Brown P, Day B L, Rothwell J C, Thompson P D, Marsden C D
MRC Human Movement and Balance Unit, Institute of Neurology, London, UK.
J Neurol Neurosurg Psychiatry. 1991 Oct;54(10):892-7. doi: 10.1136/jnnp.54.10.892.
The effect of posture on the EMG pattern of the normal auditory startle reflex was investigated. The startle response to an unexpected auditory tone was studied in eleven normal subjects when standing, and in six normal subjects when sitting relaxed or tonically plantar flexing both feet. Reflex EMG activity was recorded in the tibialis anterior and soleus about twice as frequently when standing, than when sitting relaxed. In addition, the median latencies to onset of reflex EMG activity in the tibialis anterior and soleus were about 40 and 60 ms shorter during standing, than when sitting relaxed. No short latency EMG activity was recorded in the calf muscles during tonic plantar flexion of the feet, while sitting. The effect of posture on the EMG pattern of the pathological auditory startle reflex was studied in five patients with hyperekplexia. In three patients the latency to onset of reflex EMG activity in the tibialis anterior was shorter when standing, than when sitting relaxed. The EMG pattern of the reflex response to sound was studied in detail in two of these patients and consisted of up to three successive components. The expression of each EMG component depended on the postural set of the limbs. In particular, a distinct short latency component was found in posturally important muscles following auditory stimulation. This short latency component was not recorded when sitting relaxed. It is concluded that the EMG pattern of the physiological and pathological auditory startle response is not fixed, but may change with the postural stance of the body. This finding supports the theory that the normal startle reflex and the abnormal startle reflex in hyperekplexia have a common brainstem origin.
研究了姿势对正常听觉惊吓反射肌电图模式的影响。在11名正常受试者站立时以及6名正常受试者放松坐姿或双脚强直性跖屈时，研究了对意外听觉音调的惊吓反应。站立时，胫前肌和比目鱼肌的反射肌电图活动记录频率约为放松坐姿时的两倍。此外，站立时胫前肌和比目鱼肌反射肌电图活动开始的中位潜伏期比放松坐姿时短约40和60毫秒。坐着时，双脚强直性跖屈期间小腿肌肉未记录到短潜伏期肌电图活动。在5名惊恐症患者中研究了姿势对病理性听觉惊吓反射肌电图模式的影响。在3名患者中，站立时胫前肌反射肌电图活动开始的潜伏期比放松坐姿时短。对其中2名患者的声音反射反应的肌电图模式进行了详细研究，其由多达三个连续成分组成。每个肌电图成分的表达取决于肢体的姿势状态。特别是，在听觉刺激后，在姿势重要的肌肉中发现了一个明显的短潜伏期成分。放松坐姿时未记录到这个短潜伏期成分。结论是，生理和病理性听觉惊吓反应的肌电图模式不是固定的，而是可能随身体的姿势而变化。这一发现支持了正常惊吓反射和惊恐症中的异常惊吓反射有共同脑干起源的理论。
