Sources of signal-dependent noise during isometric force production
Sources of signal-dependent noise during isometric force production
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DOI：
10.1152/jn.2002.88.3.1533
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发表时间：
2002-09-01
影响因子：
2.5
通讯作者：
Wolpert, DM
中科院分区：
文献类型：
--
作者：
Jones, KE;Hamilton, AFD;Wolpert, DM
有人提出，在目标导向运动过程中观察到的不变运动学是由于减少了信号相关噪声（SDN）对电机输出的影响。本研究的目的是调查SDN的存在等长力生产过程中，并确定如何中央和外围组件有助于这一功能的电机控制。外周和中央组件进行了区分实验比较自愿收缩引起的电刺激拇长伸肌。为了确定可能导致SDN的运动单元生理学的其他因素，构建了一个模型，并将其输出与经验数据进行了比较。SDN是明显的自愿等长收缩力变异性（SD）相对于平均力水平的线性缩放。然而，在电刺激收缩到相同的力水平，变异性保持不变，在相同的范围内的平均力。当受试者被要求结合联合收割机自愿与刺激引起的收缩，SD和平均力之间的线性比例关系恢复。建模结果强调，许多基本的生理组织的运动单元池，如范围的抽搐幅度和范围的招聘阈值，偏置力输出表现出线性缩放的SDN。这与变异性的平方根标度形成对比，平均力存在于池中的任何单个运动单元中。有序的招聘抽搐幅度是一个必要条件，产生线性规模的SDN。令人惊讶的是，SDN的缩放是独立的运动神经元放电的变异性，因此通过推断，独立的突触前噪声的电机命令。我们的结论是，在自愿等长收缩的SDN的线性缩放是一个自然的副产品的组织的电机单元池，不依赖于信号依赖的噪声在电机命令。在运动指令和共同驱动器中的突触噪声，引起运动神经元尖峰的变异性和同步性，确定在给定水平的平均力输出下的力变异性的大小。
It has been proposed that the invariant kinematics observed during goal-directed movements result from reducing the consequences of signal-dependent noise (SDN) on motor output. The purpose of this study was to investigate the presence of SDN during isometric force production and determine how central and peripheral components contribute to this feature of motor control. Peripheral and central components were distinguished experimentally by comparing voluntary contractions to those elicited by electrical stimulation of the extensor pollicis longus muscle. To determine other factors of motor-unit physiology that may contribute to SDN, a model was constructed and its output compared with the empirical data. SDN was evident in voluntary isometric contractions as a linear scaling of force variability (SD) with respect to the mean force level. However, during electrically stimulated contractions to the same force levels, the variability remained constant over the same range of mean forces. When the subjects were asked to combine voluntary with stimulation-induced contractions, the linear scaling relationship between the SD and mean force returned. The modeling results highlight that much of the basic physiological organization of the motor-unit pool, such as range of twitch amplitudes and range of recruitment thresholds, biases force output to exhibit linearly scaled SDN. This is in contrast to the square root scaling of variability with mean force present in any individual motor-unit of the pool. Orderly recruitment by twitch amplitude was a necessary condition for producing linearly scaled SDN. Surprisingly, the scaling of SDN was independent of the variability of motoneuron firing and therefore by inference, independent of presynaptic noise in the motor command. We conclude that the linear scaling of SDN during voluntary isometric contractions is a natural by-product of the organization of the motor-unit pool that does not depend on signal-dependent noise in the motor command. Synaptic noise in the motor command and common drive, which give rise to the variability and synchronization of motoneuron spiking, determine the magnitude of the force variability at a given level of mean force output.