Ascending Sensory Pathways in the Cord White Matter

Abstract

Clues about the function of the sensory pathways come both from clinical and from animal studies. The clinical evidence is of particular importance, since the human patients can provide a subjective report of alterations in their sensory experience, and objective tests of changes in reaction to particular sensory stimuli can be used to confirm the subjective information. The difficulty with clinical studies is that most disease processes do not produce sufficiently localized damage 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 precision in the surgical interruption of 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. The discussion to follow will consider the evidence concerning the sensory pathways that ascend in the dorsal columns, the dorsolateral fasciculus, and the ventral quadrant of the spinal cord.