Biomedical subjects

Claire Murphy

Publications and source records attributed to Claire Murphy.

34 records · Page 2Linked to original sources

PubMed2004

Differences in olfactory and visual memory in patients with pathologically confirmed Alzheimer's disease and the Lewy body variant of Alzheimer's disease.

Recognition and remote memory for odors, faces, and symbols were assessed in patients with pathologically confirmed Lewy body variant of Alzheimer's disease (LBV), patients with pathologically confirmed Alzheimer's disease (AD), and healthy elderly controls. On recognition memory tasks, LBV and AD patients showed significantly lower discriminability (d') than controls, particularly for olfactory stimuli. However no significant differences were found in the bias measure (c). When participants rated familiarity (a proposed measure of remote memory) of olfactory stimuli LBV and AD patients reported significantly lower familiarity than controls. Familiarity ratings were significantly lower in LBV patients than in AD patients for olfactory, but not for visual stimuli. Consistent with prior reports, the LBV patients showed significantly poorer odor thresholds than AD patients. The results suggest that recognition memory for olfactory stimuli is impaired in LBV and AD. However, patients with LBV are more impaired than patients with AD on tasks requiring remote memory for olfactory but not visual stimuli. The findings suggest that odor memory tasks may be useful in the assessment of LBV and AD.

Aged↗

PubMed2004

The effect of the ApoE epsilon4 allele on recognition memory for olfactory and visual stimuli in patients with pathologically confirmed Alzheimer's disease, probable Alzheimer's disease, and healthy elderly controls.

Episodic recognition memory for odors, faces, and unfamiliar symbols was assessed in apolipoprotein episilon4 positive and epsilon4 negative individuals with pathologically-confirmed Alzheimer's disease (AD), individuals diagnosed with probable AD, and healthy age- and gender-matched controls. The analyses revealed significant differences in performance between the AD patients and nondemented elderly controls based on the presence of the epsilon4 allele and the modality of the stimulus to be remembered. Measures of hits did not discriminate among groups but an analysis of false positive errors revealed significant differences, particularly for olfactory stimuli. Nondemented epsilon4 positive controls committed fewer false positive errors for olfactory stimuli compared to all other groups. In contrast, nondemented epsilon4 positive controls committed false positive errors for olfactory stimuli at rates similar to the AD patients. The performance of epsilon4 positive and epsilon4 negative controls was indistinguishable on the visual recognition memory tasks suggesting the particular vulnerability of olfactory memory to the early neuropathology of AD resulting in false positive errors in recognition memory for olfactory stimuli. The results of the present study offer new insight into how recognition memory is affected by AD, the epsilon4 allele, and the modality of the stimulus to be remembered.

Aged↗

PubMed2004

Effects of the ApoE epsilon4 allele on olfactory function in Down syndrome.

The present study investigated the effects of the apolipoprotein E (ApoE) epsilon4 allele, a risk factor for Alzheimer's disease (AD), on olfactory function in Down syndrome (DS). Brain areas critical to olfactory processing, particularly the entorhinal cortex, show the earliest neuropathological changes in AD. Functionally, odor identification has been shown to be impaired in AD and in persons with the epsilon4 allele. DS is also a risk factor for AD. Thus, we hypothesized greater impairment in epsilon4 positive DS participants. Olfactory function was assessed with the San Diego Odor Identification Test in 34 participants with DS and 34 normal controls. Genomic DNA was prepared from blood samples to obtain ApoE status for the DS participants. Results indicate (1) that participants with DS had significant deficits in olfactory functioning; and (2) that among DS participants, those with an epsilon4 allele had poorer odor identification than those without an epsilon4 allele. The results support the hypothesis that individuals with DS who have an additional genetic risk factor for AD, the ApoE epsilon4 allele, exhibit greater deficits in odor identification. Areas of the brain involved in odor identification may be particularly affected in individuals with DS who carry the epsilon4 allele.

Adolescent↗

PubMed2003

FMRI brain activation in response to odors is reduced in primary olfactory areas of elderly subjects.

Olfactory function is affected by aging and deficits often result in decreasing quality of life, health and safety. The present study investigated the cortical substrate of olfactory deficits related to aging with functional Magnetic Resonance Imaging (fMRI), with a retronasal olfactory stimulation protocol using flavored aqueous solutions presented to the mouth. Activation was found in young subjects in the piriform/amygdalar region and in the orbitofrontal cortex and in other areas previously found activated in neuroimaging studies using odorized air, including insula and cerebellum. Activation was seen in similar areas in old subjects but the degree of activation was significantly lower in regions receiving primary olfactory projections (piriform cortex, entorhinal cortex, and amygdala). This result supports the hypothesis of dysfunction and/or degeneration in areas critical to olfactory processing as a major cause of olfactory deficits in the older population.

