Brain Asymmetry in Structure-Function Decoupling: Perspective from Graph Signal Processing

1987 

Abstract Submission 

Xiaoyu Zhang¹

¹School of Artificial Intelligence, Beijing University of Posts and Telecommunications, Beijing, Beijing

Xiaoyu Zhang  
School of Artificial Intelligence, Beijing University of Posts and Telecommunications
Beijing, Beijing

The left and right hemispheres of the human brain are structurally interconnected but functionally relatively independent two modules[1,2]. Although, convergent evidence has highlighted exist the white-matter architecture asymmetry underlying for the function activity asymmetry, however, there is no direct studies on regarding whether and how the hemispheric white-matter architecture supporting coordinated fluctuations in neural activity, differs between the two hemispheres. Here, by combining the network science [2] and graph signal processing[3], we explored the hemispheric effect and the "sex X hemispheric" interaction effects on degree of structure-function dependency, which was quantified by the structural decoupling index (SDI) [4].

922 healthy adults from the HCP S1200 release were included for whom both T1, resting state fMRI and diffusion MRI were available (425 males, aged 22–37 years old). All subjects provided written informed consent, and the research protocol was approved by the Institutional Review Board of Washington University. Please refer to Van Essen et al., (2013) for more details. For rs-fMRI processing procedures were performed by using GRETNA toolkit [6], including linear detrending, regression of WM and CSF averaged signals, temporal bandpass filtering (0.01-0.1 Hz). For the diffusion MRI, the whole brain tractography were performed by using the MRtrix3 [http://www.mrtrix.org/] with the following operations: multi-shell multi-tissue response function estimation, constrained spherical deconvolution, tractogram generation with 100 million output streamlines and SIFT. To construction the individual structural connectome construction, the intrinsic connectivity of homotopic areas (AICHA) atlas was used to define the network nodes. Finally, for each subject, 2 hemispheric structural networks were constructed. For each participant, we calculated the hemispheric-level structural decoupling index (SDI) for each hemispheric region, by using the graph signal processing methodological pipeline proposed by previous studies [5]. To test hemisphere and sex effects on the hemispherical SDI, we applied a linear mixed model [7], in which "hemisphere", "sex", and "hemisphere × sex" were fixed effects and "individual identity" was a random effect. To correct multiple comparisons, we used the Bonferroni method at 0.05 level.

As shown in Figure 1 A, the overall patterns of hemispheric SDI map were highly similar between two hemispheres no matter which weighted strategy were used (mean map: averaged r = 0.74, p < 10-5). For FN-weighted and FNr-weighted networks, regions in visual, sensory, motor and auditory cortices had the lowest SDI values (dark blue nodes) while cortices dedicated to higher-level cognitive function mainly located in dorsal anterior cingulate cortex, retro splenial Cingular cortex (light blue, yellow and light red nodes) presented relatively higher SDI values. However, the spatial pattern of SDI from the FA-weighted networks were inversed, with visual cortices showed the highest SDI values. The AI maps also affected by the weighted strategy. The regions with "Sex X hemisphere" interactions are shown in Figure 2A. For FN-weighted network, the regions mainly focus on superial frontal gyrus, parietal, SMA, thalamus. For FNr-weighted network, the regions mainly focus on frontal, middle temporal, hippocampus, Para hippocampal, and thalamus.

Our findings indicates that the weighted of structural networks affects the asymmetry patterns of structural-functional relationship.

Invasive Stimulation Methods Other

Diffusion MRI Modeling and Analysis ²

Other Methods ¹

Other - brain asymmetry，Structural-functional relationship