Posts tagged neuroscience
Articles and news from the latest research reports.
How to Erase a Memory – And Restore It
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.
In terms of potential clinical applications, Malinow, who holds the Shiley Endowed Chair in Alzheimer’s Disease Research in Honor of Dr. Leon Thal, noted that the beta amyloid peptide that accumulates in the brains of people with Alzheimer’s disease weakens synaptic connections in much the same way that low-frequency stimulation erased memories in the rats. “Since our work shows we can reverse the processes that weaken synapses, we could potentially counteract some of the beta amyloid’s effects in Alzheimer’s patients,” he said.
Εngineer invents safe way to transfer energy to medical chips in the body
A Stanford electrical engineer has invented a way to wirelessly transfer power deep inside the body, and then use this power to run tiny electronic medical gadgets such as pacemakers, nerve stimulators or new sensors and devices yet to be developed.
The discoveries reported May 19 in the Proceedings of the National Academy of Sciences culminate years of efforts by Ada Poon, assistant professor of electrical engineering, to eliminate the bulky batteries and clumsy recharging systems that prevent medical devices from being more widely used.
The technology could provide a path toward a new type of medicine that allows physicians to treat diseases with electronics rather than drugs.
"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," said Poon.
Poon’s team built an electronic device smaller than a grain of rice that acts as a pacemaker. It can be powered or recharged wirelessly by holding a power source about the size of a credit card above the device, outside the body.
Using thoughts to control airplanes
Pilots of the future could be able to control their aircraft by merely thinking commands. Scientists of the Technische Universität München and the TU Berlin have now demonstrated the feasibility of flying via brain control – with astonishing accuracy.
The pilot is wearing a white cap with myriad attached cables. His gaze is concentrated on the runway ahead of him. All of a sudden the control stick starts to move, as if by magic. The airplane banks and then approaches straight on towards the runway. The position of the plane is corrected time and again until the landing gear gently touches down. During the entire maneuver the pilot touches neither pedals nor controls.
This is not a scene from a science fiction movie, but rather the rendition of a test at the Institute for Flight System Dynamics of the Technische Universität München (TUM). Scientists working for Professor Florian Holzapfel are researching ways in which brain controlled flight might work in the EU-funded project “Brainflight”.
"A long-term vision of the project is to make flying accessible to more people," explains aerospace engineer Tim Fricke, who heads the project at TUM. "With brain control, flying, in itself, could become easier. This would reduce the work load of pilots and thereby increase safety. In addition, pilots would have more freedom of movement to manage other manual tasks in the cockpit."
Surprising accuracy
The scientists have logged their first breakthrough: They succeeded in demonstrating that brain-controlled flight is indeed possible – with amazing precision. Seven subjects took part in the flight simulator tests. They had varying levels of flight experience, including one person without any practical cockpit experience whatsoever. The accuracy with which the test subjects stayed on course by merely thinking commands would have sufficed, in part, to fulfill the requirements of a flying license test. “One of the subjects was able to follow eight out of ten target headings with a deviation of only 10 degrees,” reports Fricke. Several of the subjects also managed the landing approach under poor visibility. One test pilot even landed within only few meters of the centerline.
The TU München scientists are now focusing in particular on the question of how the requirements for the control system and flight dynamics need to be altered to accommodate the new control method. Normally, pilots feel resistance in steering and must exert significant force when the loads induced on the aircraft become too large. This feedback is missing when using brain control. The researchers are thus looking for alternative methods of feedback to signal when the envelope is pushed too hard, for example.
Electrical potentials are converted into control commands
In order for humans and machines to communicate, brain waves of the pilots are measured using electroencephalography (EEG) electrodes connected to a cap. An algorithm developed by scientists from Team PhyPA (Physiological Parameters for Adaptation) of the Technische Universität Berlin allows the program to decipher electrical potentials and convert them into useful control commands.
