Patients with bipolar disorder and their first-degree relatives exhibit deficits in sustained attention, study results show.
The researchers found that euthymic bipolar I disorder (BD I) patients and their first-degree relatives had impairments in sustained attention on a continuous performance test (CPT), and these deficits were reflected in altered activity in several brain regions associated with sustained attention.
"The results of the present study suggest that behavioral and functional correlates of sustained attention seem to be useful trait markers for BD I," comment Gianna Sepede (University of Chieti, Italy) and colleagues.
The findings come from a study of 24 euthymic BD I patients, 22 of their unaffected first-degree relatives, and 24 mentally healthy individuals (controls). The groups were comparable in terms of ethnicity, gender, age, IQ, education, parental education, marital and employment status, and frequency of cigarette smoking.
All of the participants underwent a CPT in which single numbers (zero through nine) were presented on a screen for 200 milliseconds, at 2000 millisecond intervals. Participants were asked to press a "target" button when the number eight appeared or an adjacent "non-target button" for all other numbers.
Functional magnetic resonance imaging was used to assess the participants' brain activity during the task.
The researchers found that BD I patients and their relatives performed significantly worse than controls in terms of target accuracy, at 90.2% and 92.2% versus 95.6%, respectively. There were no significant differences among the groups regarding non-target accuracy.
During errors in target recognition, BDI patients and their relatives showed greater activation than controls in the bilateral insula and the posterior of the middle cingulate cortex.
During correct target recognition, relatives and controls exhibited activation of the right insula, whereas no such activation was observed in BD I patients.
The team also observed that relatives had greater deactivation in the posterior cingulate cortex/retrosplenial cortex than the other two groups during correct target recognition, as well as increased activation of the bilateral inferior parietal lobule and left insula.
Sepede and team summarize: "We found a selective impairment in error signaling and target detection that was behaviorally and functionally detectable in both euthymic BD I patients and non-affected first-degree relatives."
They add that sustained attention may be a "valid biomarker of genetic liability to BD."
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