Biomedical subjects

W W Barker

Publications and source records attributed to W W Barker.

41 records · Page 3Linked to original sources

PubMed1988

Sensitivity of cerebral glucose metabolism to age, gender, brain volume, brain atrophy, and cerebrovascular risk factors.

In 76 normal volunteers studied by positron emission tomography, with [18F]fluorodeoxyglucose, CMRglu was significantly lower in the elderly as compared with young subjects and significantly higher in females relative to males. However, in 58 of these subjects who also had magnetic resonance imaging scans, age and gender were found to be unrelated to CMRglu, when the effects of brain volume and brain atrophy on CMRglu were partialed out using covariate analyses. Individually, brain volume was found to have a significant effect on CMRglu, explaining approximately 17% of the variability in CMRglu measures and brain atrophy explaining approximately 8% of the variance in CMRglu. Together these two measures accounted for approximately 21% of the variance. Cerebrovascular risk factors in normal subjects were not found to affect mean CMRglu or the variability of CMRglu measures. In this study almost 80% of the variance in CMRglu could not be explained by any of the factors that had been considered. This implies a lack of sensitivity of absolute values of global CMRglu to the mild effects of brain dysfunction. Although some of the unexplained variance is probably methodological in origin, physiological factors that are difficult to quantify, such as the state of arousal, are likely to be contributory as well.

Adult↗

PubMed1988

Cerebral metabolic effects of a verbal fluency test: a PET scan study.

Sixteen normal volunteers were studied with [F-18] fluorodeoxyglucose and positron emission tomography scans during behavioral activation with a verbal fluency test, and 35 age-matched controls were studied with resting-state scans. There was an overall increase of the cerebral glucose metabolic rate of 23.3% during verbal fluency activation, compared to the resting state, with the greatest activation in bilateral temporal and frontal lobes. A negative correlation between test performance scores and indices of metabolism was found in frontal, temporal, and parietal regions. Damage to the left frontal lobe maximally affects scores on verbal fluency tests, but performing the test activates a network of regions, of which the left frontal lobe is only one. Proficient performance in verbal fluency seems to require less metabolic activation than poor performance, perhaps because of the efficiency of cognitive strategies employed.

Adult↗

PubMed1987

Behavioral activation and the variability of cerebral glucose metabolic measurements.

Variability in cerebral glucose metabolism was examined between and within subjects when paired studies were performed in the resting state or in a behaviorally activated state. Both normal and demented subjects were studied twice each, from 1 to 6 weeks apart, under near-identical conditions, using positron emission tomography (PET) and [18F]fluorodeoxyglucose. Resting state studies were repeated in nine normal and four demented subjects. A picture-viewing test, used for activation during PET, was used repeatedly in seven normal and five demented subjects. Within-subject variability, as assessed by the percent difference in metabolic rates in paired studies, was reduced by 60-70% for activation state compared to resting state studies in normals. It is concluded that PET studies of brain metabolism, which are designed to study the active brain, should indeed be performed in functionally activated states, as in addition to demonstrating metabolism during a defined functional state, activation studies show reduced variability of cerebral metabolic measures.

Aged↗

PubMed1987

Human task-specific somatosensory activation.

We used positron emission tomography to study normal patterns of local cortical metabolic activation induced by somatosensory stimuli. Palpation and sorting of mah-jongg tiles by textured design increased local glucose metabolic rate (lCMRgl), by 18% on average, in contralateral somatosensory cortex. A graphesthesia task gave a similar result. In contrast, vigorous vibrotactile stimulation of fingers, face, or knee did not produce a consistent focus of activation. Our results indicate that lCMRgl activation is best achieved by somatosensory tasks requiring an active perceptual effort.

Aged↗

PubMedDate not supplied

MR signal abnormalities in memory disorder and dementia.

MR imaging of the brain, performed in 86 normal subjects and 113 patients with objective memory disorder or dementia, demonstrated white- and gray-matter areas of high signal intensity on long TR images (short and long TE). Hyperintensities were analyzed with respect to size (on a scale of 0-3) and location: lesions were periventricular, subcortical, or cortical. The patients with memory disorder and dementia were categorized as having probable/possible Alzheimer disease, a combination of Alzheimer disease and multiinfarct cognitive disorder, or multiinfarct cognitive disorder alone on the basis of clinically determined Hachinski ischemic scores. Significant correlations were found between age and scores for periventricular lesions (r = .40, p less than .0005) and subcortical lesions (r = .39, p less than .0005) in normal subjects. Correlations were also found between the Hachinski ischemic score and scores for periventricular lesions (r = .21, p less than .01), subcortical lesions (r = .27, p less than .0002), and cortical lesions (r = .32, p less than .0005) in subjects with memory disorder/dementia. Comparing multiinfarct cognitive disorder, Alzheimer disease, and normal groups, the mean scores for periventricular lesions were 12.0 +/- 4.6, 7.6 +/- 4.8, and 3.4 +/- 2.6, while mean scores for subcortical lesions were 10.8 +/- 12.2, 4.1 +/- 6.4, and 0.8 +/- 1.2, respectively. Periventricular lesions were present in 99-100% of patients with Alzheimer disease and multiinfarct cognitive disorder. On the other hand, subcortical lesions, which were identified in 100% of patients with multiinfarct cognitive disorder, were present in only about half of the patients with Alzheimer disease.(ABSTRACT TRUNCATED AT 250 WORDS)

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