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 alteration 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 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 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 middle frontal gyrus(MFG) significantly decreased in mPBD patients. It was shown that thalamo-frontal hyperconnectivity with MFG in mPBD compared to HCs and ePBD subjects, and thalamo-frontal hypoconnectivity with precentral gyrus/SFG in ePBD subjects compared with that of HCs. 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.