They respond when you understand the meaning of a sentence, but not when you do other complex mental things, like mental arithmetic or holding information in memory or appreciating the complex structure in a piece of music.
它们在你理解一句话的意思时起反应， 却不在你做其他复杂心理活动起反应， 比如说心算， 或者试着记住一条信息， 或者在欣赏一段音乐的 复杂结构。