Increased resting-state brain entropy of parahippocampal gyrus and dorsolateral prefrontal cortex in manic and euthymic adolescent bipolar disorder.

Alterations of brain signal complexity may reflect brain functional abnormalities. In adolescent bipolar disorder (ABD) distribution of brain regions showing abnormal complexity in different mood states remains unclear. We aimed to analyze brain entropy (BEN) alteration of functional magnetic resonance imaging (fMRI) signal to observe spatial distribution of complexity in ABD patients, as well as the relationship between this variation and clinical variables. Resting-state fMRI data were acquired from adolescents with bipolar disorder (BD) who were in manic (n = 19) and euthymic (n = 20) states, and from healthy controls (HCs, n = 17). The differences in BEN among the three groups, and their associations with clinical variables, were examined. Compared to HCs, manic and euthymic ABD patients showed increased BEN in right parahippocampal gyrus (PHG) and left dorsolateral prefrontal cortex (DLPFC). There was no significant difference of BEN between the manic and the euthymic ABD groups. In manic ABD patients, right PHG BEN exhibited significantly positive relationship with episode times. Increased BEN in right PHG and left DLPFC in ABD patients may cause dysfunction of corticolimbic circuitry which is important to emotional processing and cognitive control. The positive correlation between PHG BEN and episode times of manic ABD patients further expressed a close association between brain complexity and clinical symptoms. From the perspective of brain temporal dynamics, the present study complements previous findings that have reported corticolimbic dysfunction as an important contributor to the pathophysiology of BD. BEN may provide valuable evidences for understanding the underlying mechanism of ABD. • Adolescent bipolar disorder(ABD) showed increased brain entropy(BEN) in parahippocampal gyrus/dorsolateral prefrontal cortex. • There is a close association between brain complexity(BEN) and clinical symptom(episode times) in manic ABD. • Altered brain temporal dynamics of the present study provided further proof of vital role of corticolimbic dysfunction in ABD. • BEN alteration may be not mood state specific, and it provide valuable evidence for the underlying mechanism of ABD. [ABSTRACT FROM AUTHOR]