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Biomedical subjects

J Haxby

Publications and source records attributed to J Haxby.

8 recordsLinked to original sources
PubMed1995

Functional magnetic resonance imaging of the brain.

This conference reviewed the potential scope of application of recently developed techniques for functional magnetic resonance imaging (fMRI) of the brain. The most successful technique is based on the sensitivity of magnetic resonance imaging (MRI) to magnetic effects caused by the modulation of the oxygenation state of hemoglobin, which is induced by local variations in blood flow during task activation. Typically, the MRI signal increases by a few percentage points during brain activation because blood flow and oxygen supply sharply increase. Brain activation images with excellent combined spatial and temporal resolution have been obtained noninvasively using visual, sensorimotor, or auditory stimuli, or during higher-order cognitive processes such as language or mental imagery. Although sensitive to misregistration artifacts and macroscopic vessels, MRI permits both the direct correlation of function with underlying anatomy and repeated studies on the same person. It may become the method of choice for studies of mental and cognitive processes, presurgical mapping, monitoring recovery from stroke or head injuries, exploration of seizure disorders, or monitoring the effects of neuropharmaceuticals.

Animals↗
PubMed1990

Assessment of AIDS-related cognitive changes: recommendations of the NIMH Workshop on Neuropsychological Assessment Approaches.

This article presents an extended (7-9 hours) and a brief (1-2 hours) battery designed to evaluate early cognitive changes associated with seropositive, asymptomatic persons. The battery was recommended by an NIMH Workgroup which was guided by 10 principles in its development. The domains assessed by the battery are: (1) Indicators of Premorbid Intelligence; (2) Attention; (3) Speed of Processing; (4) Memory; (5) Abstraction; (6) Language; (7) Visuoperception; (8) Constructional Abilities; (9) Motor Abilities; and (10) Psychiatric Assessment. Although the battery assesses a wide range of psychological functioning, specific emphasis has been placed on divided and sustained attention as well as speed of processing and retrieval from working and long-term memory. Descriptions of both the traditional clinical tests and tasks used in cognitive psychology are provided. Although the Workgroup strongly recommends the use of the extended battery in order to ensure the most sensitivity, it recognizes that there may be situations in which this is not possible. In order to increase the likelihood that neuropsychological tests will identify neurologically affected CDC Stage II and III seropositive individuals, the Workshop recommends that each patient's protocol be rated by two trained neuropsychologists using the same clinical criteria. The Workgroup also recommends that a concerted effort be made to incorporate data from the extended and the brief batteries in some central data bank.

AIDS Dementia Complex↗
PubMed1986

Positron emission tomography in Alzheimer's disease.

Twenty-one patients with a clinical diagnosis of dementia of the Alzheimer's type (DAT) and 29 healthy, age-matched controls were studied using positron emission tomography (PET) and [18F]2-fluoro-2-deoxy-D-glucose to measure regional cerebral glucose consumption in the resting state. Reductions in ratio measures of relative metabolism in some parietal, temporal, and frontal regions were found in mild, moderate, and severe DAT groups. A significant increase in right/left metabolic asymmetry, particularly in parietal regions, also was seen in mild and moderate groups. Only in the severely demented patients was the absolute cerebral metabolic rate reduced significantly from control values. Fourteen patients had repeated PET studies, but only those patients with moderate to severe dementia showed a decline in IQ over 6 to 15 months. There were no significant changes in metabolic measures over time. PET is useful in quantifying regional cerebral dysfunction in DAT, even in the early stages of the disease.

Aged↗
PubMed1985

Evaluation of zimeldine in Alzheimer's disease. Cognitive and biochemical measures.

Neuropsychological and neurochemical effects of zimeldine, a relatively specific serotonin reuptake blocker, were examined in four patients with clinically diagnosed Alzheimer's disease, in a double-blind, placebo-controlled, crossover study. Individualized doses of zimeldine were administered to achieve target plasma zimeldine concentrations of approximately 50 (low) to 100 (high) ng/mL. Overall, there was no significant effect of zimeldine on memory or reaction time measures as compared with placebo. The drug significantly reduced (by up to 38%) 5-hydroxyindoleacetic acid concentrations in the cereobrospinal fluid and almost abolished (90% reduction) platelet serotonin uptake. Cerebrospinal fluid concentrations of 3-methoxy-4-hydroxy-phenylglycol, a major metabolite of norepinephrine, and homovanillic acid, the major metabolite of dopamine, were not altered. Our findings indicate that alterations in central and peripheral serotoninergic function by a serotonin reuptake blocker (zimeldine) are unaccompanied by measurable changes in memory and/or reaction time in patients presumed to have Alzheimer's disease.

Aged↗
PubMed1984

Human brain glucose utilization and cognitive function in relation to age.

Brain oxidative metabolism was examined with positron emission tomography and [18F]2-deoxy-D-glucose in 40 healthy men aged 21 to 83 years, under conditions of reduced visual and auditory stimulation. The mean cerebral metabolic rate for glucose (CMRglc) equaled 4.6 to 4.7 mg X 100 gm-1 X min-1 and did not correlate significantly with age (p greater than 0.05). Regional cerebral metabolic rates for glucose (rCMRglc) and Q ratios (rCMRglc/CMRglc), which had lower coefficients of variation than did rCMRglc, also did not correlate with age. Hyperfrontality of cerebral metabolism was absent at all ages. Age decrements were demonstrated in the error score on the Benton Revised Visual Retention Test and in the Performance Subtest scaled score of the Wechsler Adult Intelligence Scale (WAIS) but not in the Verbal Subtest scaled score of the WAIS. The cognitive test scores did not correlate with brain metabolic rates. The results indicate that brain oxidative metabolism, when measured under resting conditions with reduced sensory input, is not reduced in relation to age in healthy men. Furthermore, no significant relations between intelligence and resting cerebral metabolism are evident.

Adult↗
PubMed1983

Down's syndrome in adults: brain metabolism.

The cerebral metabolic rate for glucose, as measured with positron emission tomography and fluorine-18-labeled 2-deoxy-D-glucose, was significantly higher in four healthy young subjects with trisomy 21 syndrome (Down's syndrome) than the mean rate in healthy young controls. The rate of cerebral glucose utilization in the frontal lobe of a 51-year-old subject with Down's syndrome was significantly lower than the rate in the young subjects with this syndrome, but approximated the rate in middle-aged controls. Thus glucose utilization by the brain appears to be excessive in young adults with Down's syndrome but may decline with age in some brain regions.

Adult↗