ABSTRACT
Electrical stimulation is a widespread method to study the form and function of the nervous system and a technique to restore function following disease or injury. The central nervous system (CNS) includes the brain and spinal cord (Figure 20.1). Both the spinal cord and brain include regions primarily populated by cell bodies (somas) of neurons, and termed gray matter for its color, and regions primarily populated by axons of neurons, and termed white matter. The diversity of neuronal elements and the complexity of the volume conductor make understanding the effects of stimulation more challenging in the case of CNS stimulation than in the case of peripheral stimulation. Specifically, it is unclear, in many cases, what neuronal elements (axons, cell bodies, presynaptic terminals; Figure 20.1) are activated by stimulation [Ranck, 1975]. Further, it is unclear how targeted neural elements can be stimulated selectively without coactivation of other surrounding elements. This chapter presents a review of the properties of CNS stimulation as required for rational design and interpretation of therapies employing electrical stimulation.
