Through = in one side and out the other, from end to end. Throughout = all the way through in every part. In the example you use, there is virtually no difference in meaning and both are correct. There is a technical difference but not everybody is so exact to make the difference. Here is another example that might be clearer in the subtle difference: I drive through Texas. (from beginning point to end but not all over). There are cacti throughout Texas. (They grow in all parts and all over the state).

I looked up your question and I found that throughout means “in or during the entire time or part.” For example, you would not say “I am driving throughout a red light.” But you could say, “love spread throughout the room.” (Love spread in the room and lasted the entire time)