medwireNews: Patients at ultra-high risk for psychosis have altered brain activation during working memory tasks, despite equivalent performance to that of mentally healthy people, research shows.
The patients had reduced activation in the left anterior insula and increased task-related deactivation within the default-mode network.
“Together, these findings highlight the potential utility of detecting early brain changes to facilitate early treatment for at-risk persons,” say study author Michael Chee (Duke-National University of Singapore) and colleagues.
The 60 patients undertook a working memory task that required them to remember and match letters while undergoing functional magnetic resonance imaging; they performed it with similar accuracy and speed to 38 mentally healthy controls.
There were three task conditions – one required participants to recall and two to recall and manipulate information – and for all three tasks patients exhibited significantly less activation of the left anterior insula than controls.
This is also seen in schizophrenia patients, say the researchers. The area is thought to be involved in reacting to relevant stimuli by switching between the task-positive central executive network and the task-negative default-mode network, so patients struggle to activate the necessary attention and memory resources to perform tasks.
Areas of the default-mode network, including the posterior cingulate, were deactivated in all groups under all task conditions, but for the two harder memory tasks deactivation was significantly greater among patients than controls.
This “could reflect the need for greater effort in suppressing self-directed thought in at-risk persons,” comment Chee et al in TheAmerican Journal of Psychiatry.
The team also examined six regions of interest in the frontal and parietal lobes, finding that one region – the right posterior dorsolateral prefrontal cortex – showed significantly increased activation in patients versus controls during the two harder tasks.
This region is believed to be involved with executive processes in working memory, and its overactivation “could be compensatory for altered recruitment of the anterior insula,” suggest the researchers.
Activation of the right posterior dorsolateral prefrontal cortex positively correlated with symptom severity on the Positive And Negative Syndrome Scale. Chee and team suggest that this could represent an adaptive response to cognitive problems, or simply that at-risk patients find it harder to switch to task-driven cognitive. “Symptomatic individuals may have to cope with intrusive thoughts or auditory hallucinations,” they note.
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