Neuronal reorganization through oscillator formation training in patients with CNS lesions

A method has been developed for the simultaneous recording with wire electrodes of extracellular action potentials from single human afferent and efferent nerve fibres of undamaged sacral nerve roots. A classification scheme of the human peripheral nervous system (PNS) could be set up in which the individual classes of nerve fibres are characterized by group conduction velocities and group nerve fibre diameters. Natural impulse patterns of several identified single afferent and efferent nerve fibres can be extracted from the multi-unit impulse patterns, and human central nervous system (CNS) functions can be analyzed under physiologic and pathophysiologic conditions. With the discovery of premotor spinal oscillators it became possible to judge upon CNS neuronal network functions based on the firing patterns of these spinal oscillators. Since oscillatory firing has also been observed in electromyographic (EMG) single motor unit firing patterns, it seems possible to follow up therapeutic intervention in patients with spinal cord lesion not only based on the activity levels and phases of motor programs during locomotion but also based on the physiologic and pathophysiologic firing patterns and recruitment of spinal oscillators. Since rhythmic, dynamic, stereotyped, symmetric movements are mainly located in the spinal cord and only little supraspinal drive is necessary to initiate, maintain (especially), and terminate them, rhythm training methods were used to enforce reorganization of the CNS following spinal cord and CNS lesions to improve the self-organization and relative coordination of spinal oscillators which became pathologic in their firing following CNS lesion. Paraparetic, tetraparetic and brain-lesioned patients relearned running and other movements by an oscillator formation training. This development in neurorehabilitation is in accordance with those of theoretical and computational neurosciences which consider self-organization of neuronal networks. In particular, jumping on a springboard 'in phase' and 'in antiphase' to relearn phase relations of oscillator coupling can be understood in the Haken-Kelso-Bunz model. By introducing broken symmetry, intention, learning and spasticity in the landscape of the potential function of the integrated CNS activity, the change in self-organization becomes understandable. In conclusion, movement patterns relearned by oscillator formation training evolve from reorganization, and perhaps regeneration, of the lesioned CNS by cooperative and competitive interplay between intrinsic coordination dynamics, extrinsic training-related inputs with physiologic re-afferent input, including intention and supervised learning, and genetic constraints including neurogenesis.