The human brain is an energy-intensive organ, consuming about a fifth of our body's energy, yet surprisingly, most of this energy is not used for the tasks we're actively engaged in, like reading or feeling our weight in a chair. Instead, the brain's energy is dedicated to its own internal activity, with neurons firing and signaling to each other regardless of our current actions. This internal brain activity, even when we're not focused on a specific task, is the foundation of our imagination. In a groundbreaking paper published in Psychological Review, researchers propose a new theory that challenges our understanding of how imagination works in the brain. They argue that imagination sculpts the images we see in our minds by carving into this background brain activity, rather than creating something entirely new. This theory suggests that imagination is more about silencing certain brain activity than generating new activity. The standard view of visual imagination is that it's the original seeing process run in reverse. When we imagine a friend's face, we start with an abstract idea, a memory or a name, and then this idea travels back down through the visual sequence of brain regions, reconstructing the face from its parts. However, prior research reveals that this feedback activity doesn't drive visual neurons to fire in the same way as when we actually see something. Instead, it modulates brain activity, increasing or decreasing the activity of brain cells to reshape what those neurons are already doing. Even behind closed eyes, early visual brain areas keep producing shifting patterns of neural activity, resembling those used to process real vision. Imagination doesn't need to build a face from scratch; the raw material is already there in the internal rumblings of our visual areas. What imagination does is hold still the currents that would otherwise carry those pieces away, like a signal carving its way through static. This new theory has significant implications for our understanding of imagination. It explains why imagination usually feels weaker than sight and why we rarely lose track of which is which. Visual perception arrives with a strength and regularity that the brain's own internal patterns don't match. Imagination works with those patterns rather than against them, reshaping what is already there into something we can almost see. This theory also provides insights into the varying degrees of mental imagery people experience. Those with weaker mental imagery have more excitable early visual areas, where neurons fire more readily on their own. This suggests that the spontaneous activity reshaping hypothesis, our new theory that imagination carves images out of the steady stream of ongoing brain activity, is a more accurate representation of how imagination works. In conclusion, this new theory offers a fascinating perspective on the nature of imagination, shedding light on the intricate workings of the human brain and the complex interplay between perception and imagination.
