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Biomedical subjects

C L Grady

Publications and source records attributed to C L Grady.

At least 91 records · Page 5Linked to original sources
PubMed1987

Neuropsychological and cerebral metabolic function in early vs late onset dementia of the Alzheimer type.

Differences in age at onset of dementia of the Alzheimer type (DAT) have been associated with differences in cognitive impairments and course of the disease. To investigate this, we examined cerebral metabolism and cognitive performance in early and late onset DAT patients, who had equivalent duration and severity of illness. Regional cerebral metabolic rates for glucose were measured in the resting state by positron emission tomography using [18F]2-fluoro-2-deoxy-D-glucose. A cross-sectional analysis showed no significant differences between the two groups in performance on neuropsychological tests, but the early onset patients showed significantly more parietal metabolic dysfunction than did the late onset patients. Longitudinal analysis showed no significant differences between early and late onset patients in rate of cognitive decline over a mean interval of 19 months. Thus, our results do not support the hypothesis of different subgroups in DAT based on age at onset, nor suggest a faster rate of cognitive decline in younger patients.

Age Factors↗
PubMed1987

Auditory evoked potentials in patients with dementia of the Alzheimer type.

Dementia of the Alzheimer type (DAT) disrupts the function of the central auditory nervous system as a result of temporal lobe pathology. Auditory brain stem response (ABR) and middle latency responses (MLR) were studied in a group of patients with DAT to determine whether a correlate of dementia existed in these electrophysiological potentials. Comparison of absolute and interwave latencies on ABR, and absolute latency and amplitude of the MLR in patients with DAT and normal aged controls showed no significant differences between groups for any measure. Further, no relationship with degree of dementia or temporal lobe involvement, as assessed through dichotic speech recognition studies, and auditory evoked potentials could be demonstrated. It was concluded that the temporal lobe atrophy and hypometabolism seen in DAT is not generally sufficient to disrupt the generating of ABR and MLR potentials; however, slow cortical and cognitive evoked potentials may be more sensitive to central auditory nervous system impairment in DAT.

Aged↗
PubMed1987

Decline in cerebral glucose utilisation and cognitive function with aging in Down's syndrome.

The cerebral metabolic rate for glucose (CMRglc) was measured with positron emission tomography and [18F]2-fluoro-2-deoxy-D-glucose in 14 healthy subjects with Down's syndrome, 19 to 33 years old, and in six healthy Down's syndrome subjects over 35 years, two of whom were demented. Dementia was diagnosed from a history of mental deterioration, disorientation and hallucinations. All Down's syndrome subjects were trisomy 21 karyotype. CMRglc also was examined in 15 healthy men aged 20-35 years and in 20 healthy men aged 45-64 years. All subjects were at rest with eyes covered and ears plugged. Mean hemispheric CMRglc in the older Down's syndrome subjects was significantly less, by 23%, than in the young Down's syndrome group; statistically significant decreases in regional metabolism (rCMRglc) also were present in all lobar regions. Comparison of the younger control group with the older control group showed no difference in CMRglc or any rCMRglc (p greater than 0.05). Assessment of language, visuospatial ability, attention and memory showed significant reductions in test scores of the old as compared with the young Down's syndrome subjects. These results show that significant age differences in CMRglc and rCMRglc occur in Down's syndrome but not in healthy controls, and that, although only some older Down's syndrome subjects are demented, significant age reductions in neuropsychologic variables occur in all of them.

Adolescent↗
PubMed1987

Topographical analysis of glucose metabolism, as measured with positron emission tomography, in dementia of the Alzheimer type: use of linear histograms.

A linear histogram method was employed to analyze brain images of glucose uptake obtained by positron emission tomography in patients with dementia of the Alzheimer type and in control subjects. A line was drawn by computer which traversed the image of a brain slice taken at 70 mm above and parallel to the inferior orbitomeatal line, and rCMRglc was plotted as a function of distance along this line in 3 brain areas: frontal, sensorimotor and parietal. Peak rCMRglc values were significantly decreased in moderately-to-severely demented patients relative to healthy age-matched controls, but not in mildly demented patients. Furthermore, both the mildly and the more severely demented patients differed from controls in having reduced ratios of parietal association to sensorimotor peak rCMRglc. The variances of right-left metabolic asymmetries did not differ significantly between Alzheimer patients and controls. Severity of dementia, as evaluated by scores on the Mini-Mental State Examination, correlated with ratios of peak rCMRglc in frontal and parietal cortex to that in sensorimotor cortex. These results indicate that measures of focal peak rCMRglc do not discriminate between mildly demented patients and controls, whereas focal ratios of rCMRglc, where the denominator corresponds to rCMRglc from a relatively spared region, provide useful measures of metabolic dysfunction in the early stages of Alzheimer's disease.

