If I were at the supermarket and I had to remember what to get, one thing that could happen would be that I got out of my pocket a list that G. had written out and given me for this purpose. If you asked me how I remembered and I told you about the list in my pocket, that would be genuinely explanatory: that would explain how I remembered the items. But if we try to use such an explanation for cognitive operations inside the head, this kind of explanation will not be explanatory. If the model claims that the brain has already stored information and "remembering" is a matter of accessing this database then the "explanation" assumes what needs to be explained, that is, how the nervous system "stores information" in the first place. In the case of the piece of paper with writing on it in my pocket this is not mysterious. Similarly with supposed explanations of dreaming, hallucinating, but most basically with theories of perception itself. As soon as perceiving something is modeled as forming a representation the problem is full-blown.
In class this week a student asked, "But then how do you explain perception, memory etc. if not with reference to mental content?" The point is that the concept of "mental content" itself fails to be explanatory, thus the question is loaded. It does no good to say that I remember my friend's face by mentally "inspecting" a mental "picture" of my friend.