Older Brain Plasticity Is in a Different Place
A widely presumed problem of aging is that the brain becomes less flexible — less plastic — and that learning may therefore become more difficult. Now a study led by Brown University researchers contradicts that notion with a finding that plasticity did occur in seniors who learned a task well, but it occurred in a different part of the brain than in younger people. The study was published in November 2014 in Nature Communications.
A release from Brown explains that when many older subjects learned a new visual task, they unexpectedly showed a significantly associated change in the white matter of the brain. White matter is the brain’s “wiring,” or axons, sheathed in a material called myelin that can make transmission of signals more efficient. Younger learners, on the other hand, showed plasticity in the cortex where neuroscientists expected to see it. The release quotes Takeo Watanabe, The Fred M. Seed Professor at Brown University and a co-author of the study, as saying, “We think that the degree of plasticity in the cortex gets more and more limited with older people. However, they keep the ability to learn, visually at least, by changing white matter structure.”
The study’s lead authors are Yuko Yotsumoto of the University of Tokyo and Li-Hung Chang of Brown University and National Yang Ming University in Taiwan. The corresponding author is Yuka Sasaki, associate professor (research) of cognitive, linguistic, and psychological sciences at Brown University.
Spotting the Differences The team’s study enrolled 18 volunteers aged 65 to 80 and 21 volunteers aged 19 to 32 to learn and perform an abstract visual perception task in the lab over the course of about a week. They saw screens showing a background texture of lines oriented in a particular direction. Sometimes a small patch of the screen would quickly show lines pointing in one of two different directions against that background. Subjects simply had to push a button indicating they saw a patch with a particular orientation. Individuals varied, but older subjects were just as likely on average as younger ones to make substantial progress in discriminating the small patch’s different texture. But the researchers weren’t just interested in whether learning occurred.
They also scanned the brains of the volunteers at the beginning and the end of the week using magnetic resonance imaging, which can indicate plasticity in the cortex, and using diffusion tensor imaging, which can indicate changes in white matter. The scans focused on the section of the brain responsible for visual learning, the early visual cortex (gray matter), and on the white matter beneath it.