Elsinger Catherine L, Rao Stephen M, Zimbelman Janice L, Reynolds Norman C, Blindauer Karen A, Hoffmann Raymond G
Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
J Int Neuropsychol Soc. 2003 Nov;9(7):1088-98. doi: 10.1017/S1355617703970123.
Studies involving brain-lesioned subjects have used the paced finger tapping (PFT) task to investigate the neural systems that govern motor timing. Patients with Parkinson's disease (PD), for example, demonstrate abnormal performance on the PFT, characterized by decreased accuracy and variability changes, suggesting that the basal ganglia may play a critical role in motor timing. Consistent with this hypothesis, an fMRI study of healthy participants demonstrated that the medial frontostriatal circuit (dorsal putamen, ventrolateral thalamus, SMA) correlated with explicit time-dependent components of the PFT task. In the current fMRI study, PD patients and healthy age-matched controls were imaged while performing the PFT. PD patients underwent 2 imaging sessions, 1 on and the other off dopamine supplementation. Relative to controls, PD patients were less accurate and showed greater variability on the PFT task relative to controls. No PFT performance differences were observed between the on and off medication states despite significantly greater motor symptoms on the Unified Parkinson's Disease Rating Scale (UPDRS) in the off medication state. Functional imaging results demonstrated decreased activation within the sensorimotor cortex (SMC), cerebellum, and medial premotor system in the PD patients compared to controls. With dopamine replacement, an increase in the spatial extent of activation was observed within the SMC, SMA, and putamen in the PD patients. These results indicate that impaired timing reproduction in PD patients is associated with reduced brain activation within motor and medial premotor circuits. Despite a lack of improvement in PFT performance, PD patient's brain activation patterns were partially "normalized" with dopamine supplementation. These findings could not be attributed to greater head movement artifacts or basal ganglia atrophy within the PD group.
涉及脑损伤受试者的研究已使用节奏性手指敲击（PFT）任务来探究控制运动计时的神经系统。例如，帕金森病（PD）患者在PFT任务中表现异常，其特征为准确性降低和变异性改变，这表明基底神经节可能在运动计时中起关键作用。与这一假设一致，一项针对健康参与者的功能磁共振成像（fMRI）研究表明，内侧额纹状体回路（背侧壳核、腹外侧丘脑、辅助运动区）与PFT任务中明确的时间依赖性成分相关。在当前的fMRI研究中，对PD患者和年龄匹配的健康对照者在执行PFT任务时进行了成像。PD患者接受了2次成像检查，一次在补充多巴胺时，另一次在未补充多巴胺时。相对于对照组，PD患者在PFT任务中的准确性较低，变异性较大。尽管在未用药状态下统一帕金森病评定量表（UPDRS）上的运动症状明显更严重，但在用药和未用药状态之间未观察到PFT表现的差异。功能成像结果显示，与对照组相比，PD患者的感觉运动皮层（SMC）、小脑和内侧运动前区系统的激活减少。随着多巴胺替代治疗，PD患者的SMC、辅助运动区和壳核内的激活空间范围增加。这些结果表明，PD患者的计时再现受损与运动和内侧运动前回路内的脑激活减少有关。尽管PFT表现没有改善，但补充多巴胺后PD患者的脑激活模式部分“正常化”。这些发现不能归因于PD组中更大的头部运动伪影或基底神经节萎缩。
