The effect of a low pyramidal transection following previous transection of the dorsal column in cats.

In order to test the working hypothesis that motor deficits after low pyramidotomy may be due to transection of the cortico-cuneate pathway, a low pyramidotomy was made 2-4 months after a C2 dorsal column (DC) transection and tested on forelimb target-reaching and food-taking. Since food-taking recovered faster than after pyramidotomy alone, it is inferred that the loss of food-taking after pyramidotomy without previous DC transection is due mainly to transection of the cortico-cuneate pathway which controls transmission from forelimb Ia afferents to the motor cortex. The dysmetria and dyscoordination of target-reaching, on the other hand, was similar whether or not the low pyramidotomy was made after a previous C2 DC transection. It is tentatively suggested that dysmetria and dyscoordination of target-reaching after pyramidotomy may be due to transection of the pathway from the motor cortex which controls spinocerebellar transmission by its effect on the lateral reticular nucleus.