Plasticity and rigidity in the nervous system: Lessons from the spinal cord

Abstract

This chapter discusses the concept of plasticity and rigidity in the nervous system. It also discusses three different situations in which lesions outside the spinal cord provide a potential for the formation of new anatomical connections. Neuroplasticity is used to summarize the responses of the nervous system to changes in its external and/or internal conditions. These responses range from changes in the expression of specific molecules, membrane properties, neural conduction, synaptic transmission, cellular structure, cellular interactions, and changes in the size of cell populations to functional and behavioral changes. Spinal cord circuitry is a useful experimental model for exploring the principles of neuroplasticity. Anatomical reorganization of connections in the spinal cord is likely to be an important process for functional restoration after an injury and, for the emergence of sensory dysfunctions, the most intriguing and clinically important one being chronic neuropathic pain. The structural and connectional plasticity of axotomized motoneurons are described in the chapter. This group of neurons serves as a prototype for the study of axotomy responses and provides substantial principal information relevant also for the reaction of other neurons to axon injury, including sensory neurons.