Cycle-to-cycle variability of neuromuscular activity in Aplysia feeding behavior
Cycle-to-cycle variability of neuromuscular activity in Aplysia feeding behavior
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DOI：
10.1152/jn.01190.2003
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发表时间：
2004-07-01
影响因子：
2.5
通讯作者：
Brezina, V
中科院分区：
文献类型：
--
作者：
Horn, CC;Zhurov, Y;Brezina, V
厌食症完成喂养行为，咬，吞咽和排斥运动的节奏循环，通常被认为是刻板的。然而，更仔细的研究表明，行为的周期是非常可变的。在这里，我们已经量化和分析了神经肌肉系统中几个互补水平的变异性。在减少的准备工作，我们记录了由中央模式发生器产生的运动程序，发射的运动神经元B15和B16，和收缩的副齿舌关闭（ARC）肌肉，而重复的程序引起的刺激食管神经。在其他类似的实验中，我们记录了运动神经元B48的放电和齿舌开肌的收缩。在完整的动物中，我们植入电极来记录神经或ARC肌肉活动，而动物则吞下受控的海藻条或自由进食。在所有情况下，我们发现在所有参数检查大的变异性。这种变异性反映了中枢运动程序特征的系统性、缓慢性和历史依赖性变化。然而，即使将这些趋势排除在外，只关注连续周期之间的差异，仍然存在相当大的差异。这种变化显然是随机的。尽管如此，它也是中枢历史依赖的产物，因为仅仅对程序的高层次时序进行规范化，也会对许多下游神经肌肉参数进行规范化。因此，中枢运动程序的变异性直接出现在行为中。关于在任何一个周期中功能行为的产生，大的可变性可能表明神经肌肉系统的操作具有广泛的耐受性。或者，某些行为周期可能是功能失调的。总体而言，变异性可能是CNS在不确定环境中采用的试验、错误和稳定的最佳策略的一部分。
Aplysia consummatory feeding behavior, a rhythmic cycling of biting, swallowing, and rejection movements, is often said to be stereotyped. Yet closer examination shows that cycles of the behavior are very variable. Here we have quantified and analyzed the variability at several complementary levels in the neuromuscular system. In reduced preparations, we recorded the motor programs produced by the central pattern generator, firing of the motor neurons B15 and B16, and contractions of the accessory radula closer ( ARC) muscle while repetitive programs were elicited by stimulation of the esophageal nerve. In other similar experiments, we recorded firing of motor neuron B48 and contractions of the radula opener muscle. In intact animals, we implanted electrodes to record nerve or ARC muscle activity while the animals swallowed controlled strips of seaweed or fed freely. In all cases, we found large variability in all parameters examined. Some of this variability reflected systematic, slow, history-dependent changes in the character of the central motor programs. Even when these trends were factored out, however, by focusing only on the differences between successive cycles, considerable variability remained. This variability was apparently random. Nevertheless, it too was the product of central history dependency because regularizing merely the high-level timing of the programs also regularized many of the downstream neuromuscular parameters. Central motor program variability thus appears directly in the behavior. With regard to the production of functional behavior in any one cycle, the large variability may indicate broad tolerances in the operation of the neuromuscular system. Alternatively, some cycles of the behavior may be dysfunctional. Overall, the variability may be part of an optimal strategy of trial, error, and stabilization that the CNS adopts in an uncertain environment.