The gating of movement depends on activity within the cortico-striato-thalamic loops. Within these loops, emerging from the cells of the striatum, run two opponent pathways—the direct and indirect basal ganglia pathway. Both are complex and polysynaptic but the overall effect of activity within these pathways is thought to encourage and inhibit movement respectively. In Huntington’s disease (HD), the preferential early loss of striatal neurons forming the indirect pathway is thought to lead to disinhibition giving rise to the characteristic motor features of the condition. But early HD is also associated with apathy, a loss of motivation and failure to engage in goal-directed movement. We hypothesised that in HD, motor signs and apathy may be selectively correlated with indirect and direct pathway dysfunction respectively. We used spectral dynamic casual modelling of resting state fMRI data to model effective connectivity in a model of these cortico-striatal pathways. We tested both of these hypotheses in vivo for the first time in a large cohort of patients with prodromal HD. Using an advanced approach at the group level by combining Parametric Empirical Bayes and Bayesian Model Reduction procedure to generate large number of competing models and compare them by using Bayesian model comparison. With this automated Bayesian approach, associations between clinical measures and connectivity parameters emerge de novo from the data. We found very strong evidence (posterior probability > 0.99) to support both of our hypotheses. Firstly, more severe motor signs in HD were associated with altered connectivity in the indirect pathway components of our model and, by comparison, loss of goal-direct behaviour or apathy, was associated with changes in the direct pathway component. The empirical evidence we provide here is demonstrates that imbalanced basal ganglia connectivity may play an important role in the pathogenesis of some of commonest and disabling features of HD and may have important implications for therapeutics.

中文翻译：

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不平衡的基底神经节连接与亨廷顿病的运动缺陷和冷漠有关

运动的门控取决于皮质-纹状体-丘脑环内的活动。在这些从纹状体细胞中出现的环路中，运行着两条对立的通路——直接和间接的基底神经节通路。两者都是复杂的和多突触的，但这些途径中活动的整体效果被认为分别促进和抑制运动。在亨廷顿氏病 (HD) 中，形成间接途径的纹状体神经元优先早期丧失被认为导致去抑制，从而产生该病的特征性运动特征。但早期 HD 也与冷漠、动力丧失和无法进行有目标的运动有关。我们假设在 HD 中，运动体征和冷漠可能分别与间接和直接通路功能障碍选择性相关。我们使用静息状态 fMRI 数据的光谱动态随机建模来模拟这些皮质纹状体通路模型中的有效连接。我们在一大群前驱期 HD 患者中首次在体内测试了这两种假设。通过组合参数经验贝叶斯和贝叶斯模型简化程序在组级别使用高级方法来生成大量竞争模型并通过使用贝叶斯模型比较来比较它们。通过这种自动化的贝叶斯方法，临床测量和连接参数之间的关联从数据中重新出现。我们发现了非常有力的证据（后验概率 > 0.99）来支持我们的两个假设。首先，HD 中更严重的运动体征与我们模型的间接通路成分的连接性改变有关，并且，相比之下，目标直接行为或冷漠的丧失与直接途径成分的变化有关。我们在这里提供的经验证据表明，不平衡的基底神经节连接可能在 HD 的一些最常见和致残特征的发病机制中发挥重要作用，并且可能对治疗具有重要意义。