Functional abnormalities of medial temporal cortex during novel picture learning among patients with chronic schizophrenia

Backround: Learning deficits are prominent among patients with chronic schizophrenia and are associated with poor everyday functioning. Little is known, however, about the brain physiology underlying these difficulties with encoding new information. Purpose: The purpose of the current study was to compare the brain response during novel picture encoding between patients with chronic schizophrenia and healthy individuals using functional magnetic resonance imaging (fMRI). Methods: Nine middle-aged patients with DSM-III-R or DSM-IV schizophrenia and 10 age- and education-comparable healthy individuals were studied. Using fMRI, the blood oxygenation level dependent (BOLD) signal was measured during novel picture encoding (experimental condition) and during presentation of a repeated picture (control condition). Encoding-related brain response was examined in both groups and compared between the patient and comparison groups in each voxel within four bilateral search regions (fusiform gyrus, parahippocampal gyrus, hippocampus, and inferior frontal gyrus). Results: Despite comparable subsequent ability to recognize the presented pictures, patients with schizophrenia showed abnormal encoding-related brain response in regions of the hippocampus and parahippocampal and fusiform gyrii compared to healthy individuals. In medial temporal regions, patients showed greater BOLD response during the control condition (repeated picture) than during the experimental condition (novel pictures). Conclusion: Abnormalities of the medial temporal brain systems examined in this study may underlie learning deficits in schizophrenia. Further research is needed to illuminate the role of these brain dysfunctions in poor everyday functioning and their amenability to treatment.