Why are we mentally sharper at certain times of day? A study led by Jonathan Lipton MD, Ph.D., at Boston Children’s Hospital spells out the relationship between circadian rhythms—the body’s natural day/night cycles—and the brain connections known as synapses.

The work is the first to provide a cellular and molecular explanation for natural fluctuations over the day in alertness, cognition, and the ability to learn and remember.

“We have known for more than a century that the time of day influences cognition and memory, but until now the mechanisms have been elusive,” says Lipton, a sleep physician in the Department of Neurology and researcher in the F.M. Kirby Neurobiology Center.

Analysis of human brain tissue reveals differences in how immune cells behave in brains with Alzheimer’s disease compared to healthy brains, indicating a potential new treatment target.

University of Washington-led research, published in August, discovered microglia in the brains of people with Alzheimer’s disease were in a pre-inflammatory state more frequently, making them less likely to be protective.

Microglia are immune cells that help keep our brains healthy by clearing waste and preserving normal brain function.