For unknown reasons, the human brain distinctly separates the handling of images of living things from images of non-living things, processing each image type in a different area of the brain. For years, many scientists have assumed the brain segregated visual information in this manner to optimize processing the images themselves, but new research shows that even in people who have been blind since birth the brain still separates the concepts of living and non-living objects.
The research, published in today's issue of Neuron, implies that the brain categorizes objects based on the different types of subsequent consideration they demand�such as whether an object is edible, or is a landmark on the way home, or is a predator to run from. They are not categorized entirely by their appearance.
"If both sighted people and people with blindness process the same ideas in the same parts of the brain, then it follows that visual experience is not necessary in order for those aspects of brain organization to develop," says Bradford Mahon, postdoctoral fellow in the Department of Brain and Cognitive Sciences at the University of Rochester, and lead author of the study. "We think this means significant parts of the brain are innately structured around a few domains of knowledge that were critical in humans' evolutionary history."
Previous studies have shown that the sight of certain objects, such as a table or mountain, activate regions of the brain other than does the sight of living objects, such as an animal or face�but why the brain would choose to process these two categories differently has remained a mystery, says Mahon. Since the regions were known to activate when the objects were seen, scientists wondered if something about the visual appearance of the objects determined how the brain would process them. For instance, says Mahon, most living things have curved forms, and so many scientists thought the brain prefers to processes images of living things in an area that is optimized for curved forms.