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Key to Learning and Forgetting Identified in Sleeping Brain

Distinct patterns of electrical activity in the sleeping brain may influence whether we remember or forget what we learned the previous day, according to a new study by UC San Francisco researchers. The scientists were able to influence how well rats learned a new skill by tweaking these brainwaves while animals slept, suggesting potential future applications in boosting human memory or forgetting traumatic experiences, the researchers say. 

In the new UCSF study, published online Oct. 3 in the journal Cell, a research team led by Karunesh Ganguly, MD, PhD, an associate professor of neurology and member of the UCSF Weill Institute for Neurosciences, used a technique called optogenetics to dampen specific types of brain activity in sleeping rats at will.

This allowed the researchers to determine that two distinct types of slow brain waves seen during sleep, called slow oscillations and delta waves, respectively strengthened or weakened the firing of specific brain cells involved in a newly learned skill – in this case how to operate a water spout that the rats could control with their brains via a neural implant.

“We were astonished to find that we could make learning better or worse by dampening these distinct types of brain waves during sleep,” Ganguly said. “In particular, delta waves are big part of sleep, but they have been less studied, and nobody had ascribed a role to them. We believe these two types of slow waves compete during sleep to determine whether new information is consolidated and stored, or else forgotten.”

“Linking a specific type of brain wave to forgetting is a new concept,” Ganguly added. “More studies have been done on strengthening of memories, fewer on forgetting, and they tend to be studied in isolation from one another. What our data indicate is that there is a constant competition between the two – it’s the balance between them that determines what we remember.”

Some Sleep to Remember, Others to Forget

Over the past two decades the centuries-old human hunch that sleep plays a role in the formation of memories has been increasingly supported by scientific studies. Animal studies show that the same neurons involved in forming the initial memory of a new task or experience are reactivated during sleep to consolidate these memory traces in the brain. Many scientists believe that forgetting is also an important function of sleep – perhaps as a way of uncluttering the mind by eliminating unimportant information.

Slow oscillations and delta waves are hallmarks of so-called non-REM sleep, which – in humans, at least – makes up half or more of a night’s sleep. There is evidence that these non-REM sleep stages play a role in consolidating various kinds of memory, including the learning of motor skills. In humans, researchers have found that time spent in the early stages of non-REM sleep is associated with better learning of a simple piano riff, for instance.

Ganguly’s team began studying the role of sleep in learning as part of their ongoing efforts to develop neural implants that would allow people with paralysis to more reliably control robotic limbs with their brain. In early experiments in laboratory animals, he had noted that the biggest improvements in the animals’ ability to operate these brain-computer interfaces occurred when they slept between training sessions.

“We realized that we needed to understand how learning and forgetting occur during sleep to understand how to truly integrate artificial systems into the brain,” Ganguly said.

Brain Waves Compete to Determine Learning During Sleep

In the new study, a dozen rats were implanted with electrodes that monitor firing among a small group of selected neurons in their brains’ motor cortex, which is involved in conceiving and executing voluntary movements. Producing a particular pattern of neural firing allowed the rats to control a water-dispensing tube in their cages. In essence, the rats were performing a kind of biofeedback – each rat learned how to fire a small ensemble of neurons together in a unique new pattern in order to move the spigot and get the water.

Ganguly’s team observed the same unique new firing pattern replaying in animals’ brains as they slept. The strength of this reactivation during sleep determined how well rats were able to control the water spout the next day. But the researchers wanted to go further – to understand how the brain controls whether rats learn or forget while they slumber.

To manipulate the effect of brain waves during non-REM sleep, the researchers genetically modified rat neurons to express a light-sensitive optogenetic control switch, allowing the team to use lasers and fiber optics to instantaneously dampen brain activity associated with the transmission of specific brain waves. With precise, millisecond timing of the laser, the scientists in separate experiments specifically dampened either slow oscillating waves or delta waves in a tiny patch of the brain around the new memory circuit.

Disruption of delta waves strengthened reactivation of the task-associated neural activity during sleep and was associated with better performance upon waking. Conversely, disruption of slow oscillations resulted in poor performance upon waking. “Slow oscillations seem to be protecting new patterns of neural firing after learning, while delta waves tend to erase them and promote forgetting,” Ganguly said.

Further analysis showed that in order to protect learning, slow oscillations had to occur at the same time as a third, well-studied brain wave phenomenon, called sleep spindles. A sleep spindle is a high-frequency, short-duration burst of activity that originates in a region called the thalamus and then propagates to other parts of the brain. They have been linked to memory consolidation, and a lack of normal sleep spindles is associated with brain maladies including schizophrenia and developmental delay, and also with aging.

“Our work shows that there is a strong drive to forget during sleep,” Ganguly said. “Very brief pairings of sleep spindles and slow oscillations can overcome delta wave-driven forgetting and preserve learning, but the balance is very delicate. Even small disturbances in these events lead to forgetting.”

It’s not yet known what tips the scales between delta wave–driven forgetting and slow oscillation–driven learning, but it’s clear that better understanding the process could have profound impacts on the study of human learning and memory, Ganguly said. “Sleep is truly driving profound changes in the brain. Understanding these changes will be critical for brain integration of artificial interfaces and may one day allow us to modify neural circuits to aid in movement rehabilitation, such as after stroke, where previous studies have shown that sleep plays an important role in successful recovery.”

reblogging for links

If you're celebrating Biden's win, consider celebrating by donating to a bail fund, planned parenthood, or the Navajo Water project.

Your action to help the marginalized shouldnt end at presidential candidates and voting.

