Neural mechanisms for control of reaching in the monkey parietal cortex

众所周知，顶叶皮质参与对空间的感知。然而，最近对清醒猴子的神经生理学研究表明，顶叶皮质中的神经元参与了伸展和操纵的控制。在这个项目中，我们首先通过在顶内沟外侧岸的几个区域内微量注射蝇草醇来识别负责控制伸展和手操作的区域，然后记录这些区域的触达神经元以研究触达的神经机制。我们在两个区域注射蝇草醇：1)顶内沟外侧岸的前部(AIP区)，2)顶内外侧区的最前部(LIP区)。AIP区注射苍蝇酚可造成严重的手部操作障碍。在注射之前，猴子预先塑造了手指的形状，拿起了一小块食物，然而，注射后，猴子伸出手指，直到他们触摸到食物。扑热息痛在…中的应用多位于唇部前部，未致伸手不到位，手部整形不明显。错误的距离很小；猴子一次又一次地试图捡起一小块食物，直到它触及指尖。这些结果似乎表明，触觉和手操作的神经控制机制在顶内沟外侧岸被分成不同的区域，与触觉运动有关的神经元也几乎在同一区域被发现。我们训练猴子完成手操作任务和伸手任务。我们确定了64个神经元到达神经元，因为这些神经元在任务的到达阶段被强烈激活。当猴子接触到特定形状的物体时，几乎60%的神经元被优先激活，而其余的神经元在猴子伸手时被激活。我们还根据活动的主要成分将到达神经元分为三种类型。在优先激活的到达神经元中，“视觉优势”型神经元的亲缘关系显著高于非选择性激活的到达神经元。优先激活的触达神经元可能参与预塑运动，而不是触达运动。我们测试了24个神经元在运动方向上的选择性，然而，大多数神经元(19/24)在运动方向上不是选择性的。只有5个神经元在运动方向上具有选择性，但它们的选择性不是很强。我们还研究了凝视方向对一些神经元的影响，发现大约一半的神经元(5/11)在猴子到达注视点时更活跃。我们发现其他一些神经元在注视任务中非常活跃，在注视任务中，猴子将手静静地放在注视点上，但当手的视野被遮盖时，不活跃。这些结果表明，该区域的这类到达神经元可能在指向运动而不是弹道运动等到达运动的微调中发挥关键作用。较少

The parietal cortex is well known to be involved in perception of space. However, recent neurophysiological studies in awake monkeys indicated that neurons in the parietal cortex were involved in the control of reaching and manipulation. In this project, first we identified the responsible areas for control of reaching and hand manipulation by micro injection of muscimol into several areas of the lateral bank of intraparietal sulcus, then recorded reaching neurons in these areas to investigate the neural mechanisms of reaching.We injected muscimol into two areas : 1) Anterior part of the lateral bank of the intraparietal sulcus (Area AIP), 2) Most anterior part of lateral intraparietal area (area LIP). The injection of muscimol into area AIP caused sever deficit of hand manipulation. Before the injection the monkey preshaped its fingers to pick up a small piece of food, however, after the injection the monkey extended its finger until they touched the food. The injection of muscimol in … More to anterior part of area LIP caused miss-reaching without any deficits in preshaping of the hand. The distance of error was small ; the monkey tried to pick up a small piece of food again and again until it touched finger tip. These results seem to indicated that the neural control mechanisms for reaching and hand manipulation are segregated into different areas in the lateral bank of the intraparietal sulcus.Neurons related to reaching movements were also identified in almost same area. We trained the monkey to perform the hand manipulation task and the reaching task. We identified sixty four neurons as reaching neurons because these were activated vigorously during reaching period of the task. Almost 60% of these neurons were preferentially activated when the monkey reached to a particular shape of object, however, the rest were activated whenever the monkey reached out. We also classified the reaching neurons into three types by predominant component of activity. In preferentially activated reaching neurons, "visual dominant" type of neurons were significantly higher parentage than in non-selectively activated reaching neurons. Preferentially activated reaching neurons are likely involved in preshaping movement rather than reaching movement. We tested the selectivity in movement direction of 24 neurons, however, most of them (19 of 24) were not selective in movement direction. Only five neurons were selective in movement direction, however, their selectivity was not so sharp. We also investigated the effect of gaze direction in some neurons and found about half of them (5 of 11) were more active when the monkey reached toward the fixation point. We found some other neurons which were very active during the fixation task in which the monkey put its hand on the fixation point quietly but not active when the view of the hand was covered. These results suggest that this type of reaching neurons in this area may play a crucial role in fine adjustment of reaching movement such as pointing rather than ballistic movement. Less