Hippocampal function distinguishes bipolar disorder from schizophrenia
MedWire News: Activation of the hippocampus and prefrontal cortex (PFC) during memory encoding and retrieval can help distinguish between schizophrenia and bipolar disorder patients, say researchers.
“The results demonstrate that these disorders can be distinguished at a group level using non-invasive neuroimaging,” say J Hall, from the University of Edinburgh, UK, and colleagues.
For the study, 15 patients with schizophrenia, 14 with bipolar disorder, and 14 mentally healthy comparison individuals performed a face–name memory task, during which functional magnetic resonance imaging was carried out.
The task involved participants learning a series of six face–name pairs in each of three task runs. Runs consisted of four blocks of encoding (40 seconds per block), four blocks of retrieval (40 seconds per block), and interspersed baseline blocks of fixation (14 seconds per block). The pairs remained the same within a given run, but changed between runs.
The patients with schizophrenia and bipolar disorder had almost identical performance across all task runs.
However, the groups showed significant differences in hippocampal and PFC activity, as measured by blood oxygen level-dependent activity.
The researchers report in the journal Psychological Medicine that patients with schizophrenia had significantly decreased anterior hippocampal activation during early encoding, compared with patients with bipolar disorder.
In contrast, bipolar disorder patients showed significantly lower activation of the left dorsal PFC during early encoding compared with patients with schizophrenia.
During early retrieval, patients with schizophrenia showed greater activation of the dorsomedial PFC, extending to the dorsal cingulated cortex, compared with bipolar disorder patients.
Hall et al also note that schizophrenia patients differed significantly from healthy comparison individuals, showing impaired superior temporal cortex activation during encoding and greater dorsal PRC activation during retrieval.
They conclude: “The ability to separate the two disorders using non-invasive imaging thus supports the view that there are separable components to the pathology underlying the two disorders and is of direct relevance to efforts to construct valid classifications of psychiatric illness.”
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By Lucy Piper