The remembered present

Chapter 6 endnote 12, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

Scientists have known for some time that knowledge from the past, wired into brain connections, creates simulated experiences of the future, such as imagination. Other scientists focus on how this knowledge creates experiences of the present moment. [...] it is metabolically inefficient to compute perceptions and plan actions from scratch in every moment of your life. We have evolved an efficient nervous system that saves costs by minimizing redundancy (which is wasteful, metabolically speaking). The brain exploits the fact that certain patterns of sensations and events tend to recur with some regularity. It learns (i.e., changes neural firing rates, and eventually grows new neurons or connections) only what is novel and relevant to the body budget; this is why the brain predicts (i.e., reconstructs, infers, or guesses) those regularities, where possible, rather than squandering resources to detect them again and again.

Neurons don't "store" information — they "remember" it (reinstate it, reconstruct it, etc.) The whole point of being able to reinstate the past is to make sense of the present so as to plan for the future. Gerald Edelman called this "the remembered present."

A brain is essentially performing pattern matching. In effect, it is asking "which combination of past experiences is the upcoming sensory inputs most similar to." This is how a brain categorizes. Without categories, everything is different from everything else, and nothing can be generalized and learned -- there is no savings. So, a brain categorizes to learn. The purpose of placing things into categories is to make the right choices about how to act.

When a brain encounters something new, it is not entirely new. It reinstates bits and pieces of the past (in various combinations) — this is conceptual combination — so that we know what to expect, how to feel, and how to act. "Concepts are a kind of mental glue." They allow us to channel our past experiences for the purpose of understanding and acting in the present. Without prior experience (without concepts), we would have no understanding of the physical world, and the social world would not exist. We would be experientially blind and helpless.