Anatomical evidence for the re-crossing of lateral corticospinal fibers via the posterior gray commissure in the cat spinal cord.

This study demonstrated the projections of the corticospinal tract (CST) by using the anterograde transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Following injection of WGA-HRP into the pre- and post-cruciate cortices (somatosensory area) on one side, labeled fibers were found in the spinal cord both in the lateral and in the anterior CSTs; both crossed, and uncrossed. The most conspicuous labeling was found in the crossed lateral CST. In addition, labeled lateral CST fibers were seen to recross via the posterior gray commissure. These re-crossed lateral CST fibers were most frequently observed in the cervical spinal segments.