ASSOCIATIONS BETWEEN NEUROMELANIN ACCUMULATION IN PATIENTS WITH SCHIZOPHRENIA AND TREATMENT RESPONSIVENESS: A CROSS- SECTIONAL NM-MRI STUDY
Bibliographic record
Abstract
Abstract Background Neuromelanin (NM) is a byproduct of monoamine metabolism, including that of dopamine. NM-sensitive Magnetic Resonance Imaging (NM-MRI) sequences enable the in vivo quantification of NM levels in the substantia nigra (SN). The NM-MRI signal is considered a surrogate marker for the integrity of SN dopamine neurons and, consequently, striatal dopaminergic functioning. Elevated striatal dopamine synthesis is associated with patients responsive to first-line antipsychotics (FLR) in schizophrenia, while normal striatal dopamine synthesis is implicated in the pathophysiology of treatment-resistant schizophrenia (TRS). Clozapine is the only antipsychotic currently approved for TRS. However, no studies have yet explored the relationship between SN accumulations, as measured by NM-MRI, and clozapine response in TRS patients. Aims & Objectives The study aims to investigate differences in dopaminergic activities among schizophrenia patients based on their treatment response, using NM-MRI. Methods The study enrolled TRS patients who either did not respond to clozapine (ultra-resistant schizophrenia [URS]) or did respond (non-URS), along with FLR patients and healthy controls (HCs). TRS was defined as resistance to at least two first-line antipsychotics and ongoing clozapine treatment at the time of the study. SN-NM levels were measured using 3T-MRI. The Contrast Ratio (CR) was calculated as the relative signal intensity difference between the SN and the crus cerebri. SN-CR values were compared between groups, controlling for age and sex. Associations between SN-CR and symptom severity scores were also explored within patient groups. Results A total of 78 participants (URS: n=16; non-URS: n=16; FLR: n=20; HCs: n=26) completed the study. Overall group differences in SN-CR values were significant (F(3,72)=3.80, η2=0.21, p=0.001). Specifically, URS patients (Cohen’ s d=0.86, p=0.049) and FLR patients (Cohen’ s d=1.27, p<0.0001) exhibited higher SN-CR values compared to HCs. No associations were found between SN-CR values and symptom severity scores within each group or the entire patient cohort. Discussion & Conclusion This study is the first to assess a proxy measure of mesostriatal dopamine function in schizophrenia patients, stratified by treatment responsiveness, using NM-MRI. We observed elevated SN-NM contrast in URS and FLR patients compared to HCs, and levels similar to HCs in non-URS patients. Longitudinal studies are warranted to determine whether SN-NM levels can serve as a reliable biomarker for predicting treatment response in schizophrenia.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".