In 2014, we began to design the Chinese Imaging Genetics (CHIMGEN) study, which aimed to create a large-sample Chinese neuroimaging genetics cohort, including genomic, environmental, neuroimaging and behavioral data, to enhance cross-ethnic and cross-geographic brain research. The data types could be divided into three sections: behavioral and environmental data, neuroimaging data and genetic data.
We evaluated verbal memory using the California verbal learning test (CVLT) Ⅱ, spatial memory using the Rey-Osterrieth (RO) complex figure test, working memory using the N-back test, executive function using the Go/No-Go task, fair decision making using the ultimatum game, information processing speed using the symbol digit modalities test (SDMT), and perspective taking using the ball tossing game. In addition, we also used the state and trait anxiety inventory (STAI) and the Beck depression inventory (BDI) Ⅱ to estimate anxiety and depressive state and used the tridimensional personality questionnaire (TPQ) to assess personality. As for environmental assessments, we adopted two methods. First, we applied the commonly used environmental questionnaires to assess urbanization and early life adversity. Second, we recorded the precise residential location of each participant in each year from birth to present which could be used to obtain more than a hundred of longitudinal natural and socioeconomic environmental assessments for each participant based on remote sensing satellite images and national survey databases.
Brain MRI data were acquired by 3.0-Tesla scanners from General Electrics, Siemens and Philips. The acquisition parameters were designed by experienced technicians and radiologists to ensure relatively consistent imaging quality across different scanners. The high-resolution structural magnetic resonance imaging (sMRI), diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) data were acquired in all centers, and diffusion kurtosis imaging (DKI) and arterial spin labeling (ASL) data were acquired in about two-thirds of the centers. These MRI modalities indicate different properties of the human brain structure and function. The sMRI can depict the cortical and subcortical structural features. The rs-fMRI and ASL can depict brain activity at rest, such as regional activity, seed-based functional connectivity and whole brain network topology. The anisotropy and orientation of white matter tracts can be identified by DTI and DKI. To reduce the influence of MRI scanners from different manufactures, we encouraged centers to acquire data using the MR 750 scanner of General Electrics for its relatively high image quality and popularity in China.
3. Genetic dataBlood samples were first collected from each participant and isolated into white blood cell and plasma, and then moved to Tianjin Medical University General Hospital (TMUGH) via professional cold-chain transportation to avoid DNA degeneration. The isolated blood samples from each participant were separately stored in five ultralow temperature refrigerators to avoid accidental data loss. Then, DNA was extracted using a semiautomatic procedure with quality control of DNA concentration and purification. A high-throughput genotyping chip designed for Asian population (Illumina Asian screening array chip) with 700,000 SNPs will be used for genome-wide genotyping with rigorous quality control.