Amazing Science
Follow
Find tag "neuroscience"
342.8K views | +90 today
Your new post is loading...
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Gene that controls nerve conduction velocity linked to multiple sclerosis.

Gene that controls nerve conduction velocity linked to multiple sclerosis. | Amazing Science | Scoop.it

A new study from the University of Lubeck identifies a novel gene that controls nerve conduction velocity. Investigators report that even minor reductions in conduction velocity may aggravate disease in multiple sclerosis (MS) patients and in mice bred for the MS-like condition experimental autoimmune encephalomyelitis (EAE).


A strong tool for investigating the pathophysiology of a complex disease is the identification of underlying genetic controls. Multiple genes have been implicated as contributing to the risk of developing MS. Unlike studies that have focused on genetic regulators of inflammation, autoimmunity, demyelination, and neurodegeneration in MS, this study focused on nerve conduction velocity. Investigators found that polymorphisms of the inositol polyphosphate-4-phosphatase, type II (Inpp4b) gene affect the speed of nerve conduction in both mice with EAE and humans with MS.


Impairment of nerve conduction is a common feature in neurodegenerative and neuroinflammatory diseases such as MS. Measurement of evoked potentials (whether visual, motor, or sensory) is widely used for diagnosis and recently also as a prognostic marker for MS.


Using several genomic approaches, the investigators narrowed their search to the genetic region controlling the enzyme inositol-polyphosphate-4-phosphatase II (INPP4B), the product of which helps to regulate the phosphatidyl inositol signaling pathway. Enzymes in this family are involved in cellular functions such as cell growth, proliferation, differentiation, motility, survival, and intracellular communication.


In one series of experiments, the researchers analyzed the genetic locus EAE31, which previously had been shown to control the latency of motor evoked potentials and clinical onset of EAE in mice. Using advanced techniques including congenic mapping, in silico haplotype analyses (computer simulations), and comparative genomics (from rats, mice and humans), they were able to ‘finemap’ the focus to Inpp4b as the quantitative trait gene for EAE31.


When the investigators analyzed this region in eight different strains of mice, they found they could divide the strains into two groups based on differences in amino acid sequences. The strains with the longer-latency SJL/J allele had the two amino acids (arginine and proline), whereas those with the shorter-latency C57BL/10S allele had others (serine and histidine).  These data suggest that Inpp4b structural polymorphism is associated with the speed of neuronal conduction.


In another experiment, the scientists compared motor conduction velocity in genetically modified mice with a mutant Inpp4b gene to that of control mice. The nerve conduction in this group was slower than in the control group.


Finally, the investigators studied INPP4B polymorphisms in MS patients. They looked at two cohorts: one from Spain (349 cases and 362 controls) and a second from Germany (562 cases and 3,314 controls). The association between the INPP4B polymorphisms and susceptibility to MS was statistically significant when the cohorts were pooled.


However, although the Spanish cohort showed a strong association between INPP4B and MS, the association was weaker in the German cohort. The exact reason for the diverging effect across these populations remains unresolved.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Nanoparticles open a new window into the brain

Nanoparticles open a new window into the brain | Amazing Science | Scoop.it

New imaging technique could help treat strokes, cancer and dementia.


Researchers at Stanford University in the US have developed the first non-invasive imaging technique that can detect micron-sized structures within blood vessels in the brains of mice. The method involves detecting near-infrared fluorescent light from single-walled carbon nanotubes (SWCNTs) that are injected into the mice. The ability to monitor the structure of blood vessels – and the blood flow within them – is extremely important for treating conditions such as strokes, dementia and brain tumors.


Today, brain imaging mainly relies on techniques such as X-ray computed tomography and magnetic resonance angiography. However, these methods cannot image structures several microns in size. In addition, with these approaches it can take several minutes to acquire an image, which means that it is not possible to use them to monitor blood flow in real time.


Fluorescence-based brain imaging in the visible and near-infrared (NIR) regions of the electromagnetic spectrum (400–900 nm) is a good alternative but at the moment it requires skull-thinning or, worse still, craniotomy – where sections of the skull are removed and replaced with a transparent "window" – to work properly. This is because light at these wavelengths can only travel about 1 mm through the skull.


Now, a team led by Hongjie Dai and Calvin Kuo at Stanford has developed a new through-scalp and through-skull fluorescence imaging technique that goes a long way in overcoming these problems. The method makes use of the intrinsic fluorescence of SWCNTs in the 1.3–1.4 µm range. "We define this wavelength as the NIR-IIa window, and it represents just about the longest wavelengths for fluorescence imaging reported thus far," explains Dai.


"Photons at these wavelengths are much less scattered than those in the 400–900 nm window when traversing biological tissues and are not absorbed significantly by water either," says Dai. "All in all, this allows us to see deeper into the brain through intact scalp skin and bone than is possible with traditional fluorescence imaging, which is mostly done with <800 nm wavelength photons."


"Compared with all other techniques for in vivo brain imaging (including MRI and CT), our technique affords higher spatial resolution", he says. "It allows us to image single capillary blood vessels that are just microns across and as deep as 3 mm inside the brain."

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Sending Red Light Through The Skull To Influence Brain Activity Using Red-Shifted Cruxhalorhodopsin named Jaws

Sending Red Light Through The Skull To Influence Brain Activity Using Red-Shifted Cruxhalorhodopsin named Jaws | Amazing Science | Scoop.it
Genetically engineered protein responds remotely to red light.


A team of biological engineers has developed a light-sensitive protein that permits scientists to control activity inside the brains of mice from outside the rodents’ skulls. The protein, called Jaws, promises to expand scientists’ ability to study brain activity in experimental animals and -- eventually -- humans. Ultimately, it holds the prospect of facilitating treatment of human conditions such as epilepsy.


Researchers are also using the protein to treat eye disease in experimental animals. Here, an immediate goal is therapy for certain eye ailments in humans.


Scientists use optogenetics, as the technology is known, to study the behavior and pathology of experimental animals’ brains by shining light on proteins known as opsins. Introduced into the brain aboard viruses, the opsins respond to the light by suppressing or stimulating electrical signals in brain cells. Optogenetic inhibition of the electrical activity of neurons enables the causal assessment of their contributions to brain functions. Red light penetrates deeper into tissue than other visible wavelengths. The red-shifted cruxhalorhodopsin, Jaws, derived from Haloarcula (Halobacteriumsalinarum (strain Shark) and engineered to result in red light–induced photocurrents three times those of earlier silencers. Jaws exhibits robust inhibition of sensory-evoked neural activity in the cortex and results in strong light responses when used in retinas of retinitis pigmentosa model mice.


