Human social activities are realized by a synergy of neuronal activity over various regions of the brain, which is supported by their connectivity. In the present study, we examined associations between social activities, represented by work hours, and brain connectivity as quantified using diffusion tensor imaging (DTI). In 483 healthy participants, DTI analysis was performed using 3 T magnetic resonance imaging, and work hours were calculated, considering hours of paid employment (the “Work for Pay” category), hours of housework (the “Work at Home” category), and hours of school-related study (the “Student” category). The correlations between each class of work time and DTI indices were analyzed. The mean diffusivity (MD) values of the anterior limb of the internal capsule (ALIC) and the superior fronto-occipital fasciculus (SFO) were negatively correlated with total work hours (ALIC: r = -0.192, p = 2.3 × 10⁻⁵; SFO: r = -0.161, p = 3.8 × 10^-4). We also found that the MD values of the ALIC and the SFO were correlated with work hours in the Work for Pay category (ALIC: r = -0.211, p = 3.2 × 10^-6; SFO: r = -0.163, p = 3.4 × 10^-4) but not with those in the Work at Home category or the Student category. These results suggest that social activity is associated with the white matter microstructure of the ALIC and the SFO. The main difference between “Work for Pay” and the other two social activities appears to be the type of motivation—for example, external versus internal. Therefore, the white matter microstructure of the ALIC and SFO may be related to externally motivated social activities.

人类社交活动是通过大脑各个区域神经元活动的协同作用来实现的，并由它们的连通性来支持。在本研究中，我们检查了以工作时间表示的社交活动与使用扩散张量成像（DTI）量化的大脑连通性之间的关联。在483名健康参与者中，使用3 T磁共振成像进行了DTI分析，并计算了工作时间，其中考虑了带薪工作时间（“有偿工作”类别），家务工作时间（“在家工作”类别），和与学校相关的学习时间（“学生”类别）。分析了每类工作时间与DTI指标之间的相关性。r = -0.192，p  = 2.3×10 ^-5 ; SFO：r＝ -0.161，p  ＝ 3.8×10 ^-4。我们还发现，ALIC和SFO的MD值与有薪工作类别中的工作时间相关（ALIC ：r = -0.211，p  = 3.2×10 ^-6； SFO：r = -0.163，p  = 3.4 ×10 ^-4），但不适用于“在家工作”类别或“学生”类别中的用户。这些结果表明，社会活动与ALIC和SFO的白质微观结构有关。“有偿工作”与其他两种社会活动之间的主要区别似乎是动机的类型，例如外部动机与内部动机。因此，ALIC和SFO的白质微观结构可能与外部动机的社会活动有关。