Posts Tagged ‘mice’

mice-x

by SUKANYA CHARUCHANDRA

The protein Bmal1, which helps regulate the body’s internal clock, is found in especially high levels in the brain and in skeletal muscles. Mice completely deficient in Bmal1 were known to suffer from sleep impairments, but the specifics at play weren’t clear. At the University of California, Los Angeles, Ketema Paul and colleagues looked to these mice for clues about the role Bmal1 plays in sleep regulation.

MUSCLE PLAY
When Paul’s team restored levels of the Bmal1 protein in the mice’s brains, their ability to rebound from a night of bad sleep remained poor. However, turning on production in skeletal muscles alone enabled mice to sleep longer and more deeply to recover after sleep loss.

SWEET DREAMS
For decades, scientists have thought sleep was controlled purely by the brain. But the new study indicates the ability to catch up on one’s sleep after a bout of sleeplessness is locked away in skeletal muscles, not the brain—at least for mice. “I think it’s a real paradigm shift for how we think about sleep,” says John Hogenesch, a chronobiologist at Cincinnati Children’s Hospital Medical Center who discovered the Bmal1 gene but was not involved in this study.

TARGET LOCKED
Paul’s group also found that having too much of the Bmal1 protein in their muscles not only made mice vigilant but also invulnerable to the effects of sleep loss, so that they remained alert even when sleep-deprived and slept fewer hours to regain lost sleep. “To me, that presents a potential target where you could treat sleep disorders,” says Paul, noting that an inability to recover from sleep loss can make us more susceptible to diseases.

The paper
J.C. Ehlen et al., “Bmal1 function in skeletal muscle regulates sleep,” eLife, 6:e26557, 2017.

https://www.the-scientist.com/the-literature/muscles-hold-a-key-to-sleep-recovery-64685?utm_campaign=TS_DAILY%20NEWSLETTER_2018&utm_source=hs_email&utm_medium=email&utm_content=66141129&_hsenc=p2ANqtz–EaFM3BB6i_l04LL2zbvjlEHCWVwrSrks2D9Aksml-wGa9f88gfOwPhtiPCXEMJRqzu6WG53_vzEvHht0oAGylLgMANQ&_hsmi=66141129

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Sleeping minds: prepare to be hacked. For the first time, conscious memories have been implanted into the minds of mice while they sleep. The same technique could one day be used to alter memories in people who have undergone traumatic events.

When we sleep, our brain replays the day’s activities. The pattern of brain activity exhibited by mice when they explore a new area during the day, for example, will reappear, speeded up, while the animal sleeps. This is thought to be the brain practising an activity – an essential part of learning. People who miss out on sleep do not learn as well as those who get a good night’s rest, and when the replay process is disrupted in mice, so too is their ability to remember what they learned the previous day.

Karim Benchenane and his colleagues at the Industrial Physics and Chemistry Higher Educational Institution in Paris, France, hijacked this process to create new memories in sleeping mice. The team targeted the rodents’ place cells – neurons that fire in response to being in or thinking about a specific place. These cells are thought to help us form internal maps, and their discoverers won a Nobel prize last year.

Benchenane’s team used electrodes to monitor the activity of mice’s place cells as the animals explored an enclosed arena, and in each mouse they identified a cell that fired only in a certain arena location. Later, when the mice were sleeping, the researchers monitored the animals’ brain activity as they replayed the day’s experiences. A computer recognised when the specific place cell fired; each time it did, a separate electrode would stimulate brain areas associated with reward.

When the mice awoke, they made a beeline for the location represented by the place cell that had been linked to a rewarding feeling in their sleep. A brand new memory – linking a place with reward – had been formed.

It is the first time a conscious memory has been created in animals during sleep. In recent years, researchers have been able to form subconscious associations in sleeping minds – smokers keen to quit can learn to associate cigarettes with the smells of rotten eggs and fish in their sleep, for example.

Previous work suggested that if this kind of subconscious learning had occurred in Benchenane’s mice, they would have explored the arena in a random manner, perhaps stopping at the reward-associated location. But these mice headed straight for the location, suggesting a conscious memory. “The mouse develops a goal-directed behaviour to go towards the place,” says Benchenane. “It proves that it’s not an automatic behaviour. What we create is an association between a particular place and a reward that can be consciously accessed by the mouse.”

“The mouse is remembering enough abstract information to think ‘I want to go to a certain place’, and go there when it wakes up,” says neuroscientist Neil Burgess at University College London. “It’s a bigger breakthrough [than previous studies] because it really does show what the man in the street would call a memory – the ability to bring to mind abstract knowledge which can guide behaviour in a directed way.”

Benchenane doesn’t think the technique can be used to implant many other types of memories, such as skills – at least for the time being. Spatial memories are easier to modify because they are among the best understood.

