Person: Undurraga, Juan
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Undurraga
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Publication Quantitative Susceptibility Mapping MRI in Deep-Brain Nuclei in First-Episode Psychosis(2023) García Saborit, Marisleydis; Jara, Alejandro; Muñoz, Néstor; Milovic, Carlos; Tepper, Angeles; Alliende, Luz María; Mena, Carlos; Iruretagoyena, Bárbara; Ramírez-Mahaluf, Juan Pablo; Díaz, Camila; Nachar, Ruben; Castañeda, Carmen Paz; González, Alfonso; Undurraga, Juan; Crossley, Nicolás; Tejos, CristianBackground: 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.Publication Longitudinal changes in striatocortical connectivity in first-episode psychosis associated with the emergence of treatment resistance(2025) Tepper, Angeles; Vásquez, Javiera; Díaz, Camila; Ramirez, Juan; Aguirre, Juan; Barbagelata, Daniella; Aceituno, David; Undurraga, Juan; Nachar, Ruben; Mena, Cristian; McCutcheon, Robert; McGuire, Philip; Gonzalez, Alfonso; Crossley, NicolasTreatment resistance affects up to one in four individuals with psychosis in the first few years of illness. However, there is limited information about the brain changes associated with treatment resistance, restricting our ability to develop effective prognostic biomarkers or new treatments. Using resting-state functional MRI, we examined striatocortical connectivity in 87 patients who presented a non-affective first-episode of psychosis and 118 healthy controls, with follow-up imaging on more than half of the participants in the next 6 years, totaling 361 images. Crucially, we identified 30 patients who presented treatment-resistant psychosis in this follow-up period. Thus, we examined baseline (at first episode) and longitudinal striatocortical differences within psychosis subgroups (treatment-responsive and treatment-resistant psychosis), and between patients subgroups and healthy controls. Compared to healthy controls, participants with treatment-responsive psychosis presented baseline differences in functional connectivity of ventral striatal systems, without changes over time; whereas patients with treatment-resistant psychosis showed both baseline and longitudinal differences in ventral striatal systems, compared to healthy controls. Treatment-responsive and treatment-resistant psychosis groups differed in longitudinal changes in connectivity between ventral striatal and temporal cortical regions. This is one of the circuits which has been previously related to symptom improvements in patients with first-episode of psychosis. No baseline differences were observed between the two psychosis groups. Overall, treatment-resistant psychosis is characterized by longitudinal changes in striatal systems in early psychosis, which might be used as the basis of future prognostic biomarkers.