Brain and Mind Centre, The University of Sydney, Sydney, NSW, Australia.
The University of Queensland, Brisbane, QLD, Australia.
Brain. 2019 Apr 1;142(4):1024-1034. doi: 10.1093/brain/awz034.
Parkinson's disease is primarily characterized by diminished dopaminergic function; however, the impact of these impairments on large-scale brain dynamics remains unclear. It has been difficult to disentangle the direct effects of Parkinson's disease from compensatory changes that reconfigure the functional signature of the whole brain network. To examine the causal role of dopamine depletion in network-level topology, we investigated time-varying network structure in 37 individuals with idiopathic Parkinson's disease, both ON and OFF dopamine replacement therapy, along with 50 age-matched, healthy control subjects using resting state functional MRI. By tracking dynamic network-level topology, we found that the Parkinson's disease OFF state was associated with greater network-level integration than in the ON state. The extent of integration in the OFF state inversely correlated with motor symptom severity, suggesting that a shift toward a more integrated network topology may be a compensatory mechanism associated with preserved motor function in the dopamine depleted OFF state. Furthermore, we were able to demonstrate that measures of both cognitive and brain reserve (i.e. premorbid intelligence and whole brain grey matter volume) had a positive relationship with the relative increase in network integration observed in the dopaminergic OFF state. This suggests that each of these factors plays an important role in promoting network integration in the dopaminergic OFF state. Our findings provide a mechanistic basis for understanding the Parkinson's disease OFF state and provide a further conceptual link with network-level reconfiguration. Together, our results highlight the mechanisms responsible for pathological and compensatory change in Parkinson's disease.
帕金森病的主要特征是多巴胺能功能下降;然而,这些损伤对大脑大尺度动力学的影响尚不清楚。很难将帕金森病的直接影响与重新配置整个大脑网络功能特征的代偿性变化区分开来。为了研究多巴胺耗竭在网络水平拓扑结构中的因果作用,我们使用静息态功能磁共振成像,对 37 名特发性帕金森病患者(多巴胺替代治疗 ON 和 OFF 期)和 50 名年龄匹配的健康对照者进行了研究。通过跟踪动态网络水平拓扑结构,我们发现帕金森病 OFF 期与更高的网络水平整合有关,而在 ON 期则相反。OFF 期的整合程度与运动症状的严重程度呈负相关,这表明向更整合的网络拓扑结构的转变可能是一种与多巴胺耗竭 OFF 期运动功能保留相关的代偿机制。此外,我们能够证明认知和大脑储备(即,发病前智力和全脑灰质体积)的测量值与在多巴胺能 OFF 状态下观察到的网络整合相对增加呈正相关。这表明这些因素中的每一个都在促进多巴胺能 OFF 状态下的网络整合中起着重要作用。我们的研究结果为理解帕金森病 OFF 状态提供了机制基础,并与网络水平重新配置建立了进一步的概念联系。总之,我们的研究结果强调了导致帕金森病病理性和代偿性变化的机制。