No two brains see the world exactly the same way, and a recent study by an international research team helps explain why. A human brain actually sees less than what meets the eye. Very early in the cortical visual pathways, the brain appears to sort images based on their significance to the observer at the moment, according to UC Davis psychologist Ron Mangun, co-author of the recent study published in the journal Nature. Each person has a spotlight of attention that shines upon certain details for special notice. Things not highlighted by this mental spotlight receive less processing in the brain. The study is the first to successfully pair two functional brain-imaging techniques to describe a mechanism of human cognition, in this case, the effect of attention on visual processing. The researchers combined a noninvasive method that accurately measures when brain activity occurs with a method that pinpoints where the activity occurs. "Attention has powerful implications for our everyday perceptions," says Mangun, a professor at the UC Davis Center for Neuroscience. "How our brains ultimately process and encode something is not just based on physical properties in the world around us, it is also dependent on internal processes, such as attention."