Role of Dorsal Columns in sequential motor acts requiring precise forelimb projection

1432-1106

Dorsal columns ; Accuracy ; Projected movements

Springer Online Journal Archives 1860-2000

Medicine

Summary Quantitative evaluation was carried out on the ability of cats to execute a sequential act requiring precise timing for its initiation (jump), accurate projection of the forelimb and appropriate visual tracking during motor performance. Comparison of results before and after section of the Dorsal Columns at the first cervical level revealed obvious postoperative inefficiency in the overall performance of the act. The accuracy of extrapersonally projected movements of the forelimbs (reaching towards a moving target) was seriously affected, as was the capacity to visually track a target in space during the jump. Testing which did not require jumping up towards the target, but merely rearing on the hindlimbs, showed no improvement in the performance of lesioned animals when compared to controls. The deficits mentioned also persisted in animals subjected to preoperative overtraining and prolonged postsurgical testing, a procedure which in certain tasks allows the animal to perform normally after surgery. Physiologically, the Dorsal Columns have been shown to be the exclusive path of fibers from muscle spindles and low threshold joint receptors from the forelimbs. The corresponding fibers from the hindlimbs reach higher centers via different pathways. The loss of this information from forelimbs resulting from high cervical Dorsal Column section may then help to explain the deficits described.

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