Functional Contribution of Direct Cortico-Spinal Connections as Studied in the Conscious Monkey

The early cortical stimulation experiments of Ferrier (6) and of Leyton and Sherrington (23) revealed a strong relationship between the motor cortex and movements of the hand and fingers. This relationship had already been stressed by Hughlings Jackson in the 1860’s on the basis of his observations of epileptic seizures. Jackson had argued that “the small muscles of the hand will be represented by much more grey matter in the highest centres than will be large muscles of the upper arm because they serve in more numerous movements” (10).