Department of Physiology and Pharmacology, SAPIENZA, University of Rome, Italy and.
Cereb Cortex. 2013 Nov;23(11):2644-56. doi: 10.1093/cercor/bhs250. Epub 2012 Aug 23.
The parietal mechanisms for online control of hand trajectory were studied by combining single-cell recording and reversible inactivation of superior parietal area 5 (PE/PEc; SPL) of monkeys while these made reaches and saccades to visual targets, when the target position changed unexpectedly. Neural activity was modulated by hand position, speed, and movement direction, and by pre- and/or postsaccadic signals. After bilateral muscimol injection, an increase in the hand reaction- and movement-time toward both the first and second targets was observed. This caused an increase in the time necessary for the trajectory correction, and therefore an elongation of the hand-path toward the first target location. Furthermore, hand trajectories were different in shape than control ones. An elongation of the eye reaction time to both first and second targets was also observed, which could partially explain the deficit of planning and correction of hand movement. These results identify the superior parietal lobule as a crucial node in the online control of hand and eye movement and highlight the role of the eye impairment in the emergence of the reaching disorder so far regarded as the hallmark of optic ataxia.
我们通过在猴子进行视觉目标的伸手和注视任务时，对其顶叶 5 区（PE/PEc；SPL）进行单细胞记录和可逆失活，研究了手轨迹在线控制的顶叶机制，当目标位置意外变化时。神经活动被手的位置、速度和运动方向以及注视前和/或注视后信号调制。在双侧毒蕈碱注射后，观察到手对第一个和第二个目标的反应和运动时间都增加了。这导致了轨迹校正所需的时间增加，因此手路径向第一个目标位置延长。此外，手轨迹的形状与对照轨迹不同。还观察到对第一个和第二个目标的眼反应时间延长，这可以部分解释手部运动计划和校正的缺陷。这些结果确定了顶叶上区作为手眼运动在线控制的关键节点，并强调了眼损伤在伸手障碍中的作用，这种障碍至今被认为是视觉共济失调的标志。
