On Intelligence: How a New Understanding of the Brain Will Lead to the Creation of Truly Intelligent Machines

by Jeff Hawkins

Every moment in your waking life, each region of your neocortex is comparing a set of expected columns driven from above with the set of observed columns driven from below. Where the two sets intersect is what we perceive. If we had perfect input from below and perfect predictions, then the set of perceived columns would always be contained in the set of predicted columns. We often don’t have such agreement. The method of combining partial prediction with partial input resolves ambiguous input, it fills in missing pieces of information, and it decides between alternative views. It is how we combine an expected pitch-invariant interval with the last heard note to predict the next specific note in a melody. It is how we decide whether a picture is of a vase or of two faces. It is how we split our motor stream either to write or to speak the Gettysburg Address. Finally, in addition to projecting to lower cortical regions, layer 6 cells can send their output back into layer 4 cells of their own column. When they do, our predictions become the input. This is what we do when daydreaming or thinking. It allows us to see the consequences of our own predictions. We do this many hours a day as we plan the future, rehearse speeches, and worry about events to come. Longtime cortical modeler Stephen Grossberg calls this “folded feedback.” I prefer “imagining.”