Saberi-Moghadam Sohrab, Ferrari-Toniolo Simone, Ferraina Stefano, Caminiti Roberto, Battaglia-Mayer Alexandra
Department of Physiology and Pharmacology, SAPIENZA University of Rome, Rome 00185, Italy.
Department of Physiology and Pharmacology, SAPIENZA University of Rome, Rome 00185, Italy
J Neurosci. 2016 Apr 20;36(16):4614-23. doi: 10.1523/JNEUROSCI.3300-15.2016.
The time course of neural variability was studied in three nodes of the parieto-frontal system: the dorsal premotor cortex (PMd, area 6), primary motor cortex (MI, area 4), and posterior parietal cortex (PPC, area 5) while monkeys made either direct reaches to visual targets or changed reach direction in response to an unexpected change of target location. These areas are crucial nodes in the distributed control of reaching and their lesion impairs trajectory formation and correction under different circumstances. During unperturbed reaches, neural variability declined before the onset of hand movement in both frontal and parietal cortex. When the original motor intention suddenly changed, neural variability displayed a complex and area-specific modulation because the perturbation of the motor state was signaled earlier in PMd than in MI and PPC. The comparison of perturbed versus unperturbed reaches revealed that, in the time between the onset of correction signal and trajectory change, identical hand movements were associated with different, therefore context-dependent, patterns of neural variability induced by the instruction to change hand movement direction. In PMd, neural variability was higher before the initiation of hand reach than before its correction, thus providing a neural underpinning to the phenomenon that it takes less time to correct than to initiate hand movement. Furthermore, neural variability was an excellent predictor of slow and fast reach corrections because it was lower during the latter than the former. We conclude that the analysis of neural variability can be an important tool for the study of complex forms of motor cognition.
No single study has been performed on neural variability during update of motor intention across monkey premotor, motor, and posterior parietal cortex. In perturbed reaches, target location changed unexpectedly during reaction time and the correction of hand trajectory required updating the original motor plan. Comparing unperturbed versus perturbed reaches revealed that neural variability displayed a complex context- and area-dependent pattern of modulation because, before trajectory correction, similar initial hand movements were associated with different patterns of variability depending on the instruction signal, and therefore on the future hand path and final destination. Furthermore, neural variability predicted both slow and fast hand movement corrections, also offering a neural underpinning to the phenomenon that it takes less time to correct than to initiate hand movement.
在顶叶 - 额叶系统的三个节点研究了神经变异性的时间进程：背侧运动前皮层（PMd，6区）、初级运动皮层（MI，4区）和后顶叶皮层（PPC，5区），实验中猴子要么直接伸向视觉目标，要么在目标位置意外改变时改变伸手方向。这些区域是伸手动作分布式控制中的关键节点，它们的损伤会在不同情况下损害轨迹形成和校正。在无干扰的伸手动作中，额叶和顶叶皮层的神经变异性在手部运动开始前就下降了。当原始运动意图突然改变时，神经变异性表现出复杂且区域特异性的调制，因为运动状态的扰动在PMd中比在MI和PPC中更早被信号化。对受干扰与无干扰伸手动作的比较表明，在校正信号开始与轨迹改变之间的时间内，相同的手部动作与由改变手部运动方向的指令所诱导的不同的、因此依赖于上下文的神经变异性模式相关。在PMd中，伸手开始前的神经变异性高于校正前，从而为校正比开始手部运动花费更少时间这一现象提供了神经学基础。此外，神经变异性是慢速和快速伸手校正的良好预测指标，因为后者期间的神经变异性低于前者。我们得出结论，神经变异性分析可以成为研究复杂形式运动认知的重要工具。
尚未有针对猴子运动前区、运动区和后顶叶皮层在运动意图更新期间神经变异性的单一研究。在受干扰的伸手中，目标位置在反应时间内意外改变，手部轨迹的校正需要更新原始运动计划。比较无干扰与受干扰的伸手动作发现，神经变异性表现出复杂的依赖于上下文和区域的调制模式，因为在轨迹校正之前，类似的初始手部动作根据指令信号，因此根据未来的手部路径和最终目的地，与不同的变异性模式相关。此外，神经变异性预测了慢速和快速手部运动校正，也为校正比开始手部运动花费更少时间这一现象提供了神经学基础。
