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Biomedical subjects

Claire Murphy

Publications and source records attributed to Claire Murphy.

At least 19 recordsLinked to original sources
PubMed2006

On-line psychophysical data acquisition and event-related fMRI protocol optimized for the investigation of brain activation in response to gustatory stimuli.

An experimental method for event-related functional magnetic resonance imaging that allows for the presentation of several chemosensory stimuli in the oral cavity during the same run, the collection of psychophysical measures (intensity or pleasantness) during the presentation of the stimuli, and the analysis of the data in an event-related fashion are described. The automatic pumps used to present taste stimuli allowed for multiple tastes to be delivered in small amounts under computer control. Psychophysical ratings of pleasantness or intensity were collected after each presentation of a taste stimulus and water, with the general labeled magnitude scale, using a joystick that controlled the movement of an arrow on the visual display. Performing these cognitive tasks required that the participant remained focused, and aided in the interpretation of the data collected. The perceived pleasantness differed across stimuli for all conditions; however, pleasantness ratings for the same stimulus displayed consistency, over the duration of the run and before each scan on separate days. Activation in response to sucrose and caffeine while the participant rated pleasantness was found in the insula, frontal operculum, rolandic operculum and orbitofrontal cortex which is consistent with previous taste fMRI studies.

Adult↗
PubMed2006

Laterality of the olfactory event-related potential response.

In experimental practice, odors are commonly applied to only one nostril for recordings of olfactory event-related potentials (OERPs), but the lateralization aspect of the OERP response is unclear regarding both stimulated nostril and cortical topography. The purpose of the present study was to investigate whether stimulated-nostril side affects OERP amplitudes and latencies and whether these potentials indicate lateralization of brain response in healthy, right-handed, young adults. OERPs were recorded from nine electrode sites in response to monorhinal stimulation with amyl acetate in 28 participants. The results showed a general increase in amplitude from frontal to parietal electrode sites (in particular for N1/P3) and generally larger amplitudes on the left hemisphere and midline than on the right hemisphere. There was no main effect of stimulated-nostril side on amplitude. Interactions indicated that N1/P2 amplitude was larger for left- than right-nostril stimulation and larger on the left hemisphere and midline than on the right hemisphere in left-nostril stimulation. No main effect or interactions of stimulated-nostril side over latencies were found and no effects on latencies of sagittal or coronal sites. These findings suggest a general parietal, left-hemisphere predominance in response amplitude to odorous stimulation and imply that either the left or the right nostril may be sufficient for accurate assessment of OERP latency in right-handed, young adults.

Adolescent↗
PubMed2006

Predicting non-completion of treatment for latent tuberculous infection: a prospective survey.

UNLABELLED: Treatment of latent tuberculosis (TB) infection (LTBI) is essential for the elimination of TB in the United States, but treatment is often not completed. Little is known about patients' reasons for not completing treatment. We hypothesized that certain health beliefs, lifestyle, and clinic- and regimen-related barriers to provision of care could predict non-completion of LTBI treatment. METHODS: We administered a survey in English, Chinese, or Spanish to patients with LTBI at the first TB clinic visit. Using chi(2) and logistic regression analysis, we assessed demographics, TB risk factors, and survey responses as predictors of non-completion of 6 mo of isoniazid. RESULTS: 217 patients, 90% foreign-born, completed the survey, and 28.6% of which finished at least 6 mo of isoniazid under usual clinic conditions. Multivariate analysis identified two independent predictors of non-completion: low risk perception of progressing to active TB without LTBI treatment (odds ratio [OR], 0.31 [0.13-0.72], 95% confidence interval [CI]), p = 0.007, accounting for 20% of non-completers, and not wanting venipuncture (OR, 0.43 [0.22-0.85], 95% CI), p = 0.015, accounting for 37% of non-completers. Another 18% shared both predictors; thus these two predictors accounted for 75% of non-completers in total. CONCLUSIONS: Patients assess LTBI treatment risks and inconveniences relative to low perceived benefits at treatment outset. Predictors of LTBI treatment non-completion are identifiable at the first visit. Targeting TB high-risk individuals, minimizing inconveniences, further education, and use of diagnostic tests with improved specificity for TB may address these concerns.

Adult↗
PubMed2006

Neural substrates of cross-modal olfactory recognition memory: an fMRI study.

