TEMPORAL ENCODING OF MOVEMENT KINEMATICS IN THE DISCHARGE OF PRIMATE PRIMARY MOTOR AND PREMOTOR NEURONS
TEMPORAL ENCODING OF MOVEMENT KINEMATICS IN THE DISCHARGE OF PRIMATE PRIMARY MOTOR AND PREMOTOR NEURONS
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DOI：
10.1152/jn.1995.73.2.836
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发表时间：
1995-02-01
影响因子：
2.5
通讯作者：
EBNER, TJ
中科院分区：
文献类型：
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作者：
FU, QG;FLAMENT, D;EBNER, TJ
1. 一些对初级运动和前运动皮层的神经生理学研究表明，运动参数方向、距离和目标位置与单个神经元的放电有关。在这里，我们研究与这些参数的相关性是同时发生（即并行处理）还是顺序发生（即串行处理）。本文中分析使用的单单元数据与我们早期研究运动参数的神经元规格时使用的数据相同。我们记录了两只恒河猴（Macaca mulatta）在水平面上进行伸手动作时，初级运动皮层和前运动皮层单个神经元的活动。具体来说，这些动物从一个中心位置移动到48个目标中的一个（1厘米），这些目标被放置在8个不同的方向（以45度为间隔0-360度）和6个距离（以0.8厘米为间隔1.4-5.4厘米）。我们分析了其中的130个任务相关细胞，127个（99个在初级运动皮层，28个在上中央前沟附近）的平均放电随运动显著调节，并与运动方向、距离或目标位置有关。为了确定每个细胞放电与这三个参数的相关性的时间分布，我们对神经放电进行了回归分析。我们计算了每个参数的偏R(2)s和模型的总R(2)作为时间的函数。大多数机组（73.2%）的流量在一段时间内与这三个参数显著相关。其他单位被发现与参数对的不同组合相关（21.3%），少数单位似乎只编码一个参数（5.5%）。在初级运动皮层和前运动皮层中记录的细胞之间的相关性没有明显差异。平均而言，我们发现与参数相关的部分R(2)值在开始时具有明显的时间隔离和顺序：方向相关的放电首先发生（运动开始前115 ms），其次是目标位置（运动开始后57 ms）和运动距离（运动开始后248 ms）。在这些参数的相关时间上有一些重叠是很明显的。我们发现R(2)曲线的峰值潜伏期有相似的顺序（运动开始后，方向、目标位置和距离分别为48、254和515 ms）。方向的部分R(2)曲线峰值高于目标位置和距离的峰值，但持续时间较短。一组额外的单变量回归分析表明，相关性的顺序顺序保持不变，方向首先出现，距离最后出现。对于一些与两个或两个以上参数相关的细胞，部分R(2)s在过渡期间以倒数的方式增减。在给定时刻，一个参数的高偏R(2)通常与另一个参数的低偏R(2)相关联。我们开发了一个同时性指数，并测量了在这些过渡时期细胞放电与这两个参数显著相关的程度。在从方向到目标位置的过渡期间，大量细胞的同时性指数较低，说明这些细胞的放电一次只与一个参数相关。运动神经元和前运动神经元参数相关放电的时间差异有三个含义。首先，对这些参数进行串行处理。其次，由于每个参数具有相对不同的时间过程，因此与方向、目标的x - y位置和运动距离的相关性表现出相当大的独立性。第三，距离调制主要发生在峰值速度之后，说明距离编码并没有指定运动速度。这些结果表明，单个细胞可以通过时间分割方案编码多个参数。该方案避免了同时编码多个参数的发射速率的模糊性。
1. Several neurophysiological studies of the primary motor and premotor cortices have shown that the movement parameters direction, distance, and target position are correlated with the discharge of single neurons. Here we investigate whether the correlations with these parameters occur simultaneously (i.e., parallel processing), or sequentially (i.e., serial processing).2. The single-unit data used for the analyses presented in this paper are the same as those used in our earlier study of neuronal specification of movement parameters. We recorded the activity of single neurons in the primary motor and premotor cortices of two rhesus monkeys (Macaca mulatta) while the animals performed reaching movements made in a horizontal plane. Specifically, the animals moved from a centrally located start position to 1 of 48 targets (1 cm(2)) placed at eight different directions (0-360 degrees in 45 degrees intervals) and six distances (1.4-5.4 cm in 0.8-cm increments) from the start position.3. We analyzed 130 task-related cella of these, 127 (99 in primary motor cortex, 28 near the superior precentral sulcus) had average discharges that were significantly modulated with the movement and were related to movement direction, distance, or target position. To determine the temporal profile of the correlation of each cell's discharge with the three parameters, we performed a regression analysis of the neural discharge. We calculated partial R(2)s for each parameter and the total R(2) for the model as a function of time.4. The discharge of the majority of units (73.2%) was significantly correlated for some time with all three parameters. Other units were found that correlated with different combinations of pairs of parameters (21.3%), and a small number of units appeared to code for only one parameter (5.5%). There was no obvious difference in the presence of correlations between cells recorded in the primary motor versus premotor cortices.5. On average we found a clear temporal segregation and ordering in the onset of the parameter-related partial R(2) values: direction-related discharge occurred first (115 ms before movement onset), followed sequentially by target position (57 ms after movement onset) and movement distance (248 ms after movement onset). Some overlap in the timing of the correlation of these parameters was evident. We found a similar sequential ordering for the latency of the peak of the R(2) curves (48, 254, and 515 ms after movement onset, respectively, for direction, target position, and distance). The partial R(2) profile for direction had a higher peak value but a shorter duration than that for both target location and distance. An additional set of univariate regression analyses demonstrated that the sequential ordering of the correlations was preserved, with direction occurring first and distance last.6. For some cells that were related to two or more parameters, the partial R(2)s waxed and waned in a reciprocal manner during the transition period. A high partial R(2) for one parameter at a given moment in time was often associated with a low partial R(2) for the other parameter. We developed an index of simultaneity and measured the degree to which cell firing was correlated significantly with the two parameters during these transition periods. During the transition period from direction to target position, a large number of cells had a low index of simultaneity, indicating that the discharge of these cells is correlated with only one parameter at a time.7. The timing differences in the parameter-related discharge of motor and premotor neurons have three implications. First, these parameters are processed serially. Second because each parameter has a relatively distinct time course, the correlations with direction, X-Y-position of the target and movement distance exhibit considerable independence. Third the observation that distance modulation mostly occurs after the time of peak velocity suggests that the distance coding does not specify the movement velocity. These results demonstrate that single cells can encode multiple parameters by a temporal parcellation scheme. This scheme avoids the ambiguities of firing rate simultaneously encoding more than one parameter.