The opsins normally used in brain studies are sensitive to blue, green, or yellow light. Because bodily tissue absorbs those colors easily, the sources of such light must lie inside the brain. Typically, the light is delivered through an optical fiber implanted in an experimental animal’s brain. Jaws can noninvasively mediate transcranial optical inhibition of neurons deep in the brains of awake mice. The noninvasive optogenetic inhibition opened up by Jaws enables a variety of important neuroscience experiments and offers a powerful general-use chloride pump for basic and applied neuroscience.


A team led by Ed Boyden, associate professor of biological engineering and brain and cognitive sciences at the Massachusetts Institute of Technology, in Cambridge, reporting in Nature Neuroscience, demonstrated that red light shone from outside a mouse’s head can influence the Jaws protein up to three millimeters deep inside the brain. In fact, Boyden said, "we think the light goes further into the brain." A mouse’s brain is only about four millimeters thick.


"This is a huge advance, in that it allows for much deeper penetration of effective light," said David Lyon, an associate professor of anatomy and neurobiology at the University of California, Irvine School of Medicine. Lyon was not involved in the research on Jaws.

more...
Scooped by Dr. Stefan Gruenwald
Scoop.it!

First time transplantation of inhibitory neuron progenitor cells reverses memory loss in Alzheimer's disease model

First time transplantation of inhibitory neuron progenitor cells reverses memory loss in Alzheimer's disease model | Amazing Science | Scoop.it
A new study has revealed a way to alleviate the learning and memory deficits caused by apoE4, the most important genetic risk factor for Alzheimer's disease, improving cognition to normal levels in aged mice. The success of the treatment in older mice, which corresponded to late adulthood in humans, is particularly important, as this would be the age that would be targeted were this method ever to be used therapeutically in people.


In the study, which was conducted in collaboration with researchers at UC San Francisco and published today in the Journal of Neuroscience, scientists transplanted inhibitory neuron progenitors -- early-stage brain cells that have the capacity to develop into mature inhibitory neurons -- into two mouse models of Alzheimer's disease, apoE4 or apoE4 with accumulation of amyloid beta, another major contributor to Alzheimer's. The transplants helped to replenish the brain by replacing cells lost due to apoE4, regulating brain activity and improving learning and memory abilities.


"This is the first time transplantation of inhibitory neuron progenitors has been used in aged Alzheimer's disease models," said first author Leslie Tong, a graduate student at the Gladstone Institutes and UCSF. "Working with older animals can be challenging from a technical standpoint, and it was amazing to see that the cells not only survived but affected activity and behavior."


The success of the treatment in older mice, which corresponded to late adulthood in humans, is particularly important, as this would be the age that would be targeted were this method ever to be used therapeutically in people.


"This is a very important proof of concept study," said senior author Yadong Huang, MD, PhD, an associate investigator at Gladstone Institutes and associate professor of neurology and pathology at UCSF. "The fact that we see a functional integration of these cells into the hippocampal circuitry and a complete rescue of learning and memory deficits in an aged model of Alzheimer's disease is very exciting."

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Noninvasive brain control: New light-sensitive protein enabling neurons to be silenced noninvasively

Noninvasive brain control: New light-sensitive protein enabling neurons to be silenced noninvasively | Amazing Science | Scoop.it
New light-sensitive protein enables simpler, more powerful optogenetics.


MIT engineers have developed the first light-sensitive protein molecule that enables neurons to be silenced noninvasively. Using a light source outside the skull makes it possible to do long-term studies without an implanted light source.


The protein, known as Jaws, also allows a larger volume of tissue to be influenced at once. The researchers described the protein in Nature Neuroscience.


Optogenetics, a technology that allows scientists to control brain activity by shining light on neurons, relies on opsins, light-sensitive proteins that act as channels or pumps that influence electrical activity by controlling the flow of ions in or out of cells.


Researchers insert a light source, such as an optical fiber, into the brain to suppress or stimulate electrical signals within cells. This technique requires a light source to be implanted in the brain, where it can reach the cells to be controlled. The neurons to be studied must be genetically engineered to produce the opsins.


Also, inserting optical fibers into the brain “displaces brain tissue and can lead to side effects such as brain lesion, neural morphology changes, glial inflammation and motility, or aseptic compromise,” the researchers say in the paper.


In addition, such implants can be difficult to insert and can be incompatible with many kinds of experiments, such as studies of development, during which the brain changes size, or of neurodegenerative disorders, during which the implant can interact with brain physiology. And it is difficult to perform long-term studies of chronic diseases with these implants.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

A single nerve tract deep within the brain of mice influences the animal's tendency to socialize

A single nerve tract deep within the brain of mice influences the animal's tendency to socialize | Amazing Science | Scoop.it

A team of Stanford Universityinvestigators has linked a particular brain circuit to mammals’ tendency to interact socially. Stimulating this circuit — one among millions in the brain — instantly increases a mouse’s appetite for getting to know a strange mouse, while inhibiting it shuts down its drive to socialize with the stranger.


The new findings, published June 19 in Cell, may throw light on psychiatric disorders marked by impaired social interaction such as autism, social anxiety, schizophrenia and depression, said the study’s senior author, Karl Deisseroth, MD, PhD, a professor of bioengineering and of psychiatry and behavioral sciences. The findings are also significant in that they highlight not merely the role of one or another brain chemical, as pharmacological studies tend to do, but rather the specific components of brain circuits involved in a complex behavior. A combination of cutting-edge techniques developed in Deisseroth’s laboratory permitted unprecedented analysis of how brain activity controls behavior.


Deisseroth, the D.H. Chen Professor and a member of the interdisciplinary Stanford Bio-X institute, is a practicing psychiatrist who sees patients with severe social deficits. “People with autism, for example, often have an outright aversion to social interaction,” he said. They can find socializing — even mere eye contact — painful.


Deisseroth pioneered a brain-exploration technique, optogenetics, that involves selectively introducing light-receptor molecules to the surfaces of particular nerve cells in a living animal’s brain and then carefully positioning, near the circuit in question, the tip of a lengthy, ultra-thin optical fiber (connected to a laser diode at the other end) so that the photosensitive cells and the circuits they compose can be remotely stimulated or inhibited at the turn of a light switch while the animal remains free to move around in its cage.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

TLX gene stimulates growth of new brain cells in adults, leading to faster learning in the animal model

TLX gene stimulates growth of new brain cells in adults, leading to faster learning in the animal model | Amazing Science | Scoop.it

Over-expressing a specific gene could prompt growth in adults of new neurons in the hippocampus, where learning and memory are regulated, City of Hope researchers have found.


The study, which used an animal model, found that over-expression of the TLX gene resulted in smart, faster learners that retained information better and longer.


Understanding the link between this gene and the growth of new neurons — or neurogenesis — is an important step in developing therapies to address impaired learning and memory associated with neurodegenerative diseases and aging.


The new research was published June 9 in the Proceedings of the National Academy of Sciences.


