[Neural basis of learning new movements: evolution of classical concepts].
According to classical consepts, the role of the motor cortex in performance of skilled movements of distal parts of extremities is confined to control of appropriate motoneurons by the "point-to-point" principle. However, much evidence of plasticity of the motor cortex and its active role in motor learning appeared in last decade. Fos-gene expression in the motor cortex was found to accompany learning a skill. Strengthening of horizontal pathways in layers II-III was revealed, and cholinergic input to tese layers was found to be important. The imaging data show that activity of the motor cortex increases during motor practice as well. This raises the question of specificity of the motor cortex in the motor learning per se. During acquisition of new movements some previously used synergies prevent the necessary coordination from being learned, so they must be suppressed in the process of motor learning. Investigations of central mechanisms of coordination interference in humans are still at the beginning. However, there are some animal models of reorganization and suppression of interfering synergies. The reorganization and suppression of coordination preventing realization of a new movement is shown to be a specific function of the motor cortex. After automation of new synergies the cortical control is still present, as distinct from the learned movements, which do not require suppression of interfering synergies. However, it does not mean that the conscious control of the performance is still present.
Ioffe
M E
ME
Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. labdo@mail.ru
D001921:Brain / Q000502:physiology; D006801:Humans; D007858:Learning; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D011187:Posture / Q000502:physiology