Adult↗

PubMed2003

A paradigm for measuring the olfactory event-related potential in the clinic.

Recent research on the olfactory event-related potential (OERP) using inter-stimulus intervals (ISIs) of 90 s and shorter has revealed a marked decrease in component amplitude after the first trial, with a leveling off for the remaining trials. Studies manipulating the ISI in olfactory and other modalities demonstrate an association between higher amplitudes and longer ISIs, suggesting that habituation occurs at short time intervals between each stimulus presentation. The present study attempted to reduce the effects of habituation by using a 10-min ISI and fewer trials. OERPs were recorded monopolarly at the Fz, Cz and Pz electrode sites in ten subjects (five males, five females), for three trials using a 10-min ISI. Results demonstrated no significant reduction in component amplitudes across trials and no significant difference in latencies over trials, indicating no habituation effect at this ISI. These results indicate that with a 10-min ISI and three trial recordings, a complete reduction in habituation can be achieved. These findings may prove to be clinically useful to physicians who can implement this technique to assess olfactory functioning in cognitively impaired individuals or to assess malingering.

Adult↗

PubMed2003

The cerebellum and olfaction in the aging brain: a functional magnetic resonance imaging study.

The present study investigated activation of distinct cerebellar regions as a result of olfactory stimulation in healthy young and elderly adults using functional magnetic resonance imaging (fMRI). Ten young and 10 elderly adults were imaged using a 1.5-TMR scanner. The odorant amyl acetate was delivered in 12-s on, 40-s off cycles. Throughout the scan participants responded with a button press at first detection of each stimulus interval followed by a second button press upon odorant extinction. Images were processed with AFNI software. Elderly participants showed significantly decreased cerebellar activation in both the superior semilunar lobule (Crus I) and the inferior semilunar lobule (Crus II), two of three previously identified regions of interest for odor processing, compared to young adults. Interestingly, both groups showed similar levels of activation in the third region of interest, the posterior quadrangular lobule (VI), although the elderly showed more variability than the young did. Previous research identifying this area to be involved in attention may reflect the possibility that elderly adults engaged in olfactory tasks may show more variability than young participants in the degree of attentional demands needed for these tasks as a result of decreased olfactory abilities.

Adult↗

PubMed2003

Left hippocampal volume loss in Alzheimer's disease is reflected in performance on odor identification: a structural MRI study.

The very high sensitivity and specificity of odor identification tasks in discriminating between Alzheimer's patients and normals suggests that they reflect the presence of underlying neuropathology. Significant neuropathological changes are seen in areas critical to processing olfactory information, even in the early stages of Alzheimer's disease (AD). The current study was designed to investigate whether performance on olfactory tasks (odor threshold and odor identification) was related to volumetric MRI measures of mesial temporal areas central to olfactory information processing and important in the neuropathology of AD. Participants were 8 male and 5 female patients with probable AD, and 10 male and 12 female normal age-matched controls, diagnosed at the UCSD Alzheimer's Disease Research Center. The study investigated correlations between volumetric measures of hippocampus, the parahippocampal gyrus and the amygdala, and the psychophysical measures of olfactory function. Robust relationships were observed between mesial temporal lobe volumes and olfactory functional measures. The finding of a strong relationship between left hippocampal volume and performance on the odor identification task (r = .85) is compatible with a left-hemisphere superiority for verbally mediated olfactory tasks. The findings suggest a neural substrate for the breakdown in functional performance on verbally mediated odor identification tasks in Alzheimer's disease and suggest the utility of quantitative MRI measures and psychophysical performance in the assessment of AD. These results support the potential clinical utility of inclusion of odor identification tests in diagnostic batteries for detecting AD.

Aged↗

PubMed2003

Circadian rhythm and desensitization in chemosensory event-related potentials in response to odorous and painful stimuli.

Olfactory (H2S) and trigeminal (CO2) event-related potentials (ERPs) were studied with respect to circadian rhythm and desensitization. ERPs, perceived odor and pain intensity, oral temperature, blood pressure, heart rate, nasal volume, and sleepiness were assessed four times at 04:00, 08:00, 12:00, 16:00, 20:00, and 24:00 hr in five young men. For each of these 24 sessions per participant, H2S and CO2 were each presented in 15 series of five stimuli with a 5-s ISI within and 30-s ISI between series. ERP amplitudes, but not latencies, followed a circadian rhythm (largest at 16:00 and smallest at 04:00) similar to oral temperature and opposite to sleepiness. Amplitudes decreased (most pronounced at 16:00 and 20:00) and latencies increased with repeated stimulation, suggesting desensitization, in accordance with odor and pain intensity. These findings imply that circadian rhythm and desensitization should be considered in chemosensory ERP studies.

