Edwards D H
Department of Biology, Georgia State University, Atlanta 30302-4010.
J Neurosci. 1991 May;11(5):1210-23. doi: 10.1523/JNEUROSCI.11-05-01210.1991.
Mutual inhibition among behavioral command systems frequently has been suggested as a possible mechanism for switching between incompatible behaviors. Several neural circuits in crayfish that mediate incompatible behaviors have been found to interact through inhibition; this accounts for increased stimulus threshold of one behavior (e.g., escape tailflip) during performance of others (eating, walking, defense). To determine whether mutual inhibition between command systems can provide a mechanism that produces adaptive behavior, I developed a model crayfish that uses this mechanism to govern its behavioral choices in a simulated world that contains a predator, a shelter, and a food source. The crayfish uses energy that must be replaced by eating while it avoids capture by the predator. The crayfish has seven command systems (FORAGE, EAT, DEFENSE, RETREAT, ESCAPE, SWIM, HIDE) that compete through mutual inhibition for control of its behavior. The model crayfish was found to respond to changing situations by making adaptive behavioral choices at appropriate times. Choice depends on internal and external stimuli, and on recent history, which determines the pattern of those stimuli. The model's responses are unpredictable: small changes in the initial conditions can produce unexpected patterns of behavior that are appropriate alternate responses to the stimulus conditions. Despite this sensitivity, the model is robust; it functions adaptively over a large range of internal and external parameter values.
行为指令系统之间的相互抑制常被认为是在不相容行为之间进行切换的一种可能机制。已发现小龙虾体内介导不相容行为的几个神经回路通过抑制作用相互作用；这解释了在执行其他行为（如进食、行走、防御）时，一种行为（如逃避性甩尾）的刺激阈值为何会升高。为了确定指令系统之间的相互抑制是否能提供一种产生适应性行为的机制，我构建了一个模拟小龙虾模型，该模型利用这种机制在一个包含捕食者、庇护所和食物源的模拟世界中做出行为选择。小龙虾在躲避捕食者的同时需要消耗能量，而这必须通过进食来补充。小龙虾有七个指令系统（觅食、进食、防御、撤退、逃避、游泳、躲藏），它们通过相互抑制来竞争对其行为的控制权。研究发现，模拟小龙虾能够通过在适当的时候做出适应性行为选择来应对不断变化的情况。行为选择取决于内部和外部刺激，以及最近的经历，而最近的经历决定了这些刺激的模式。该模型的反应是不可预测的：初始条件的微小变化可能会产生意想不到的行为模式，这些模式是对刺激条件的适当替代反应。尽管具有这种敏感性，但该模型仍很稳健；它能在很大范围的内部和外部参数值上自适应地发挥作用。
