Increased hippocampal CA1 cerebral blood volume in schizophrenia

• Hippocampal hyperactivity has been proposed as a biomarker in schizophrenia
• Subfield-specificity hyperactivity (anterior CA1 versus CA2/3) is currently debated
• We used contrast-enhanced MRI to test hyperactivity in these two subfields
• We find a significant diagnosis by group interaction due to the combined effect of a trend of increased CA1 CBV and non-significantly decreased CA2/3 CBV in patients compared to healthy controls
• No significant group differences in the anterior subiculum and dentate gyrus CBV

Hippocampal hyperactivity has been proposed as a biomarker in schizophrenia. However, there is a debate whether the CA1 or the CA2/3 subfield is selectively affected. We studied 15 schizophrenia patients and 15 matched healthy control subjects with 3T steady state, gadolinium-enhanced, absolute cerebral blood volume (CBV) maps, perpendicular to the long axis of the hippocampus. The subfields of the hippocampal formation (subiculum, CA1, CA2/3, and hilus/dentate gyrus) were manually segmented to establish CBV values. Comparing anterior CA1 and CA2/3 CBV between patients and controls revealed a significant subfield-by-diagnosis interaction. This interaction was due to the combined effect of a trend of increased CA1 CBV (p = .06) and non-significantly decreased CA2/3 CBV (p = 0.14) in patients relative to healthy controls. These results support the emerging hypothesis of increased hippocampal activity as a biomarker of schizophrenia and highlight the importance of subfield-level investigations.