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.
Reaccionan cando entendemos o significado dunha frase, pero non cando realizamos outros procesos mentais complexos coma o cálculo mental ou cando memorizamos información ou apreciamos a complexa estrutura dunha peza musical.