| Summary: | 碩士 === 國立陽明大學 === 神經科學研究所 === 99 === Sex is a key factor that shapes neural system and accounts for behavioral and cognitive variability at the level of populations. Some studies have indicated sex-related neuroanatomical differences might be derived from the white matter microarchitecture that further contributes to the sex differences in cognitive performances. However, sex differences in the overall topological organization of brain networks and the relation between sex-linked network properties and neuropsychological differences remain to be determined. In this thesis, we utilized diffusion tensor image (DTI) tractography to construct the fractional anisotropy (FA) weighted brain structural networks concurrently with the self-report assessments of empathizing quotient (EQ) and systemizing quotient (SQ) from 48 females and 50 males. Applying a graph theoretical analysis, both female and male brain exhibited a small-world topology (i.e., high local clustering and short path lengths linking nodes) in the FA-weighted brain network, implying an optimal balance between structurally segregated and integrative organization. This result was consistent with the previous sex-related brain network studies of healthy subjects. Moreover, we found that the overall network organization has no difference in sex. Further focusing on the regional level, males showed higher nodal efficiency at left orbital part of superior frontal gyrus, bilateral gyrus rectus, and right superior parietal gyrus. More importantly, we also demonstrated that the nodal efficiency of left orbital part of superior frontal was positive correlated with EQ score in female group, rather than males, which showed the interaction between network properties and dispositional measures. These finding provided the evidence for sexual dimorphism of structural brain networks. The variant correlations of neuropsychological behaviors and structural brain network between sexes might have implication for understanding specific diseases of breakdown in normal sexual dimorphism, such as schizophrenia or autism spectrum disorders.
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