A Northwestern Medicine scientist and colleagues from Wayne State University discovered that as brains mature, the precise ways in which two key memory regions in the brain communicate improve our ability to form lasting memories in a new, rare study of direct brain recordings in children and adolescents. The findings also point to how the brain learns to multitask as it gets older.
The study will be published February 15, 2022 in Current Biology.
Due to a dearth of high-resolution data from children’s brains in the past, our understanding of how the developing brain develops memories has been limited. The study was the first to use an intracranial electroencephalogram (iEEG) on pediatric patients to look at how brain growth affects memory.
During that 16-year span, scientists discovered a correlation between how people’s brains developed and how well they were able to form memories. For example, younger children with less developed brains than the adolescent participants were unable to form as many memories as the adolescents.
“Our study helps us actually explain how memory develops, not just that it develops,” said corresponding author Lisa Johnson, assistant professor of medical social sciences and pediatrics at Northwestern University Feinberg School of Medicine.
“By understanding how something comes to be memory, in this instance it gives us windows into why it eventually falls apart. Human memory develops throughout childhood, peaks in your 20s and, for most people, declines with age, even in those who don’t develop dementia.”
By understanding how something comes to be memory, in this instance it gives us windows into why it eventually falls apart. Human memory develops throughout childhood, peaks in your 20s and, for most people, declines with age, even in those who don’t develop dementia.Lisa Johnson
To address this, her research focuses on memory across the lifetime to provide a comprehensive understanding of brain development and memory, which is why this study focused on children.
Rhythms of key memory regions of the brain
The research looked at communication between two brain regions that are important in memory formation: the medial temporal lobe (MTL) and the prefrontal cortex (PFC).
The scientists looked at two brain signals, a slowly oscillating brain wave and a quicker oscillating brain wave, to see how these regions communicate with one another. The rhythms determined whether a memory was successfully established and distinguished top-performing adolescents and children from those who did not.
Pioneering intracranial EEG in pediatric patients
The researchers took advantage of a rare opportunity to analyse data from electrodes placed directly on the exposed surface of the brain because the volunteers were already undergoing brain surgery for another reason (typically to treat their epilepsy).
Patients stayed in the hospital for a week after brain surgery to be monitored. Johnson’s team conducted their research around this time, asking participants to look at photos of scenes to assess how well they remembered them.
The researchers showed them the same photographs plus fresh settings they hadn’t seen before (for example, a different image of an outside region) to determine whether there were any age-related differences in how well they remembered what they’d seen.
Our brains learn to multitask with age
Another interesting result in the study is that rapid and slow theta oscillations rhythms in the brain, which aid cognition, behavior, learning, and memory, appear to alter with age. With aging, the slow theta frequency decreases, while the rapid theta frequency increases.
“These rhythms seemed to diverge with age so that they were similar in 5-year-olds and different in 20-year-olds,” Johnson said. “The fact that key memory regions are interacting at both frequencies suggests how your brain is learning to multitask as you get older.”
Johnson’s research, which she completed while at Wayne State University, lays the groundwork for a new research program she’s beginning with the Ann & Robert H. Lurie Children’s Hospital of Chicago. Noa Ofen of Wayne State University is the study’s senior author.