Caminiti R, Johnson P B, Galli C, Ferraina S, Burnod Y
Istituto di Fisiologia umana, Facoltà di Medicina e Chirurgia, Università degli Studi di Roma La Sapienza, Italy.
J Neurosci. 1991 May;11(5):1182-97. doi: 10.1523/JNEUROSCI.11-05-01182.1991.
The activity of 156 individual arm-related neurons was studied in the premotor cortex (area 6) while monkeys made arm movements of similar directions within different parts of 3-dimensional space. This study was aimed at describing the relationship between premotor cortical cell activity and direction of arm movement and assessing the coordinate system underlying this relationship. We found that the activity of 152 (97.4%) cells varied in an orderly fashion with the direction of movement, in at least some region of the work space. Premotor cortical cells fired most for a given preferred direction and less for other directions of movement. These preferred directions covered the directional continuum in a uniform fashion across the work space. It was found that, as movements of similar directions were made within different parts of the work space, the cells' preferred directions changed their orientation. Although these changes had different magnitudes for different cells, at the population level, they followed closely the changes in orientation of the arm necessary to move the hand from one to another part of the work space. This shift of cells' preferred direction with the orientation of the arm in space has been observed with similar characteristics in the motor cortex (see Caminiti et al., 1990). In both premotor and motor cortices, neuronal movement population vectors provide a good description of movement direction. Unlike the individual cell preferred directions upon which they are based, movement population vectors did not change their spatial orientation across the work space, suggesting that they remain good predictors of movement direction regardless of the region of space in which movements are made. The firing frequency of both premotor and motor cortical neurons varied significantly with the position occupied by the hand in space. These static positional effects were observed in 88.5% of premotor and 91.8% of motor cortical cells. In a second task, monkeys made movements from differing origins to a common end point. This task was performed within 3 different parts of space and was aimed at dissociating movement direction from movement end point. It was found that in both premotor and motor cortices virtually all cells were related to the direction and not to the end point of movement. These data suggest that premotor and motor cortices use common mechanisms for coding arm movement direction. They also provide a basis for understanding the coordinate transformation required to move the hand toward visual targets in space.
在猴子于三维空间不同部分做出相似方向的手臂运动时，研究了运动前区皮质（6区）中156个与手臂相关的单个神经元的活动。本研究旨在描述运动前区皮质细胞活动与手臂运动方向之间的关系，并评估这种关系背后的坐标系。我们发现，在工作空间的至少某些区域，152个（97.4%）细胞的活动随运动方向呈有序变化。运动前区皮质细胞在给定的偏好方向上放电最多，而在其他运动方向上放电较少。这些偏好方向在整个工作空间中以均匀的方式覆盖了方向连续体。结果发现，当在工作空间的不同部分做出相似方向的运动时，细胞的偏好方向会改变其取向。尽管不同细胞的这些变化幅度不同，但在群体水平上，它们紧密跟随为了将手从工作空间的一个部分移动到另一个部分而使手臂取向的变化。细胞偏好方向随手臂在空间中的取向而发生的这种转变，在运动皮质中也观察到了具有相似特征的情况（见卡米尼蒂等人，1990年）。在运动前区皮质和运动皮质中，神经元运动群体向量都能很好地描述运动方向。与它们所基于的单个细胞偏好方向不同，运动群体向量在整个工作空间中不会改变其空间取向，这表明无论在哪个空间区域进行运动，它们仍然是运动方向的良好预测指标。运动前区皮质和运动皮质神经元的放电频率都随手在空间中占据的位置而显著变化。在88.5%的运动前区皮质细胞和91.8%的运动皮质细胞中观察到了这些静态位置效应。在第二项任务中，猴子从不同起点向一个共同终点进行运动。该任务在空间的3个不同部分进行，目的是将运动方向与运动终点区分开来。结果发现，在运动前区皮质和运动皮质中，几乎所有细胞都与运动方向相关，而与运动终点无关。这些数据表明，运动前区皮质和运动皮质使用共同机制来编码手臂运动方向。它们还为理解将手朝向空间中的视觉目标移动所需的坐标转换提供了基础。