Ten young adults (aged 20 to 25 years) participated in a functional Magnetic Resonance Imaging (fMRI) study to investigate neural substrates of cross-modal olfactory recognition memory. Before entering the scanner, participants were presented with 16 familiar odors selected from the COLT (Murphy, C., Nordin, S., Acosta, L., 1997. Odor learning, recall, and recognition memory in young and elderly adults. Neuropsychology 11, 126-137) and were then scanned for 3 runs according to a paradigm derived from Stark and Squire (Stark, C.E., Squire, L.R., 2000. Functional magnetic resonance imaging (fMRI) activity in the hippocampal region during recognition memory. J. Neurosci. 20, 7776-7781). During each run, participants were shown names of odors presented (targets) or not presented (foils) at encoding. Participants distinguished targets from foils via button press. Each run alternated 4 'ON' periods containing 7 targets and 2 foils (36 s) and 4 'OFF' periods with 7 foils and 2 targets (36 s). Data were processed with AFNI (Cox, R.W., 1996. AFNI: software for analysis and visualization of functional magnetic resonance neuroimages. Comput. Biomed. Res. 29, 162-173) and compared ON and OFF periods, extracting activation in regions that responded during the cross-modal olfactory recognition memory task. Group analysis showed that regions activated during the first run included right hippocampus, piriform/amygdalar area, superior temporal gyrus, anterior cingulate gyrus, inferior frontal/orbitofrontal gyrus, superior/medial frontal gyrus, and bilateral parahippocampal gyrus, inferior parietal lobule, supramarginal gyrus, cerebellum, lingual/fusiform area and middle/posterior cingulate gyrus. Region of interest analysis showed that degree of activation significantly decreased from run 1 to run 3 in the right hippocampus, fusiform gyrus, lingual gyrus, parahippocampal gyrus and middle frontal gyrus but not in other regions, suggesting that these regions sustain a specific function in olfactory recognition memory that attenuates as foils become more familiar with repeated presentation.

Adult↗
PubMed2006

Restrained eaters show altered brain response to food odor.

Do restrained and unrestrained eaters differ in their brain response to food odor? We addressed this question by examining restrained eaters' brain response to food (chocolate) and non-food (geraniol, floral) odors, both when odor was attended to and when ignored. Using olfactory event-related potentials (OERPs), we found that restrained eaters and controls responded similarly to the non-food odor; however, unlike controls, restrained eaters showed no increase in brain response to the food odor when they focused attention on it. Rather, restrained eaters showed attenuated OERP amplitudes to the food odor in both attended and ignored conditions, suggesting that the brain's response to attended food odor was abnormally suppressed.

Adolescent↗
PubMed2006

Nasal health in Down syndrome: a cross-sectional study.

OBJECTIVE: To investigate peripheral nasal pathology as a contributor to olfactory impairment in DS. STUDY DESIGN: Twenty DS and 16 non-DS subjects were recruited. Nasal history and symptoms were assessed by self-report or informant. Olfactory threshold, odor identification, and nasal endoscopy were assessed on each subject. RESULTS: DS subjects were impaired on olfactory threshold (P<0.0001) and odor identification (P<0.001). Although DS subjects tended toward upper-respiratory infections, sleep-disordered breathing, and nasal itching, differences were not significant (P=0.07, 0.06, and 0.058, respectively). There were no significant differences on self-reported nasal history or symptoms. Endoscopy showed equivalent health in DS and control subjects. CONCLUSION: This DS population shows olfactory impairment. However, nasal health is comparable in DS subjects and controls. Nasal dysfunction is unlikely to contribute to olfactory impairment in DS. SIGNIFICANCE: Olfactory deficits in DS appear to be secondary to central, rather than rhinologic, pathology. EBM RATING: B-2b.

Adolescent↗
PubMed2006

Estrogen and performance in recognition memory for olfactory and visual stimuli in females diagnosed with Alzheimer's disease.

Patients with Alzheimer's disease (AD) exhibit a deficit in episodic recognition memory for odors. It is hypothesized that the higher rate of AD in women may be due to estrogen-deprivation in postmenopausal women. Research suggests that estrogen may help to minimize cognitive decline in AD as well as postmenopausal olfactory loss. The current study examined the effects of estrogen replacement therapy (ERT) on performance of a recognition memory task for olfactory and visual stimuli in women AD patients. Participants included 24 women AD patients who were ERT users and 77 women AD patients who never used ERT. Compared with the ERT non-users, the ERT users committed significantly less false-positive memory errors for olfactory stimuli, whereas performance for visual stimuli did not differentiate between ERT users and non-users. The results suggest benefits of ERT could help ameliorate the earliest symptoms of AD, olfactory dysfunction, and memory impairment.

Aged↗
PubMed2006

The effects of normal aging on source memory for odors.

Source and item memory for olfactory stimuli were assessed in healthy older (65+) and young adults. During the study phase, a male and a female source presented 16 odors to each participant one at a time. Each source presented 8 odors to the participant. As a way to assess source memory, the participant was asked to indicate whether an odor from the study phase was presented by the male or female. As a way to assess item memory, a study phase odor and a novel odor were presented and the participant was asked to indicate which was presented previously. Source memory for odors was impaired in older adults compared with young adults. However, there were no significant differences in odor item memory between young and older adults. Thus, source memory for olfactory stimuli may be a task that is particularly sensitive to age-related changes in the brain.