“Memory loss is a major health problem, both in diseases like Alzheimer’s, but also just associated with aging,”said Yanhong Shi, Ph.D., lead author of the study and a neurosciences professor at City of Hope.


“In our study, we manipulated the expression of this receptor by introducing an additional copy of the gene — which obviously we cannot do outside the laboratory setting. The next step is to find the drug that can target this same gene.”


Researchers found that over-expression of the gene was actually associated with a physically larger brain, as well as the ability to learn a task quickly. Furthermore, over-expression of the gene was linked with the ability to remember, over a longer period of time, what had been learned.


The discovery creates a new potential strategy for improving cognitive performance in elderly patients and those who have a neurological disease or brain injury.


The bulk of the brain’s development happens before birth, and there are periods — largely in childhood and young adulthood — when the brain experiences bursts of new growth. In the past couple of decades, however, scientists have found evidence of neurogenesis in later adulthood — occurring mostly in the hippocampus, the region of the brain associated with learning and memory.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Consciousness more complex thought: after anesthesia, brain passes through multiple metastable activity states

Consciousness more complex thought: after anesthesia, brain passes through multiple metastable activity states | Amazing Science | Scoop.it
Research shows that recovery from deep anesthesia is not a smooth, linear process but is instead a dynamic journey with specific states of activity the brain must temporarily occupy on the way to full recovery.


"I always found it remarkable that someone can recover from anesthesia, not only that you blink your eyes and can walk around, but you return to being yourself. So if you learned how to do something on Sunday and on Monday, you have surgery, and you wake up and you still know how to do it," says Alexander Proekt, a visiting fellow in Don Pfaff's Laboratory of Neurobiology and Behavior at Rockefeller University and an anesthesiologist at Weill Cornell Medical College. "It seemed like there ought to be some kind of guide or path for the system to follow."


The obvious explanation is that as the anesthetic washes out of the body, electrical activity in the brain gradually returns to its conscious patterns. However, new research by Proekt and colleagues suggests the trip back is not so simple.


In the awake brain, of both humans and rats, neurons generate electrical voltage that oscillates. Many of these oscillations together form a signal that appears as a squiggly line on a recording of brain activity, such as an LFP. When someone is asleep, under anesthesia, or in a coma, these oscillations occur more slowly, or at a low frequency. When he or she is awake, they speed up. The researchers examined the recordings from the rats' brains to figure out how the electrical activity in these regions changed as they moved from anesthetized to awake.


"Recordings from each animal wound up having particular features that spontaneously appeared, suggesting their brain activity was abruptly transitioning through particular states," Hudson says. "We analyzed the probability of a brain jumping from one state to another, and we found that certain states act as hubs through which the brain must pass to continue on its way to consciousness." While the electrical activity in all the rats' brains passed through these hubs, the precise path back to consciousness was not the same each time, the team reports today in the Proceedings of the National Academy of Sciences.


Reference:

Andrew E. Hudson, Diany Paol Calderon, Donald W. Pfaff and Alex Proekt.Recovery of consciousness is mediated by a network of discrete metastable activity statesProceedings of the National Academy of Sciences, June 9, 2014 DOI: 10.1073/pnas.1408296111

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Rats Show Regret After Making Wrong Choices, Scientists Say

Rats Show Regret After Making Wrong Choices, Scientists Say | Amazing Science | Scoop.it

Researchers studied brain areas involved in decision making, evaluating outcomes.


Could've, should've, would've. Everyone has made the wrong choice at some point in life and suffered regret because of it. Now a new study shows we're not alone in our reaction to incorrect decisions. Rats too can feel regret.


Regret is thinking about what you should have done, says David Redish, a neuroscientist at the University of Minnesota in Minneapolis. It differs from disappointment, which you feel when you don't get what you expected. And it affects how you make decisions in the future.


Redish and colleague Adam Steiner at the University of Minneapolis, found that rats expressed regret through both their behavior and their neural activity. Those signals, researchers report today in the journal Nature Neuroscience, were specific to situations the researchers set up to induce regret, which led to specific neural patterns in the brain and in behavior.


When Redish and Steiner looked for neural activity, they focused on two areas known in people—and in some animals—to be involved in decision-making and the evaluation of expected outcomes: the orbitofrontal cortex and the ventral striatum. Brain scans have revealed that people with a damaged orbitofrontal cortex, for instance, don't express regret. To record nerve-cell activity, the researchers implanted electrodes in the brains of four rats—a typical sample size in this kind of experiment—then trained them to run a "choice" maze.


Each rat had its own preferences regarding flavor and patience. And those preferences manifested in specific nerve-cell patterns in its brain. Redish and Steiner could thus tell when a particular rat was thinking about, say, the chocolate-flavored versus the cherry-flavored food. When a rat passed up food at one spoke and moved on to the next, then realized it would have to wait even longer for food at the second spoke, two things happened: It would look back to the previous spoke, and the specific nerve-cell pattern in its brain that represented that first choice would light up.


"That's the regret," says Redish. Not only were the rats physically looking backward; they were also thinking about the choice they hadn't made. What's more, "just like humans," says Redish, the rats were more likely to take a "bad deal"—or wait longer than they normally would for their next piece of food—after a regretful decision. The rats would also hastily consume food that stemmed from a bad choice, spending only about five seconds with the treat. Normally the rats would spend about 20 seconds grooming themselves and eating their food.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Neuron tells stem cells to grow new neurons

Neuron tells stem cells to grow new neurons | Amazing Science | Scoop.it

Duke researchers have found a new type of neuron in the adult brain that is capable of telling stem cells to make more new neurons. Though the experiments are in their early stages, the finding opens the tantalizing possibility that the brain may be able to repair itself from within.


Neuroscientists have suspected for some time that the brain has some capacity to direct the manufacturing of new neurons, but it was difficult to determine where these instructions are coming from, explains Chay Kuo, M.D. Ph.D., an assistant professor of cell biology, neurobiology and pediatrics.


In a study with mice, his team found a previously unknown population of neurons within the subventricular zone (SVZ) neurogenic niche of the adult brain, adjacent to the striatum. These neurons expressed the choline acetyltransferase (ChAT) enzyme, which is required to make the neurotransmitter acetylcholine. With optogenetic tools that allowed the team to tune the firing frequency of these ChAT+ neurons up and down with laser light, they were able to see clear changes in neural stem cell proliferation in the brain.


The mature ChAT+ neuron population is just one part of an undescribed neural circuit that apparently talks to stem cells and tells them to increase new neuron production, Kuo said. Researchers don't know all the parts of the circuit yet, nor the code it's using, but by controlling ChAT+ neurons' signals Kuo and his Duke colleagues have established that these neurons are necessary and sufficient to control the production of new neurons from the SVZ niche.


