Connectome analysis of the human brains structural and functional architecture provides a unique opportunity to understand the organization of brain networks. Recently, connectome fingerprinting using brain functional connectivity profiles as the unique traits was able to identify individuals from the group in the Human Connectome Project (HCP) datasets. In HCP s900 datasets, we extend connectome fingerprinting from functional to structural connectivity, identifying multiple relationships between behavioral traits and brain connectivity.
We included images from the HCP s900 release dataset 2. We focused on 144 unrelated subjects (64/80 male/female, age 28.5 ± 4.0) for which both diffusion MRI and resting state fMRI scans are available (3T Prisma, 32-channel head coil). Resting state fMRI time series data were acquired with TR/TE=720/33.1 ms, 2 mm³ isotropic resolution, multiband acceleration of factor 8, and a total scan time of 14:33 mins. Diffusion MRI scan parameters were b-max = 3000 s/mm², TR/TE=5520/89.5 ms, 1.25 mm³ resolution, multiband acceleration of factor 3, and the total scan time of 9:50 mins. T1-weighted imaging with TR/TE=2400/2.14ms, 0.7 mm³ isotropic resolution was used for registration.
Preprocessing of the functional pipeline includes artifact removal, motion correction (Friston 24-parameter motion-model) and registration to the standard space. We employ a functional parcellation into 268 regions which was recently reported by Shen et al. 3. The Pearson’s correlation was used to calculate the functional connectivity matrices, here referred to as the functional connectome (FC). This FC can be subdivided into eight resting-state cortical and subcortical networks (see Fig. 1) based on location. To obtain meaningful fiber bundles, we employed, besides the previously mentioned functional parcellation, a tractography-based twenty-five fiber bundle template as the structural parcellation (see Fig. 1). For each subject, the structural connectivity matrices (SC) were calculated as the number of the streamlines connecting each pair of regions. Similar to the FC, the SC were subdivided in seven major fiber bundles (CC, Cingulum, OR, Fx+CP+CA, MCP+SCP+ICP, CST+FPT+POPT, UF+SLF+ILF; see Fig. 1) 4,5. All the SC/FC parcellations were transformed to individual diffusion spaces using Elastix 6 and tractography was performed with a deterministic streamline tracking algorithm 7 (turning angle threshold 45⁰, fiber length between 20-500 mm, one million tracts). We selected 29 non-image subject demographic (age, sex, income, education level, etc.) and cognitive behavior (including handedness, working memory, control attention, intelligent score, language score and visual spatial) measurements from the HCP data dictionary 8,9. The fingerprinting evaluation model used leave-one-out cross validation (LOOCV) and false discovery rate (FDR) correction in order to train and test correlations of these measurements with functional/structural connectivity.
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4. “ISMRM Tractography challenge.” http://www.tractometer.org/ismrm_2015_challenge/
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7. Yeh FC, Verstynen TD, Wang Y, Fernández-Miranda JC, Tseng WYI (2014) Correction: Deterministic Diffusion Fiber Tracking Improved by Quantitative Anisotropy. PLOS ONE 9(1): 10.1371
8. https://wiki.humanconnectome.org/display/PublicData/HCP+Data+Dictionary+Public-+500+Subject+Release
9. Smith, Stephen, Thomas Nichols, Diego Vidaurre, Anderson Winkler, Timothy Behrens, Matthew Glasser, Kamil Ugurbil, Deanna Barch, David Van Essen, and Karla Miller. “A Positive-Negative Mode of Population Covariation Links Brain Connectivity, Demographics and Behavior.” Nature Neuroscience 18, no. 11 (November 2015): 1565–67. https://doi.org/10.1038/nn.4125.
10. Waller, Lea, Henrik Walter, Johann D. Kruschwitz, Lucia Reuter, Sabine Müller, Susanne Erk, and Ilya M. Veer. “Evaluating the Replicability, Specificity, and Generalizability of Connectome Fingerprints.” NeuroImage 158 (September 2017): 371–77. https://doi.org/10.1016/j.neuroimage.2017.07.016.
11. Powell, Michael, Javier Garcia, Fang-Cheng Yeh, Jean Vettel, and Timothy Verstynen. “Local Connectome Phenotypes Predict Social, Health, and Cognitive Factors.” bioRxiv, January 1, 2017. https://doi.org/10.1101/122945.
12. Fukushima, Makoto, Richard F. Betzel, Ye He, Martijn P. van den Heuvel, Xi-Nian Zuo, and Olaf Sporns. “Structure–function Relationships during Segregated and Integrated Network States of Human Brain Functional Connectivity.” Brain Structure and Function, October 31, 2017. https://doi.org/10.1007/s00429-017-1539-3.