For most parts of the brain, our teen years are either as good as it gets or at least as large as it will be. Brain development goes on into our twenties, but it involves the addition of extra connections, not adding bulk. However, a new study has found that one section of the human cortex keeps on growing long after related areas have stopped. The area in question is the part of the fusiform gyrus responsible for recognizing other people's faces.
The capacity to recognize faces develops early – when you are as helpless as an infant, it is pretty important to be able to differentiate between family and strangers. Nevertheless, it doesn't stop there, with the capacity improving as we grow up.
The capacity to do this is located in the fusiform gyrus, which also controls recognition of places and words. It has other capabilities as well, such as color processing. Even our closest relatives are so different in this area that studies have to be done on humans. Using both quantitative and functional magnetic resonance imaging, a team led by Stanford University PhD student Jesse Gomez compared the brains of children aged 5-12 and adults to see how the fusiform gyrus changes as we age. The quantitative scans helped them to see structural changes in the brain, while functional imaging allowed them to see which brain regions are active when given tasks such as identifying faces from partial images.
After examining the areas of the brain that light up when matching an image to a distorted version of the same face, Gomez found that our face recognition centers keep growing into adulthood, while the equivalent areas for location recognition do not. This growth was not in vain, however. The researchers found a correlation between the size of the relevant brain region and the ability to match a face under difficult conditions.
Given how closely entwined these two regions are within the fusiform gyrus, this is a surprising finding. It also might be thought that adults, who have presumablely been a lot more places than children, might benefit from a greater capacity to store those memories. Nevertheless, Gomez confirmed the findings through autopsies.
Children's brains, fortunately, are seldom available for dissection, making it difficult to establish which brain components are responsible for the expansion. Nevertheless, Gomez notes in Science that while a thickening of the myelin sheaths that protect neurons is known to occur during teenage years, this cannot account for the growth on its own. Instead, the paper suggests that cell bodies and dendrites are growing as well.