"We have been working to determine how neurogenesis is sustained in the adult brain. It is very unexpected and exciting to uncover this hidden gateway, a neural circuit that can directly instruct the stem cells to make more immature neurons," said Kuo, who is also the George W. Brumley, Jr. M.D. assistant professor of developmental biology and a member of the Duke Institute for Brain Sciences. "It has been this fascinating treasure hunt that appeared to dead-end on multiple occasions!"


Kuo said this project was initiated more than five years ago when lead author Patricia Paez-Gonzalez, a postdoctoral fellow, came across neuronal processes contacting neural stem cells while studying how the SVZ niche was assembled.


The young neurons produced by these signals were destined for the olfactory bulb in rodents, as the mouse has a large amount of its brain devoted to process the sense of smell and needs these new neurons to support learning. But in humans, with a much less impressive olfactory bulb, Kuo said it's possible new neurons are produced for other brain regions. One such region may be the striatum, which mediates motor and cognitive controls between the cortex and the complex basal ganglia.


"The brain gives up prime real estate around the lateral ventricles for the SVZ niche housing these stem cells," Kuo said. "Is it some kind of factory taking orders?" Postdoctoral fellow Brent Asrican made a key observation that orders from the novel ChAT+ neurons were heard clearly by SVZ stem cells.


Studies of stroke injury in rodents have noted SVZ cells apparently migrating into the neighboring striatum. And just last month in the journal Cell, a Swedish team observed newly made control neurons called interneurons in the human striatum for the first time. They reported that interestingly in Huntington's disease patients, this area seems to lack the newborn interneurons.


"This is a very important and relevant cell population that is controlling those stem cells," said Sally Temple, director of the Neural Stem Cell Institute of Rensselaer, NY, who was not involved in this research. "It's really interesting to see how innervations are coming into play now in the subventricular zone."

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Seeing sound: visual cortex processes auditory information too

Seeing sound: visual cortex processes auditory information too | Amazing Science | Scoop.it

Ten healthy subjects wearing blindfolds were given solely auditory stimulation in the absence of visual stimulation. In a separate session, retinotopic mapping.


University of Glasgow scientists studying brain process involved in sight have discovered that the visual cortex also uses information gleaned from the ears when viewing the world.


They suggest this auditory input enables the visual system to predict incoming information and could confer a survival advantage.


“Sounds create visual imagery, mental images, and automatic projections,” said Professor Lars Muckli, of the University of Glasgow’s Institute of Neuroscience and Psychology, who led the research. “For example, if you are in a street and you hear the sound of an approaching motorbike, you expect to see a motorbike coming around the corner.”


The study, published in the journal Current Biology (open access), involved conducting five different experiments using functional Magnetic Resonance Imaging (fMRI) to examine the activity in the early visual cortex in 10 volunteer subjects.


In one experiment they asked the blindfolded volunteers to listen to three different sounds: birdsong, traffic noise and a talking crowd. Using a special algorithm that can identify unique patterns in brain activity, the researchers were able to discriminate between the different sounds being processed in early visual cortex activity.

A second experiment revealed that even imagined images, in the absence of both sight and sound, evoked activity in the early visual cortex.


“This research enhances our basic understanding of how interconnected different regions of the brain are,” Muckli said. “The early visual cortex hasn’t previously been known to process auditory information, and while there is some anatomical evidence of interconnectedness in monkeys, our study is the first to clearly show a relationship in humans.


“This might provide insights into mental health conditions such as schizophrenia or autism and help us understand how sensory perceptions differ in these individuals.”

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Illuminating neuron activity in 3-D: New technique lets scientists monitor small worm's entire nervous system

Illuminating neuron activity in 3-D: New technique lets scientists monitor small worm's entire nervous system | Amazing Science | Scoop.it

Researchers at MIT and the University of Vienna have created an imaging system that reveals neural activity throughout the brains of living animals. This technique, the first that can generate 3-D movies of entire brains at the millisecond timescale, could help scientists discover how neuronal networks process sensory information and generate behavior.


The team used the new system to simultaneously image the activity of every neuron in the worm Caenorhabditis elegans, as well as the entire brain of a zebrafish larva, offering a more complete picture of nervous system activity than has been previously possible.

“Looking at the activity of just one neuron in the brain doesn’t tell you how that information is being computed; for that, you need to know what upstream neurons are doing. And to understand what the activity of a given neuron means, you have to be able to see what downstream neurons are doing,” says Ed Boyden, an associate professor of biological engineering and brain and cognitive sciences at MIT and one of the leaders of the research team. “In short, if you want to understand how information is being integrated from sensation all the way to action, you have to see the entire brain.”


The new approach, described May 18 in Nature Methods, could also help neuroscientists learn more about the biological basis of brain disorders. “We don’t really know, for any brain disorder, the exact set of cells involved,” Boyden says. “The ability to survey activity throughout a nervous system may help pinpoint the cells or networks that are involved with a brain disorder, leading to new ideas for therapies.”


Scanning the brain with a laser beam can produce 3-D images of neural activity, but it takes a long time to capture an image because each point must be scanned individually. The MIT team wanted to achieve similar 3-D imaging but accelerate the process so they could see neuronal firing, which takes only milliseconds, as it occurs.


The new method is based on a widely used technology known as light-field imaging, which creates 3-D images by measuring the angles of incoming rays of light. Ramesh Raskar, an associate professor of media arts and sciences at MIT and an author of this paper, has worked extensively on developing this type of 3-D imaging. Microscopes that perform light-field imaging have been developed previously by multiple groups. In the new paper, the MIT and Austrian researchers optimized the light-field microscope, and applied it, for the first time, to imaging neural activity.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Four Paraplegic Men Voluntarily Move Their Legs Again

Four Paraplegic Men Voluntarily Move Their Legs Again | Amazing Science | Scoop.it

 Four young men who have been paralyzed for years achieved groundbreaking progress -- moving their legs -- as a result of epidural electrical stimulation of the spinal cord, an international team of life scientists at the University of Louisville, UCLA and the Pavlov Institute of Physiology reported today in the medical journal Brain. The study was funded in part by the Christopher & Dana Reeve Foundation and the National Institutes of Health.


All four participants were classified with a chronic motor complete spinal cord injury and were unable to move their lower extremities prior to the implantation of an epidural stimulator. This research builds on an initial study, published in the May 2011 edition of The Lancet, which evaluated the effects of epidural stimulation in the first participant, Rob Summers, who recovered a number of motor functions as a result of the intervention.


Now three years later, the key findings documented in Brain detail the impact of epidural stimulation in four participants, including new tests conducted on Summers. What is truly revolutionary is that the second, third and fourth participants were able to execute voluntary movements immediately following the implantation and activation of the stimulator. The results and recovery time were unexpected, leading researchers to speculate that some pathways may be intact post-injury and therefore able to facilitate voluntary movements.


