Effects of motor training on the recovery of manual dexterity after primary motor cortex lesion in macaque monkeys.

Murata Y, Higo N, Oishi T, Yamashita A, Matsuda K, Hayashi M, Yamane S.

To investigate the effects of postlesion training on motor recovery, we compared the motor recovery of macaque monkeys that had received intensive motor training with those that received no training after a lesion of the primary motor cortex (M1). An ibotenic acid lesion in the M1 digit area resulted in impairment of hand function, with complete loss of digit movement. In the monkeys that had undergone intensive daily training (1 h/day, 5 days/wk) after the lesion, behavioral indexes used to evaluate manual dexterity recovered to the same level as in the prelesion period after 1 or 2 mo of postlesion training period. Relatively independent digit movements, including precision grip (prehension of a small object with finger-to-thumb opposition), were restored in the trained monkeys. Although the behavioral indexes of manual dexterity recovered to some extent in the monkeys without the postlesion training, they remained lower than those in the prelesion period until several months after M1 lesion. The untrained monkeys frequently used alternate grip strategies to grasp a small object with the affected hand, holding food pellets between the tip of the index finger and the dorsum of the thumb. These results suggest that the recovery after M1 lesion includes both use-dependent and use-independent processes and that the recovery of precision grip can be promoted by intensive use of the affected hand in postlesion training.

J Neurophysiol. 2008 Feb;99(2):773-86.

　精密把握に代表されるような、指を独立に動かす必要のある繊細な運動は大脳皮質一次運動野によってコントロールされている。一次運動野損傷後に起きる指の運動障害の回復に対する、訓練の効果の有無を調べた。イボテン酸によって一次運動野の指の領域を局所破壊したサルを、訓練群（週に５日、１日につき１時間運動訓練）と非訓練群に分け、指の器用さをテストした。訓練群では、親指の先と人差し指の先で小さなエサをつまむ精密把握が回復したが、非訓練群では数ヶ月経っても精密把握はできず、人差し指の先と親指の背でエサをつまむ代償的な把握ができるにとどまった。一次運動野損傷後の運動機能回復には訓練を要するものと要しないものがあること、精密把握の回復は訓練によって促進されることが明らかになった。 　この研究は産業技術総合研究所、日本大学、前橋工科大学との共同研究で、科学技術振興機構のCRESTの助成を得て行われたものである。

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