Stehouwer D J, Farel P B
Dev Psychobiol. 1984 May;17(3):217-32. doi: 10.1002/dev.420170303.
Hindlimb motor behavior of the larval frog (tadpole) begins during midlarval life and occurs with increasing frequency until the tail degenerates during metamorphosis. The threshold for hindlimb withdrawal in response to tactile stimulation is low during premetamorphic stages and rises dramatically during metamorphosis. Testing tadpoles in different environments altered the stage of development at which different hindlimb behaviors were first observed but did not change the ontogenetic sequence of behavioral development. However, even under conditions most favorable to hindlimb locomotion, behavioral expression lagged behind electrophysiological expression. The rates of tail beating, hindlimb stepping, and frog kicks are similar to the rate of bursting of tail and hindlimb motoneurons of the isolated nervous system, but their coordination is variable, whereas that recorded from the isolated CNS is fixed. Because neural mechanisms of hindlimb locomotion are functional prior to their behavioral use, the basic hindlimb locomotor circuits must develop without benefit of practice or sensory feedback. However, sensory activity modulates coordination and alters the probability that particular behaviors will be expressed. Implications of these results for studies of early behavior in other species, and the problem of inferring neural maturity from behavioral observations, are discussed.
幼蛙（蝌蚪）的后肢运动行为始于幼体中期，且出现频率不断增加，直至变态过程中尾巴退化。在变态前阶段，后肢对触觉刺激做出退缩反应的阈值较低，而在变态过程中该阈值会急剧上升。在不同环境中测试蝌蚪，改变了首次观察到不同后肢行为的发育阶段，但并未改变行为发育的个体发生顺序。然而，即使在最有利于后肢运动的条件下，行为表达仍落后于电生理表达。尾巴摆动、后肢迈步和蛙踢的频率与孤立神经系统中尾巴和后肢运动神经元的爆发频率相似，但其协调性是可变的，而从孤立中枢神经系统记录到的协调性是固定的。由于后肢运动的神经机制在行为使用之前就已发挥作用，基本的后肢运动回路必须在没有练习或感觉反馈的情况下发育。然而，感觉活动会调节协调性，并改变特定行为表达的概率。本文讨论了这些结果对其他物种早期行为研究的意义，以及从行为观察推断神经成熟度的问题。
