___ the dream has started,his body relaxes and his eyes become more active.填once,整句意思是什么

题目

___ the dream has started,his body relaxes and his eyes become more active.填once,整句意思是什么

答案

当实验人开始做梦的时候,他的肌肉放松下来,并且眼球运动变得更加活跃.
这是研究做梦时找人做实验的记录.