Loss of directed fore-limb reaching after destruction of spinal grey matter

The use of the ipsilateral fore-paw to retrieve food pellets was studied in 55 rats with unilateral lesions in the dorsal spinal cord at the C1/2 level. Of these rats 30 either retained (16) or recovered (14) function within 25 days after the lesion. The remaining 25 rats showed no return of function over an 8 week postoperative testing period. Plotting the extent of the lesions showed that all 30 rats showing retrieval had complete destruction of the main dorsal corticospinal tract in the dorsal columns and some damage to the adjacent medial part of the grey matter of Rexed's laminae V to VII, but sparing the dorsolateral CST and more than half of the grey matter. In the 25 rats with no return of function the lesions also included extensive destruction through the medio-lateral extent of the grey matter.