姿勢反應時間可隨著外來干擾時間之可預期性而變化

Postural Response Time Varies with Temporal Predictability of External Disturbance

可預期的平衡干擾實驗設計可用以研究姿勢反應控制中的預期因素。為了研究外來干擾時間之可預期性對於站立平衡反應時間的影響，本研究設計了一連串規律出現的平衡干擾。為了誘發十二位健康年輕受試者的平衡反應，我們使用電腦控制之制動系統以製造20或80公厘的橫向髖部位移，在可預期的狀況中，每1,500毫秒即出現一次聲音提示並於50毫秒後發生髖部位移干擾，不可預期的狀況中，每1,500毫秒即出現一次聲音提示但一連串平衡干擾是隨機發生的；除了干擾時間的可預期性，向左或向右的干擾方向可預期性也為操作因子之一。三維重複測量變異量分析結果顯示，可預期的干擾發生時間會導致健康年輕人較短的平衡反應時間，雖然只有五點四毫秒（p =.008），但此差異若在姿勢反應時間變長的病患身上則可能會放大；干擾強度（p = .086）和干擾方向（p = .997）的可預期性以及交互作用則沒有造成姿勢反應時間的變化。我們認為干擾時間之可預期性的效應機轉可能來自對特定時間點的注意力提高了、或是在平衡刺激的感覺訊息被處理之前或同時即已產生預期認知。

Designing paradigms with predictable disturbances to balance allows for the study of anticipatory factors in the control of postural responses. To probe the effects of temporal predictability on postural response time in standing balance, this study identified a balance perturbation paradigm with a regularly spaced series of perturbations. A computer-controlled actuator applied horizontal hip displacements of 20 mm or 80 mm in twelve healthy young adults. In one condition, the timing interval between onsets of a series of hip displacements was set at 1,500 ms, and each perturbation was accompanied by a metronome beat 50 ms in advance. This was contrasted with conditions in which metronome beats every 1,500 ms were played but perturbations were introduced with random timing. In addition to the variable of timing certainty, another variable of direction certainty was factorially added -- directed either alternately to the right and left or randomly. A three-way repeated measures ANOVA revealed that the temporally predictable perturbations resulted in a shorter response time -5.4 ms (p = .008), which may be magnified in patients with prolonged postural response times. Effects of disturbance amplitude (p = .086) or direction certainty (p = .997) or their interaction on response time were not observed. Possible mechanisms of the effect of temporal anticipation include heightened attention directed to a particular moment in time, or faster recognition of the balance stimulus parallel or prior to its actual sensory processing.