External authors:

• Marisleydis Garcia Saborit ( Pontificia Universidad Catolica de Chile , Millennium Inst Intelligent Healthcare Engn )
• Alejandro Jara ( Pontificia Universidad Catolica de Chile )
• Nestor Munoz ( Pontificia Universidad Catolica de Chile , Millennium Inst Intelligent Healthcare Engn )
• Carlos Milovic ( Pontificia Universidad Catolica de Valparaiso )
• Angeles Tepper ( Pontificia Universidad Catolica de Chile , Millennium Inst Intelligent Healthcare Engn )
• Luz Maria Alliende ( Pontificia Universidad Catolica de Chile )
• Carlos Mena ( Pontificia Universidad Catolica de Chile )
• Barbara Iruretagoyena ( Pontificia Universidad Catolica de Chile )
• Juan Pablo Ramirez-Mahaluf ( Pontificia Universidad Catolica de Chile )
• Camila Diaz ( Inst Psiquiatr Dr J Horwitz Barak )
• Ruben Nachar ( Inst Psiquiatr Dr J Horwitz Barak )
• Carmen Paz Castaneda ( Inst Psiquiatr Dr J Horwitz Barak )
• Alfonso Gonzalez ( Universidad Finis Terrae , Inst Psiquiatr Dr J Horwitz Barak )
• Juan Undurraga ( Universidad del Desarrollo , Inst Psiquiatr Dr J Horwitz Barak )
• Nicolas Crossley ( Pontificia Universidad Catolica de Chile , Millennium Inst Intelligent Healthcare Engn )

Abstract:

Background Psychosis is related to neurochemical changes in deep-brain nuclei, particularly suggesting dopamine dysfunctions. We used an magnetic resonance imaging-based technique called quantitative susceptibility mapping (QSM) to study these regions in psychosis. QSM quantifies magnetic susceptibility in the brain, which is associated with iron concentrations. Since iron is a cofactor in dopamine pathways and co-localizes with inhibitory neurons, differences in QSM could reflect changes in these processes. Methods We scanned 83 patients with first-episode psychosis and 64 healthy subjects. We reassessed 22 patients and 21 control subjects after 3 months. Mean susceptibility was measured in 6 deep-brain nuclei. Using linear mixed models, we analyzed the effect of case-control differences, region, age, gender, volume, framewise displacement (FD), treatment duration, dose, laterality, session, and psychotic symptoms on QSM. Results Patients showed a significant susceptibility reduction in the putamen and globus pallidus externa (GPe). Patients also showed a significant R2* reduction in GPe. Age, gender, FD, session, group, and region are significant predictor variables for QSM. Dose, treatment duration, and volume were not predictor variables of QSM. Conclusions Reduction in QSM and R2* suggests a decreased iron concentration in the GPe of patients. Susceptibility reduction in putamen cannot be associated with iron changes. Since changes observed in putamen and GPe were not associated with symptoms, dose, and treatment duration, we hypothesize that susceptibility may be a trait marker rather than a state marker, but this must be verified with long-term studies.