"Two of the four subjects were diagnosed as motor and sensory complete injured with no chance of recovery at all," Claudia Angeli, Ph.D., senior researcher, Human Locomotor Research Center at Frazier Rehab Institute, and assistant professor, University of Louisville's Kentucky Spinal Cord Injury Research Center (KSCIRC) and lead author. "Because of epidural stimulation, they can now voluntarily move their hips, ankles and toes. This is groundbreaking for the entire field and offers a new outlook that the spinal cord, even after a severe injury, has great potential for functional recovery."


These results were achieved through continual direct epidural electrical stimulation of the participants' lower spinal cords, mimicking signals the brain normally transmits to initiate movement. Once the signal was triggered, the spinal cord reengaged its neural network to control and direct muscle movements. When coupling the intervention with rehabilitative therapy, the impact of epidural stimulation intensified. Over the course of the study, the researchers noted that the participants were able to activate movements with less stimulation, demonstrating the ability of the spinal network to learn and improve nerve functions.


"We have uncovered a fundamentally new intervention strategy that can dramatically affect recovery of voluntary movement in individuals with complete paralysis even years after injury," said Susan Harkema, Ph.D., University of Louisville professor and rehabilitation research director at KSCIRC, Frazier Rehab Institute, director of the Reeve Foundation's Neuro Recovery Network and primary author of The Lancet article. "The belief that no recovery is possible and complete paralysis is permanent has been challenged."

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Reprogrammed human neurons extend axons to almost the entire length of the central nervous system

Reprogrammed human neurons extend axons to almost the entire length of the central nervous system | Amazing Science | Scoop.it

Building upon previous research, scientists at the University of California, San Diego School of Medicine and Veteran’s Affairs San Diego Healthcare System report that neurons derived from human induced pluripotent stem cells (iPSC) and grafted into rats after a spinal cord injury produced cells with tens of thousands of axons extending virtually the entire length of the animals’ central nervous system.


Writing in the August 7 early online edition of Neuron, lead scientist Paul Lu, PhD, of the UC San Diego Department of Neurosciences and colleagues said the human iPSC-derived axons extended through the white matter of the injury sites, frequently penetrating adjacent gray matter to form synapses with rat neurons. Similarly, rat motor axons pierced the human iPSC grafts to form their own synapses.


The iPSCs used were developed from a healthy 86-year-old human male.

“These findings indicate that intrinsic neuronal mechanisms readily overcome the barriers created by a spinal cord injury to extend many axons over very long distances, and that these capabilities persist even in neurons reprogrammed from very aged human cells,” said senior author Mark Tuszynski, MD, PhD, professor of Neurosciences and director of the UC San Diego Center for Neural Repair.


For several years, Tuszynski and colleagues have been steadily chipping away at the notion that a spinal cord injury necessarily results in permanent dysfunction and paralysis. Earlier work has shown that grafted stem cells reprogrammed to become neurons can, in fact, form new, functional circuits across an injury site, with the treated animals experiencing some restored ability to move affected limbs. The new findings underscore the potential of iPSC-based therapy and suggest a host of new studies and questions to be asked, such as whether axons can be guided and how will they develop, function and mature over longer periods of time.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Implanted Neurons made from Skin Cells become Part of the Brain

Implanted Neurons made from Skin Cells become Part of the Brain | Amazing Science | Scoop.it

Scientists at the Luxembourg Centre for Systems Biomedicine (LCSB) of the University of Luxembourg have grafted neurons reprogrammed from skin cells into the brains of mice for the first time with long-term stability. Six months after implantation, the neurons had become fully functionally integrated into the brain. This successful, because lastingly stable, implantation of neurons raises hope for future therapies that will replace sick neurons with healthy ones in the brains of Parkinson’s disease patients, for example. The Luxembourg researchers published their results in the current issue of ‘Stem Cell Reports’.


The LCSB research group around Prof. Dr. Jens Schwamborn and Kathrin Hemmer is working continuously to bring cell replacement therapy to maturity as a treatment for neurodegenerative diseases. Sick and dead neurons in the brain can be replaced with new cells. This could one day cure disorders such as Parkinson’s disease. The path towards successful therapy in humans, however, is long. “Successes in human therapy are still a long way off, but I am sure successful cell replacement therapies will exist in future. Our research results have taken us a step further in this direction,” declares stem cell researcher Prof. Schwamborn, who heads a group of 15 scientists at LCSB.


In their latest tests, the research group and colleagues from the Max Planck Institute and the University Hospital Münster and the University of Bielefeld succeeded in creating stable nerve tissue in the brain from neurons that had been reprogrammed from skin cells. The stem cell researchers’ technique of producing neurons, or more specifically induced neuronal stem cells (iNSC), in a petri dish from the host’s own skin cells considerably improves the compatibility of the implanted cells. The treated mice showed no adverse side effects even six months after implantation into the hippocampus and cortex regions of the brain. In fact it was quite the opposite – the implanted neurons were fully integrated into the complex network of the brain. The neurons exhibited normal activity and were connected to the original brain cells via newly formed synapses, the contact points between nerve cells.


Reference:

Hemmer K., Zhang M., van Wüllen, T., Sakalem M., Tapia N., Baumuratov A., Kaltschmidt C., KaltschmidtB, Schöler H. R., Zhang W., Schwamborn J. C. (2014) Induced neural stem cells achieve long-term survival and functional integration in the adult mouse brain. Stem Cell Reports, accepted,


DOI: http://dx.doi.org/10.1016/j.stemcr.2014.06.017

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

The social origins of intelligence in the brain

The social origins of intelligence in the brain | Amazing Science | Scoop.it

By studying the injuries and aptitudes of Vietnam War veterans who suffered penetrating head wounds during the war, researchers have found that brain regions that contribute to optimal social functioning are also vital to general intelligence and emotional intelligence.


This finding, reported in the journal Brain, bolsters the view that general intelligence emerges from the emotional and social context of one’s life.

“We are trying to understand the nature of general intelligence and to what extent our intellectual abilities are grounded in social cognitive abilities,” said Aron Barbey, a University of Illinois professor of neuroscience, psychology, and speech and hearing science.


Barbey, an affiliate of the Beckman Institute and he Institute for Genomic Biology at the University of Illinois, led the new study with an international team of collaborators.


The study involved 144 Vietnam veterans injured by shrapnel or bullets that penetrated the skull, damaging distinct brain tissues while leaving neighboring tissues intact. Using CT scans, the scientists painstakingly mapped the affected brain regions of each participant, then pooled the data to build a collective map of the brain.


The researchers used a battery of carefully designed tests to assess participants’ intellectual, emotional and social capabilities. They then looked for damage in specific brain regions tied to deficits in the participants’ ability to navigate intellectual, emotional or social realms. Social problem solving in this analysis primarily involved conflict resolution with friends, family and peers at work.


