Droulez J, Berthoz A
Laboratoire de Physiologie Neurosensorielle, Centre National de la Recherche Scientifique, Paris, France.
Proc Natl Acad Sci U S A. 1991 Nov 1;88(21):9653-7. doi: 10.1073/pnas.88.21.9653.
Coordinated orienting movements can be accurately performed without direct sensory control. Ocular saccades, for instance, have been shown to be reprogrammed after target disappearance when an intervening eye movement is electrically triggered before the saccade onset. Saccadic eye movements can also be executed toward memorized targets, even when the subject has been passively moved in darkness. Two hypotheses have been proposed to account for this goal-invariance property: either (i) the goal is reconstructed and memorized in the stable frame of reference linked to the environment ("allocentric, coordinates") or (ii) the goal is selected and memorized in the sensors-related maps ("egocentric coordinates") and is continuously updated by efferent copies of the motor commands. In this paper, we shall describe a formal neural network based on this second hypothesis. The results of the simulation show that target position can be memorized and accurately updated in a topologically ordered map, using a velocity-signal feedback. Moreover, this network has been submitted to a simple learning procedure by using the intermittent visual recurring afferent signal as the teaching signal. A similar mechanism could be involved in control of limb movement.
协调的定向运动可以在没有直接感觉控制的情况下准确执行。例如，当在扫视开始前通过电刺激引发中间的眼球运动时，已经表明在目标消失后眼球扫视会被重新编程。即使受试者在黑暗中被被动移动，朝向记忆目标的眼球扫视运动也可以执行。已经提出了两种假设来解释这种目标不变性特性：要么（i）目标在与环境相关联的稳定参考系中被重建和记忆（“异心坐标系”），要么（ii）目标在与传感器相关的地图中被选择和记忆（“自我中心坐标系”），并通过运动命令的传出副本不断更新。在本文中，我们将描述基于这第二种假设的形式化神经网络。模拟结果表明，使用速度信号反馈，可以在拓扑有序的地图中记忆并准确更新目标位置。此外，通过使用间歇性视觉重复传入信号作为教学信号，该网络已被提交到一个简单的学习过程中。类似的机制可能参与肢体运动的控制。
