Functional and neurochemical brain changes in first episode

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Bipolar disorder is a dynamic condition with symptomatic fluctuations throughout its course. These fluctuations suggest that bipolar neurophysiology involves dysfunction of brain networks that maintain emotional homeostasis. Human emotional behavior appears to be modulated by ventral prefrontal cortical and subcortical brain regions that form the 'anterior limbic network.' Consequently, we hypothesize that the symptoms of bipolar disorder arise from dysfunction within this network. Specifically, functional imaging (fMRI) studies suggest that the anterior limbic network may be over-activated in bipolar patients, thereby producing the symptoms of this condition. Additionally, magnetic resonance spectroscopy (MRS) studies suggest that this over-activation results from anterior limbic hypermetabolism. Moreover, during mania, MRS studies report elevated glutamate (Glx) concentrations; excessive glutamatergic neurotransmission may underlie the excessive anterior limbic metabolism and activation of bipolar disorder. Bipolar disorder is progressive with increasing episode frequency early in the illness course, leading to an established, recurrent illness. Repeated increases in excitatory neurotransmission associated with manic episodes may cause glutamatergic neurotoxicity, thereby initiating neurophysiologic changes that produce progressive emotional instability. It is not known whether any of the standard treatments for bipolar disorder prevent these changes. Nonetheless, perhaps by decreasing excitatory glutamatergic neurotransmission, these medications might correct the hypothesized excessive anterior limbic activation and hypermetabolism, and diminish the risk of neurotoxicity, thereby preventing disease progression. Studies of early course patients, prior to significant disease progression, are needed to make these determinations. With these consideration in mind, the goals of this study are: 1) To use 1H-MRS to identify neurometabolic abnormalities in bipolar disorder at the time of the first manic episode, and then determine how these abnormalities change in response to lithium and olanzapine treatment; 2) To identify corresponding changes in fMRI brain activation to a cognitive probe (CRT-END) while receiving lithium and olanzapine therapy; and 3) To demonstrate that regional brain activation changes are associated with regional metabolic changes. To accomplish these aims, we will acquire integrated neurometabolic (MRS) and functional neuroanatomic (fMRI) measurements in first-episode manic bipolar and healthy subjects in order to refine neurophysiological models of bipolar disorder (Center goal 1); to identify MRS and fMRI markers of treatment response of acute mania to two mechanistically different medications (Center goal 2); and to identify potential predictors of treatment response for future studies (Center goal 3).