Want to ace that test tomorrow? Here’s a tip: Put down the coffee and hit the sack.

Scientists have long known that sleep, memory and learning are deeply connected. Most animals, from flies to humans, have trouble remembering when sleep deprived, and studies have shown that sleep is critical in converting short-term into long-term memory, a process known as memory consolidation.

But just how that process works has remained a mystery.

The question is, does the mechanism that promotes sleep also consolidate memory, or do two distinct processes work together? In other words, is memory consolidated during sleep because the brain is quiet, allowing memory neurons to go to work, or are memory neurons actually putting us to sleep?

In a recent paper in the journal eLife, graduate students Paula Haynes and Bethany Christmann in the Griffith Lab make a case for the latter.

Haynes and Christmann focused their research on dorsal paired medial (DPM) neurons, well-known memory consolidators in Drosophila. They observed, for the first time, that when DPM neurons are activated, the flies slept more; when deactivated, the flies kept buzzing.

These memory consolidators inhibit wakefulness as they start converting short-term to long-term memory. All this takes place in a section of the Drosophila brain called the mushroom body, similar to the hippocampus, where our memories are stored. As it turns out, the parts of the mushroom body responsible for memory and learning also help keep the Drosophila awake.

“It’s almost as if that section of the mushroom body were saying ‘hey, stay awake and learn this,’” says Christmann. “Then, after a while, the DPM neurons start signaling to suppress that section, as if to say ‘you’re going to need sleep if you want to remember this later.’”

Understanding how sleep and memory are connected in a simple system, like Drosophila, can help scientists unravel the secrets of the human brain.

“Knowing that sleep and memory overlap in the fly brain can allow researchers to narrow their search in humans,” Christmann says. “Eventually, it could help us figure out how sleep or memory is affected when things go wrong, as in the case of insomnia or memory disorders.”

To learn more about this and other fly research, check out Christmann’s blog, Fly on the Wall. 

This research was funded by the National Institute of Health. 

Take a deep breath. You just inhaled dust, dirt, pollen, bacteria and probably more than a few of these dust mites — but don’t worry, your cilia are on it.

Cilia, the cell’s tails and antennae, are among the most important biological structures. They line our windpipe and sweep away all the junk we inhale; they help us see, smell and reproduce. When a mutation disrupts the function or structure of cilia, the effects on the human body are devastating and sometimes lethal.

The challenge in diagnosing, studying and treating these genetic disorders, called ciliopathies, is the small size of cilia — about 500-times thinner than a piece of paper. It’s been difficult to examine them in molecular detail until now.

Professor Daniela Nicastro and postdoctoral fellow Jianfeng Lin have captured the highest-resolution images of human cilia ever, using a new approach developed jointly with Lawrence Ostrowski and Michael Knowles from the University of North Carolina School of Medicine. They reported on the approach in a recent issue of Nature Communications.

About 20 different ciliopathies have been identified so far, including primary ciliary dyskinesia (PCD) and polycystic kidney disease (PKD), two of the most common ciliopathies. They are typically diagnosed through genetic screening and examination of a patient’s cilia under a conventional electron microscope.

The problem is, conventional electron microscopy is not powerful enough to detect all anomalies in the cilia, even when genetic mutations are present. As a result, the cause of ciliary malfunctions can be elusive and patients with ciliopathies can be misdiagnosed or undiagnosed.

Nicastro and her team developed an approach that includes an advanced imaging technique that entails rapidly freezing human samples to preserve their native structure, imaging them with transmission electron microscopy, and turning those images into 3D models. This cutting-edge imaging was in part made possible by the advanced instrumentation in the Louise Mashal Gabbay Cellular Visualization Facility at Brandeis. It is the first time this approach has been used on human cilia and patient samples.

We have a new window into the structure and defects in human cilia, says Nicastro.

“For so long, researchers haven’t been able to see the small defects in human cilia,” Nicastro says. “Now, we can fill in the pieces of the puzzle.”