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Exercise alters brain chemistry to protect aging synapses: Enhanced nerve transmission seen in older adults who remained active -- ScienceDaily

Honer and Casaletto found that elderly people who remained active had higher levels of proteins that facilitate the exchange of information between neurons. This result dovetailed with Honer's earlier finding that people who had more of these proteins in their brains when they died were better able to maintain their cognition late in life. To their surprise, Honer said, the researchers found that the effects ranged beyond the hippocampus, the brain's seat of memory, to encompass other brain regions associated with cognitive function. "It may be that physical activity exerts a global sustaining effect, supporting and stimulating healthy function of proteins that facilitate synaptic transmission throughout the brain," Honer said.
#exercise #synapses #dementia - sciencedaily.com

What sponges can tell us about the evolution of the brain -- ScienceDaily

Sponges use their digestive chambers to filter out food from the water and interact with environmental microbes. To understand what the cells expressing synaptic genes do, the Arendt group joined forces with six EMBL teams as well as collaborators in Europe and worldwide. Working with EMBL's Electron Microscopy Core Facility, Yannick Schwab's team and Thomas Schneider's group operating synchrotron beamlines at EMBL Hamburg the researchers developed a new correlative imaging approach. "By combining electron microscopy with X-ray imaging on a synchrotron beamline we were able to visualize the stunning behaviour of these cells," Dr Schwab explained. The scientists captured three-dimensional snapshots of cells crawling throughout the digestive chamber to clear out bacterial invaders and sending out long arms that enwrap the feeding apparatus of specific digestive cells. This behaviour creates an interface for targeted cell-cell communication, as it also happens across synapses between neuronal cells in our brains.
#micro-biome #evolution #gut #synapses - sciencedaily.com

Often overlooked glial cell is key to learning and memory: Biomedical scientists offer simple advice: Keep the brain active -- ScienceDaily

In the lab, the researchers artificially increased levels of ephrin-B1 in mice and then tested them for memory retention. They found that the mice could not remember a behavior they had just learned. In cell culture studies, they added neurons to astrocytes that overexpressed ephrin-B1 and were able to see synapse removal, with the astrocytes "eating up" the synapses. "Excessive loss of synapses is a problem," Ethell said. "The hippocampus, the region of the brain associated primarily with memory, is plastic. Here, new neuronal connections are formed when we learn something new. But the hippocampus has a limited capacity; some connections need to go to 'make space' for new connections -- new memories. To learn, we must first forget." In contrast to an ephrin-B1 increase, when this protein decreases (or is down-regulated) it results in more synapses -- and better learning. The astrocytes, in this case, are not able to attach to the synapses. "But you don't want to remember everything," said Amanda Q Nguyen, a Neuroscience Graduate Program student working in Ethell's lab, and a co-first author of the research paper. "It's all about maintaining a balance: being able to learn but also to forget." Advice the researchers have for the public is simple: keep the brain -- that is, the neurons -- active. "Reading and solving puzzles is a good start," Ethell said.
#exercise #memory #synapses #glia - sciencedaily.com

The Brain Learns Completely Differently than We've Assumed Since the 20th Century - Neuroscience News

The newly suggested learning scenario indicates that learning occurs in a few dendrites that are in much closer proximity to the neuron, as opposed to the previous notion. “Does it make sense to measure the quality of air we breathe via many tiny, distant satellite sensors at the elevation of a skyscraper, or by using one or several sensors in close proximity to the nose? Similarly, it is more efficient for the neuron to estimate its incoming signals close to its computational unit, the neuron,” says Kanter. Hebb’s theory has been so deeply rooted in the scientific world for 70 years that no one has ever proposed such a different approach. Moreover, synapses and dendrites are connected to the neuron in a series, so the exact localized site of the learning process seemed irrelevant. Another important finding of the study is that weak synapses, previously assumed to be insignificant even though they comprise the majority of our brain, play an important role in the dynamics of our brain. They induce oscillations of the learning parameters rather than pushing them to unrealistic fixed extremes, as suggested in the current synaptic learning scenario.
#neurons #synapses #dendrites - neurosciencenews.com