Aged↗
PubMed1987

Neocortical metabolic abnormalities precede nonmemory cognitive impairments in early dementia of the Alzheimer type: longitudinal confirmation.

Patterns or regional cerebral metabolism and neuropsychological function were studied longitudinally in 10 mildly demented patients with dementia of the Alzheimer type (DAT) and compared to those of moderately demented patients and controls. As reported previously (Haxby et al., 1986), the mildly demented patients initially had significant neocortical metabolic abnormalities, namely parietal reductions and right-left asymmetries, but did not differ from controls on any test of neocortically-mediated visuospatial and language functions. Right-left metabolic asymmetries correlated with neuropsychological discrepancies between visuospatial and language function in moderately demented but not mildly demented patients. We now report that longitudinal studies of these mildly demented patients showed significant decline of nonmemory cognitive function. Moreover, correlations of metabolic asymmetries with neuropsychological discrepancies between visuospatial and language functions became significant. These longitudinal results confirm our previous conclusion that neocortical metabolic abnormalities precede neocortically-mediated neuropsychological impairments in early DAT.

Alzheimer Disease↗
PubMed1986

Neocortical metabolic abnormalities precede nonmemory cognitive defects in early Alzheimer's-type dementia.

Neuropsychological function and resting regional neocortical glucose metabolism, as measured by positron-emission tomography, were studied in 22 patients with mild and moderate Alzheimer's-type dementia. Metabolic reductions in the parietal association cortex and increased left-right metabolic asymmetry were observed in patients with mild and moderate degrees of dementia. Five patients with mild dementia had no impairment of neocortically mediated neuropsychological function, yet they demonstrated these same neocortical metabolic abnormalities. Asymmetry of neocortically mediated, neuropsychological functions correlated with metabolic asymmetries in patients with moderate but not mild dementia. These results suggest that physiological dysfunction in the that physiological dysfunction in the association neocortex is evident in early Alzheimer's-type dementia before the neuropsychological consequences of that dysfunction are demonstrable.

Aged↗
PubMed1986

Relations among age, visual memory, and resting cerebral metabolism in 40 healthy men.

Visual memory, as measured by the Benton Visual Retention Test (BVRT), and resting regional cerebral metabolic rates for glucose (rCMRglc), as measured by positron emission tomography (PET) and [18-F]fluorodeoxyglucose, were examined in 40 very healthy men, aged 21 to 83 years. Age-related differences in visual memory were found but were significantly smaller than differences reported in the general population. This discrepancy is attributable to our rigorous health screening. The age-related differences found in this sample are estimates of the lower limit of population differences unconfounded by disease. Age-related differences on undistracted delayed visual memory were greater than differences on immediate visual memory, suggesting age-related differences in spontaneous elaborative visual information processing. No relation between visual memory and resting rCMRglc was found, supporting the hypothesis that mental abilities are unrelated to resting brain metabolism unless both functions are influenced by disease.

Adult↗
PubMed1986

Alzheimer's disease: metabolic uncoupling of associative brain regions.

Evidence indicates that Alzheimer's disease (AD) causes functional disconnection of neocortical association areas. In midly demented AD patients without measurable neocortically-mediated cognitive abnormalities, positron emission tomography demonstrates reduced parietal lobe glucose metabolism and left/right metabolic asymmetries in neocortical association areas. Similar metabolic abnormalities occur in moderately demented patients, but are accompanied by appropriate language and visuospatial discrepancies. Left/right metabolic asymmetries correspond with reduced numbers of partial correlations between metabolic rates in homologous right and left regions, and in the frontal and parietal cortices, indicating metabolic uncoupling among these regions. The affected association regions are those which demonstrate Alzheimer-type neuropathology post-mortem.

