Language lateralization reduced in first-episode schizophrenia
MedWire News: First-episode, antipsychotic-naïve schizophrenia patients show reduced language lateralization, suggesting that this deficiency is not a result of treatment, say researchers.
Writing in the journal Schizophrenia Research, Nicoletta van Veelen (University Medical Center Utrecht, The Netherlands) and team explain: "Diminished functional lateralization in language-related areas is found in chronic schizophrenia."
But they add: "It is not clear at what stage of illness these abnormalities in lateralization arise, or whether they are affected by medication."
To investigate further, and to study whether reduced language lateralization is related to positive symptoms, the team enrolled 35 first-episode, medication-naive schizophrenia patients, aged an average of 24 years, and 43 age- and parental education-matched mentally healthy controls.
All of the participants underwent functional magnetic resonance imaging of the brain while performing three language tasks: a paced verb generation task, an antonym generation task, and a semantic decision task.
The team calculated a lateralization index (LI), defined as the difference in signal intensity changes in the left versus the right hemisphere divided by the total sum of signal intensity changes, in seven regions of interest, including the main language-related areas.
The patients with schizophrenia were also assessed for symptoms using the Positive and Negative Syndrome Scale (PANSS).
The researchers found that over all seven regions of interest, the LI was significantly smaller in schizophrenia patients than controls, at an average 0.07 versus 0.18.
Regional LI differences between schizophrenia patients and controls were most prominent in the inferior frontal gyrus (Broca's area), at 0.12 versus 0.24, and the superior temporal gyrus (Wernicke's area), at 0.02 versus 0.23.
Subsequent comparison of left- and right-sided activation in these areas revealed no significant differences between patients and controls, suggesting that both sides contributed to the differences in LI.
In schizophrenia patients, LI was not associated with scores on the positive subscale of the PANSS, or with hallucinations or disorganization.
van Veelen and team conclude: "These findings suggest that language lateralization is impaired already in the first episode of the illness and is not a confound of medication use."
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By Mark Cowen