巴金森氏症患者於觸覺刺激區辨之神經機制與失能

Abstract

正常人類的感覺功能和大腦的感覺動作迴路息息相關，而在動作迴路中多巴胺濃度低下的巴金森氏症患者上常有體感覺異常之情形，尤其是空間區辨與時間區辨之能力，這暗示著混亂的動作迴路與感覺動作功能之交互作用也許是導致巴金森氏症患者感覺異常的機制，然而對於相關機制之論述卻相當缺乏。在本篇研究中，我們藉由功能性磁振造影之方法探索此議題的大腦相關運作情形。總共有１６位巴金森氏症患者及１８位健康成人對照組參與本研究，實驗過程需執行二項主要任務：空間區辨（區分刺激位置）及時間區辨（區分刺激數目）任務。我們發現巴金森氏症患者在空間與時間區辨任務上之閾值都較健康對照組為高，此外，二組之腦部神經活化形態也有所不同。進行空間區辨的過程中，健康成年人主要徵召大腦皮質區域，相反地，患者則主要使用皮質下之區域。而在處理時間區辨任務時，正常受試者之皮質與皮質下腦區皆會參與運作，然而患者則主要利用雙側小腦完成任務。這些發現提供了我們對於巴金森氏症患者感覺異常之致病機轉的全新觀點。

In humans, somatosensory functioning relies on the interaction of the sensory and motor circuits in the brain. Patients with Parkinson’s disease (PD), a disease related to the decreased dopamine level in the motor circuits, frequently exhibit somatosensory abnormalities, especially in the spatial and temporal discrimination abilities. These observations suggest that deranged motor circuits and sensorimotor interactions may underlie sensory abnormalities in PD. However, little attention has been paid to elucidate the underlying neural mechanisms. In the current study, we address this issue by using functional magnetic resonance imaging (fMRI) to explore brain responses, when sixteen patients with PD and eighteen healthy controls (HC) performed spatial discrimination (SD; to differentiate the location of stimulation) and temporal discrimination (TD; to differentiate the number of stimuli) tasks. We found that PD patients exhibited increased discrimination thresholds in both temporal and spatial domains. On the neural level, fMRI patterns differ between PD and HC. For SD tasks, HC recruited more cortical brain regions, whereas PD patients mainly engaged subcortical areas. With regard to TD, HC recruited brain structures in both cortical and subcortical circuits, but PD patients employed bilateral cerebellum to achieve TD tasks. These findings provide new insights into the pathogenic mechanisms of sensory abnormalities in PD.