Sengul, Gulgun and Watson, Charles (2012). Spinal Cord: Connections. In Juergen K. Mai and George Paxinos (Ed.), The Human Nervous System3rd ed. (pp. 233-258) Ausralia: Elsevier Inc.. doi:10.1016/B978-0-12-374236-0.10007-0
Connections of the spinal cord have been studied extensively in experimental animals, mostly in the rat, cat, and monkey. These studies are based on electrophysiological and anatomical tract tracing methods. In humans, our direct knowledge of spinal cord tracts is mostly based on data obtained from patients with localized traumatic and inflammatory lesions, or surgical interventions, which have resulted in ascending fiber degeneration or retrograde changes in spinal cells of origin. Sensory-evoked potentials in the human spinal cord can be safely recorded from the epidural space. Evaluation of the discharge rate and probability of one or more motor units in response to stimulation of peripheral afferents or corticospinal fibers has also been used to study functional connection of neurons in humans. Recent development of diffusion tensor tractography allows visualization and localization of neural tracts in three dimensions and provides helpful and important information for clinicians. This information allows clinicians to evaluate the state of a neural tract to predict clinical outcomes, or to set up scientific management strategies for patients with brain injury. This chapter deals with propriospinal, ascending, and descending pathways of the human spinal cord. We refer to the rat, cat, and monkey data where there is no or limited information for humans.