12 posts tagged neurons
Neurons reveal the brain’s learning limit
Carnegie Mellon University, Stanford University, University of Pittsburgh Original Study
Scientists have discovered a fundamental constraint in the brain that may explain why it’s easier to learn a skill that’s related to an ability you already have. For example, a trained pianist can learn a new melody easier than learning how to hit a tennis serve. As reported in Nature, the researchers found for the first time that there are limitations on how adaptable the brain is during learning and that these restrictions are a key determinant for whether a new skill will be easy or difficult to learn. Understanding how the brain’s activity can be “flexed” during learning could eventually be used to develop better treatments for stroke and other brain injuries. Lead author Patrick T. Sadtler, a Ph.D. candidate in the University of Pittsburgh department of bioengineering, compared the study’s findings to cooking. “Suppose you have flour, sugar, baking soda, eggs, salt, and milk. You can combine them to make different items—bread, pancakes, and cookies—but it would be difficult to make hamburger patties with the existing ingredients,” Sadtler says. “We found that the brain works in a similar way during learning. We found that subjects were able to more readily recombine familiar activity patterns in new ways relative to creating entirely novel patterns.” (via Neurons reveal the brain’s learning limit - Futurity)
Scientists at A*STAR’s Genome Institute of Singapore (GIS) have discovered an unusual gene that controls the generation of neurons. This important finding is crucial in understanding serious diseases of the brain such as Alzheimer’s disease, the researchers say. The central nervous system is composed of numerous cell types that develop into a complex, higher-ordered structure. The birth of neurons (neurogenesis) is a process that requires exquisite temporal and spatial control of hundreds of genes. The expression of these genes is controlled by regulatory networks, usually involving proteins, which play critical roles in establishing and maintaining the nervous system. Problems with neurogenesis are the basis of many neurological disorders, so understanding the molecular details of neurogenesis is crucial for developing treatments of serious diseases.
By Tamily Weissman, Harvard University
“Brainbow" mice are engineered with a gene that includes three different fluorescent proteins, but only one color is actually expressed from each copy of the DNA construct. Pairs of "incompatible lox sites" are nested around different portions of the gene, allowing for recombination to snip out different parts of the gene randomly. Depending on what DNA is excised, a different color results.
Image: Here individual neurons of the dentate gyrus, a layer of the hippocampus, project their dendrites to the outer layer, where they receive input from the cortex. Neurogenesis occurs inside the “V,” where neurons are born and then migrate outward toward the dentate gryus. (via Cell - Cell_Picture_Show-Brainbow2)
What is an itch? Scientists have speculated that it is a mild manifestation of pain or perhaps a malfunction of overly sensitive nerve endings stuck in a feedback loop. They have even wondered whether itching is mostly psychological (just think about bed bugs for a minute). Now a study rules out these possibilities by succeeding where past attempts have failed: a group of neuroscientists have finally isolated a unique type of nerve cell that makes us itch and only itch.
In previous research, neuroscientists Liang Han and Xinzhong Dong of Johns Hopkins University and their colleagues determined that some sensory neurons with nerve endings in the skin have a unique protein receptor on them called MrgprA3. They observed under a microscope that chemicals known to create itching caused these neurons to generate electrical signals but that painful stimuli such as hot water or capsaicin, the potent substance in hot peppers, did not. (via Scientists Identify Neurons That Register Itch: Scientific American)
Neurons in the brain switch identity and re-route fibres
New findings could one day lead to gene therapies for stroke and spinal cord injuries
These drawings by Santiago Ramón y Cajal show the cellular structure of three different areas of the human cerebral cortex. The cortex is the seat of higher mental functions such as language and decision-making, and contains dozens of distinct, specialised areas. As Cajal’s drawings show, it has a characteristic layered structure, which differs somewhat from one area to the next, so that the layers vary in thickness according to the number of cells they contain. Cells throughout the cortex are arranged in a highly ordered manner. Those in layers 2 and 3, for example, send fibres to the other side of the brain, whereas those in layers 5 and 6 send theirs straight downwards. This organization is under genetic control and, once established, was thought to be fixed. Now, though, researchers at Harvard University report that fully matured neurons in the intact brain can be made to switch identity and re-route their fibres to acquire the characteristics of cells in other layers. (via Neurons in the brain switch identity and re-route fibres | Mo Costandi | Science | guardian.co.uk)
Computing hardware is composed of a series of binary switches; they’re either on or off. The other piece of computational hardware we’re familiar with, the brain, doesn’t work anything like that. Rather than being on or off, individual neurons exhibit brief spikes of activity, and encode information in the pattern and timing of these spikes. The differences between the two have made it difficult to model neurons using computer hardware. In fact, the recent, successful generation of a flexible neural system required that each neuron be modeled separately in software in order to get the sort of spiking behavior real neurons display. But researchers may have figured out a way to create a chip that spikes. The people at HP labs who have been working on memristors have figured out a combination of memristors and capacitors that can create a spiking output pattern. Although these spikes appear to be more regular than the ones produced by actual neurons, it might be possible to create versions that are a bit more variable than this one. And, more significantly, it should be possible to fabricate them in large numbers, possibly right on a silicon chip. (via “Neuristor”: Memristors used to create a neuron-like behavior | Ars Technica)
BRAIN POWER: From Neurons to Networks
BRAIN POWER: From Neurons to Networks is a 10-minute film and accompanying TED Book (ted.com/tedbooks) from award-winning Director Tiffany Shlain and her team at The Moxie Institute. Based on new research on how to best nurture children’s brains from Harvard University’s Center on the Developing Child and University of Washington’s I-LABS, the film explores the parallels between a child’s brain development and the development of the global brain of Internet, offering insights into the best ways to shape both. Made through a new crowd-sourcing creativity process the Moxie team calls “Cloud Filmmaking,” Brain Power was created by putting into action the very ideas that the film is exploring: the connections between neurons, networks, and people around the world. (H\T @Dìgitag)
Humans can focus on one thing amidst many. “Searchlight of attention” is the metaphor. You recall a childhood friend’s face one moment, then perhaps the dog you loved back then, and then…what you will. Your son’s face on stage rivets your attention; the rest of the cast is unseen. No “ghost” in the brain aims that searchlight. What does? Neurons do, somehow, but how is a mystery that new research actually deepened. The experiment used monkeys. They can focus attention like people do. They can zero in on a red square on a screen full of distractions, for instance. When the square moves, a trained monkey will press a button. Electrodes inserted in a monkey neuron will reveal “firing” (minuscule electrical ripples) simultaneous with attention. This may locate brain areas by which the monkey watched that red square. (via How the Brain Does “Attention” Is Still Unknown | Guest Blog, Scientific American Blog Network)
THE DEVICE: Whole-cell patch clamping, a Nobel Prize-winning technique to record the electrical activity of neurons, has never looked so good. A shoebox-sized robot lowers a thin glass pipette, its tip sharpened to 1 micrometer in diameter, into the brain of an anesthetized mouse. The robot moves the pipette around inside the brain, almost imperceptibly, hunting for neurons. When the glass tip bumps into a neuron, the robot arm instantly halts and applies suction through the pipette to form a seal with the cell membrane. Once attached, the pipette tears a small hole in the membrane and records the cell’s internal electrical activity. (via Next Generation: The Brain Bot | The Scientist)