Ascending Sensory Pathways in the Cord White Matter

Abstract

Clues about the functions of sensory pathways come both from human and from animal studies. The evidence from human subjects is of particular importance, since a subjective report of alterations in sensory experience can be obtained and sometimes correlated with objective tests of changes in reactions to particular sensory stimuli. However, investigations on humans are limited by the degree to which interventions are permissible. In clinical studies, most disease processes and many surgical interventions are insufficiently localized to allow the assignment of a particular deficit to the interruption of a particular neural pathway in an unambiguous fashion, even when postmortem examination is possible. Lesion studies in animals have the advantage of a greater precision in the performance of surgical damage to specific neural structures and in the postmortem verification of the area damaged, but the role of an ascending pathway in sensory experience can be evaluated only indirectly. Two ways in which the effects of lesions in animals can be investigated are studies of behavioral changes that are produced by lesions and recordings of alterations in neuronal activity.