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To date, the ketamine/PCP model of psychosis has been proposed to be one of the best pharmacological models to mimic schizophrenic psychosis in healthy volunteers, since ketamine can induce both positive and negative symptoms of schizophrenia. At subanesthetic doses, ketamine has been reported to primarily block N-methyl-D-aspartate (NMDA) receptor complex(More)
OBJECTIVE To assess the relationship between striatal dopa decarboxylase capacity, D2 dopamine receptor binding, and energy metabolism in Parkinson's disease (PD). DESIGN Positron emission tomographic (PET) studies of glucose and dopa metabolism and D2 dopamine receptor binding in the caudate nucleus and putamen of patients with PD at different Hoehn and(More)
This study investigated the processing of increasing monetary reward in nonsmoking and smoking subjects. The choice of the subject populations has been motivated by the observation of differences between nonsmokers and smokers in response to rewarding stimuli in a previous study. Subjects performed a pattern recognition task with delayed response, while(More)
We used PET with the tracers [18F]fluorodeoxyglucose (FDG), [18F]fluorodopa (FDOPA) and [11C]raclopride (RACLO) to study striatal glucose and dopa metabolism, and dopamine D2 receptor binding, respectively, in nine patients with multiple system atrophy. Ten patients with classical Parkinson's disease were investigated with the same three PET tracers' and(More)
This article reviews neuronal activity related to reward processing in primate and human brains. In the primate brain, neurophysiological methods provide a differentiated view of reward processing in a limited number of brain structures. Dopamine neurons respond to unpredictable rewards and produce a global reinforcement signal. Some neurons in the striatum(More)
With the purpose of studying neural activation associated with reward processing in humans, we measured regional cerebral blood flow in 10 right-handed healthy subjects performing a delayed go-no go task in two different reinforcement conditions. Correct responses were either rewarded by money or a simple "ok' reinforcer. Behaviour rewarded by money, as(More)
UNLABELLED The identification of discrete patterns of altered functional brain circuitry in preclinical Huntington's disease (HD) gene carriers is important to understanding the pathophysiology of this disorder and could be useful as a biologic disease marker. The purpose of this study was to use PET imaging of regional cerebral glucose metabolism to(More)
Regional cerebral blood flow (rCBF) in healthy controls and non-demented, non-depressed Parkinsonian patients was measured using H2(15)O PET while subjects performed a prelearned pattern recognition task with delayed response. To investigate differences between the two groups in response to reward, the experimental design consisted of three reinforcement(More)
The primary sensorimotor cortex of the adult brain is capable of significant reorganization of topographic maps after deafferentation and de-efferentation. Here we show that patients with spinal cord injury exhibit extensive changes in the activation of cortical and subcortical brain areas during hand movements, irrespective of normal (paraplegic) or(More)
BACKGROUND Neuroanatomical determinants of motor skill recovery after stroke are still poorly understood. Although lesion load onto the corticospinal tract is known to affect recovery, less is known about the effect of lesions to cortical sensorimotor areas. Here, we test the hypothesis that lesions of somatosensory cortices interfere with the capacity to(More)