Differential Anterior Cingulate Activity During Response Inhibition in Depressed Adolescents with Bipolar and Unipolar Major Depressive Disorder

Objective: Cognitive control deficits are commonly seen in Depression of Bipolar Disorder (BDd) and Unipolar Major Depressive Disorder (UDd). Because failure to differentiate BDd from UDd has significant clinical consequences we aimed to identify differential patterns of neural activity in BDd versus UDd underlying response inhibition and motor control in adolescents.

Methods: Functional MRI was used to compare 12 BDd adolescents (mean age= 15.5±1.2) with age- and sex-matched ten UDd and ten healthy control (HC) adolescents during the performance of well-validated Go/NoGo task. NoGo response inhibition versus Go motor control blocks was used in whole-brain analysis and results were corrected for multiple comparisons.

Results: There were no significant behavioral or neuroimaging findings between adolescents with BDd and UDd. However, both groups relative to HC showed significantly higher left superior temporal and left caudate activity during the NoGo condition. Moreover, left anterior cingulate (ACC) activity relative to HC was significantly higher only in BDd - not UDd - adolescents during the NoGo condition, and left caudate activity was higher only in UDd - not BDd - adolescents during the Go condition. In addition, several neural regions including dorsolateral prefrontal (DLPFC) were positively correlated with increased reaction time in UDd - not BDd - adolescents.

Conclusions: Despite some similarities, neural correlates of depression are different in BDd and UDd relative to HC, and greater recruitment of ACC resources during response inhibition can help distinguish BDd.