Sleep Shrinks the Brain--and That's a Good Thing - Scientific American

Cirelli said that one interesting finding was that this pruning occurred in about 80 percent of the synapses but spared the largest ones. These larger synapses may be associated with the most stable and important memories, connections the brain does not want to lose, the researchers speculated. Yet, the way in which the brain decides what synaptic connections to prune is another mystery to explore, Cirelli said. "It is critical to have pruning back at night, so that the huge amount of information encoded by temporary synapses during the day won't overwhelm the brain," said Foster. "Pruning ensures that only the most important information is retained."
#sleep #synapses - scientificamerican.com

Cells communicate in a dynamic code: A critically important intercellular communication system is found to encode and transmit more messages than previously thought. -- ScienceDaily

The team studied two chemically similar Notch ligands, dubbed Delta1 and Delta4. They discovered that despite the ligands' similarity the two activated the same receptor with strikingly different temporal patterns. Delta1 ligands activated clusters of receptors simultaneously, sending a sudden burst of transcription factors down to the nucleus all at once, like a smoke signal consisting of a few giant puffs. On the other hand, Delta4 ligands activated individual receptors in a sustained manner, sending a constant trickle of single transcription factors to the nucleus, like a steady stream of smoke.
#synchronize #time #synapses #rhythm - sciencedaily.com

Neurons aren't binary

In an article published today in the journal Scientific Reports, the researchers go against conventional wisdom to show that each neuron functions as a collection of excitable elements, where each excitable element is sensitive to the directionality of the origin of the input signal. Two weak inputs from different directions (e.g., "left" and "right") will not sum up to generate a spike, while a strong input from "left" will generate a different spike waveform than that from the "right." "We reached this conclusion using a new experimental setup, but in principle these results could have been discovered using technology that has existed since the 1980s. The belief that has been rooted in the scientific world for 100 years resulted in this delay of several decades," said Prof. Kanter and his team of researchers, including Shira Sardi, Roni Vardi, Anton Sheinin, and Amir Goldental.
#brain #neurons #synapses - sciencedaily.com

Synapses shrink 20% every night?!

The team deliberately did not know whether they were analyzing the brain cells of a well-rested mouse or one that had been awake. When they finally "broke the code" and correlated the measurements with the amount of sleep the mice had during the six to eight hours before the image was taken, they found that a few hours of sleep led on average to an 18 percent decrease in the size of the synapses. These changes occurred in both areas of the cerebral cortex and were proportional to the size of the synapses. The scaling occurred in about 80 percent of the synapses but spared the largest ones, which may be associated with the most stable memory traces.
#neurons #sleep #synapses #editing - sciencedaily.com

Brain has internal ‘odometer’ and ‘stopwatch’

To prove the contrary, researchers put rats on treadmills and recorded the activity of grid cells, keeping either distance or duration of running unchanged, and only varying the speed. As a result, 92% of grid cells in rats emitted signals at specific moments: for instance, one cell would fire 8 seconds into the run, not taking into account speed or distance covered, and another cell would emit a signal every 400 cm, not depending on speed or duration of the run. 50 percent of the cells were affected by distance, another half by time, and around 40 percent by both factors. "Space and time are ever-present dimensions by which events can be organized in memory," senior study author Howard Eichenbaum, a psychologist and neuroscientist at Boston University, said in the official press release.
#synchronize #memory #history #maps #time #synapses #space - rt.com

EyeWire game to map mouse eye neurons

In 2012, Seung started EyeWire, an online game that challenges the public to trace neuronal wiring — now using computers, not pens — in the retina of a mouse’s eye. Seung’s artificial-­intelligence algorithms process the raw images, then players earn points as they mark, paint-by-numbers style, the branches of a neuron through a three-dimensional cube. The game has attracted 165,000 players in 164 countries. In effect, Seung is employing artificial intelligence as a force multiplier for a global, all-volunteer army that has included Lorinda, a Missouri grandmother who also paints watercolors, and Iliyan (a.k.a. @crazyman4865), a high-school student in Bulgaria who once played for nearly 24 hours straight. Computers do what they can and then leave the rest to what remains the most potent pattern-recognition technology ever discovered: the human brain.
#neurons #connectome #collaboration #synapses - nytimes.com

