Brain growth: MRI shows lifelong development

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  • Published: Jan 6, 2017
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Brain growth: MRI shows lifelong development

Lifelong learning

Stanford Professor Kalanit Grill-Spector, left, research associate Kevin Weiner and graduate student Jesse Gomez study growth in brain tissue enabling face recognition. (Image credit: Brianna Jeska)

It turns out to be nothing more than deceived wisdom that our brains no longer grow in adulthood, according to a Stanford study. Magnetic resonance imaging (MRI) reveals in the work that the brain tissues involved in face recognition continues to grow and develop throughout our lives.

There are myriad connections between neurones in our brains when we are born, many of these are gradually lost during childhood as our thoughts and memories grow, there is a second phase of rewiring during puberty, but science had assumed that once we reach adulthood the brain's structure is relatively stable. Now, Stanford University's Kalanit Grill-Spector, Kevin Weiner and Jesse Gomez and their colleagues have investigated this notion with regard to the parts of the brain tissue involved in face recognition and found the old hypothesis to be somewhat lacking.

In two studies, one published in the journal Science and the other in the journal Cerebral Cortex, they demonstrated how the rewiring and brain development processes are much more complicated than it was assumed. Indeed, the team has demonstrated tissue growth at the microscopic level in those brain regions as well as showing that actual changes in function also occur here too. The findings essentially subvert one of the central tenets of neuroscience showing that the tissue of our brains do not head in one direction from cradle to grave going from too much to just enough.

Ten-year developments

"I would say it's only in the last ten years that psychologists started looking at children’s brains," explains psychologist Grill-Spector, senior author on both papers. "The issue is, kids are not miniature adults and their brains show that. Our lab studies children because there's still a lot of very basic knowledge to be learned about the developing brain in that age range."

The team investigated particular regions of the brain, the one that allows us to discern faces from other familiar, and unfamiliar objects and the one that allows us to recognise places (both regions are near neighbours but have visible differences in structure). Face recognition is a critical faculty of the brain's repertoire, essential to survival for many different reasons, of course. In the Cerebral Cortex paper, which was published online in November 2016, they found that brain regions that recognize faces have a unique cellular make-up. In the Science paper, they reveal that the microscopic structures within the region change from childhood into adulthood over a timescale that correlates with improvements in our ability to recognize faces as we get older.

"We actually saw that tissue is proliferating," says graduate student Gomez. In conventional thought we have assumed that the brain diminishes as we get older. "Many people assume a pessimistic view of brain tissue: that tissue is lost slowly as you get older. We saw the opposite - that whatever is left after pruning in infancy can be used to grow," Gomez adds. "If you could walk across an adult brain and you were to look down at the cells, it would be like walking through different neighbourhoods," Gomez adds. "The cells look different. They’re organized differently."

Cell bodies

In addition to the differences revealed by the MRI work, the team also wanted to look at deeper cellular structures invisible to this technique and so worked with colleagues at the Institute of Neuroscience and Medicine, Research Centre Jülich in Germany. The team studied thin tissue slices of post-mortem brains and over the course of a year, the international team worked out how to match brain regions identified with functional MRI in living brains with the corresponding brain slices. This investigation then allowed them to determine which microscopic cellular structures of the areas they scanned with fMRI were involved in the processes, something that is not yet possible with the living brain. The microscopic images showed visible differences in the cellular structure between face and place recognition regions.

"There's been this pipedream in the field that we will one day be able to measure cellular architecture in living humans' brains and this shows that we're making progress," explains Kevin Weiner, a Stanford social science research associate.

Fundamentally, the research has demonstrated that the two parts of the brain look different in adults, but Grill-Spector and her colleagues were curious about how face recognition improves as we get older and whether or not the brain is changing from childhood and on through adolescence to allow that to happen. To investigate yet further how the development of this skill relates to changes in brain structure, the team scanned 22 children (aged 5 to 12 years) and 25 adults (aged 22 to 28 years) using fMRI and quantitative MRI. The latter measures the proportion of tissue to water in the brain and so can reveal changes in the fatty insulation surrounding the long neuronal connections connecting brain regions over a person's lifetime. This is the first study to report the use of this technique to directly measure changes in the cells' bodies.

Related Links

Science, 2017, 355, 68-71: "Microstructural proliferation in human cortex is coupled with the development of face processing"

Cerebral Cortex, 2017, online: "The Cytoarchitecture of Domain-specific Regions in Human High-level Visual Cortex"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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