A Study Investigating the Relationship Between the Antipsychotic Response and Non-invasive Proxies of Neurochemistry in Schizophrenia

Currently, we cannot predict who will get better on first-line antipsychotic versus clozapine treatment. Although much evidence shows that dopamine and glutamate function are related to treatment response in schizophrenia, the utility of neuromelanin sensitive MRI (NM-MRI) as a measure of dopamine and magnetic resonance spectroscopy (MRS) as a measure of glutamate & glycine (a co-agonist of glutamate receptors) in predicting response to treatment have never been measured in the same sample. The evidence suggests that the function of these two neurotransmitter systems partially determines the response to antipsychotic medications. Additionally, an emerging type of resting-state functional MRI (rsfMRI), naturalistic movie-watching, has been shown to outperform traditional rsfMRI for functional connectivity-based prediction of behaviour and will be explored in the current study. Given the background information, our hypotheses are:

1.1) First-line antipsychotic users will have higher dopamine turnover resulting in a higher NM-MRI signal in the substantia nigra relative to clozapine users.

1.2) First-line antipsychotic users will have lower glutamate and/or glycine concentration as indicated by the MRS signal in the dorsal anterior cingulate relative to clozapine users.