Group Differences of Multiregion Glutamate Concentration in Clinical High Risk and Schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Glutamatergic system alterations are hallmarks of psychotic disorders, observed across clinical high-risk states (CHR), first episode psychosis (FEP), and schizophrenia.
• Previous research using proton magnetic resonance spectroscopy (¹H-MRS) has quantified glutamate, but a comprehensive pattern of regional changes remains uncharacterized.

Purpose of the Study:

• To investigate group differences in glutamate concentrations across key brain regions in individuals with CHR, schizophrenia spectrum (SCZ) disorders, and healthy controls.
• To explore the relationship between glutamate levels, diagnosis, and positive symptom severity.

Main Methods:

• Utilized ¹H-MRS to quantify glutamate concentrations in the left dorsal lateral prefrontal cortex, anterior cingulate cortex, associative striatum, and hippocampus.
• Analyzed data from 99 participants: 31 CHR, 30 SCZ (minimal antipsychotic exposure), and 38 healthy controls.
• Normalized ¹H-MRS data against white matter, gray matter, and cerebrospinal fluid fractions within regions of interest (ROIs).

Main Results:

• No significant differences in glutamate concentrations were found across the four ROIs between the CHR, SCZ, and control groups.
• Exploratory analyses revealed a significant interaction between brain region and positive symptom severity concerning glutamate concentration.
• Post hoc analyses indicated that higher positive symptom severity was significantly associated with elevated hippocampal glutamate concentrations.

Conclusions:

• Glutamate concentrations do not significantly differ between CHR, SCZ, and healthy individuals across the studied brain regions.
• Positive symptom severity in psychotic disorders may be specifically linked to altered glutamate levels in the hippocampus.