In the March 15 issue of Neuron, the research team provides the first human evidence for a two-stage model of how a person learns to place objects into categories ?discerning, for example, that a green apple, and not a green tennis ball, belongs to "food." They describe it as a complex interplay between neurons that process stimulus shape ("bottom-up") and more sophisticated brain areas that discriminate between these shapes to categorize and "label" that information ("top-down").
A human can't function without the ability to sort between objects and organize them in fluid ways, said the study's lead author, Maximilian Riesenhuber, Ph.D., the principal investigator for the Laboratory for Computational Cognitive Neuroscience. "We make sense of the world by learning to recognize objects as members of categories such as 'food,' 'friend,' or 'foe,' but it has not been clear how the human brain does this," he said.
The researchers theorized that a very simple yet efficient way of doing this kind of learning would be for the brain to first learn how objects vary in shape, and then, in a second stage, to learn which shapes go with which labels, allowing the brain to sort an object into different labeled "bins" when necessary. For example, a green apple and a green tennis ball are both green and round, but only an apple can be eaten and only a green tennis ball belongs to a sport.
In this study, the research team asked human volunteers to undertake a series of tasks presented to them on a computer screen. All of them involved cars that were generated with a computer graphics morphing system, allowing
Source:Georgetown University Medical Center