Wiping reflex in the intact and spinal frogs

Abstract

Studying the rostral wiping reflex, RWR, in intact grass frogs allowed us to identify two of its forms: flexor and extensor reflexes (FWR and EWR, respectively). Reflex fields of FWR and EWR considerably overlap; when the common zones are stimulated, both reflex forms can be observed. “Mixed” forms of the reflex are also possible. The probability of initiation of a certain RWR form depends on the stimulus position. Both FWR and EWR are preserved after spinalization, but their receptive fields are somewhat displaced. The hindlimb movement was divided into three phases: positioning (P), lowering, or orientation (L), and brushing aside (BA). In the intact frog, each phase is of approximately similar duration. The reflex phases and their temporal relations are preserved after spinalization. Total movement duration became longer in spinal animals, as compared with that in intact ones; in addition, this duration began to depend on the stimulus position. In the intact frogs, the position of a “working” limb shows the linear dependence on the stimulus localization; this dependence is preserved after spinalization. Our results allow us to conclude that the central generator of wiping reflex includes several subsystems determining the reflex form in a probabilistic manner.