Adolescent↗
PubMed2006

Source and item memory for odors and objects in children and young adults.

Recall and recognition memory for odors are poorer in children than in adolescents. In addition, children perform worse than young adults on source memory tasks using visual and auditory stimuli. However, source memory for odor stimuli has not been examined in children. This study investigated source and item memory for odors and objects in children (7-10 years old) and young adults (18-24 years old). During the study phase, 1 male and 1 female experimenter (sources) randomly presented either 16 odors or 16 objects to the participant. Presentation alternated between sources so that each source presented 8 stimuli. Once the 16 stimuli were presented, the sources exited and a third experimenter began the test phase. To assess item recognition memory, a stimulus from the study phase and a novel stimulus were presented to the participant who was asked to choose the stimulus presented during the study phase. Source memory was assessed with the 8 stimuli from the study phase not used in the item memory task. The experimenter presented a stimulus and asked whether the male or female experimenter had presented the stimulus during the study phase. Results indicate that difference scores between item and source memory for odors were significantly larger for children than for young adults, indicating poorer source memory for children than adults. Difference scores for objects did not distinguish between groups. It has been suggested that the frontal lobes play a critical role in source memory and odor memory--a brain region that continues to develop into adolescence. Poor performance among children on the source memory task for odors may be due in part to immaturity of the frontal lobes.

Adolescent↗
PubMed2005

Olfactory dysfunction: a sequela of pediatric blunt head trauma.

OBJECTIVE: To evaluate olfactory function in children with blunt head trauma. METHODS: Eligible subjects were consecutive children presenting at San Diego Children's Hospital Emergency Department or Trauma Service with blunt head trauma. Thirty-seven head injured children mean age 10.11+/-2.74 were evaluated; 36 healthy age and gender matched community children, mean age 10.08+/-2.99, served as controls. The medical record was reviewed for clinical measures related to head injury (HI). All children underwent olfactory assessment with the San Diego Children's Odor Identification Test (SDOIT). Olfactory event-related potentials were recorded on a subset of head injured and control children. RESULTS: Three of 37 head injured children had olfactory dysfunction. The head injured hyposmics had signs of more severe head injury represented by lower Glasgow Coma Scores (GCS), 10.33+/-5.51, when compared to their normosmic counterparts with mean GCS of 14.06+/-2.82. When stratifying the head injured children by clinical measures, lower Glasgow Coma Score, and abnormalities on head CT scan were associated with poorer olfactory performance. CONCLUSION: Children with blunt head injury may suffer post-traumatic olfactory impairment. More severe head injuries are more likely to produce olfactory deficits. In cases of significant head injury, cranial nerve I evaluation is imperative.

Adolescent↗
PubMed2005

Olfactory and auditory event-related potentials in Huntington's disease.

The influence of Huntington's disease (HD) on the olfactory event-related potential (OERP), an electrophysiological measure of olfactory information processing, has not been reported to date. In the present study, olfactory and auditory event-related potentials (ERPs) were recorded monopolarly from Fz, Cz, and Pz electrode sites in 8 patients with HD and 8 age- and gender-matched control participants. Results demonstrated that individuals with HD were delayed compared with controls on the P3 component of the OERP (p<.001), with a trend toward a significant delay on the auditory ERP P3 (p<.06). The effect size for OERP P3 latency (pi(2)=.72) was larger than that for the auditory P3 (pi(2)=.24), which has previously been shown to be delayed in HD. Patients performed significantly worse than controls did on all neuropsychological measures. These measures significantly correlated with several components of the OERP. These findings extend the understanding of olfactory deficits in HD.

Acoustic Stimulation↗
PubMed2005

Eyeblink classical conditioning to auditory and olfactory stimuli: performance among older adults with and without the apolipoprotein E epsilon 4 allele.

Patients with Alzheimer's disease (AD) demonstrate slowed acquisition of the conditioned response (CR) in eyeblink classical conditioning paradigms (EBCC), although it is unknown how early in the course of the disease CR acquisition is affected. This study investigated whether changes in the rate of CR acquisition were apparent in nondemented older adults at greater genetic risk for developing AD (i.e., carriers of the apolipoprotein E [APOE] epsilon 4 allele). Both epsilon 4+ and epsilon 4- participants demonstrated CR acquisition to auditory and olfactory CSs; however, rate of acquisition to the olfactory CS was significantly slower in epsilon 4+ persons. Both groups acquired the CR to an auditory CS at the same rate. Results support olfactory compromise in the earliest stages of the AD disease process. ((c) 2005 APA, all rights reserved).

Acoustic Stimulation↗
PubMed2004

Apolipoprotein epsilon4 is associated with more rapid decline in odor identification than in odor threshold or Dementia Rating Scale scores.