As in their earlier studies of general intelligence and emotional intelligence, the researchers found that regions of the frontal cortex (at the front of the brain), the parietal cortex (further back near the top of the head) and the temporal lobes (on the sides of the head behind the ears) are all implicated in social problem solving. The regions that contributed to social functioning in the parietal and temporal lobes were located only in the brain’s left hemisphere, while both left and right frontal lobes were involved.

more...
Eric Chan Wei Chiang's curator insight, August 2, 9:30 AM

There is a popular myth that humans use no more than 10% of their brains throughout their entire life. This has been shown to be untrue as brain damage consistently results in loss of function. Nonetheless, this myth provided the premise for some great movies such as the 2014 film, Lucy 

http://en.wikipedia.org/wiki/Lucy_(2014_film)

 

Read more scoops on the brain here:

http://www.scoop.it/t/biotech-and-beyond/?tag=Brain

Helen Teague's curator insight, August 3, 6:32 AM

From Dr. Stefan Gruenwald:

By studying the injuries and aptitudes of Vietnam War veterans who suffered penetrating head wounds during the war, researchers have found that brain regions that contribute to optimal social functioning are also vital to general intelligence and emotional intelligence.

 

This finding, reported in the journal Brain, bolsters the view that general intelligence emerges from the emotional and social context of one’s life.

“We are trying to understand the nature of general intelligence and to what extent our intellectual abilities are grounded in social cognitive abilities,” said Aron Barbey, a University of Illinois professor of neuroscience, psychology, and speech and hearing science.

 

Barbey, an affiliate of the Beckman Institute and he Institute for Genomic Biology at the University of Illinois, led the new study with an international team of collaborators.

 

The study involved 144 Vietnam veterans injured by shrapnel or bullets that penetrated the skull, damaging distinct brain tissues while leaving neighboring tissues intact. Using CT scans, the scientists painstakingly mapped the affected brain regions of each participant, then pooled the data to build a collective map of the brain.

 

The researchers used a battery of carefully designed tests to assess participants’ intellectual, emotional and social capabilities. They then looked for damage in specific brain regions tied to deficits in the participants’ ability to navigate intellectual, emotional or social realms. Social problem solving in this analysis primarily involved conflict resolution with friends, family and peers at work.

 

As in their earlier studies of general intelligence and emotional intelligence, the researchers found that regions of the frontal cortex (at the front of the brain), the parietal cortex (further back near the top of the head) and the temporal lobes (on the sides of the head behind the ears) are all implicated in social problem solving. The regions that contributed to social functioning in the parietal and temporal lobes were located only in the brain’s left hemisphere, while both left and right frontal lobes were involved.

Jocelyn Stoller's curator insight, August 13, 1:55 AM

Strange that CT scans were used. High resolution Functional MRI would show both structure and activity. Other imaging methods such as optogenetics, MEG, TMS, BOLD, etc. could also help to pinpoint these areas without using radiation on an already-injured brain.

Scooped by Dr. Stefan Gruenwald
Scoop.it!

Glass Brain: Virtual Reality Meets Neuroscience

Glass Brain: Virtual Reality Meets Neuroscience | Amazing Science | Scoop.it
Bridging the worlds of neuroscience and high-tech virtual realty, the Glass Brain, a project of the new Neuroscape Lab at the University of California San Francisco may open up new insights into the complicated mechanisms of the brain.


Researchers have developed a new way to explore the human brain through virtual reality. The system, called Glass Brain, initiated by Philip Rosedale, creator of the famous game Second Life, and Adam Gazzaley, a neuroscientist at the University of California San Francisco, combines brain scanning, brain recording and virtual reality to allow a user to journey through a person’s brain in real-time.

 For a recent demonstration at the South by Southwest (SXSW) Interactive festival in Austin, Texas, Rosedale made his wife a cap studded with electroencephalogram (EEG) electrodes that measure differences in electric potential in order to record brain activity, while he wore a virtual reality headset to explore her brain in 3D, as flashes of light displayed her brain activity from the EEG.

The Glass Brain didn’t actually show what Rosedale’s wife was thinking, but Gazzaley’s team ultimately hopes to get closer to decoding brain signals and displaying them using the virtual reality system.


This is an anatomically-realistic 3D brain visualization depicting real-time source-localized activity (power and "effective" connectivity) from EEG (electroencephalographic) signals. Each color represents source power and connectivity in a different frequency band (theta, alpha, beta, gamma) and the golden lines are white matter anatomical fiber tracts. Estimated information transfer between brain regions is visualized as pulses of light flowing along the fiber tracts connecting the regions.


The modeling pipeline includes MRI (Magnetic Resonance Imaging) brain scanning to generate a high-resolution 3D model of an individual's brain, skull, and scalp tissue, DTI (Diffusion Tensor Imaging) for reconstructing white matter tracts, and BCILAB (http://sccn.ucsd.edu/wiki/BCILAB) / SIFT (http://sccn.ucsd.edu/wiki/SIFT) to remove artifacts and statistically reconstruct the locations and dynamics (amplitude and multivariate Granger-causal (http://www.scholarpedia.org/article/G...) interactions) of multiple sources of activity inside the brain from signals measured at electrodes on the scalp (in this demo, a 64-channel "wet" mobile system by Cognionics/BrainVision (http://www.cognionics.com)).

The final visualization is done in Unity and allows the user to fly around and through the brain with a gamepad while seeing real-time live brain activity from someone wearing an EEG cap.

more...
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Hebbs Rule Shown: Researchers have for the first time directly created and destroyed neural connections

Hebbs Rule Shown: Researchers have for the first time directly created and destroyed neural connections | Amazing Science | Scoop.it

Researchers from UCSD have for the first time directly created and destroyed neural connections that connect high level sensory input and high level behavioral responses. 


Donald Hebb in 1949 was one of the first to seize upon this observation.  He proposed that on the biological level, neurons were rewired so that coordinated inputs and outputs get wired together.  As such, were there a nausea neuron and a boat neuron, through the effects of association, the two would get wired together so that the “boat” itself fires up pathways in the “nausea” part of the brain.


In the field of neural networks, this has a name: Hebbian learning.  Pavlov of course also described this phenomenon, and tested it in animals, bequeathing its name the “conditioned response”.


Until now the wiring of neural inputs and outputs was a theory with good but indirect evidence.  At UCSD, neuroscientists teamed up with molecular biologists to engineer a mouse whose neurons can be directly controlled for forming and losing connections.


They did this by injecting an engineered virus into the auditory nerve cells.  The viruses, largely harmless, carry a light responsive molecular switch (a membrane protein “channel” actually) which gets inserted into cells of the auditory region.  Using laser light of certain frequencies it is possible to both “potentiate” or “depress” the auditory nerve cells.


