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Oxygen utilization increase is fractionally much less than that seen in glucose metabolism and blood flow soon after onset of neuronal activation, however its behavior during continued activation is less certain. We evaluated the effects of 25 min of visual stimulation on CBF, CMRO(2), and OEF using [(15)O] water and [(15)O] oxygen PET. Seven healthy(More)
Coupling of cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO(2)) in physiologically activated brain states remains the subject of debates. Recently it was suggested that CBF is tightly coupled to oxidative metabolism in a nonlinear fashion. As part of this hypothesis, mathematical models of oxygen delivery to the brain have been(More)
Amyloid-β (Aβ) plaque deposition can precede the clinical manifestations of dementia of the Alzheimer type (DAT) by many years and can be associated with changes in brain metabolism. Both the Aβ plaque deposition and the changes in metabolism appear to be concentrated in the brain's default-mode network. In contrast to prior studies of brain metabolism(More)
Amyloid-beta (Aβ) accumulation was evaluated with 2 [(11)C]Pittsburgh compound B (PiB) positron emission tomography scans about 2.5 years apart in 146 cognitively normal adults. Seventeen of 21 participants with initially elevated Aβ deposition demonstrated subsequent Aβ plaque growth (approximately 8.0% per year), and none reverted to a state of no Aβ(More)
The factors regulating cerebral blood flow (CBF) changes in physiological activation remain the subject of great interest and debate. Recent experimental studies suggest that an increase in cytosolic NADH mediates increased blood flow in the working brain. Lactate injection should elevate NADH levels by increasing the lactate/pyruvate ratio, which is in(More)
IMPORTANCE Individuals in the presymptomatic stage of Alzheimer disease (AD) are increasingly being targeted for AD secondary prevention trials. How early during the normal life span underlying AD pathologies begin to develop, their patterns of change over time, and their relationship with future cognitive decline remain to be determined. OBJECTIVE To(More)
In vivo quantification of β-amyloid deposition using positron emission tomography is emerging as an important procedure for the early diagnosis of the Alzheimer's disease and is likely to play an important role in upcoming clinical trials of disease modifying agents. However, many groups use manually defined regions, which are non-standard across imaging(More)
In human brain, short-term physiological stimulation results in dramatic and proportional increase in blood flow and metabolic rate of glucose but minimal change in oxygen utilization, however, with continuing stimulation, we have observed that blood flow response diminishes and oxygen utilization increases. Given the temporal limitation of conventional(More)
BACKGROUND Serotonin 5-HT(2A) receptors play an important role in the regulation of many functions that are disturbed in patients with major depressive disorder. Postmortem and positron emission tomography studies have reported both increased and decreased 5-HT(2A) receptor binding in different limbic and paralimbic regions. METHODS We conducted a(More)
In 19 patients with major depressive disorder, effective treatment with selective serotonin reuptake inhibitors (SSRIs) or amesergide (AMSG) was associated with increased cerebral perfusion in anterior cingulate cortex (SSRI and AMSG) and in medial prefrontal cortex (AMSG). Both selective serotonin reuptake inhibitors and AMSG exert antidepressant action(More)