The effects of muscimol inactivation of small regions of motor and somatosensory cortex on independent finger movements and force control in the precision grip
The effects of muscimol inactivation of small regions of motor and somatosensory cortex on independent finger movements and force control in the precision grip
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DOI：
10.1007/s002210050814
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发表时间：
1999-09-01
影响因子：
2
通讯作者：
Smith, AM
中科院分区：
文献类型：
--
作者：
Brochier, T;Boudreau, MJ;Smith, AM
这项研究调查了初级体感（SI）和运动（MI）皮层小区域失活对精确握持中手指力控制的影响。一只猴子被训练用拇指和食指抓住并举起计算机控制的物体，并在狭窄的位置窗口内将其保持静止 2 秒。垂直于物体表面施加的抓握力、垂直方向切向施加的提升力或负载力以及垂直位移以 100 Hz 采样。此外，还通过录像带分析了猴子从 Kluver 板的狭窄孔中提取小块食物的能力。初步的单单元记录和微刺激研究用于绘制 SI 和 MI 内拇指和食指表示的范围。两次局部注射各1μl（5μg/μl）的GABA(A)-激动剂蝇蕈醇来灭活拇指和食指区域的前中央回或后中央回。 SI 或 MI 中注射蕈醇对精确握力的影响不同。 MI注射导致猴子独立手指运动的能力出现缺陷，手指肌肉普遍无力。为了抓住仪器物体或食物，不恰当地进行了全手抓握动作。尽管对手部内在肌肉的影响似乎最强，但也注意到手指伸展的明显缺陷。结果，猴子无法在所需的 2 秒内举起物体并将其保持在位置窗口内，并且随着时间的推移，抓握力逐渐减小，直到动物停止工作。 SI 注射后，最明显的影响是手指协调能力丧失。在抓握时，手指在物体上的放置位置经常不正常，猴子似乎无法控制抓握和举起力量的应用。然而，对力的详细分析表明，在注意到手指运动协调性出现任何缺陷之前，握力就已经大幅增加。这一观察结果表明，皮肤对 SI 的反馈对于握力的精细控制至关重要。
This study investigated the effects of inactivating small regions of the primary somatosensory (SI) and motor (MI) cortex on the control of finger forces in a precision grip. A monkey was trained to grasp and lift a computer-controlled object between the thumb and index finger and to hold it stationary within a narrow position window for 2 s. The grip force applied perpendicular to the object surface, the lifting or load force applied tangentially in the vertical direction, and the vertical displacement were sampled at 100 Hz. Also, the ability of the monkey to extract small pieces of food from narrow wells of a Kluver board was analyzed from video-tape. Preliminary single-unit recordings and microstimulation studies were used to map the extent of the thumb and index-finger representation within SI and MI. Two local injections of 1 yl each (5 mu g/mu l) of the GABA(A)-agonist muscimol were used to inactivate the thumb and index region of either the pre- or post-central gyrus. The precision grip was differently affected by muscimol injection into either SI or MI. MI injections produced a deficit in the monkey's ability to perform independent finger movements and a general weakness in the finger muscles. Whole-hand grasping movements were inappropriately performed in an attempt to grasp either the instrumented object or morsels of food. Although the effect seemed strongest on intrinsic hand muscles, a clear deficit in digit extension was also noted. As a result, the monkey was unable to lift and maintain the object within the position window for the required 2 s, and, over time, the grip force decreased progressively until the animal stopped working. Following SI injections, the most obvious effect was a loss of finger coordination. In grasping, the placement of the fingers on the object was often abnormal and the monkey seemed unable to control the application of prehensile and lifting forces. However, the detailed analysis of forces revealed that a substantial increase in the grip force occurred well before any deficit in the coordination of finger movements was noted. This observation suggests that cutaneous feedback to SI is essential for the fine control of grip forces.