The upshot is that the researchers could directly make the auditory nerve cells increase or decrease their signal strength to other nerve cells, without needing a real, external noise.  In effect, they’ve short-circuited the noise input.  In experiments, they used a light electrical pulse to shock mice while simultaneously stimulating the auditory input with the laser-activated switch.


Basically they flashed the laser light at the ear of the mouse.  Over time, the mouse began to associate the laser pulse induced nerve signal with the electrical shock.  The mice were conditioned to exhibit fear even when there was no shock.


The crux of the experiment is what happened when the scientists flashed the laser in a way to weaken the auditory nerve.  Now the mouse stopped responding in fear to the laser auditory stimulus.

The experiments showed for the first time that associative learning was indeed the wiring together of sensory and response neurons.  The study was published in Nature.


Nature (2014) doi:10.1038/nature13294

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Not as random as thought: Modeling how neurons work together to perform complex movements

Not as random as thought: Modeling how neurons work together to perform complex movements | Amazing Science | Scoop.it

In a bid to better understand the brain and also to create robotics limbs that behave more realistically, a team of three European universities has developed a highly accurate new model of how neurons behave when performing complex movements.


The results from the University of CambridgeUniversity of Oxford, and the Ecole Polytechnique Fédérale de Lausanne (EPFL) are published in the June 18 edition of the journal Neuron.


The new theory was inspired by recent experiments carried out at Stanford University, which had uncovered some key aspects of the signals that neurons emit before, during, and after a movement. “There is a remarkable synergy in the activity recorded simultaneously in hundreds of neurons,” said Guillaume Hennequin, PhD, of EPFL’s Department of Engineering, who led the research. “In contrast, previous models of cortical circuit dynamics predict a lot of redundancy, and therefore poorly explain what happens in the motor cortex during movements.”


I addition to helping us better understand the brain, better models of how neurons behave will aid in designing prosthetic limbs controlled via electrodes implanted in the brain. “Our theory could provide a more accurate guess of how neurons would want to signal both movement intention and execution to the robotic limb,” said Hennequin.


References:
more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Human language's deep origins appear to have come directly from birds and primates

Human language's deep origins appear to have come directly from birds and primates | Amazing Science | Scoop.it
Human language builds on birdsong and speech forms of other primates, researchers hypothesize in new research. From birds, the researchers say, we derived the melodic part of our language, and from other primates, the pragmatic, content-carrying parts of speech. Sometime within the last 100,000 years, those capacities fused into roughly the form of human language that we know today.


The expressive layer and lexical layer have antecedents, the researchers believe, in the languages of birds and other mammals, respectively. For instance, in another paper published last year, Miyagawa, Berwick, and Okanoya presented a broader case for the connection between the expressive layer of human language and birdsong, including similarities in melody and range of beat patterns.


Birds, however, have a limited number of melodies they can sing or recombine, and nonhuman primates have a limited number of sounds they make with particular meanings. That would seem to present a challenge to the idea that human language could have derived from those modes of communication, given the seemingly infinite expression possibilities of humans.


Reference:

  1. Shigeru Miyagawa, Shiro Ojima, Robert C. Berwick, Kazuo Okanoya. The integration hypothesis of human language evolution and the nature of contemporary languagesFrontiers in Psychology, 2014; 5 DOI:10.3389/fpsyg.2014.00564
more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Complex Neural Circuitry Keeps You from Biting Your Own Tongue

Complex Neural Circuitry Keeps You from Biting Your Own Tongue | Amazing Science | Scoop.it

Eating, like breathing and sleeping, seems to be a rather basic biological task. Yet chewing requires a complex interplay between the tongue and jaw, with the tongue positioning food between the teeth and then moving out of the way every time the jaw clamps down to grind it up. If the act weren't coordinated precisely, the unlucky chewer would end up biting more tongue than burrito.


Duke University researchers have used a sophisticated tracing technique in mice to map the underlying brain circuitry that keeps mealtime relatively painless. The study, which appears June 3 in eLife, could lend insight into a variety of human behaviors, from nighttime teeth grinding to smiling or complex vocalizations.


"Chewing is an activity that you can consciously control, but if you stop paying attention these interconnected neurons in the brain actually do it all for you," said Edward Stanek IV, lead study author and graduate student at Duke University School of Medicine. "We were interested in understanding how this all works, and the first step was figuring out where these neurons reside."


Previous mapping attempts have produced a relatively blurry picture of this chewing control center. Researchers know that the movement of the muscles in the jaw and tongue are governed by special neurons called motoneurons and that these are in turn controlled by another set of neurons called premotor neurons. But the exact nature of these connections -- which premotor neurons connect to which motoneurons -- has not been defined.


Senior study author Fan Wang, Ph.D., associate professor of neurobiology and a member of the Duke Institute for Brain Sciences, has been mapping neural circuits in mice for many years. Under her guidance, Stanek used a special form of the rabies virus to trace the origins of chewing movements.


The rabies virus works naturally by jumping backwards across neurons until it has infected the entire brain of its victim. For this study, Stanek used a genetically disabled version of rabies that could only jump from the muscles to the motoneurons, and then back to the premotor neurons. The virus also contained a green or red fluorescent tag, which enabled the researchers to see where it landed after it was done jumping.


Stanek injected these fluorescently labeled viruses into two muscles, the tongue-protruding genioglossus muscle and the jaw-closing masseter muscle. He found that a group of premotor neurons simultaneously connect to the motoneurons that regulate jaw opening and those that trigger tongue protrusion. Similarly, he found another group that connects to both motoneurons that regulate jaw closing and those responsible for tongue retraction. The results suggest a simple method for coordinating the movement of the tongue and jaw that usually keeps the tongue safe from injury.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Frontiers in Neuroscience: Physical principles for scalable neural recording of the brain

Frontiers in Neuroscience: Physical principles for scalable neural recording of the brain | Amazing Science | Scoop.it

Neuroscience depends on monitoring the electrical activities of neurons within functioning brains (Alivisatos et al., 2012Bansal et al., 2012Gerhard et al., 2013) and has advanced through steady improvements in the underlying observational tools. The number of neurons simultaneously recorded using wired electrodes, for example, has doubled every 7 years since the 1950s, currently allowing electrical observation of hundreds of neurons at sub-millisecond timescales (Stevenson and Kording, 2011). Recording techniques have also diversified: activity-dependent optical signals from neurons endowed with fluorescent indicators can be measured by photodetectors, and radio-frequency emissions from excited nuclear spins allow the construction of magnetic resonance images modulated by activity-dependent contrast mechanisms. Ideas for alternative methods have been proposed, including the direct recording of neural activities into information-bearing biopolymers (Kording, 2011Zamft et al., 2012Glaser et al., 2013).


