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CONTEXT Postmortem studies have found evidence of γ-aminobutyric acid (GABA) deficits in fast-spiking, parvalbumin-positive interneurons in the prefrontal cortex in schizophrenia. Magnetic resonance spectroscopy studies in unmedicated patients have reported glutamine or glutamate-glutamine (Glx) elevations in this region. Abnormalities in these transmitters(More)
Glutamatergic abnormalities in corticostriatal brain circuits are thought to underlie obsessive-compulsive disorder (OCD). Whether these abnormalities exist in adults with OCD is not clear. We used proton magnetic resonance spectroscopy (¹H MRS) to test our hypothesis that unmedicated adults with OCD have reduced glutamate plus glutamine (Glx) levels in the(More)
BACKGROUND An imaging method to probe glutamate levels in vivo would allow the study of glutamate transmission in disease states and in response to therapeutic interventions. Here we demonstrate the feasibility of this approach for the first time using positron emission tomography and [(11)C] ABP688, a radiotracer for an allosteric site on the metabotropic(More)
The support vector machine (SVM) has been applied to the problem of bankruptcy prediction, and proved to be superior to competing methods such as the neural network, the linear multiple discriminant approaches and logistic regression. However, the conventional SVM employs the structural risk minimization principle, thus empirical risk of misclassification(More)
D₁ receptors are the main mediators of dopamine transmission in the cortex and subserve cognitive functions that are affected in patients with schizophrenia. Prior imaging studies have suggested abnormalities in the expression of these receptors in schizophrenia, but no conclusive picture has emerged yet. One source of discrepancy may have been prior(More)
Positron emission tomography (PET) and the high affinity D(2/3) radiotracer [(18)F]fallypride allow the assessment of D(2/3) receptor occupancy of antipsychotic drugs in striatal and extrastriatal brain regions. We measured regional occupancy attained across a range of clinical dosing by the partial D(2) agonist aripiprazole using these methods.(More)
The amphetamine challenge, in which positron emission tomography (PET) or single photon emission computed tomography radioligand binding following administration of amphetamine is compared to baseline values, has been successfully used in a number of brain imaging studies as an indicator of dopaminergic function, particularly in the striatum. [(18)F](More)