Genetic risk for schizophrenia and brain function

Variation in a gene linked with schizophrenia is associated with the occurrence of psychotic symptoms and cognitive deficits, along with reduced activity in the frontal and temporal lobes of the brain, reports a paper in the December issue of Nature Neuroscience.

The most notable symptoms of schizophrenia are delusions and hallucinations, but the full syndrome is preceded by milder psychotic behaviours and includes general cognitive deficits. Over a 10-year period, Jeremy Hall and colleagues studied young people with schizophrenic relatives, who were therefore at high risk of developing schizophrenia themselves, to assess the differences between individuals who develop symptoms and those who do not. They report that people with a variant of the neuregulin 1 - NRG1 - gene that has been previously associated with schizophrenia were more likely to develop psychotic symptoms, and to have low IQ scores, than those without the variant. Furthermore, they found that people with the risky neuregulin 1 variant showed lower activation in parts of the frontal and temporal lobes of the brain as measured with functional magnetic resonance imaging - fMRI.The findings of this study suggest that the behavioural and neural precursors of schizophrenia may have a significant genetic contribution. Further research is required to determine the causal nature of the relationship between the reduction in brain activation and the effects of both genetic variation and cognitive dysfunction.(Source: Nature Neuroscience : University of Edinburgh : November 2006.)