MedWire News: In schizophrenia, levels of cell membrane fatty acids are associated with semantic memory and language and, subsequently, to clinical symptoms, US study findings suggest.

Previous studies have shown that semantic memory and language deficits are a feature of schizophrenia and are related to cognition and dopamine levels. It is likely that such deficits are due to a range of factors.

Noting that cell membrane compositions and dynamics have been linked to schizophrenia, Ruth Condray, from the University of Pittsburgh School of Medicine in Pennsylvania, and colleagues studied 37 male schizophrenia inpatients and 34 male normal controls.

The participants underwent processing speed, visuoperceptual, and executive function testing, as well as event-related brain potential (ERP) testing to determine the N400 measure of semantic memory and language during a semantic priming-lexical decision task that varied semantic association and the presentation rate, measured as stimulus onset asynchrony (SOA).

“N400 is an electrophysiological measure of semantic memory and language that is sensitive to deficits in schizophrenia,” explains the team.

Blood samples were also collected to assess red blood cell membrane fatty acid levels. Patients were examined under medicated and placebo conditions.

There were no significant differences between patients and controls in terms of age or performance on the word reading ability and premorbid intelligence tests, the researchers note in the journal Schizophrenia Research.

The findings indicated that N400 and word reading ability correlated only in unmedicated patients, with a significant negative association. N400 and digit symbol performance correlated negatively in both unmedicated patients and controls, with the relationships influenced by SOA.

N400 and vocabulary showed a positive correlation in unmedicated patients, while symptoms of paranoia correlated negatively with N400 priming effect. Furthermore, total polyunsaturated fatty acids levels correlated positively with N400 priming.

In medicated patients, N400 negatively correlated with cognitive performance, while N400 and picture completion score positively correlated. In addition, thought disturbances correlated positively with N400 priming effect.

The team concludes: “Results suggest cell membrane fatty acid composition and dynamics are associated with semantic memory in schizophrenia.

“Findings also suggest a series of linkages that are modulated by dopamine: cell membrane fatty acids are associated with N400 semantic priming; N400 semantic priming is associated with clinical symptoms.”

• Schizophr Res 2008; 106: 13–28