In a new brain imaging study, researchers at the University of Iowa identified specific areas activated when children were being tested on how much they could see and remember at any given time.
Using optical neuroimaging, researchers found that 3-year-olds can hold a maximum of 1.3 objects in their visual working memory, while 4-year-olds reach capacity at 1.8 objects. The maximum for adults is three to four objects, the researchers said.
Visual working memory is a core cognitive function, in which we stitch together what we see at any given point in time to help focus attention, according to the researchers.
For the study, the researchers used a series of object-matching tests on a computer.
“This is literally the first look into a 3- and 4-year-old’s brain in action in this particular working memory task,” said Dr. John Spencer, a psychology professor at the university and corresponding author of the study, which appears in the journal NeuroImage.
The research is important, he noted, because visual working memory has been linked to a variety of childhood disorders, including attention-deficit/hyperactivity disorder (ADHD), autism, and developmental coordination disorder. The goal is to use the new brain imaging technique to detect these disorders early, he said.
“At a young age, children may behave the same, but if you can distinguish these problems in the brain, then it’s possible to intervene early and get children on a more standard trajectory,” he explained.
A lot of research has been conducted in the past in an effort to get a better understanding of visual working memory in children and adults. But past studies used functional magnetic resonance imaging (fMRI). That worked for adults, but not with children, especially young ones, whose jerky movements threw the machine’s readings off, Spencer said.
That led his team to use functional near-infrared spectroscopy (fNIRS), which has been around since the 1960s but has never been used to look at working memory in children as young as 3, he said.
“It’s not a scary environment — no tube, no loud noises,” he said. “You just have to wear a cap.”
Like fMRI, fNIRS records neural activity by measuring the difference in oxygenated blood concentrations in different regions of the brain.
When a region is activated, neurons fire, using up the oxygen in the blood. The fNIRS measures the contrast between oxygen-rich and oxygen-deprived blood to gauge which area of the brain is going full tilt at a certain point in time.
The researchers outfitted the children with ski hats in which fiber optic wires had been woven. The children then played a computer game in which they were shown a card with one to three objects of different shapes for two seconds.
After a one-second pause, the children were then shown a card with either the same or different shapes. They were asked to respond if they had seen a match.
The tests revealed that neural activity in the right frontal cortex was an important barometer of higher visual working memory capacity in both age groups.
This could help evaluate children’s visual working memory at a younger age than before, allowing professionals to begin working with those whose capacity falls below the norm, according to the researchers.
The study also found that 4-year-olds showed greater use than 3-year-olds of the parietal cortex, located in both hemispheres of the brain below the crown of the head. It is believed to guide spatial attention, the researchers noted.
“This suggests that improvements in performance are accompanied by increases in the neural response,” added Aaron Buss, a UI graduate student in psychology and the first author on the paper. “Further work will be needed to explain exactly how the neural response increases — either through changes in local tuning, or through changes in long-range connectivity, or some combination.”
Source: The University of Iowa