His team’s findings also provide some of the strongest evidence for the way in which place cells work. It is almost impossible to test whether place cells function as an internal map while animals are awake, says Benchenane, because these animals also use external cues, such as landmarks, to navigate. By specifically targeting place cells while the mouse is asleep, the team were able to directly test theories that specific cells represent specific places.

“Even when those place cells fire in sleep, they still convey spatial information,” says Benchenane. “That provides evidence that when you’ve got activation of place cells during the consolidation of memories in sleep, you’ve got consolidation of the spatial information.”

Benchenane hopes that his technique could be developed to help alter people’s memories, perhaps of traumatic events (see “Now it’s our turn”, below).

Loren Frank at the University of California, San Francisco, agrees. “I think this is a really important step towards helping people with memory impairments or depression,” he says. “It is surprising to me how many neurological and psychiatric illnesses have something to do with memory, including schizophrenia and obsessive compulsive disorder.”

“In principle, you could selectively change brain processing during sleep to soften memories or change their emotional content,” he adds.

Journal reference: Nature Neuroscience, doi:10.1038/nn.3970

http://www.newscientist.com/article/dn27115-new-memories-implanted-in-mice-while-they-sleep.html#.VP_L9uOVquD

Thanks to Kebmodee for bringing this to the attention of the It’s Interesting community.

mice

It is a cruel world out there, particularly for young animals born into social groups where infanticide occurs. This dark side of evolution is revealed when adults – often males – kill offspring to promote their own genes being passed on, by reducing competition for resources or making females become sexually receptive more quickly.

This behaviour proves expensive for females, who have evolved strategies to avoid this fate. One strategy is to join forces with other females to physically ward off killer males. A more interesting strategy is to mate with several males, known as “polyandry”, so fathers can’t distinguish their young from others’, which means they avoid killing pups so that they don’t accidently kill their own.

Now, researchers at the University of Zurich have found a new type of infanticide counter-strategy: mothers can achieve paternity confusion even if they don’t mate with multiple males, through nesting with other females, which they call “socially mediated polyandry”. And such a strategy might be happening close to home, in the unassuming house mouse.

Yannick Auclair and his colleagues put their theory to the test on a wild population of mice living in an old agricultural building outside Zurich. They measured the genetic relationships within litters and found a complex picture of female social relationships and mating patterns. These allowed them to identify mothers nesting alone or with others and those who mated with one or more males. To examine the risk of infanticide for pups born into these different types of litters, they assessed survival until just before weaning, which is about two weeks after birth.

Direct observations of infanticide are extremely rare in natural systems. But studying an enclosed population without the presence of a predator meant that infanticide becomes the most likely cause of death for young pups. And indeed, from the corpses of pups that were recovered, most gave direct evidence – missing limbs or holes in the skull – of this harsh fate.

The results of the study were published in the journal Behavioral Ecology. The researchers found that pups born to females nesting alone and who had only one mate had the lowest survival rate (50% surviving, the rest presumably killed by males who were confident they were not the father). Meanwhile, those born to females nesting together were better off (80% surviving).

Key evidence supporting their theory was that some of these communal litters were composed of pups whose mothers had actually only mated once, but the different females had different mates. These litters had similar survival to those where paternity was mixed for individual mothers, suggesting that mothers can achieve the same survival benefits of communal nesting without mating with multiple males.

There were also a few communal litters (nine of the 90 studied) where the different females had mated with the same male and, as such, featured multiple mothers but no paternity confusion. These litters had worse survival rate (40% surviving) suggesting that – as predicted by the theory – paternity confusion is a more important driving factor of communal nesting than the physical warding off of males.

According to Elise Huchard of CNRS Montpelier: “This study presents an interesting idea, and an interesting system to test it.” Yet the data raise more questions than they answer – and additional experiments or comparative work would be insightful.

For example, it is not clear whether higher survival in litters with multiple fathers might actually reflect variation among females if, as in the case of mouse lemurs, higher-quality females have more mates. Dieter Lukas of Cambridge University concurs that the theory is interesting, but believes it is too early to assess its generality.

Infanticide occurs across diverse mammal systems – from meerkats and rabbits, to lions and gorillas – and comparative analyses could help assess how this theory fares among the many hypotheses about the evolution of infanticide.

Communal nesting may have evolved as an alternative to mating with multiple mates (which is costly when males harass females during mating or transmit disease) as a strategy to avoid infanticide through paternity confusion. “We don’t know whether other social behaviours may have evolved through similar ways,” said Auclair.

Comparative analyses will lead to new insights and future research on the nest-box population will also address such interesting questions as how females choose their nesting partners – and why some still nest alone even if this comes at a cost to offspring survival.

http://theconversation.com/whos-your-daddy-mice-nest-together-to-confuse-paternity-and-reduce-infanticide-31796