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30.1 RELATIONSHIP BETWEEN CORTICAL EXCITATION AND INHIBITION, TASK-INDUCED BOLD RESPONSE AND FUNCTIONAL CONNECTIVITY: A COMBINED MR SPECTROSCOPY AND FUNCTIONAL MRI STUDY AT 7T IN FIRST EPISODE PSYCHOSIS

2019; Oxford University Press; Volume: 45; Issue: Supplement_2 Linguagem: Inglês

10.1093/schbul/sbz022.122

1745-1701

Adrienne C. Lahti, Gregory Overbeek, Timothy J. Gawne, Nina V. Kraguljac, Meredith A. Reid,

Advanced Neuroimaging Techniques and Applications

Schizophrenia (SZ) is a disorder of brain connectivity characterized by faulty interactions between spatially distinct brain regions. An imbalance between cortical excitation/inhibition has also been implicated, but the link between these abnormalities remains unclear. The present study used proton magnetic resonance spectroscopy (H-MRS) and fMRI to investigate how measurements of glutamate and GABA relate to the blood-oxygen-level-dependent (BOLD) response during a cognitive task and to functional connectivity (FC) between brain regions during a resting state, and how these relationships are altered in SZ. The use of a high field 7T scanner allowed for the separate measurements of glutamate, GABA, and glutamine. Twenty-one first episode psychosis patients (FEP) and matched healthy controls (HC) completed a Stroop task and a resting state fMRI scan. Neurochemical levels were measured in the dorsal anterior cingulate cortex (ACC). Within and between group comparisons of the BOLD Stroop response (incongruent>congruent trials) and of the ACC functional connectivity were performed. Multiple-regressions investigated how glutamate, glutamine, and GABA related to the BOLD response and to the ACC functional connectivity in HC and FEP separately. Another multiple–regression investigated between group-differences in the relationships between the BOLD response, the ACC functional connectivity and each of these neurochemicals. Compared to HC, FEP showed increased BOLD response within regions of the executive and default mode networks. There were significant between groups’ differences in ACC functional connectivity to the precuneus, right inferior parietal cortex, bilateral insula, and bilateral dorsolateral prefrontal cortex. Glutamate levels, but not glutamine or GABA, were significantly lower in FEP compared to HC. In FEP, the relationship between ACC glutamate levels and the BOLD response in regions of the posterior default mode network (DMN) was opposite to that of HC. Likewise, the relationship between ACC glutamate and ACC functional connectivity to the precuneus, a key region of the posterior DMN, was opposite between the groups. In FEP, but not HC, ACC GABA correlated with the local BOLD response and with the Stroop reaction time. FEP showed a significant relationship between ACC GABA and the ACC functional connectivity to the caudate; this relationship was absence in HC. In both groups, glutamine negatively correlated with the BOLD response in diverse regions, but these relationships were stronger and broader in HC. Between groups analysis revealed that in FEP, the relationship between ACC glutamine and the ACC functional connectivity to the right dorsolateral prefrontal cortex was significantly more positive in FEP compared to HC. These results suggest a mechanism whereby, in FEP, alterations in the relationship between cortical glutamate/GABA, and both the BOLD response during the Stroop and the ACC functional connectivity during a resting state is disrupting the dynamic of major neural networks, including DM, executive and fronto-striatal networks.