Yoshitaka Kumakura

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Sensation seeking is a core personality trait that declines with age in both men and women, as do also both density and availability of the dopamine D(2/3) receptors in striatum and cortical regions. In contrast, novelty seeking at a given age relates inversely to dopamine receptor availability. The simplest explanation of these findings is an(More)
OBJECTIVE In abstinent alcoholic patients, a low availability of dopamine D2/3 receptors in the ventral striatum and adjacent putamen was associated with a high level of craving for alcohol. Alcohol craving may also depend on presynaptic dysfunction of striatal dopamine production, which may contribute to the risk of relapse. In this study, positron(More)
Dopamine neurotransmission influences those cognitive processes, which are generally regarded as prefrontal cortical functions. In previous positron-emission-tomography (PET) studies, net blood-brain clearance of [18F]-fluoro-l-DOPA (FDOPA) correlated with impaired cognitive performance in patients with Parkinson's disease or schizophrenia. We hypothesized(More)
Dopamine is released under stress and modulates processing of aversive stimuli. We found that dopamine storage capacity in human amygdala, measured with 6-[(18)F]fluoro-L-DOPA positron emission tomography, was positively correlated with functional magnetic resonance imaging blood oxygen level-dependent signal changes in amygdala and dorsal anterior(More)
Fluid intelligence represents the capacity for flexible problem solving and rapid behavioral adaptation. Rewards drive flexible behavioral adaptation, in part via a teaching signal expressed as reward prediction errors in the ventral striatum, which has been associated with phasic dopamine release in animal studies. We examined a sample of 28 healthy male(More)
UNLABELLED In the management of rectal cancer after the combined therapy of the radiation and surgical operation, the evaluation of the prognosis is important. Although fluoro- 18-deoxyglucose positron emission tomography (FDG-PET) is considered as a useful tool for evaluation of therapeutic effect of this cancer as well as the other cancers, however, there(More)
Conventional methods for the graphical analysis of 6-[(18)F]fluorodopa (FDOPA)/positron emission tomography (PET) recordings (K(in)(app)) may be prone to negative bias because of oversubtraction of the precursor pool in the region of interest, and because of diffusion of decarboxylated FDOPA metabolites from the brain. These effects may reduce the(More)
Conventional indices of the utilization of FDOPA in living human brain have not consistently revealed important declines in dopamine function with normal aging. However, most methods of kinetic analysis have assumed irreversible trapping of decarboxylated FDOPA metabolites in brain, an assumption that is violated even in PET recordings of short duration.(More)
OBJECTIVES Levodopa is the immediate precursor of dopamine and the substrate for DOPA decarboxylase, an enzyme subject to regulation in living brain. To test whether this regulation changes in disease, we used Positron Emission Tomography (PET) with parametric mapping to measure the effect of levodopa on the net clearance of [(18)F]fluorodopa to brain (K,(More)
[(18)F]Fluoro-3,4-dihydroxyphenyl-L-alanine (FDOPA) was one of the first successful tracers for molecular imaging by positron emission tomography (PET), and has proven immensely valuable for studies of Parkinson's disease. Following intravenous FDOPA injection, the decarboxylated metabolite [(18)F] fluorodopamine is formed and trapped within terminals of(More)