By Carol Clark
The ancient philosophers Descartes, Aristotle and Plato are among those who have pondered variations on the question: How much of our brain and mind are we born with and how much comes from being in the world?
“It’s an age-old debate, and one that we’re still having because it’s one of the most difficult questions to answer,” says Emory psychologist Daniel Dilks. “You can’t do controlled experiments to fully test the question in humans because you would have to take away a person’s experiences.”
Modern-day techniques, such as functional magnetic resonance imaging, or fMRI, offer a window into neural activity. Subjects must remain perfectly still and alert during scanning, however, making it difficult to do experiments with very young children. As a result, most measurements of children’s neural activity only go back to age four, at the earliest.
Until now, that is. As a post-doctoral fellow at MIT, Dilks was part of a team that successfully scanned the brains of awake human infants using fMRI. The researchers wanted to learn whether infants used similar neural mechanisms as adults to visually distinguish specific types of input, such as faces and objects.
“Two thirds of the adult brain is involved in visual processing, so the origins of how we process visual stimuli is particularly important to understanding the brain and the mind,” Dilks says.
The researchers adapted fMRI technology to make it baby friendly. They built a special fMRI head coil – the receiving antenna of the scanner – that allows a subject to recline in what resembles an infant car seat. A mirror attached to the seat allows a baby to watch videos while in the scanner. The researchers also muffled the noise of the scanner.
Using this technology, and other modifications, they conducted fMRI experiments on babies just four to six months old. The babies watched movies of faces and places and other stimulus categories while in the scanner, as data was collected on their neural activity. Their responses were then compared to those of adults.
The results, published this year by Nature Communications, found that the visual cortex of the infants responded preferentially to the categories of faces and places, with a spatial organization similar to adults. The adult responses, however, were more sensitive.
“We’ve provided the first neural evidence that our basic mechanisms for face and place recognition are in place in infancy and only a little weaker than that of adults,” Dilks says.
The work adds to the growing evidence that babies do not come into the world as what the ancient philosophers referred to as tabular rasa, or blank slates.
“Thirty years ago, we thought that infants were basically little sponges, absorbing everything around them,” Dilks says. “We now know that babies are full of knowledge really early — and we’re learning that some of that knowledge is pretty complex. It’s a big paradigm shift.”
Dilks has brought the fMRI scanning technology for infants and children to Emory, where his lab will build on the research to learn more about the development of visual processing. One goal is to map the progression of the category-selective visual cortex from infancy to adulthood. In addition to adding to basic scientific knowledge, the research may one day have medical applications.
“We can’t fix most neurological problems right now, partly because we don’t know enough about the brain,” Dilks says. “By continuing to learn more about how the brain develops and functions normally, we may keep moving closer to being able to repair it when something goes wrong.”
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