A neural network for pattern generation in the scratch reflex

The authors approach the problem of translating sensory information to a coordinated pattern of muscular activation by presenting a model for the initial positioning and rhythmic behavior of the hindlimb in the scratch reflex. This model draws heavily on a set of hypotheses proposed by M.B. Berkinblit et al. (1978) regarding apparent localization of the pattern generator in lamina VII of the fourth and fifth lumbar segments of the spinal cord. The authors propose a network based exclusively on interneurons residing in this area. Given a tonic input, the activities of the network´s neurons produce the initial positioning phase. This in turn leads to a rhythmic phase that correlates well with the required motor output during a scratch cycle. A mechanism is suggested for varying the length of the initial positioning phase (and presumably location of the hindlimb), independent of the period of the rhythmic phase.<>