, and (c) monitor function over time.

Episodic odor memory: Influences of handedness, sex, and side of nose

It is not known whether, or to what degree, odor memory is influenced by lateralized brain processes. In this study, we administered a 12-item match-to-sample odor memory test separately to the left and right sides of the nose of 30 left- and 30 right-handed subjects of equivalent age, sex distribution, and overall general smell ability. For each test item, one of three delay intervals (10-, 30-, and 60-s) was interspersed between smelling the target stimulus and smelling the first of four response alternatives. Women, but not men, performed significantly better on the left than on the right side of the nose, conceivably reflecting greater reliance upon left-hemisphere semantic processes. Subjects who received the first test on the right side of the nose outperformed those who received the first test on the left side of the nose. As in previous work, an age-related decrement in odor memory test scores was present. These data contribute to the debate on the role of lateralized brain processes in episodic odor memory, and suggest that performance on a standardized match-to-sample odor memory task is influenced by a number of interacting factors.