'Sleep Inertia' is Real, and Scientists Can Measure It in Your Brain


Naps can be a great way to catch up on sleep—if you do them right. Wake up at the wrong stage of sleep, and you’ll feel groggy and terrible, not refreshed and perky. When your brain isn’t allowed to get through a full sleep cycle, you’re likely to experience what scientists call “sleep inertia,” or what regular folks might just call grogginess. Researchers are now able to tell us why our cognitive performance is so poor right when we wake up. In a new study that scanned the brains of volunteer nappers, PsyPost reports, scientists found that waking up from a nap disrupts the functional connectivity between brain networks, among other neurophysical changes.

The recent study published in the journal NeuroImage looked at the brains of 34 volunteers before and after they took a 45-minute nap. Researchers at the University of California, Berkeley and the Lyon Neuroscience Research Center in France measured the subjects’ brain activity five minutes and 25 minutes after waking up using EEG, fMRI, and behavioral observation (having them do mental subtraction) to see exactly how sleep inertia affects the body. The participants were asked to stay awake from 10 p.m. to 5 a.m. the night before to ensure they would fall asleep during the test. Some were woken up during relatively light sleep (stage 2 sleep) while others were woken up during deep sleep (stage 3 sleep).

They found that both groups showed decreased performance on the subtraction task. Right after they woke up, the participants’ EEG readings showed more delta brainwave activity (associated with deep sleep), and the fMRI scans showed decreased functional connectivity between brain networks. The brain connectivity disruption was worse for those awoken during the deep sleep stage.

By the 25-minute period, though, most of the effects on the brain had worn off, with participants’ brains returning to states similar to pre-test measurements. However, the light-sleep group seemed to recover better, while the sleep inertia didn’t dissipate as quickly for the deep-sleep group.

So yes, the dangers of waking up at the wrong sleep stage are real. The researchers tell PsyPost that people should limit their naps to 25 minutes or less—ensuring they don’t reach the deep sleep phase at all—or spend 90 minutes sleeping through an entire cycle.

[h/t PsyPost]

A Simple Skin Swab Could Soon Identify People at Risk for Parkinson's


More than 200 years have passed since physician James Parkinson first identified the degenerative neurological disorder that bears his name. Over five million people worldwide suffer from Parkinson’s disease, a neurological condition characterized by muscle tremors and other symptoms. Diagnosis is based on those symptoms rather than blood tests, brain imaging, or any other laboratory evidence.

Now, science may be close to a simple and non-invasive method for diagnosing the disease based on a waxy substance called sebum, which people secrete through their skin. And it’s thanks to a woman with the unique ability to sniff out differences in the sebum of those with Parkinson's—years before a diagnosis can be made.

The Guardian describes how researchers at the University of Manchester partnered with a nurse named Joy Milne, a "super smeller" who can detect a unique odor emanating from Parkinson's patients that is unnoticeable to most people. Working with Tilo Kunath, a neurobiologist at Edinburgh University, Milne and the researchers pinpointed the strongest odor coming from the patients' upper backs, where sebum-emitting pores are concentrated.

For a new study in the journal ACS Central Science, the researchers analyzed skin swabs from 64 Parkinson's and non-Parkinson's subjects and found that three substances—eicosane, hippuric acid, and octadecanal—were present in higher concentrations in the Parkinson’s patients. One substance, perillic aldehyde, was lower. Milne confirmed that these swabs bore the distinct, musky odor associated with Parkinson’s patients.

Researchers also found no difference between patients who took drugs to control symptoms and those who did not, meaning that drug metabolites had no influence on the odor or compounds.

The next step will be to swab a a much larger cohort of Parkinson’s patients and healthy volunteers to see if the results are consistent and reliable. If these compounds are able to accurately identify Parkinson’s, researchers are optimistic that it could lead to earlier diagnosis and more effective interventions.

[h/t The Guardian]

World’s Oldest Stored Sperm Has Produced Some Healthy Baby Sheep

A stock photo of a lamb
A stock photo of a lamb

It’s not every day that you stumble across a 50-year-old batch of frozen sheep sperm. So when Australian researchers rediscovered a wriggly little time capsule that had been left behind by an earlier researcher, they did the obvious: they tried to create some lambs. As Smithsonian reports, they pulled it off, too.

The semen, which came from several prize rams, had been frozen in 1968 by Dr. Steve Salamon, a sheep researcher from the University of Sydney. After bringing the sample out of storage, researchers thawed it out and conducted a few lab tests. They determined that its viability and DNA integrity were still intact, so they decided to put it to the ultimate test: Would it get a sheep pregnant? The sperm was artificially inseminated into 56 Merino ewes, and lo and behold, 34 of them became pregnant and gave birth to healthy lambs.

Of course, this experiment wasn’t just for fun. They wanted to test whether decades-old sperm—frozen in liquid nitrogen at -320°F—would still be viable for breeding purposes. Remarkably, the older sperm had a slightly higher pregnancy rate (61 percent) than sheep sperm that had been frozen for 12 months and used to impregnate ewes in a different experiment (in that case, the success rate was 59 percent).

“We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring,” researcher Dr. Jessica Rickard said in a statement.

Researchers say this experiment also lets them assess the genetic progress of selective breeding over the last five decades. “In that time, we’ve been trying to make better, more productive sheep [for the wool industry],” associate professor Simon de Graaf said. “This gives us a resource to benchmark and compare.”

[h/t Smithsonian]