Book Review: Surfing Uncertainty
slatestarcodex.com
slatestarcodex.com
The post itself, and the follow-up posts about predictive processing on the above blog are probably the easiest way to get into the subject, and it's an insanely interesting subject.
The core of the idea is written a bit into the blogpost: "The key insight: the brain is a multi-layer prediction machine. All neural processing consists of two streams: a bottom-up stream of sense data, and a top-down stream of predictions. These streams interface at each level of processing, comparing themselves to each other and adjusting themselves as necessary."
Deeper into the post, there's a breakdown of how this theory fits into various areas of research in novel ways (autism and schizophrenia among them), and I strongly suggest reading through at least that.