In the science news this week, scientists implant false memories into the minds of mice, bottlenose dolphins use names to identify each other, scientists track cell death in a roundworm, and finally…a full moon may be the cause of a bad night’s sleep.
False memories implanted into mice
Scientists have activated memory forming cells in the brains of mice creating false memories and associations, reported the BBC .
The mice wrongly associated a benign environment with an unpleasant experience they had had in different surroundings. The researchers conditioned a network of neurons to respond to light, which made the mice recall the unpleasant environment.
The mice were genetically engineered and had optic fibres implanted in their brains to deliver pulses of light to specific groups of neurons. Known as optogenetics, this technique makes individual neurons responsive to light.
Our memories are stored in collections of cells, the same as they are in the brains of mice, and when we recall an event we reconstruct it from parts of these cells, almost like reassembling small pieces of a puzzle.
This can make our memories unreliable, something that has been well documented over the past few decades.
The researchers in this study found that when the mice recalled a false memory, it was indistinguishable from a real memory, in that it created a fear response in the memory forming cells of the mouse’s brain.
"If you want to grab a specific memory you have to get down into the cell level. Every time we think we remember something, we could also be making changes to that memory - sometimes we realise sometimes we don't," explained Dr Xu Liu from the RIKEN-MIT Center for Neural Circuit Gentics.
"Our memory changes every single time it's being 'recorded'. That's why we can incorporate new information into old memories and this is how a false memory can form without us realising it."
Neil Burgess from UCL, who was not involved in the study, told the BBC that the research was a good first step in understanding the fearful response to situations where nothing fearful has happened.
“One day this type of knowledge may help scientists to understand how to remove or reduce the fearful associations experienced by people with conditions like post-traumatic stress disorder," he said.
However, he also explained that this is still very early stages on this type of research and that any benefits for people with conditions like PTSD would still be many years away.
"But basic science always helps in the end, and it may be possible, one day, to use similar techniques to silence neurons causing the association to fear."
Bottlenose dolphins identify each other using distinct “names”
A group of bottlenose dolphins off the east coast of Scotland identify individuals within the pod using distinct whistles. They use the “names” in order to broadcast their location to other dolphins, reported the Guardian .
Many animals are capable of copying sounds and can use them to display how fit they are, for example. But few are capable of learning to associate specific sounds with particular individuals or objects.
"If we look at complex ability in communication in human language, one of the key features that is important to us is that we can copy sounds, we can invent new sounds," said Vincent Janik, a biologist at St Andrews University, who led the research. "We can then use those sounds and attach some kind of meaning to them and use them to refer to objects and to refer to external things in the world."
The team from St Andrews watched a population of around 150-180 dolphins that live off the east coast of Scotland, following groups of between two and 20 dolphins at once. The team initially identified and recorded the signature whistles for individual dolphins and then played these whistles back to the entire group.
The sounds that the researchers played back were computerised reconstructions of the original sounds. They did this to remove the chance that what the dolphins were actually recognising was the voice of another rather than the sound.
The results showed that the dolphins responded to their own signature whistle by whistling their own “name” back but would ignore the whistles of others.
"The interesting thing about these is that they are not voice recognition," said Janik. "In humans you can have different people say the same word and I'd still be able to tell who's speaking. What we also do is have names, so they are very different call types. The dolphins do the same thing; they're developing a completely new call type, a melody or whistle, which is not dependent on their voice features."
Fluorescent cells cause a blue wave of death in roundworms
Dying cells in a species of roundworm release a chemical that glows under ultraviolet light, revealing how death spreads like a wave through the animals. Scientists at University College London captured the phenomenon on camera, and produced a video, shown on the New Scientist  website. The Caenorhabditis elegans roundworm is around one millimetre long and lives in temperate climates.
Researchers previously thought that the glow emitted by the worm was caused by a process that also happens in mammals. As mammalian cells age, they are damaged by oxidation, which causes the release of a coloured pigment called lipofuscin. Professor David Gems from the UCL Institute of Health Ageing  and his team placed the worms in an oxidising environment to test the idea, but the worms’ glow remained steady.
Under a microscope, the process became clearer. The blue wave always started in the same part of the intestine, and the UCL researchers discovered that the intestinal cells released calcium as they died. The calcium causes surrounding cells to die, producing another chemical, anthranilic acid. It’s this acid that glows under the blacklight.
Gems, who led the study, explains: “We’ve identified a chemical pathway of self-destruction that propagates cell death in worms, which we see as this glowing blue fluorescence travelling through the body. It’s like a blue grim reaper, tracking death as it spreads throughout the organism until all life is extinguished.”
The research may bring useful developments for the study of human health. “In a stroke or heart attack, cells are killed by blood supply being blocked off,” Gems told the New Scientist. “They are left surrounded by living cells, and this damaged area can start to kill off the cells around it. If we can understand how this death propagation works in C. elegans, we might be able to one day reduce [similar] damage in patients.”
Full moon may affect sleeping patterns
New research from Basel University in Switzerland shows that the full moon might make it harder to sleep. The BBC reports  that researchers identified the pattern in a sleep study, where participants were placed in a completely darkened room. It was previously thought that the brightness of the moon in its full phase was the cause of disturbed sleep, but these isolated sleepers show otherwise.
The researchers are yet to discover the exact cause of the disturbance, but it is suspected that our long relationship with the moon has left a cultural imprint on our sleeping patterns.