Motor intention activity in the macaque's lateral intraparietal area .2. Changes of motor plan
Motor intention activity in the macaque's lateral intraparietal area .2. Changes of motor plan
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DOI：
10.1152/jn.1996.76.3.1457
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发表时间：
1996-09-01
影响因子：
2.5
通讯作者：
Andersen, RA
中科院分区：
文献类型：
--
作者：
Bracewell, RM;Mazzoni, P;Andersen, RA
1.在配套文件中，我们报告说，在猴子的后顶叶皮层（PPC）的外侧顶内区（区LIP）的神经元的人口的主要信号编码的下一个预期的眼跳眼球运动在延迟期的记忆眼跳任务。这个结果预测，如果猴子改变了下一次扫视的意图，LIP活动应该相应地改变以反映新的计划。我们通过训练猴子根据命令改变扫视计划并记录LIP神经元在计划改变过程中的活动来测试这一预测。我们训练恒河猴（Macaca mulatta）保持对一个光点的注视，只要这个光点一直亮着，在此期间，我们简单地依次呈现一个、两个或三个周边视觉刺激，每个刺激之后都有一个延迟（记忆期，M）。在最后一次延迟之后，固定点消失了，猴子必须迅速扫视到最后一个目标出现的位置。猴子无法预测每次试验会出现哪些刺激，也无法预测有多少刺激。因此，他必须计划对每个刺激的扫视，因为它出现，并改变他的扫视计划，每当刺激出现在不同的位置。本实验记录了2只猴3个半球81个LIP区神经元的M期活动。我们预测，如果一个神经元的活动反映了猴子的计划眼跳，它的活动应该是高的，而猴子计划眼跳在神经元的运动场（MF），和低，而计划眼跳是在相反的方向。在我们的样本中，大多数神经元的活动随着猴子计划的眼跳的改变而改变，这与我们的假设一致。在一种情况下，猴子被视觉刺激指示改变他的计划，从在神经元的首选方向扫视到相反方向的扫视。在此条件下，81个神经元中有65个（80%）的活性显著降低（P < 0.05）。这些神经元的活动发生变化，以反映新的眼跳计划，即使这种变化的线索并没有出现在他们的RF。作为对照，我们在需要改变计划的试验中随机交错进行试验，在这些试验中，猴子必须制定两个连续的计划，以便在神经元的首选方向上进行扫视。22/31个神经元（79%）的活性保持不变（P < 0.05），表明神经元继续编码相同的扫视计划。在这项任务的一个变体中，所需扫视位置的提示是一个光点或扬声器发出的噪音。在这项任务中测试的22个神经元中，16个（73%）显示出与视觉或听觉刺激提示的计划变化一致的活动变化。猴子意图的改变，即使没有明显的行为，也表现在LIP活动的改变上。这些活动的变化可以诱导视觉或听觉线索是否被用来指示所需的计划的变化。因此，大多数LIP神经元不仅编码视觉刺激的位置，而且还编码将目光引导到特定位置的意图，而与目光转移是否实际发生无关。
1. In the companion paper we reported that the predominant signal of the population of neurons in the lateral intraparietal area (area LIP) of the monkey's posterior parietal cortex (PPC) encode the next intended saccadic eye movement during the delay period of a memory-saccade task. This result predicts that, should the monkey change his intention of what the next saccade will be, LIP activity should change accordingly to reflect the new plan. We tested this prediction by training monkeys to change their saccadic plan on command and recording the activity of LIP neurons across plan changes.2. We trained rhesus monkeys (Macaca mulatta) to maintain fixation on a light spot as long as this spot remained on. During this period we briefly presented one, two, or three peripheral visual stimuli in sequence, each followed by a delay (memory period, M). After the final delay the fixation spot was extinguished, and the monkey had to quickly make a saccade to the location of the last target to have appeared. The monkey could not predict which stimuli, nor how many, would appear on each trial. He thus had to plan a saccade to each stimulus as it appeared and change his saccade plan whenever a stimulus appeared at a different location.3. We recorded the M period activity of 81 area LIP neurons (from 3 hemispheres of 2 monkeys) in this task. We predicted that, if a neuron's activity reflected the monkey's planned saccade, its activity should be high while the monkey planned a saccade in the neuron's motor field (MF), and low while the planned saccade was in the opposite direction. The activity of most of the neurons in our sample changed in accordance with our hypothesis as the monkey's planned saccade changed.4. In one condition the monkey was instructed by visual stimuli to change his plan from a saccade in the neuron's preferred direction to a saccade planned in the opposite direction. In this condition activity decreased significantly (P < 0.05) in 65 (80%) of 81 neurons tested. These neurons' activity changed to reflect the new saccade plan even though the cue for this change was not presented in their RF.5. As a control we randomly interleaved, among trials requiring a plan change, trials in which the monkey had to formulate two consecutive plans to make a saccade in the neuron's preferred direction. The activity remained unchanged (P < 0.05) in 22 of 31 neurons tested (79%), indicating that the neurons continued to encode the same saccade plan.6. In a variant of the task, the cue to the location of the required saccade was either a light spot or a noise burst from a loudspeaker. Of 22 neurons tested in this task, 16 (73%) showed activity changes consistent with plan changes cued by visual or auditory stimuli.7. Alterations in the monkey's intentions, even in the absence of overt behavior, are manifested in altered LIP activity. These activity changes could be induced whether visual or auditory cues were used to indicate the required plan changes. Most LIP neurons thus do not encode only the locations of visual stimuli, but also the intention to direct gaze to specific locations, independently of whether a gaze shift actually occurs.