Institute of Psychology, Brain and Development Laboratory, Leiden University, Leiden, The Netherlands.
Cereb Cortex. 2013 Jul;23(7):1695-702. doi: 10.1093/cercor/bhs163. Epub 2012 Jun 12.
Delay discounting, a measure of impulsive choice, has been associated with decreased control of the prefrontal cortex over striatum responses. The anatomical connectivity between both brain regions in delaying gratification remains unknown. Here, we investigate whether the quality of frontostriatal (FS) white matter tracts can predict individual differences in delay-discounting behavior. We use tract-based diffusion tensor imaging and magnetization transfer imaging to measure the microstructural properties of FS fiber tracts in 40 healthy young adults (from 18 to 25 years). We additionally explored whether internal sex hormone levels affect the integrity of FS tracts, based on the hypothesis that sex hormones modulate axonal density within prefrontal dopaminergic circuits. We calculated fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity, radial diffusivity (RD), and magnetization transfer ratio (MTR), a putative measure of myelination, for the FS tract. Results showed that lower integrity within the FS tract (higher MD and RD and lower FA), predicts faster discounting in both sexes. MTR was unrelated to delay-discounting performance. In addition, testosterone levels in males were associated with a lower integrity (higher RD) within the FS tract. Our study provides support for the hypothesis that enhanced structural integrity of white matter fiber bundles between prefrontal and striatal brain areas is associated with better impulse control.
延迟折扣，一种冲动选择的衡量标准，与前额叶皮层对纹状体反应的控制能力下降有关。在延迟满足中，这两个大脑区域之间的解剖连接仍然未知。在这里，我们研究了额纹状体（FS）白质束的质量是否可以预测延迟折扣行为的个体差异。我们使用基于束的扩散张量成像和磁化传递成像来测量 40 名健康年轻成年人（18 至 25 岁）的 FS 纤维束的微观结构特性。我们还根据激素调节前额叶多巴胺能回路中轴突密度的假设，探索了内部性激素水平是否会影响 FS 束的完整性。我们计算了 FS 束的分数各向异性（FA）、平均扩散系数（MD）、纵向扩散系数、径向扩散系数（RD）和磁化转移比（MTR），这是一种髓鞘化的可能测量方法。结果表明，FS 束内的完整性较低（MD 和 RD 较高，FA 较低），预示着两性的折扣速度更快。MTR 与延迟折扣表现无关。此外，男性的睾丸激素水平与 FS 束内的完整性较低（RD 较高）有关。我们的研究支持了这样一种假设，即前额叶和纹状体大脑区域之间的白质纤维束的结构完整性增强与更好的冲动控制有关。
