Videos of messages being typed showed Wouters quickly moving Houben's hand around his keypad, apparently following the indications of the locked-in patient.

【分析】本句的主要结构是：show sb. doing sth.  即：

Videos showed Wouters moving Houben's hand

following the indications of the locked-in patient：是现在分词短语作伴随状语，修饰moving。

如果改为followed，那么就是跟showed 并列，而showed 的主语Videos，视频无法follow。实际上，following 的逻辑主语是Wouters。此外，如果是并列的话，followed 之前应加连词and。

【翻译】输入字幕的视频显示，沃特斯迅速在键盘周围移动胡本的手，显然是在按照自闭症患者的意图做。