遗传和环境对脑默认网络功能连接的影响：静息态功能磁共振成像的青少年双生子研究

The brain default mode network (DMN)is thought to play roles in internal mentation and spontaneous cogniton. Aberrant default-mode functional connectivity has been reported in a host of neurological and psychitric illness and in persons at genetic risk for such illness. Whereas the neurophysiological mechanisms underlying the default-mode connectivity are unclear, there is growing evidence that genetic factors play a role. In this study, we aim to estimate the relative contribution of genetic and environmental factors to individual differences in default-mode functional connectivity by employing a resting-state fMRI twin study.Subjects were 180 pairs of healthy same-sex adolescent twins aged 15 to 17 years old. The low frequency （0.01-0.08 Hz）BOLD signal time series were extrated from 11 regions of interest (ROI)in DMN.Pearson correlation coefficients were computed between each pairs of ROIs to represent the intensity of functional connectivity.The genetic and enviornmental contributions to default-mode functional connectivities were estimated by twin statistical models. This study can help us understand the origins of individual differences in default-mode functional connectivity. The estimates of heritability of default-mode functional connectivity can provide evidence required before it can be considered as endophenotype for psychiatric illness or to identify genes influencing intrinsic brain function.

研究表明，大脑默认网络在个体的内在精神活动和自发认知中起作用，默认网络功能连接的异常存在于很多神经和精神疾病患者以及具有遗传风险的个体中。虽然默认网络功能连接的神经生理基础还不清楚，越来越多的证据表明其具有遗传基础。本研究采用静息态fMRI的双生子设计,估计遗传和环境对青少年脑默认网络功能连接个体差异的影响程度。研究被试为180对15-17岁的同性别健康青少年双生子。提取默认网络内11个脑区的低频(0.01-0.08赫兹)静息态BOLD信号时间序列。每两个脑区之间计算皮尔逊相关系数来表示功能连接的强度。采用双生子统计模型对遗传和环境对每对脑区之间功能连接的影响程度进行估计。本研究可以帮助我们理解默认网络功能连接个体差异的起源。对默认网络功能连接遗传度的估计为其作为精神疾病内表型以及寻找影响大脑内在功能的基因提供了依据。

研究表明，大脑默认网络功能连接的异常与多种精神障碍存在相关。本研究主要考察了大脑默认网络功能连接的遗传基础，即采用双生子设计估计遗传和环境对青少年默认网络功能连接的影响程度。我们发现，默认网络脑区之间的功能连接的遗传基础存在异质性。其中，aMPFC, PCC, 和 pIPL 三个脑区的功能连接存在中等强度的遗传基础，其他脑区的功能连接遗传基础较弱，主要受环境因素的影响。本研究揭示了默认网络的功能连接存在起源的异质性，有助于今后精神疾病内表型的选取以及寻找默认网络功能连接的相关基因。