Individuals with the apolipoprotein E epsilon4 genetic risk factor for Alzheimer's disease (AD) show deficits in olfactory function. The purpose of the present study was to examine longitudinally odor identification (odor ID), odor threshold, picture identification, and global cognitive status in allele positive (epsilon4+) and negative (epsilon4-) persons. Participants were initially given the San Diego Odor Identification test, an odor threshold test, and the Dementia Rating Scale (DRS). Participants were re-tested approximately four years later. The results indicate: (1) odor ID declined more rapidly in epsilon4+ than in epsilon4- normal elderly adults; (2) neither group exhibited a significant decline in odor threshold, picture identification or DRS scores. These results suggest that declines in odor identification occur before declines in other measures of dementia in persons at risk for AD because of their APOE allele genetic status.

Aged↗
PubMed2004

Differences between recognition memory and remote memory for olfactory and visual stimuli in nondemented elderly individuals genetically at risk for Alzheimer's disease.

Recognition and remote memory for olfactory and visual stimuli were assessed in nondemented elderly individuals positive for the apolipoprotein E 4 allele and in 4 negative controls to examine whether the 4 allele differentially affects recognition and/or remote memory depending on the modality of stimulus to be remembered. Compared to controls, 4 positive individuals committed more false positive recognition memory errors for olfactory but not visual stimuli suggesting that 4 positive individuals may show false positive errors for olfactory stimuli before deficits for other stimuli are detectable. There were no significant differences in familiarity ratings (a proposed measure of remote memory) suggesting that brain areas involved in remote memory are not affected in nondemented 4 positive individuals. The results suggest that neuropathological changes in nondemented individuals genetically at risk for Alzheimer's disease may differentially affect memory processes.

Aged↗
PubMed2004

Olfactory, auditory, and visual ERPs from single trials: no evidence for habituation.

Event-related potentials (ERPs) using olfactory, auditory, and visual stimuli were recorded from young adults to assess possible component habituation across single trials among modalities. A single-stimulus ERP paradigm was used that employed a 10-min inter-stimulus interval (ISI) to minimize possible sensory adaptation and three stimulus trials for each modality to assess initial habituation effects. The present findings were: (1) P3 amplitude does not habituate appreciably over the initial three trials but may increase from the first to second trial. (2) ERPs from a single-stimulus paradigm with a very long ISI produce significantly correlated component amplitudes for the olfactory, auditory, and visual modalities. (3) P3 amplitude from olfactory stimuli demonstrated scalp topography similar to that for auditory and visual ERPs. These findings suggest that the single-stimulus task using a long ISI produces highly comparable and stable P3 components from olfactory, auditory, and visual stimuli. Application of single-stimulus paradigm to olfactory ERP methods is supported.

Adult↗
PubMed2004

Improvement of fMRI data processing of olfactory responses with a perception-based template.

Neuroimaging and in particular functional magnetic resonance imaging (fMRI) of olfactory function relies on the ability to model the time course of brain responses elicited by odor stimuli. In this study we compared two templates of olfactory brain activation by comparing levels of correlation in regions critical to olfactory processing with either a stimulation-based template or a perception-based template, derived from perception profiles acquired off-line during a simulated fMRI session. fMRI signal was more correlated with the perception-based template than with the stimulation-based template in all regions. This effect was not observed when comparing correlations obtained with the exact same templates shifted in time by 12 s. Therefore, the improvement due to the use of the perception-based template was not only caused by a difference of shape between the stimulation-based and the perception-based template but was specifically related to the olfactory stimulation performed. These results suggest that the perception-based template better represents brain activity in response to olfactory stimulation and might help improve data processing of fMRI studies investigating olfactory function.

Adult↗
PubMed2004

Validation of a stimulation protocol suited to the investigation of odor-taste interactions with fMRI.

A protocol suited to the investigations of odor-taste interactions in a functional magnetic resonance imaging (fMRI) scanner is described and results that confirm the validity of that protocol are presented. Stimuli were dissolved in water and presented to the mouth of the participant through plastic syringes and plastic tubes as 50 microl every 3 s for 18 s. Participants were lying on the back to simulate the conditions in a fMRI scanner and gave pleasantness and intensity ratings in response to each stimulus using a Labeled Magnitude Scale (LMS). Stimuli were three concentrations of two tastants (i.e., sucrose and NaCl) and two odorants [i.e., ethyl butyrate (fruity) and citral (citrus)] and all possible odor-taste mixtures. Results showed that additivity of intensity in odor-taste mixtures was linear and did not depend on the pleasantness of the mixture. This study showed the feasibility of acquiring reliable psychophysical data with a stimulation device compatible with the fMRI environment and provided the foundation for the interpretation of future fMRI investigations of odor-taste interactions in flavor.

Acyclic Monoterpenes↗