Alzheimer Disease↗
PubMed1986

Stability of metabolic and neuropsychological asymmetries in dementia of the Alzheimer type.

We examined right/left asymmetries in cerebral glucose utilization and neuropsychological performance in 16 patients with dementia of the Alzheimer type (DAT) who were studied twice over a mean interval of 15 months. Neuropsychological asymmetry was expressed as the difference between performance on a visuoconstructive task and a language task. Test/retest comparisons showed significant declines on the neuropsychological measures, but no significant changes in the neuropsychological and metabolic asymmetry indices. At both evaluations, significant correlations were found between neuropsychological asymmetry and metabolic asymmetry in frontal and parietal cortex. Individual patterns of metabolic and neuropsychological asymmetry in these patients with DAT seem to be stable.

Aged↗
PubMed1985

Computed tomographic analysis of brain morphometrics in 30 healthy men, aged 21 to 81 years.

Computed transverse axial tomography (CT) was employed to examine brain morphometrics in 30 healthy men, aged 21 to 81 years. Seven consecutive CT slices 30 to 80 mm above the inferior orbitomeatal line were analyzed. CT numbers in gray and white matter regions were not correlated significantly with age (p greater than 0.05), nor were right/left ratios for derived parameters. The volume of gray matter was correlated negatively with age (p less than 0.05), and the volume of cerebrospinal fluid correlated positively with age, in the seven slices. The volumes of the lateral and third ventricles were elevated in the elderly, and volumes of the thalamus and lenticular nucleus were reduced. The results demonstrate that brain atrophy, evidenced by a loss of gray matter and by dilatation of cerebrospinal fluid spaces, occurs in the healthy elderly, and provide baseline CT-derived brain morphometric data for healthy men in relation to age.

Adult↗
PubMed1985

Clinical history, brain metabolism, and neuropsychological function in Alzheimer's disease.

Data concerning 7 patients with a diagnosis of presumptive Alzheimer's disease (mean age, 65.6 years) are presented in detail in relation to the patients' regional cerebral metabolic rates for glucose. Rates were measured by positron emission tomography with fluorine 18-labeled fluoro-2-deoxy-D-glucose under conditions of reduced visual and auditory stimulation. A relationship was found between severity of dementia and brain metabolism. In patients with mild to moderate Alzheimer's disease, memory and intellectual deficits were evident without major reductions in absolute metabolic rates, while ratios of regional to whole brain metabolism revealed reductions in regions of the parietal lobes. In the late, severe form of the disease, brain metabolic rates were consistently and significantly reduced. The findings suggest that memory and intellectual deficits are reflected in reductions of brain metabolism in some brain regions in mild to moderate forms of Alzheimer's disease and that, in the late, severe form of the disease, reductions occur consistently throughout the brain.

Aged↗
PubMed1985

Relations between neuropsychological and cerebral metabolic asymmetries in early Alzheimer's disease.

Regional CMRglc (rCMRglc) values were determined with positron emission tomography (PET) in 10 patients with mild to moderate clinically diagnosed Alzheimer's disease (AD) and in 26 healthy controls. rCMRglc in frontal, parietal, and temporal association cortices were significantly more laterally asymmetrical in AD patients than in controls (p less than 0.05). Furthermore, lateral asymmetry of rCMRglc in AD patients but not in the control subjects correlated significantly with asymmetry of language and visuospatial functions such that lower left than right rCMRglc was associated with relatively greater impairment of language and vice versa. The results demonstrate that discrepancies between language and visuospatial deficits in patients with early AD are related to asymmetrical reductions in cerebral cortical glucose metabolism.

Aged↗
PubMed1985

Brain metabolism as measured with positron emission tomography: serial assessment in a patient with familial Alzheimer's disease.

This paper presents, for the first time, repeated assessments of cerebral metabolism and neuropsychological competence in early Alzheimer's disease. Regional cerebral metabolic rates for glucose were measured with positron emission tomography and 18F-fluoro-2-deoxy-D-glucose on three occasions at 8-month intervals, in a 57-year-old man with Alzheimer's disease of 2 1/2 years' duration and with a family history of neuropathologically confirmed Alzheimer's disease. Data were compared with mean cerebral metabolic rates from 12 healthy men. No differences in regional cerebral metabolic rates for glucose were found on the initial patient scan, whereas metabolism on the second and third scans was reduced significantly in the parietal lobes and bilaterally in some parietal lobe regions. Memory loss was demonstrable at the first scan, but then and at later scans, other aspects of cognitive performance remained within normal limits (Wechsler Adult Intelligence Scale, Boston Naming Test, Two-dimensional Block Construction). The results show that memory loss can precede a measurable reduction of cerebral metabolism in early Alzheimer's disease, but that later reductions in parietal lobe metabolism may not be accompanied by additional measurable neuropsychological deficits.

