Schieber M H, Poliakov A V
Department of Neurology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
J Neurosci. 1998 Nov 1;18(21):9038-54. doi: 10.1523/JNEUROSCI.18-21-09038.1998.
After large lesions of the primary motor cortex (M1), voluntary movements of affected body parts are weak and slow. In addition, the relative independence of moving one body part without others is lost; attempts at individuated movements of a given body part are accompanied by excessive, unintended motion of contiguous body parts. The effects of partial inactivation of the M1 hand area are comparatively unknown, however. If the M1 hand area contains the somatotopically ordered finger representations implied by the classic homunculus or simiusculus, then partial inactivation might produce weakness, slowness, and loss of independence of one or two adjacent digits without affecting other digits. But if control of each finger movement is distributed in the M1 hand area as many studies suggest, then partial inactivation might produce dissociation of weakness, slowness, and relative independence of movement, and which fingers movements are impaired might be unrelated to the location of the inactivation along the central sulcus. To investigate the motoric deficits resulting from partial inactivation of the M1 hand area, we therefore made single intracortical injections of muscimol as trained monkeys performed visually cued, individuated flexion-extension movements of the fingers and wrist. We found little if any evidence that which finger movements were impaired after each injection was related to the injection location along the central sulcus. Unimpaired fingers could be flanked on both sides by impaired fingers, and the flexion movements of a given finger could be unaffected even though the extension movements were impaired, or vice versa. Partial inactivation also could produce dissociated weakness and slowness versus loss of independence in a given finger movement. These findings suggest that control of each individuated finger movement is distributed widely in the M1 hand area.
在初级运动皮层（M1）发生大面积损伤后，受影响身体部位的自主运动变得虚弱且缓慢。此外，独立移动一个身体部位而不带动其他部位的能力丧失；试图单独移动某个特定身体部位时，相邻身体部位会出现过度的、无意识的运动。然而，M1手部区域部分失活的影响相对未知。如果M1手部区域包含经典的矮人图或类人猿图所暗示的按身体部位排列的手指表征，那么部分失活可能会导致一两个相邻手指出现无力、缓慢和独立性丧失，而不影响其他手指。但如果正如许多研究所表明的那样，每个手指运动的控制分布在M1手部区域，那么部分失活可能会导致无力、缓慢和运动相对独立性的分离，并且哪些手指运动受损可能与沿着中央沟的失活位置无关。因此，为了研究M1手部区域部分失活导致的运动缺陷，我们在受过训练的猴子进行视觉提示的手指和手腕单独屈伸运动时，对其进行了单次皮质内注射蝇蕈醇。我们发现几乎没有证据表明每次注射后哪些手指运动受损与沿着中央沟的注射位置有关。未受损的手指两侧可能都有受损的手指，并且即使伸展运动受损，给定手指的屈曲运动也可能不受影响，反之亦然。部分失活还可能在给定的手指运动中产生无力和缓慢与独立性丧失的分离。这些发现表明，每个单独手指运动的控制广泛分布在M1手部区域。
