Eye position effects on the neuronal activity of dorsal premotor cortex in the macaque monkey
Eye position effects on the neuronal activity of dorsal premotor cortex in the macaque monkey
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DOI：
10.1152/jn.1998.80.3.1132
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发表时间：
1998-09-01
影响因子：
2.5
通讯作者：
Bremmer, F
中科院分区：
文献类型：
--
作者：
Boussaoud, D;Jouffrais, C;Bremmer, F
大脑的视觉输入映射在以视网膜为中心的参考系中，但运动系统在以身体为中心的参考系中规划运动。这一基本观察意味着大脑必须将目标坐标从一个参考系转换到另一个参考系。生理学研究表明，后顶叶皮层可能对这种转变做出了很大的贡献，但问题仍然是前运动区是否从顶叶皮层接收视觉信息，这些信息很容易编码在以身体为中心的坐标中。为了回答这个问题，我们研究了两只猴子的背侧前运动皮层 (PMd) 神经元，同时它们执行条件视觉运动任务并在不同的注视角度保持注视。视觉刺激呈现在视频监视器上，猴子在监视器底部的三个触摸板面板上进行肢体运动。当猴子将手放在中央垫上时，试验就开始了。然后，在试验后期，彩色提示指示肢体向左触摸板移动（如果是红色）或向右移动（如果是绿色）。提示持续了可变的延迟、指示的延迟周期，并且它们的偏移量充当开始信号。固定点出现在屏幕的中心或四个外围位置之一。由于猴子的头部受到限制，外围注视导致眼眶内眼睛的偏差，但对于每个注视角度，指导提示会在具有恒定视网膜中心坐标的九个位置呈现。在给出指导提示后，133 个 PMd 细胞表现出相态放电（信号相关活动），157 个 PMd 细胞在指示延迟期间处于紧张性活动（与组相关或准备活动），104 个在与运动相关的 go 信号后处于活动状态（运动相关活动）。大部分细胞显示出与肢体运动方向相关的放电率变化，但只有适度比例的细胞对提示的位置敏感（信号，43％；设置，34％；运动，29％）。更重要的是，大多数神经元的活动（信号，74%；集合，79%；运动，79%）随着眼眶位置的不同而显着变化（方差分析，P < 0.05）。回归分析表明，神经元活动沿水平轴和垂直轴随眼睛位置线性变化，并且可以通过二维回归平面来近似。这些数据提供的证据表明，眼睛位置信号调节感觉区域以外的神经元活动，包括涉及视觉引导的肢体运动的神经元活动。此外，他们还表明，与运动准备和执行相关的神经元活动至少结合了两个方向参数：手臂运动方向和空间注视方向。研究表明，大量 PMd 细胞在以头部为中心的参考系中编码肢体运动方向。
Visual inputs to the brain are mapped in a retinocentric reference frame, but the motor system plans movements in a body-centered frame. This basic observation implies that the brain must transform target coordinates from one reference frame to another. Physiological studies revealed that the posterior parietal cortex may contribute a large part of such a transformation, but the question remains as to whether the premotor areas receive visual information, from the parietal cortex, readily coded in body-centered coordinates. To answer this question, we studied dorsal premotor cortex (PMd) neurons in two monkeys while they performed a conditional visuomotor task and maintained fixation at different gaze angles. Visual stimuli were presented on a video monitor, and the monkeys made Limb movements on a panel of three touch pads located at the bottom of the monitor. A trial begins when the monkey puts its hand on the central pad. Then, later in the trial, a colored cue instructed a limb movement to the left touch pad if red or to the right one if green. The cues lasted for a variable delay, the instructed delay period, and their offset served as the go signal. The fixation spot was presented at the center of the screen or at one of four peripheral locations. Because the monkey's head was restrained, peripheral fixations caused a deviation of the eyes within the orbit, but for each fixation angle, the instructional cue was presented at nine locations with constant retinocentric coordinates. After the presentation of the instructional cue, 133 PMd cells displayed a phasic discharge (signal-related activity), 157 were tonically active during the instructed delay period (set-related or preparatory activity), and 104 were active after the go signal in relation to movement (movement-related activity). A large proportion of cells showed variations of the discharge rate in relation to limb movement direction, but only modest proportions were sensitive to the cue's location (signal, 43%; set, 34%; movement, 29%). More importantly, the activity of most neurons (signal, 74%; set, 79%; movement, 79%) varied significantly (analysis of variance, P < 0.05) with orbital eye position. A regression analysis showed that the neuronal activity varied linearly with eye position along the horizontal and vertical axes and can be approximated by a two-dimensional regression plane. These data provide evidence that eye position signals modulate the neuronal activity beyond sensory areas, including those involved in visually guided reaching limb movements. Further, they show that neuronal activity related to movement preparation and execution combines at least two directional parameters: arm movement direction and gaze direction in space. It is suggested that a substantial population of PMd cells codes Limb movement direction in a head-centered reference frame.