Rest and remembering
Research investigates the sleep-memory link in older adults
Rebecca Spencer, psychological and brain sciences, has received a five-year, $2.6 million grant from the National Institutes of Health, which renews an earlier grant from NIH’s National Institutes of Aging to support work on sleep and memory in older adults.
Spencer and colleagues will use the MRI in the Human Magnetic Resonance Center at the Institute of Applied Life Sciences to look at how memories are encoded in the brain before sleep and how they are changed by sleep compared to wakefulness in older adults compared to younger adults.
As she explains, “In the first five years of this work, we had several significant findings, and among them we found that sleep’s role in memory processing was particularly reduced by aging for tasks that required motor learning, for example, learning a sequence of finger movements. The good news is that when we looked at more ‘traditional’ learning tasks, things like learning a list of words, we found that sleep is still beneficial for older adults.”
In the next five years of the award, she adds, “we will continue to try to understand this. If we can understand why sleep’s role is preserved for declarative memory, then we can perhaps design interventions to improve sleep function for procedural memories.”
Spencer says her group predicts that there are different brain regions engaged in older adults when learning something, compared to young adults. By not engaging the critical brain area, older adults don’t tap into the ability for sleep to work on memories. “We predict that you MUST use the hippocampus on a task in order for that task to benefit from sleep,” she says.
Another possibility the sleep researchers are considering is that older adults perhaps use the same brain areas, but to a lesser extent. “Older people just don’t learn things quite as deeply before sleep compared to young adults,” she suggests. “So we are going to do a study in which we over-train the older adults prior to sleep to see if that brings them up to the place the young adults are.”
In addition to the human MRI center at IALS, Spencer and colleagues will use high-density polysomnography during sleep in this series of experiments.
A further aspect of the research will be to explore the observation that changes in sleep precede the onset of Alzheimer’s disease, Spencer says. “Given that sleep benefits memory in healthy young adults, it has been proposed that changes in sleep may contribute to cognitive impairments in Alzheimer’s disease, particularly early in the disease. Yet what remains unknown, and is a long-term goal of our research, is whether sleep-dependent memory benefits persist even when changes in sleep and memory-encoding deficits that accompany healthy aging are observed.”
Understanding healthy brain aging and factors underlying cognitive resilience (such as sleep and hippocampal function) is essential to inform interventions and preventions for Alzheimer’s disease and other age-related diseases with impaired sleep, Spencer says.