Children’s brain development is fueled when they find their own way.
When Jon was born prematurely at 26 weeks, he weighed around two pounds and had trouble breathing on his own. For two months he lived in an incubator and eventually grew into a healthy baby and toddler. At age four, he had two epileptic seizures. About a year later his parents began to notice that Jon couldn’t remember things that happened in his daily life. He didn’t recall watching TV or what happened at school or what book he read. Jon’s IQ was normal, he could read and write, and did well at school. He could remember facts but not episodes from the past.
By the time Jon was 19, he couldn’t find his way anywhere. He didn’t remember familiar environments, or where his belongings were kept, or routes from one place to another.
The cause of these strange impairments was revealed when neuroscientists used magnetic resonance techniques to look at his brain. They discovered that his hippocampus, the bilateral brain region deep in the temporal lobe, was abnormally small, about half the size of a healthy hippocampus. It seemed that the lack of oxygen to his brain as an infant, known as hypoxia, and the subsequent convulsions, had caused severe damage to the cells in this specific structure and stunted its growth.
Jon, whose real name has not been made public to protect his privacy, has been the subject of research papers since the 1990s. His medical case illustrates the extraordinary function that the hippocampus plays in human life. It not only enables us to build cognitive maps of space so we can remember places and navigate, but shows that these cognitive maps are the locus of our memories of the past, what’s called episodic memory.
“The hippocampus evolved to do spatial navigation,” explains Nora S. Newcombe, a professor of psychology at Temple University. “One conjecture is that at some point in our evolutionary history, it was hijacked for the purpose of episodic memory because its neural architecture was appropriate.”
Spatial cognition and memory have deeper importance to humans beyond daily survival: They inform our sense of self. Memories of the past are like pillars of our identity; we use them to build narratives about our lives. These stories inform our actions and choices, and create a framework for imagining our possible futures.
New research is shedding light on how the hippocampus develops in infancy and childhood, a time in which circuits are maturing, and new cells are firing and encoding space to create cognitive maps. It turns out that kids’ experiences—exploring environments, navigating space, self-locomotion—can influence how the hippocampus develops.
“This is very exciting because the maturation of the brain is often considered dependent on time and a genetic program,” says Alessio Travaglia, a researcher at New York University’s Center for Neural Science. “What we’re showing is that the development of the brain is not a program, it’s about experience. So if I am a baby in New York City or in a desert or a forest, the experiences I’m facing are different.”
News of such plasticity is both fascinating and alarming. It comes at a time when pediatricians are warning that children are given less time and freedom to play, and are more sedentary than ever before…