Fronto-hippocampal function during temporal context monitoring in schizophrenia.

BACKGROUND: Patients with schizophrenia have difficulty using contextual information to recall the source of information. Given the importance of the hippocampus and prefrontal cortex (PFC) in this type of memory, we hypothesized that this cognitive deficit stemmed from aberrant fronto-hippocampal activation during memory retrieval.
METHODS: Patients with schizophrenia (n = 16) and age-matched comparison subjects (n = 16) underwent functional magnetic resonance imaging while performing a verbal memory task that requires intact use of temporal context. Blood oxygen-level dependent (BOLD) signal during correct memory decisions was compared between the two groups with statistical parametric mapping.
RESULTS: Contrary to our hypotheses, patients with schizophrenia demonstrated nearly identical memory performance to that of the comparison subjects. Despite this, there were significant between-group BOLD signal differences, including a pattern of task-dependent hypofrontality or hyperfrontality. In addition, whereas the highest-performing subset of the comparison group demonstrated robust modulation of hippocampal activity, this pattern was not seen in the highest-performing patients with schizophrenia.
CONCLUSIONS: Despite memory performance similar to that of comparison subjects, patients with schizophrenia activated different neural pathways to achieve this success. This might reflect underlying neuropathology in fronto-hippocampal circuitry, the use of an alternate cognitive strategy to accomplish task performance, or both.