Arthur has two posts about the current unit. He starts with his strong experience in looking at the “chain” or “train” of thoughts that we are usually so caught in, but is pleased that he can “rest” there, without getting caught in the content.
My only comment is how important this practice is. In many forms of Buddhist meditation, being able to distance yourself from thoughts, and rest in the activity of mind, is a kind of precondition for going deeper in meditation. In TSK, it functions a little differently: as an opportunity to understand the workings of mind, seen in terms of space-like presentations.
In his second post (I am going chronologically, and so from bottom to top), Arthur raises interesting issues that grew out of his practice of DTS 2: where is a remembered image while I am not remembering it; how do I have access to it so that it can again appear in the stream of thoughts. Notice that there are a lot of assumptions about time that operate in putting the question in this way, based on our usual linear model. That linear model may make more sense when we are always caught up in the train of thoughts, and less sense when we arrive at deeper connection to space. I say that not as answer to the question Arthur raises, but as a way of inviting in another dimension.
As to the question about linking thoughts to brain activity, I personally do not find that the most fruitful line of inquiry. Trying to connect mind and brain is always a question of explanation, and explanations are by definition far removed from experience.
Jack