Altered activity in functional brain networks involved in lexical decision making in bipolar disorder: An fMRI case-control study.

Background: Brain networks involved in language, attentional and response processes are detectable by fMRI during lexical decision (LD). Here, we investigated possible abnormalities in the functional networks involved in LD in patients with bipolar disorder (BD).
Methods: fMRI and behavioural data were compared between BD (n = 25) and control (n = 21), with groups matched for age and sex. The functional brain networks involved in LD were extracted by manipulating the "word-likeness" of LD stimuli and using a multidimensional analysis method.
Results: Attentional, response and language processes were captured in separate function-specific brain networks (default mode network, response network, linguistic processing network, respectively) in the BD and control groups, replicating the results of our previous study in an independent group of healthy adults. Behaviourally, the BD group showed higher performance than the control group in the LD task. Activity in the default mode network (DMN) and the linguistic processing network (LPN) did not differ between the groups, but the BD group had higher activation than the control group in the response network (RESP).
Limitations: Due to the small sample, the study is underpowered, capable of only detecting large effects.
Conclusions: The results suggest that BD may be associated with sustained activity in the RESP network, which might contribute to psychomotor dysfunction in BD. Future studies should investigate the possible link between altered RESP activation and psychomotor disturbances in BD, as well as the basis for altered RESP activity in BD.
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