Neuronal control of locomotion in the lobsterHomarus americanus

Summary

• 1. The dynamic properties of lobster walking leg reflexes were determined by quantitative analysis of the spike trains evoked by passive sinusoidal movements of single leg joints over a broad range of movement frequencies.

• 2. The evoked reflexes follow movements as rapid as those which occur during normal locomotion (Figs. 3D, 4D, 5D, 6D, 7D, 8D) and thus exhibit the prerequisite property for modulation of locomotory output on a cycle by cycle basis.

• 3. In most cases, the reflexes evoked by passive joint movement are selectively tuned to the joint movement velocities which characterize normal locomotion as determined by cinematography (Fig. 1, Table 1). Most inappropriate reflexes (i.e., reflexes which have no overt counterpart during locomotion) occur at different joint movement velocities than the normal locomotory movements.

• 4. The coxo-basal depression movement and both thoraco-coxal joint movements evoke reflexes which are appropriate to serve as amplifiers of ongoing power stroke discharge during forward and backward walking (Fig. 9). Similarly, distributed and positive feedback reflexes resulting from the coxo-basal elevation movement are competent to both activate the appropriate coxal bifunctional muscle (Table 1), and augment ongoing return stroke discharge (Fig. 9).

• 5. Most power stroke reflexes in bifunctional muscles are selectively tuned to low movement velocities (Table 1). It is suggested that this property makes them appropriate to function in load compensation.