A relaxing timeframe

curled up in a nice little nook, listening to Seven Lions, alternating between a cool cup of water and a nice warm mug of Jasmine tea, writing a story. It is very calm. I should do this more often. I wish you calm as well.

the skull is so big compare to her! Marvelous

@brittikitty on insta

What a wonderful Johnny! All the little touches on him are so magnificent!

Older Johnny

O great goldfish, I have a question. What happens to crocodiles/alligators when their skin dries out? Does it get stiff, or cracked? Do their scales start to peel? Thank you for the animal wisdom

nothin, their skin is pretty impermeable and doesn't actually dry out all the way unless the animal dies first!

crocodilians live just fine in arid environments as long as there's a body of water for them drink and hunt in, the hot dry winds don't hurt them near as badly as the lack of water does out there.

Spectober 2020: Day 13

Get ready for Spectober Day 13!

Art Prompt: Graveyard

Writing Prompt: A graveyard seems like the perfect place to search for spirits, but will Stephen get more than he bargained for?

Don’t forget to tag your submissions with #spectober2020 ! Away you go!

Neat!

For a short time in February – if the conditions are perfect – Horsetail Fall at Yosemite National Park in #California glows red and orange and looks like lava falling down the side of El Capitan. Visitors flock to the park every year to see this phenomenon, which happens when sunset hits the waterfall at just the right angle, illuminating the water and mist in brilliant orange light. If you have a chance to witness #Yosemite’s Firefall, remember to go slow, plan ahead, mask up and share the amazing views. Photo of 2019 #Firefall courtesy of Daniel Berson.

#crocodiles #cool shit!

New Evidence Suggests Ancient Crocodiles Swam From Africa to America

https://sciencespies.com/news/new-evidence-suggests-ancient-crocodiles-swam-from-africa-to-america/

New Evidence Suggests Ancient Crocodiles Swam From Africa to America

Most American crocodiles don’t need to look far to find the feature that sets them apart from Nile crocodiles. The difference lies right between their eyes and their nostrils. Of crocodiles living today, only the four crocodile species that live in the Americas have a small bump in the middle of their snouts.

But about seven million years ago, a ten-foot-long crocodile living in what’s now Libya had the same tell-tale lump, according to research published in Scientific Reports last week. A fossil skull of the extinct Crocodylus checchiai provides more evidence that crocodiles spread across the world by migrating from Australia, through Africa and finally to South America.

The fossil “fills a gap between the Nile crocodile in Africa and the four extant American species,” University of Turin paleoherpetologist Massimo Delfino says to Science News’ Carolyn Wilke.

The fact that crocodiles live on both sides of the Atlantic Ocean has long puzzled biologists trying to figure out which direction the giant reptiles migrated. Genetic research in 2011 provided molecular evidence that crocodiles migrated from Africa to the Americas, but fossil evidence was scant.

“The main problem for palaeobiologists is the rarity and fragmentary nature of fossil remains,” Delfino and co-author David Iurino told the Agence France-Presse by email.

The seven million-year-old Crocodylus checchiai skull was first collected in 1939.

(Image by Bruno Mercurio)

The fossil described in the new paper is one of four that were first described in the 1930s. Three that were stored in the Natural History Museum in Tripoli, Libya, were lost or destroyed during World War II, according to the Scientific Reports paper. But the researchers found the fourth skull, originally collected in 1939, stored in the Sapienza University of Rome.

“This fossil is twice-old,” Delfino tells Nina Pullano at Inverse, referencing the fact that the skull is millions of years old and had then been forgotten for decades.The researchers used CT scanning to create a 3D model of the inside and outside of the skull for closer study and confirmed the presence of the American crocodile-like snout bump.

At seven million years old, the C. checchiai skull predates all known crocodile fossils in America, the oldest of which are about five million years old, Lucy Hicks reports for Science magazine. That means that the timeline checks out: it’s possible that C. checchiai may have made their way from Libya to the western coast of Africa, swam across the Atlantic and landed on the shores of South America.

The continents were about the same distance apart seven million years ago as they are today, making the journey across the ocean quite a feat—but not impossible. The researchers point out in a statement that the Australian marine crocodile has been recorded travelling more than 300 miles in a day. The prehistoric croc may have also bobbed along on one of the ocean’s surface currents that travel west from Africa to the Americas.

Crocodiles are also not the only flightless animal thought to have reached the New World by crossing the Atlantic. As the Inverse reports, a study published in April suggests that on two instances, monkeys made their way across the ocean on floating vegetation.

“If you think that the monkey can cross the Atlantic Ocean, very probably it’s much easier to accept that the crocodile can do it,” Delfino tells Inverse. Ancient crocodiles had the specialized glands necessary to swim and survive in saltwater and may have snacked on sea turtles along the way.

As a changing climate wiped out local species, crocodiles were well adapted to the late-Miocene environment and replaced them, the researchers write in the paper. The original crew of ocean-crossing crocs may have included many individuals or at least one pregnant female, Science News reports.

And after situating themselves in South America, they evolved and diversified into the four species found in the Americas today. (Only the American crocodile and American alligator are found in the United States.)

But whether or not the crocodilians mourn their C. checchiai ancestors is hard to tell—they might just be crocodile tears, after all.

#News

If there's one thing that will instantly brighten up your day it is seeing the wildly different approaches each contestant took to eating a watermelon. Including completely obliterating it on the floor.

Taskmaster one task per episode 1.01 eat as much watermelon as possible in one minute (Romesh Ranganathan)