Isabel Valli

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CONTEXT A major limitation on the development of biomarkers and novel interventions for schizophrenia is that its pathogenesis is unknown. Although elevated striatal dopamine activity is thought to be fundamental to schizophrenia, it is unclear when this neurochemical abnormality develops in relation to the onset of illness and how this relates to the(More)
BACKGROUND Cognitive models propose that faulty appraisal of anomalous experiences is critical in developing psychosis, particularly delusions. A data gathering bias may be fundamental to abnormal appraisal. AIMS To examine whether there is a data gathering bias in people at high risk of developing psychosis. METHOD Individuals with an at-risk mental(More)
OBJECTIVE While there is robust evidence of elevated dopamine synthesis capacity once a psychotic disorder has developed, little is known about whether it is altered prior to the first episode of frank illness. The authors addressed this issue by measuring dopamine synthesis capacity in individuals at ultra-high risk of psychosis and then following them to(More)
Despite robust evidence of hippocampal abnormalities in schizophrenia, it is unclear whether hippocampal dysfunction predates the onset of psychosis. We used functional magnetic resonance imaging to investigate hippocampal function in subjects with an at-risk mental state (ARMS). Eighteen subjects meeting criteria for an ARMS and 22 healthy controls,(More)
Schizophrenia is characterized by altered prefrontal activity and elevated striatal dopaminergic function. To investigate the relationship between these abnormalities in the prodromal phase of the illness, we combined functional Magnetic Resonance Imaging and 18F-Dopa Positron Emission Tomography. When performing a verbal fluency task, subjects with an(More)
BACKGROUND The glutamate model of schizophrenia proposes that altered glutamatergic neurotransmission is fundamental to the development of the disorder. In addition, its potential to mediate neurotoxicity raises the possibility that glutamate dysfunction could underlie neuroanatomic changes in schizophrenia. Here we determine whether changes in brain(More)
Brain derived neurotrophic factor (BDNF) is a critical component of the molecular mechanism of memory formation. Variation in the BDNF gene, particularly the rs6265 (val(66)met) single nucleotide polymorphism (SNP), has been linked to variability in human memory performance and to both the structure and physiological response of the hippocampus, which plays(More)
CONTEXT Alterations in glutamatergic neurotransmission and cerebral cortical dysfunction are thought to be central to the pathophysiology of psychosis, but the relationship between these 2 factors is unclear. OBJECTIVE To investigate the relationship between brain glutamate levels and cortical response during executive functioning in people at high risk(More)
BACKGROUND People at ultra high risk (UHR) of psychosis have an elevated risk of developing a psychotic disorder, but it is difficult to predict which individuals will make a transition to frank illness. We investigated whether functional magnetic resonance imaging (fMRI) in conjunction with a phonological fluency task at presentation could distinguish(More)
Converging in vivo evidence from neuroimaging studies indicates that psychotic disorders are associated with dysregulated striatal dopaminergic function, but whether the latter leads to the de novo onset of psychosis remains unclear (see reviews). We investigated this by using positron emission tomography to measure the longitudinal change in presynaptic(More)