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MRI shows abnormal cognitive activity in patients with psychosis

By Andrew Czyzewski
11 September 2007
Arch Gen Psychiatry 2007; 64: 999-1014

MedWire News: Patients with psychosis show reduced temporal brain activity when performing certain memory-encoding tasks, study findings indicate.

Among 26 patients with first-episode psychosis, the hippocampus showed normal modulation of activation during successful memory encoding, but abnormal activity during encoding of arbitrary pairs, compared with 20 healthy controls.

Amélie Achim (Brain Imaging Group, Douglas Hospital Research Université de Montréal, Quebec, Canada) and colleagues speculate that people who struggle to discriminate between arbitrary and related pieces of information may be prone to psychotic disorders.

The researchers note, however, that "the normal modulation of hippocampal activation observed during successful memory encoding in first-episode psychosis argues against a general inability to recruit this region."

Memory is greatly affected in schizophrenia. Behavioral observations suggest that episodic memory is affected early in the course of schizophrenia. Brain volume data suggest subtle structural abnormalities in the prefrontal cortex of schizophrenia patients.

For the current study, the researchers used functional magnetic resonance imaging (fMRI) to examine regional brain activity during three specific memory processes. These were associative versus item-oriented encoding, encoding of arbitrary versus semantically related image pairs, and successful versus unsuccessful memory encoding.

Patients with first-episode psychosis showed normal activation of several brain regions, including the prefrontal cortex, hippocampus, and parahippocampal cortex, during successful memory encoding and associative encoding. In contrast, the hippocampus and surrounding medial temporal areas showed reduced activity during the encoding of arbitrary pairs.

The hippocampus therefore shows either normal or abnormal modulation of activation depending on the specific cognitive process that was examined, says the team.

The researchers were surprised to find that patients with first-episode psychosis were still somewhat able to recruit brain regions involved in memory encoding, and suggest that this could be capitalized on to improve memory performance in such patients.

Achim et al comment in the Archives of General Psychiatry: "Because episodic memory has been shown to have a great influence on the functioning of patients with schizophrenia, improving memory performance could have a significant effect on the functional outcome of patients with first-episode psychosis."

Click here to see the rest of this article in MedWire News

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