Ira A. Fulton Schools of Engineering, Arizona State University, 699 S Mill Ave, Tempe, AZ, 85281, USA.
Arizona State University, Mailcode 9709, 611 E Orange St, Tempe, AZ, 85281, USA.
Exp Brain Res. 2021 Mar;239(3):745-753. doi: 10.1007/s00221-020-06005-4. Epub 2021 Jan 3.
When movements of individuals with stroke (iwS) are elicited by startling acoustic stimulus (SAS), reaching movements are faster, further, and directed away from the body. However, these startle-evoked movements also elicit task-inappropriate flexor activity, raising concerns that chronic exposure to startle might also induce heightened flexor activity during voluntarily elicited movement. The objective of this study is to evaluate the impact of startle exposure on voluntary movements during point-to-point reaching in individuals with moderate and severe stroke. We hypothesize that startle exposure will increase task-inappropriate activity in flexor muscles, which will be associated with worse voluntarily initiated reaching performance (e.g. decreased distance, displacement, and final accuracy). Eleven individuals with moderate-to-severe stroke (UEFM = 8-41/66 and MAS = 0-4/4) performed voluntary point-to-point reaching with 1/3 of trials elicited by an SAS. We used electromyography to measure activity in brachioradialis (BR), biceps (BIC), triceps lateral head (TRI), pectoralis (PEC), anterior deltoid (AD), and posterior deltoid (PD). Conversely to our hypothesis, exposure to startle did not increase abnormal flexion but rather antagonist activity in the elbow flexors and shoulder horizontal adductors decreased, suggesting that abnormal flexor/extensor co-contraction was reduced. This reduction of flexion led to increased reaching distance (18.2% farther), movement onset (8.6% faster), and final accuracy (16.1% more accurate) by the end of the session. This study offers the first evidence that exposure to startle in iwS does not negatively impact voluntary movement; moreover, exposure may improve volitionally activated reaching movements by decreasing abnormal flexion activity.
当脑卒中患者（iwS）的运动被惊声刺激（SAS）引出时，其伸手运动速度更快、距离更远，且方向远离身体。然而，这些惊跳诱发的运动也会引起不适当的屈肌活动，这引发了人们的担忧，即慢性暴露于惊跳可能也会在自愿诱发运动时引起更高的屈肌活动。本研究的目的是评估惊跳暴露对中重度脑卒中患者的点对点伸手运动的影响。我们假设惊跳暴露会增加屈肌中不适当的活动，这将与自愿发起的伸手运动表现更差相关（例如，距离、位移和最终准确性降低）。11 名中重度脑卒中患者（UEFM=8-41/66 和 MAS=0-4/4）在 1/3 的试验中通过 SAS 引出进行自愿的点对点伸手运动。我们使用肌电图测量肱桡肌（BR）、肱二头肌（BIC）、肱三头肌外侧头（TRI）、胸大肌（PEC）、三角肌前束（AD）和三角肌后束（PD）的活动。与我们的假设相反，惊跳暴露并没有增加异常的屈肌活动，而是肘部屈肌和肩部水平内收肌的拮抗肌活动减少，这表明异常的屈肌/伸肌协同收缩减少。这种屈肌活动的减少导致在整个测试过程中伸手距离（远 18.2%）、运动起始（快 8.6%）和最终准确性（高 16.1%）得到提高。本研究首次提供了证据，证明 iwS 中惊跳的暴露不会对自愿运动产生负面影响；此外，暴露可能通过减少异常的屈肌活动来改善自愿激活的伸手运动。
