Increased hippocampal blood volume and normal blood flow in schizophrenia

•Hippocampal activity is abnormal in schizophrenia.•CBV or CBF is typically reported to indirectly assess hippocampal activity.•We used DSC-MRI to assess several hippocampal hemodynamic parameters.•Hippocampal CBV, but not CBF or MTT, is increased in schizophrenia.•Complementary imaging methods are needed to best understand hippocampal dysfunction.

Neuroimaging studies have provided compelling evidence for abnormal hippocampal activity in schizophrenia. Most studies made inferences about baseline hippocampal activity using a single hemodynamic parameter (e.g., blood volume or blood flow). Here we studied several hemodynamic measures in the same cohort to test the hypothesis of increased hippocampal activity in schizophrenia. We used dynamic susceptibility contrast- (DSC-) magnetic resonance imaging (MRI) to assess blood volume, blood flow, and mean transit time in the hippocampus of 15 patients with chronic schizophrenia and 15 healthy controls. Left and right hippocampal measurements were combined for absolute measures of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT). We found significantly increased hippocampal CBV, but normal CBF and MTT, in schizophrenia. The uncoupling of CBV and CBF could be due to several factors, including antipsychotic medication, loss of cerebral perfusion pressure, or angiogenesis. Further studies need to incorporate several complementary imaging modalities to better characterize hippocampal dysfunction in schizophrenia.