Neurons as adventurous voyagers

Each neuron is imprisoned in your brain. I now think of these as cells within cells, as cells within prison cells. Realize that every neuron in your brain, every human cell in your body (leaving aside all the symbionts), is a direct descendent of eukaryotic cells that lived and fended for themselves for about a billion years as free-swimming, free-living little agents. They fended for themselves, and they survived.              They had to develop an awful lot of know-how, a lot of talent, a lot of self-protective talent to do that. When they joined forces into multi-cellular creatures, they gave up a lot of that. They became, in effect, domesticated. They became part of larger, more monolithic organizations. My hunch is that that's true in general. We don't have to worry about our muscle cells rebelling against us, or anything like that. When they do, we call it cancer, but in the brain I think that (and this is my wild idea) maybe only in one species, us, and maybe only in the obviously more volatile parts of the brain, the cortical areas, some little switch has been thrown in the genetics that, in effect, makes our neurons a little bit feral, a little bit like what happens when you let sheep or pigs go feral, and they recover their wild talents very fast. Maybe a lot of the neurons in our brains are not just capable but, if you like, motivated to be more adventurous, more exploratory or risky in the way they comport themselves, in the way they live their lives. They're struggling amongst themselves with each other for influence, just for staying alive, and there's competition going on between individual neurons. As soon as that happens, you have room for cooperation to create alliances, and I suspect that a more free-wheeling, anarchic organization is the secret of our greater capacities of creativity, imagination, thinking outside the box and all that, and the price we pay for it is our susceptibility to obsessions, mental illnesses, delusions and smaller problems.
#synchronize #neurons #networks #consciousness #synapses - edge.org

Sleep trimming synapses

While we’re awake, your brain is forming memories. Memory formation involves a process called long-term potentiation (LTP), which is essentially the strengthening of synaptic connections between nerve cells. We also know that learning can actually cause neurons to sprout entirely new synapses. Yet this poses a problem for the brain. If LTP and synapse formation is constantly strengthening our synapses, and we are learning all our lives, might the synapses eventually reach a limit? Couldn’t they “max out,” so that they could never get any stronger? Worse, most of the synapses that strengthen during memory are based on glutamate. Glutamate is dangerous. It’s the most common neurotransmitter in the brain, and it’s also a popular flavouring: “MSG”, monosodium glutamate. But in the brain, too much of it is toxic. Glutamate works as a transmitter molecule by opening channels on the cells that receive it. The channels allow calcium into the cells on the receiving end, which activates them, allowing messages to go through. But too much glutamate can cause excess calcium to build up inside the very cells that receive the message, a harmful process called excitotoxicity. So, if our brains were constantly forming stronger glutamate synapses, we might eventually run into serious problems. One function of sleep, according to the theory, is to protect the brain against excitotoxicity or other “synaptic overload” problems by pruning the synapses. If the brain is essentially removing the “extra” synaptic strength formed during the previous day, it must do so in a way that preserves the new information. One possible mechanism for this is synaptic scaling. After some of the neural connections into a given cell, or “inputs,” become stronger, then all of the synapses on that cell could be weakened. This would preserve the relative strength of the different inputs, while keeping the total inputs constant. It’s as if each neuron were a cup, and each synapse corresponds to a different liquid. During the day, memories form and certain synapses get stronger, which means pouring more of those particular liquids into the cup. At night, synaptic scaling pours some of the mixture back out, bringing it back to the baseline level without changing the relative proportions of the mix. We know that synaptic scaling happens in the brain, but it’s not yet clear whether it has anything to do with sleep. This is an area of ongoing research. While synaptic scaling seems to treat each neuron like a cup to be kept from overfilling, the effect of sleep on for the brain overall may be more like disk defragmentation, according to this idea. After heavy use, hard disks tend to get “fragmented.” This is because when data gets stored, it is written to wherever there happens to be free space on the disk. This makes it inefficient to keep track of it all as files may be split and written in many different places. A defrag consolidates the same data into a more logical order. Defragmentation is a taxing chore for the computer, so many people schedule it to happen overnight. In the same way, sleep may serve to reorganize and reconsolidate memories. The mechanics of how this defragmentation works remain unclear; synaptic scaling might be just one of several processes at work. Defragmentation is not an exact analogy, however. The process could also be likened to archiving your emails to make room in your inbox, or compressing data into zipped files, to free up room on the disk. (This theory is specifically about slow-wave sleep (SWS). It doesn’t try to explain rapid eye movement (REM) sleep, when dreams happen. Interestingly, some animals do not have REM, but they all have SWS. In some animals, like dolphins, only one side of the brain has it at a time, which is strong evidence that SWS, but not REM, is vital for life.)
#sleep #synapses - blogs.discovermagazine.com