Adult↗

PubMed2002

Prevalence of olfactory impairment in older adults.

CONTEXT: Older adults represent the fastest-growing segment of the US population, and prevalences of vision and hearing impairment have been extensively evaluated. However, despite the importance of sense of smell for nutrition and safety, the prevalence of olfactory impairment in older US adults has not been studied. OBJECTIVE: To determine the prevalence of olfactory impairment in older adults. DESIGN, SETTING, AND PARTICIPANTS: A total of 2491 Beaver Dam, Wis, residents aged 53 to 97 years participating in the 5-year follow-up examination (1998-2000) for the Epidemiology of Hearing Loss Study, a population-based, cross-sectional study. MAIN OUTCOME MEASURES: Olfactory impairment, assessed by the San Diego Odor Identification Test and self-report. RESULTS: The mean (SD) prevalence of impaired olfaction was 24.5% (1.7%). The prevalence increased with age; 62.5% (95% confidence interval [CI], 57.4%-67.7%) of 80- to 97-year-olds had olfactory impairment. Olfactory impairment was more prevalent among men (adjusted prevalence ratio, 1.92; 95% CI, 1.65-2.19). Current smoking, stroke, epilepsy, and nasal congestion or upper respiratory tract infection were also associated with increased prevalence of olfactory impairment. Self-reported olfactory impairment was low (9.5%) and this measure became less accurate with age. In the oldest group, aged 80 to 97 years, sensitivity of self-report was 12% for women and 18% for men. CONCLUSIONS: This study demonstrates that prevalence of olfactory impairment among older adults is high and increases with age. Self-report significantly underestimated prevalence rates obtained by olfaction testing. Physicians and caregivers should be particularly alert to the potential for olfactory impairment in the elderly population.

Aged↗

PubMed2002

Olfactory event-related potentials in Alzheimer's disease.

Areas of the brain affected in the early stages of Alzheimer's disease are also areas heavily involved in the processing of olfactory information. Olfactory event-related potentials (OERPs) and auditory ERPs were recorded from the Fz, Cz, and Pz electrode sites in 12 Alzheimer's disease (AD) patients and 12 age and gender matched normal controls (NC) in a single-stimulus paradigm with a 45 s inter-trial interval, using amyl acetate as the olfactory stimulus, and in a separate session a 500 Hz tone as the auditory stimulus. Odor identification (ID) was also used to assess ability to identify odors. The results indicate that (1) OERP P2 and P3 latencies were significantly longer in AD patients than normal controls; (2) olfactory ERP latency measures correlated significantly with dementia status as measured by the Dementia Rating Scale (DRS), indicating that as participants performed more poorly on the DRS, reflecting increased dementia, OERP latencies increased; (3) olfactory ERP latency measures better differentiated AD patients from normal controls than auditory ERP latency measures; (4) olfactory ERP measures alone correctly classified up to 92% of participants; (5) odor ID measures, namely the UPSIT and San Diego-Odor-ID tests also classified participants at a high rate. Combining scores for odor identification with olfactory P3 latency measures resulted in a correct classification rate of 100%. The results strongly support the use of olfactory measures in the assessment of AD.

Aged↗

PubMed2002

Utility of olfactory identification test for diagnosing Chinese patients with Alzheimer's disease.

The present study examined the utility of two tests, the olfactory identification test and the olfactory threshold test, in detecting dementia of the Alzheimer's type in Chinese patients in Hong Kong. The olfactory identification test developed by Murphy, Anderson, and Markinson (1994) was utilized with some modifications of odor stimuli suitable for the Chinese culture. Results showed that patients with Alzheimer's disease (AD) identified significantly fewer odors and had significantly higher olfactory threshold than their age- and education-matched normal control subjects. With the cut-off point of 5 identified odors (out of 6), the olfactory identification test yielded a sensitivity of 83% in discriminating AD patients from normal controls which was consistent with that reported by Morgan, Nordin, and Murphy (1995). Thus, the present results suggested that the olfactory identification test could be applied cross-culturally for identifying patients with dementia of the Alzheimer's type.

Aged↗

PubMed2002

Reliability analysis of event-related brain potentials to olfactory stimuli.

