TUESDAY, Sept. 25 (HealthDay News) -- Memory formation in patients with a first episode of psychosis is selectively affected in the hippocampus only during the encoding of arbitrary pairs of images and not during successful memory encoding and associative processing, according to a report in the September issue of the Archives of General Psychiatry.
Martin Lepage, Ph.D., from McGill University in Montreal, Quebec, Canada, and colleagues performed functional magnetic resonance imaging during three memory processes in 26 patients with a first episode of psychosis and 20 healthy controls.
The researchers found that the activation of several brain regions, including the hippocampus, was normal in patients with psychosis during successful memory encoding and associative encoding. In contrast, there was reduced activity in the hippocampus and surrounding medial temporal areas during the encoding of arbitrary pairs of images in these patients. This was associated with a reduced ability to subsequently recognize arbitrary pairs relative to semantically related pairs.
"In a group of patients being treated for a first episode of non-affective psychosis, the hippocampus showed abnormal activation only in response to a manipulation of semantic relatedness and not during successful memory encoding and associative processing," the authors conclude.
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