Aged↗
PubMed1985

Central auditory function in Alzheimer's disease.

The central auditory (dichotic) function of 38 patients with Alzheimer's disease was found to be significantly impaired when compared with a control group. Significant relationships were observed between dichotic scores and intelligence quotient, cortical atrophy in the temporal lobes, and cerebral glucose metabolism in the left temporal lobe. Comparing atrophy and glucose metabolism in the temporal lobes, we observed contralateral ear effects in dichotic performance as well as an interaction of asymmetry of atrophy with dichotic performance, consistent with previous models of dichotic listening in other forms of temporal lobe pathology.

Adult↗
PubMed1984

Alterations in auditory processing of speech stimuli during aging in healthy subjects.

Studies of auditory processing during aging in man have not provided a consensus on whether aging affects the ability to process speech stimuli. To evaluate the relationship between speech recognition tasks and age, we examined 36 male subjects between the ages of 21 and 83 years, who were screened for the absence of disease, particularly in the cardiovascular and neurologic systems. Measures were obtained on the following tests: pure tone thresholds, speech reception threshold, speech discrimination, low-pass filtered speech, and binaural fusion. A statistically significant correlation was found between pure tone thresholds and age for all frequencies. When the effect of peripheral hearing loss was taken into account, speech measures did not correlate with age, with the exception of low-pass filtered speech in the left ear. Our findings suggest that the aging process in healthy man is not necessarily accompanied by deficits in the processing of speech stimuli beyond those which are due to peripheral hearing loss.

Adult↗
PubMed1984

NIH Conference. Brain imaging: aging and dementia.

The brain imaging techniques of positron emission tomography using [18F]-fluoro-2-deoxy-D-glucose, and computed tomography, together with neuropsychological tests, were used to examine overall brain function and anatomy in three study populations: healthy men at different ages, patients with presumptive Alzheimer's disease, and adults with Down's syndrome. Brain glucose use did not differ with age, whereas an age-related decrement in gray matter volume was found on computed tomographic assessment in healthy subjects. Memory deficits were found to precede significant reductions in brain glucose utilization in mild to moderate Alzheimer's dementia. Furthermore, differences between language and visuoconstructive impairments in patients with mild to moderate Alzheimer's disease were related to hemispheric asymmetry of brain metabolism. Brain glucose utilization was found to be significantly elevated in young adults with Down's syndrome, compared with controls. The importance of establishing strict criteria for selecting control subjects and patients is explained in relation to the findings.

Adult↗
PubMed1982

Prediction of spike-wave bursts in absence epilepsy by EEG power-spectrum signals.

The EEGs of subjects with absence seizures were examined to determine if changes occurred prior to spike-wave bursts that could be used to predict bursts. A number of 20-s epochs of EEG prior to spike-wave bursts (preburst epochs) and during periods remote from bursts (control epochs) were examined in 5 subjects. Power-spectrum analysis was carried out on each epoch and frequency bands from 0 to 50 c/s were combined into 2-c/s bandwidths. Logarithmically transformed power values in each frequency band were entered into a discriminant analysis algorithm for each subject separately. Results were expressed in terms of a test for significant differences between preburst and control epochs (F statistic) and a "success ratio" of discriminant analysis classification, defined as the proportion of correct classifications in both groups, as obtained using a cross-validation procedure. A significant preburst EEG pattern was found in 4 of the 5 subjects, and success ratios ranged from 0.64. to 0.83. Each subject's preburst EEG seemed to be characterized by a unique pattern of changes, and thus no common prodromal signal was found. The EEG changes did not appear to be caused by overt behaviors, such as eye closure or drowsiness. The findings suggest that the preburst EEG pattern represents a functional alteration in brain activity which could arise from the burst-producing mechanism directly.

Adolescent↗