The hidden layer captures the 5 the fact that we can classify accurately during windows 300-400ms indicates that the classifier is taking advantage of the N400 response discussed in the introduction context before word i is seen.
it seems reasonable that the hidden layer is not only related to the activity when the word is on the screen, but also related to the activity before the word is presented, which is the time when the brain is integrating the previous words to build that context.