When we perceive the world around us, certain objects appear to be more noticeable than others, depending on what we do. For example, when we view a forest-covered mountain from a distance, the forest looks like a large green carpet. But as we get closer, we start noticing the individual trees, and the forest fades to the background. What happens in the brain as our experience changes so drastically?
For decades, scientists studying the visual system thought that individual brain cells, called neurons, operate as filters. Some neurons would prefer coarse details of the visual scene and ignore fine details, while others would do the opposite. Every neuron was thought to do its own filtering.