Mergner T
Neurologische Klinik, Universität Freiburg, Breisacher Str 64, 79106 Freiburg, Germany.
Arch Ital Biol. 2004 May;142(3):175-98.
Postural reflexes are replaced soon after birth by automatic reactions that allow for volition and cognition. It is still an enigma how this change in postural control is achieved. We suggest that the change involves the formation of a sensory processing level (meta level) that becomes interleaved in between the tight sensor-actuator coupling of the classic reflexes. We assume that the brain applies at this level intersensory interactions to reconstruct the physical stimuli which are causing the physiological stimuli and sensory signals. The thus derived estimates of the physical stimuli are then used as feedback signals in the posture control system. We present this concept on the background of the classic reflex concept and earlier attempts in the literature to overcome it. The earlier attempts were often motivated by the question how the brain prevents voluntary movements from being hampered by reflexive stabilisation of posture (so-called posture-movement problem). We compare our new concept with the classic reflex concept in a theoretical approach, by implementing both concepts into simple postural control models. In simulations of the two models we superimpose external perturbations (the physical stimuli) and a voluntary body lean movement. We show that it is possible to achieve successful stimulus compensation and unperturbed lean movement with both, the model derived from the new concept and the one of the classic reflex concept. With both approaches, the posture-movement problem does not arise. Based on preliminary considerations that include experimental findings from the literature, however, we conclude that the new concept provides more explanatory power than the classic reflex concept.
出生后不久，姿势反射就被允许有意志和认知的自动反应所取代。姿势控制的这种变化是如何实现的仍然是一个谜。我们认为，这种变化涉及形成一个感觉处理层次（元层次），该层次插入到经典反射紧密的传感器-执行器耦合之间。我们假设大脑在这个层次应用感觉间相互作用来重构引起生理刺激和感觉信号的物理刺激。由此得出的对物理刺激的估计随后被用作姿势控制系统中的反馈信号。我们在经典反射概念以及文献中早期克服该概念的尝试的背景下提出这一概念。早期的尝试往往是受大脑如何防止自愿运动受到姿势反射性稳定的阻碍（所谓的姿势-运动问题）这一问题的驱动。我们通过将这两个概念都应用到简单的姿势控制模型中，以理论方法将我们的新概念与经典反射概念进行比较。在两个模型的模拟中，我们叠加外部扰动（物理刺激）和身体的自愿倾斜运动。我们表明，源自新概念的模型和经典反射概念的模型都能够实现成功的刺激补偿和不受干扰的倾斜运动。然而，基于包括文献中的实验结果在内的初步考虑，我们得出结论，新概念比经典反射概念具有更强的解释力。