Olfactory event-related potentials (OERP) have been used to investigate olfactory processing in health and disease. However, the reliability of the OERP has yet to be established statistically. The present study examined test-retest reliability of the OERP over a 4-week interval. EEG was recorded from Fz, Cz, and Pz, using a single-stimulus paradigm with amyl acetate. Reliabilities for ERP component latencies and interpeak amplitudes were assessed as intraclass and Pearson product-moment correlation coefficients. Reliabilities were higher for latency than for amplitude. Highest correlation coefficients were observed for P2 latency, specifically at Cz and Pz P3 amplitude and latency exhibited high reliability at Cz and Pz. Fz demonstrated weakest correlation coefficients. The data suggest that OERP reliability is comparable to that of auditory and visual ERPs, supporting the use of OERPs in both basic research and clinical assessment.

Adult↗

PubMed2002

Olfactory acuity and cognitive function converge in older adulthood: support for the common cause hypothesis.

Visual and auditory thresholds and cognitive variables have shown converging losses in old age, which might exist because standard cognitive tests rely on these modalities for assessment. The present study investigated the common cause hypothesis in another sensory modality. Structural equation modeling tested the fit of a model representing the common cause hypothesis for olfactory acuity and cognitive function data from 98 nondemented older adults and 103 younger adults. The model fit better the data from the older adults, consistent with the common cause hypothesis. In addition, unique influences of age beyond those shared between cognitive and sensory variables were also demonstrated. The results suggest that olfactory functioning may be a valid indicator of the integrity of the aging brain in older adults.

Adolescent↗

PubMedDate not supplied

Olfactory impairment increases as a function of age in persons with Down syndrome.

Neuropathology similar to that found in the brains of patients with Alzheimer's disease (AD) has consistently been observed in older individuals with Down syndrome (DS) and this neuropathology is particularly prevalent in areas involved in olfaction. The present study investigated the effects of age on the expression of olfactory impairment in Down syndrome to address the hypothesis that older adults with DS show greater deficits in olfactory function compared with younger persons with DS and compared with age and IQ matched control groups. Between group differences showed that persons with DS had significant deficits in olfactory functioning compared to the two control groups. Further, within the DS group, older adults performed more poorly than the young adults or children. Results support the hypothesis that in a group of persons at risk for AD because of DS, olfactory impairment is greater in older individuals, suggesting progressive impairment over time. Deficits in olfactory function may be useful in signalling incipient dementia in DS.

Adolescent↗

PubMedDate not supplied

Age-associated increases in intensity discrimination for taste.

Impaired taste sensation in the aging person may affect the appreciation of food and beverages and compromise nutritional status. Changes in flavor perception may be due to altered ability to discriminate between intensities of suprathreshold taste stimuli. An interesting question is whether all taste qualities (sweet, salty, sour, bitter) show similar age-associated decline in intensity discrimination. Taste intensity discrimination has been shown to be significantly poorer in elderly than in young women for the bitter stimulus caffeine, but not for the sweet stimulus sucrose. The present experiment investigated effects of taste substance and age on taste intensity discrimination by assessing Weber ratios (WRs) for citric acid and sodium chloride (NaCl) in 60 people, half elderly, and half women. Results indicate a significant effect of age on WRs for citric acid and NaCl, suggesting the importance of suprathreshold intensity discrimination for taste perception in the elderly.

Adult↗

PubMedDate not supplied

Clinical evaluation and symptoms of chemosensory impairment: one thousand consecutive cases from the Nasal Dysfunction Clinic in San Diego.

BACKGROUND: The aim of this study was to measure olfactory impairment in patients with various etiologies using symptom ratings and psychophysical measures of olfactory function. METHODS: We performed a cross-sectional, population-based study at the Nasal Dysfunction Clinic of the University of California, San Diego (UCSD), Medical Center. One thousand consecutive patients presented to the UCSD Nasal Dysfunction Clinic for evaluation of chemosensory dysfunction. Olfactory impairment was assessed by odor threshold and odor identification and symptom scores were assessed by self-report. RESULTS: The degree of olfactory impairment was driven by diagnostic category, age, and gender. Postviral disturbance was more prevalent in women and among elderly people. Elderly people and patients under 20 years of age showed the highest incidence of head trauma. Overall, older patients had poorer thresholds. Men showed higher prevalence of olfactory loss secondary to inflammation and toxin exposure. Patients with inflammation scored better than patients with other diagnoses (i.e., congenital, head trauma, postviral, toxin exposure, and miscellaneous causes). Patients with congenital etiologies and head trauma had the poorest scores. Symptom ratings were significantly different depending on diagnostic category, age, and gender. Patients with inflammation rated the majority of symptoms as most bothersome. Patients with postviral diagnoses were most likely to report parosmias. Patients with head trauma rated taste and smell loss as significantly more severe than other patients. CONCLUSION: Evaluation of 1000 patients at the UCSD Nasal Dysfunction Clinic in San Diego revealed differential olfactory impairment and differential symptom complaints based on diagnostic category, age, and gender.

Adolescent↗