Abstract
Bipolar disorder (BD) is clinically defined by alternating depressive and manic episodes with a separated period of euthymia. Thalamo-frontal loop plays vital role in psychotic symptoms, altered motor control and executive difficulties in BD. It remains unclear that structural and functional alterations of thalamo-frontal loop among the different mood states in BD, especially in pediatric BD(PBD).Twenty manic PBD (mPBD), 20 euthymic PBD (ePBD) and 19 healthy controls (HCs) were included in the study. By analyzing the T1 images and fMRI signals, thalamus volume and frontal grey matter cortical thickness were tested, and functional connectivity (FC) between bilateral thalamus and frontal cortex was calculated. Relationship between clinical indices and thalamo-frontal FC was also evaluated in mPBD and ePBD adolescents.Compared to HCs, the cortical thickness of left middle frontal gyrus (MFG), bilateral superior frontal gyrus (SFG) was significantly decreased in both mPBD and ePBD patients, and volume of left thalamus and cortical thickness of right MFG significantly decreased in mPBD patients. Compared to that of the HCs and ePBD subjects, thalamo-frontal hyperconnectivity with MFG was found in mPBD, and compared with that of HCs, thalamo-frontal hypoconnectivity with precentral gyrus/SFG was found in ePBD. In ePBD patients, episode times positively correlated with FC values between thalamus and precentral gyrus.The findings of the present study demonstrate detailed knowledge regarding shared and specific structural and functional disruption in thalamo-frontal loop in mPBD and ePBD subjects. Thalamo-frontal abnormalities reported in adult BD subjects were also observed in adolescent BD patients, and thalamo-frontal dysfunction may be a crucial treatment target in BD.
Highlights
Bipolar disorder is a psychiatric disorder characterized by severe intermittent mood disorders that vary between mania, depression, and euthymia(Altinay et al, 2016), affected about 3.9% of youth under age of 18(Van Meter, Moreira, & Youngstrom, 2019)
The goal of the present study is to explore alterations in volume of the thalamus, cortical thickness of the frontal regions and thalamo-frontal functional connectivity (FC) by analyzing T1 and BOLD signals of manic PBD, euthymic PBD and healthy controls (HCs)
While decreased volume of left thalamus and decreased cortical thickness of right IFG.ope and right middle frontal gyrus (MFG) were only found in manic PBD (mPBD)
Summary
Bipolar disorder is a psychiatric disorder characterized by severe intermittent mood disorders that vary between mania, depression, and euthymia(Altinay et al, 2016), affected about 3.9% of youth under age of 18(Van Meter, Moreira, & Youngstrom, 2019). Corticolimbic model, including ventrolateral circuit, ventromedial circuit, dorsolateral circuit and anterior cingulate circuit, had been put forward to explain internal and external emotional control along with cognition in bipolar disorder(Brooks & Vizueta, 2014). In this model, thalamus play a critical role through its bilateral projections with prefrontal cortex. Inconsistent results had been reported showing increased, decreased and no different volume and functional connectivity (FC) in thalamo-frontal loop in BD subjects. Little attention has been paid to the structural and functional changes of thalamo-frontal loop among different mood states in BD, especially in pediatric BD. Investigation of thalamus and frontal cortex networks in manic PBD (mPBD) and eythymic PBD(ePBD) may be crucial for understanding the pathophysiology of PBD
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