前動作皮質區在中風病患執行快速向前跨步動作之預期性姿勢控制角色

Abstract

目的：探討前動作皮質區受損與未受損之中風病患及年齡相當的健康成年人，在執行快速向前跨步動作時預期性姿勢控制及下肢動作選擇表現的差異。方法：共計13位栓塞性首度中風且大腦皮質區受損的中風病患參與此研究，其中前動作皮質區受損者(PMC+組)有6位，前動作皮質區未受損者有7位(PMC-組)。另有8位年齡性別與中風病患相當的健康受試者作為對照組。當受試者看到跨步訊號出現時，受試者需以最快的速度向前跨步。跨步動作測試情境依跨步訊號之預期程度分為兩種情境：簡單反應時間(simple reaction time, SRT)情境與選項反應時間(choice reaction time, SRT)情境。本研究以動作反應正確率(behavioral response accuracy rate)及反應時間(reaction time, RT)探討下肢動作選擇表現。以行為與肌電整體反應之型態分佈(distribution of the combined behavioral-EMG response patterns)、脛前肌作用潛時(TA onset latency)及脛前肌－自主動作潛時(TA-Movement latency) 探討跨步時之預期性姿勢控制。結果與討論：所有受試者之動作反應正確率沒有顯著組間差異，但前動作皮質區受損組患腳跨步之反應時間有較健康受試組長之趨勢(p = .059; 效應值(effect size) = .94)，表示前動作皮質區受損組需要較長的時間來選擇正確的跨步反應。預期性姿勢控制方面，前動作皮質區受損組在選擇情境下，脛前肌較腓腸肌延遲出現的跨步次數皆顯著較健康受試者多(p = .007)。且其站立腳之脛前肌作用潛時在以健側腳(p = .040)和患側腳(p = .024)跨步時皆顯著較健康受試組延遲。然而其脛前肌－自主動作潛時卻沒有顯著組間差異，這些結果表示前動作皮質區受損不只會影響患側腳的預期性姿勢控制，同時也會藉由皮質下的傳導路徑影響健側腳的姿勢準備。本文最後提出了一個前動作皮質區參與預期性姿勢控制及動作選擇之假說式模型(hypothetical model)。結論：本研究結果提供了前動作皮質區受損在預期性姿勢控制及動作選擇上扮演重要角色的證據。臨床上應針對這些缺損設計有效的治療方式。

Objective: To investigate the influence of PMC lesion on human proactive postural control as well as the preparation and selection of lower extremity voluntary movement by comparing the performance on proactive postural control and voluntary movement during a rapid stepping task between patients with stroke and healthy adults. Methods: Six stroke patients with the premotor cortex involved (PMC+), seven patients with PMC spared (PMC-), and eight age- and sex-matched healthy adults participated in this study. The subjects were required to respond as quickly as possible with a rapid forward step when the go signal appeared on the screen under two conditions with different predictability level (simple reaction time (SRT) and choice reaction time (CRT)). The accuracy rate of the behavioral responses and reaction time (RT) were assessed to indicate the selection ability. The distribution of combined behavioral-EMG response patterns, the tibialis anterior muscle onset latency (TAOL) and postural-movement latency (TA-Movement latency, TA-Mov) of the stepping leg were analyzed to indicate preparation ability. Results and Discussion: No significant group main effect was found for the accuracy rate of the behavioral responses, but the RT of the PMC+ group was marginally longer than the healthy group (p = .059, effect size = .94). This result may indicate that the PMC+ group required longer time for selecting the appropriate stepping response. For movement-related postural preparation, the PMC+ and PMC- groups displayed significantly more TA delayed trials than the healthy adult group in the CRT condition (p = .007). The TAOL of the stance leg of the PMC+ group was significantly longer than that of the healthy controls while stepping with the unaffected leg (p = .040) and affected leg (p = .024). The TA-Mov showed no significant difference between groups regardless of the stepping legs. These results may suggest that the PMC lesion not only influenced the postural preparation of the affected stepping leg, but also that of the unaffected stance leg through a subcortical pathway. A hypothetical model is proposed to describe the involvement of the PMC in postural preparation and movement selection. Conclusions: This study provided evidence that lesion of the PMC affects the postural preparedness and selection of lower extremity voluntary movement. These findings can be used by clinicians to design effective interventions for improving postural preparedness and selection of voluntary movement for PMC involved patients.