Neural mechanisms for control of reaching in the monkey parietal cortex

众所周知，顶叶皮层与空间感知有关。然而，最近对清醒猴子的神经生理学研究表明，顶叶皮层的神经元参与了伸手和操纵的控制。在本项目中，我们首先通过将蝇蕈醇微量注射到顶内沟外侧库的几个区域来确定控制伸手和手操作的负责区域，然后记录这些区域的到达神经元以研究伸手的神经机制。我们将蝇蕈醇注射到两个区域：1）顶内沟外侧岸前部（AIP区）; 2）外侧顶内区最前部（LIP区）。AIP区注射蝇蕈醇可造成严重的手操作功能障碍。在注射之前，猴子预先塑造了它的手指来拿起一小块食物，然而，在注射之后，猴子伸出手指，直到它们接触到食物。蝇蕈醇注射液 ...更多信息 LIP区的前部导致手的预成形没有任何缺陷。误差的距离很小，猴子一次又一次地试图拿起一小块食物，直到它碰到指尖。这些结果似乎表明，在顶内沟外侧岸，控制伸手和手操作的神经元分布在不同的区域，与伸手运动有关的神经元也几乎分布在同一区域。我们训练猴子执行手部操作任务和伸手任务。我们确定了64个神经元作为到达神经元，因为这些神经元在任务的到达期间被强烈激活。这些神经元中有近60%在猴子接触到特定形状的物体时被优先激活，而其余的神经元则在猴子伸出手时被激活。我们还根据活动的主要成分将到达神经元分为三类。在优先激活的到达神经元中，“视觉优势”类型的神经元比非选择性激活的到达神经元的父母显着更高。预激活的到达神经元可能参与预成形运动，而不是到达运动。我们测试了24个神经元的运动方向选择性，然而，大多数神经元（19/24）对运动方向没有选择性。只有5个神经元对运动方向有选择性，但选择性不明显。我们还研究了注视方向对一些神经元的影响，发现当猴子到达注视点时，大约一半的神经元（11个中的5个）更加活跃。我们还发现了其他一些神经元，它们在猴子安静地将手放在注视点的注视任务中非常活跃，但当手的视野被遮住时就不活跃了。这些结果表明，这种类型的到达神经元在这方面可能发挥了至关重要的作用，在微调达到运动，如指向，而不是弹道运动。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