Simultaneously measuring the activities of all neurons in a mammalian brain at millisecond resolution is a challenge beyond the limits of existing techniques in neuroscience. Entirely new approaches may be required, motivating an analysis of the fundamental physical constraints on the problem. We outline the physical principles governing brain activity mapping using optical, electrical, magnetic resonance, and molecular modalities of neural recording. Focusing on the mouse brain, we analyze the scalability of each method, concentrating on the limitations imposed by spatiotemporal resolution, energy dissipation, and volume displacement. Based on this analysis, all existing approaches require orders of magnitude improvement in key parameters. Electrical recording is limited by the low multiplexing capacity of electrodes and their lack of intrinsic spatial resolution, optical methods are constrained by the scattering of visible light in brain tissue, magnetic resonance is hindered by the diffusion and relaxation timescales of water protons, and the implementation of molecular recording is complicated by the stochastic kinetics of enzymes. Understanding the physical limits of brain activity mapping may provide insight into opportunities for novel solutions. For example, unconventional methods for delivering electrodes may enable unprecedented numbers of recording sites, embedded optical devices could allow optical detectors to be placed within a few scattering lengths of the measured neurons, and new classes of molecularly engineered sensors might obviate cumbersome hardware architectures. We also study the physics of powering and communicating with microscale devices embedded in brain tissue and find that, while radio-frequency electromagnetic data transmission suffers from a severe power–bandwidth tradeoff, communication via infrared light or ultrasound may allow high data rates due to the possibility of spatial multiplexing. The use of embedded local recording and wireless data transmission would only be viable, however, given major improvements to the power efficiency of microelectronic devices.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

How to erase a memory –- and restore it: Researchers reactivate memories in rats

How to erase a memory –- and restore it: Researchers reactivate memories in rats | Amazing Science | Scoop.it
Researchers have erased and reactivated memories in rats, profoundly altering the animals’ reaction to past events. The study is the first to show the ability to selectively remove a memory and predictably reactivate it by stimulating nerves in the brain at frequencies that are known to weaken and strengthen the connections between nerve cells, called synapses.


Researchers at the University of California, San Diego School of Medicine have erased and reactivated memories in rats, profoundly altering the animals' reaction to past events.


The study, published in the June 1 advanced online issue of the journal Nature, is the first to show the ability to selectively remove a memory and predictably reactivate it by stimulating nerves in the brain at frequencies that are known to weaken and strengthen the connections between nerve cells, called synapses.


"We can form a memory, erase that memory and we can reactivate it, at will, by applying a stimulus that selectively strengthens or weakens synaptic connections," said Roberto Malinow, MD, PhD, professor of neurosciences and senior author of the study.


Scientists optically stimulated a group of nerves in a rat's brain that had been genetically modified to make them sensitive to light, and simultaneously delivered an electrical shock to the animal's foot. The rats soon learned to associate the optical nerve stimulation with pain and displayed fear behaviors when these nerves were stimulated.


Analyses showed chemical changes within the optically stimulated nerve synapses, indicative of synaptic strengthening.


In the next stage of the experiment, the research team demonstrated the ability to weaken this circuitry by stimulating the same nerves with a memory-erasing, low-frequency train of optical pulses. These rats subsequently no longer responded to the original nerve stimulation with fear, suggesting the pain-association memory had been erased.


In what may be the study's most startlingly discovery, scientists found they could re-activate the lost memory by re-stimulating the same nerves with a memory-forming, high-frequency train of optical pulses. These re-conditioned rats once again responded to the original stimulation with fear, even though they had not had their feet re-shocked.


"We can cause an animal to have fear and then not have fear and then to have fear again by stimulating the nerves at frequencies that strengthen or weaken the synapses," said Sadegh Nabavi, a postdoctoral researcher in the Malinow lab and the study's lead author.


Reference:

  1. Sadegh Nabavi, Rocky Fox, Christophe D. Proulx, John Y. Lin, Roger Y. Tsien and Roberto Malinow. Engineering a memory with LTD and LTPNature, 2014 DOI:10.1038/nature13294
more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

Flies pause while 200 neurons help with tough decisions

Flies pause while 200 neurons help with tough decisions | Amazing Science | Scoop.it

They spend more time choosing between a strong and a weak smell if the difference is small. The research links this deliberation to a particular gene, FoxP, and the activity of fewer than 200 neurons.


Mutations in FoxP, also associated with cognition and language in humans, made flies' decisions even slower without affecting which choice they made.


Gathering information before committing to a decision is a hallmark of intelligence. If the information is unclear, the choice is trickier and the decision takes more time. We do it, other primates do it, even rats and mice do it - but now it seems that flies do too.


"This is the clearest evidence yet of a cognitive process running in a very simple brain," said Prof Gero Miesenböck, whose team did the work at the University of Oxford's Centre for Circuits and Behaviour.

"People tended to think of insects as tiny robots that just respond reflexively to signals from the environment. Now we know that's not true."


After training fruit flies to avoid a new smell at a specific intensity, the researchers offered them a choice between that dangerous odour level and a weaker one. The flies did well when the safe option was four or five times weaker, but chose randomly if the difference was only 10%.


Crucially, as the differences became smaller and trickier to distinguish, the flies took more and more time to make a decision, waiting much longer in an intermediate zone between the two odour levels.


This is a pattern that psychologists have studied for many decades. "The same mathematical models that describe human decision-making also capture the flies' behaviour perfectly," said Prof. Miesenböck.

more...
No comment yet.
Scooped by Dr. Stefan Gruenwald
Scoop.it!

New brain cells erase old memories

New brain cells erase old memories | Amazing Science | Scoop.it
Neurogenesis interferes with past learning in infant and adult mice.


For anyone fighting to save old memories, a fresh crop of brain cells may be the last thing they need. Research published today in Sciencesuggests that newly formed neurons in the hippocampus — an area of the brain involved in memory formation — could dislodge previously learned information1. The work may provide clues as to why childhood memories are so difficult to recall.


“The finding was very surprising to us initially. Most people think new neurons mean better memory,” says Sheena Josselyn, a neuroscientist who led the study together with her husband Paul Frankland at the Hospital for Sick Children in Toronto, Canada.


Humans, mice and several other mammals grow new neurons in the hippocampus throughout their lives — rapidly at first, but more and more slowly with age. Researchers have previously shown that boosting neural proliferation before learning can enhance memory formation in adult mice23. But the latest study shows that after information is learned, neuron growth can degrade those memories.


Although seemingly counterintuitive, the disruptive role of these neurons makes some sense, says Josselyn. She notes that some theoretical models have predicted such an effect4. “More neurons increase the capacity to learn new memories in the future,” she says. “But memory is based on a circuit, so if you add to this circuit, it makes sense that it would disrupt it.” Newly added neurons could have a useful role in clearing old memories and making way for new ones, says Josselyn.

more...
No comment yet.