Cue processing altered in siblings of schizophrenia patients
medwireNews: The siblings of patients with schizophrenia have altered activity in the ventral striatum during reward anticipation and receipt, a study shows.
“Since siblings share on average 50% of their genes with their ill relative, these results suggest that impaired reward processing may be related to the genetic vulnerability for schizophrenia”, say study author Max de Leeuw (University Medical Center Utrecht, the Netherlands) and colleagues.
However, they note that environmental influences cannot be ruled out, and suggest that further studies include monozygotic and dizygotic twin pairs in which one twin has schizophrenia.
For the study, 27 unaffected siblings of schizophrenia patients undertook computer-based tasks, some of which offered the potential to win a reward (€ 1). During tasks in which they were anticipating a reward, siblings’ brain activity in the left ventral striatum, the left supplementary motor area (SMA) and the right anterior insula was significantly reduced relative to that in 29 mentally healthy controls during reward anticipation.
The researchers say that reduced ventral striatal activity, when seen in schizophrenia patients, has been attributed to a “ceiling effect due to an overall increased dopaminergic tone”.
However, during the receipt of a reward, siblings had significantly increased activity in the bilateral ventral striatum and left orbitofrontal cortex relative to controls, and the size of the increase versus controls correlated with the size of the attenuation during reward anticipation.
“This argues against a dopaminergic ceiling effect as explanation for reduced ventral striatum during anticipation in siblings of patients”, the team writes in Schizophrenia Bulletin.
The researchers believe that dopamine dysfunction in the siblings means that brain activity is not properly triggered by cues signalling a potential reward, whereas activation during reward receipt is, relatively speaking, increased.
In support of this, siblings with the largest changes in activity relative to controls had very little change in response times during a task with a potential reward versus one without, whereas controls improved their response times if there was a potential reward.
“The failure in siblings to shift activation from outcome to cue is probably not specific for reward, but may reflect impaired cue processing in general”, observe de Leeuw et al.
Brain activation changes correlated with subclinical psychosis symptoms, with greater attenuation of ventral striatum activation during reward anticipation associated with higher scores in the negative domain of the Community Assessment of Psychic Experiences.
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By Eleanor McDermid, Senior medwireNews Reporter