Brain ‘sees’ even when eyes can’t

U. ROCHESTER (US)—Even in cases when people have been blind since birth, the brain still processes images of living and non-living objects in separate regions, a new study finds.

Scientists have assumed the brain segregated visual information to optimize processing, but the latest finding points to the possibility that other parts of the human brain are innately structured around categories of knowledge that may have been important in human evolution, says the study’s lead author Bradford Mahon, a postdoctoral fellow in brain and cognitive sciences at the University of Rochester.

The research, published in the Aug. 13 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—rather than 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,” Mahon says. “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 those activated by 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.

To see if the appearance of objects is indeed key to how the brain conducts its processing, Mahon’s team, led by Alfonso Caramazza, director of the Cognitive Neuropsychology Laboratory at Harvard University, asked people who have been blind since birth, with no visual experience, to think about certain living and non-living objects.  Clearly, it was necessary for their brains to do the processing using some criteria other than an object’s appearance.

“When we looked at the MRI scans, it was pretty clear that blind people and sighted people were dividing up living and non-living processing in the same way,” says Mahon.

“We think these findings strongly encourage the view that the human brain’s organization innately anticipates the different types of computations that must be carried out for different types of objects.”

Mahon thinks it’s possible that other parts of the human brain are innately structured around categories of knowledge that may have been important in human evolution. For instance, he says, facial expressions need a specific kind of processing linked to understanding emotions, whereas a landmark needs to be processed in conjunction with a sense of spatial awareness. The brain might choose to process these things in different areas of the brain because those areas have strong connections to other processing centers specializing in emotion or spatial awareness, adds Mahon.

The data for the study were collected at the Center for Mind/Brain Sciences at the University of Trento in Italy.

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