On coupling and decoupling of spinal interneuronal networks

This review addresses the question of interrelations between spinal interneuronal networks. On the basis of electrophysiological, pharmacological, morphological and immunohistochemical analysis of interneurones mediating various reflex actions from muscle receptors and of reticulospinal neurones a considerable degree of interweaving between networks of these neurones has been established. The coupling has been found to occur at the level of several sites of these networks but the review focuses on two of these sites. The first is between dorsal horn interneurones with group II input and their target ipsilaterally and contralaterally projecting intermediate zone and commissural interneurones. The second is between commissural interneurones with input from reticulospinal neurones and their target interneurones. Several ways of both strengthening and weakening of coupling between various interneuronal networks are also briefly reviewed.