肌肉振動時間對大拇指運動誘發電位與控制能力之影響

Abstract

先前研究指出，給予肌肉振動刺激之當下，可活化大腦神經傳導，增加大腦皮質可激度，並提高受振動肌肉之運動誘發電位(Motor-evoked potential, MEP)。然而，對於給予不同長時間肌肉振動刺激結束後，其MEP之改變情況尚不明確。有鑑於此，本研究給予不同之長時間肌肉振動刺激後，量化受振動肌肉MEP改變之情形，並進一步探討此振動刺激對於手指肌肉選擇性控制能力改變之影響。本研究共有13位年輕受測者(平均年齡為24.6 ± 4.19歲；6位女性)與9位較高齡受測者(平均年齡為61.8 ± 12.9歲；6位女性)參與實驗，分別給予受測者慣用手Abductor pollicis brevis (APB) 5、10與15分鐘之微幅振動，於振動前後利用分別經顱磁刺激(Transcranial magnetic stimulation, TMS)與肌肉選擇性控制能力指標(Index of selective activation, ISA)，量化振動對於APB之MEP及ISA之影響。對於年輕受測者而言，不同時間振動刺激後對於APB之MEP與ISA產生不同之影響(p<0.05)，振動5分鐘後MEP與ISA具有顯著提升情形(p<0.05)，振動10分鐘後MEP與ISA則無顯著改變，而振動15分鐘後MEP卻是被顯著抑制(p<0.05)，但ISA則無明顯改變，進一步量化MEP與ISA之改變幅度關連性，則可用二次曲線進行解釋(p<0.05)。然而針對不同性別探討MEP與ISA變化之關連性，女性則較偏向於線性(Linear)關係(p<0.05)，男性仍以二次曲線有最高解釋力，但不具統計顯著性。對於較高齡受測者而言，無論何種振動時間後，MEP與ISA之改變皆無顯著差異，同時兩者關連性亦不顯著。透過本研究結果可知給予不同振動刺激時間後，可能會因年紀不同而對MEP與ISA之改變產生不同影響，而性別不同亦可能會影響運動神經可激度與肌肉選擇性控制能力改變幅度之關連性。

Previous studies have reported that muscle vibration could induce a rapid plasticity of motor cortex and increase the corticomotor excitability. However, less has been addressed on how long the duration of prolong muscle vibration would induce corticomotor modulations and muscle selectivity after vibration. To examine the effect of vibration duration on corticomotor excitability and muscle selectivity of hand muscle, a small amplitude muscle vibration was applied to a hand intrinsic muscle, abductor pollicis brevis (APB), of thirteen younger healthy subjects (24.6 ± 4.19 yrs; six females) and nine older healthy subjects (61.8 ± 12.9 yrs; six females) for five, ten and 15 minutes, respectively. Transcranial magnetic stimulation (TMS) was utilized to quantify motor-evoked potentials (MEPs) in the rested APB, and an index of selective activation (ISA) in APB muscle was calculated before and after each muscle vibration condition. In the younger healthy subjects, different muscle vibration duration induced different effects on MEP and ISA changes (p<0.05). MEPs increased after the 5-minute vibration but decreased after the 15-minute vibration as compared with before vibration (p<0.05). In addition, ISA was significantly increased after 5-minute vibration as compared with before vibration. Moreover, the relationship between vibration-modulated MEP and ISA changes could be represented as a second-order polynomial (p<0.05) for the 13 healthy young subjects. However, the relationship was different between two genders. For the female subjects, the relationship was better explained by a linear function (p<0.05); for the males, the relationship was better fitted with a second-order polynomial (p>0.05). For the older healthy subjects, different muscle vibration duration did not induce any significant changes in MEP or ISA. We conclude that different muscle vibration duration would induce different effects in motor pathway excitability and the ability to control finger muscle in different age and genders.