Only the very clearly defined electrical brain impulses required for control are recognized by the brain-computer interface. “This is pure signal processing,” emphasizes Fricke. Mind reading is not possible.
A Mexican Scientist Just Invented a ‘Telekinesis’ Helmet
A researcher just made a remarkable breakthrough in the area of brain-computer interfaces—creating a rig that allows a user to operate machines with thought alone, almost literally granting a form of ‘telekinesis’ over attached devices.
Brain-computer interfaces are a rapidly expanding area of research and industry. Though the technology to read brainwaves from the head’s surface has been around for decades, scientists and engineers have only recently created numerous systems to read signals directly from the brain and translate them into commands that control computers.
In the future, these technologies could allow people with physical disabilities to control their environment through thought alone—the brain-computer interface effectively grants users a form of telekinesis. With an increasingly digital world, brain-computer interfaces (BCIs) could allow future generations to interact with technology telepathically. Many of the early BCI studies were promising, but the technology was difficult to use and mentally exhausting.
Environmental Influences May Cause Autism in Some Cases
Research by scientists at Albert Einstein College of Medicine of Yeshiva University may help explain how some cases of autism spectrum disorder (ASD) can result from environmental influences rather than gene mutations. The findings, published online today in PLOS Genetics, shed light on why older mothers are at increased risk for having children with ASD and could pave the way for more research into the role of environment on ASD.
The U.S. Centers for Disease Control and Prevention announced in March that one in 68 U.S. children has an ASD—a 30 percent rise from 1 in 88 two years ago. A significant number of people with an ASD have gene mutations that are responsible for their condition. But a number of studies—particularly those involving identical twins, in which one twin has ASD and the other does not—show that not all ASD cases arise from mutations.
In fact, a major study of more than 14,000 children with ASDs published earlier this month in the Journal of the American Medical Association concluded that gene abnormalities could explain only half the risk for developing ASD. The other half of the risk was attributable to “nongenetic influences,” meaning environmental factors that could include the conditions in the womb or a pregnant woman’s stress level or diet.
(Source: einstein.yu.edu)
Exceptional Evolutionary Divergence of Human Muscle and Brain Metabolomes Parallels Human Cognitive and Physical Uniqueness
Metabolite concentrations reflect the physiological states of tissues and cells. However, the role of metabolic changes in species evolution is currently unknown. Here, we present a study of metabolome evolution conducted in three brain regions and two non-neural tissues from humans, chimpanzees, macaque monkeys, and mice based on over 10,000 hydrophilic compounds. While chimpanzee, macaque, and mouse metabolomes diverge following the genetic distances among species, we detect remarkable acceleration of metabolome evolution in human prefrontal cortex and skeletal muscle affecting neural and energy metabolism pathways. These metabolic changes could not be attributed to environmental conditions and were confirmed against the expression of their corresponding enzymes. We further conducted muscle strength tests in humans, chimpanzees, and macaques. The results suggest that, while humans are characterized by superior cognition, their muscular performance might be markedly inferior to that of chimpanzees and macaque monkeys.
Research details how developing neurons sense a chemical cue
Symmetry is an inherent part of development. As an embryo, an organism’s brain and spinal cord, like the rest of its body, organize themselves into left and right halves as they grow. But a certain set of nerve cells do something unusual: they cross from one side to the other. New research in mice delves into the details of the molecular interactions that help guide these neurons toward this anatomical boundary.
In an embryo, a neuron’s branches, or axons, have special structures on their tips that sense chemical cues telling them where to grow. The new findings, by researchers at Memorial Sloan Kettering Cancer Center and The Rockefeller University, reveal the structural details of how one such cue, Netrin-1, interacts with two sensing molecules on the axons, DCC and a previously less well characterized player known as neogenin, as a part of this process.
“Our work provides the first high-resolution view of the molecular complexes that form on the surface of a developing axon and tell it to move in one direction or another,” says Dimitar Nikolov, a structural biologist at Memorial Sloan Kettering. “This detailed understanding of these assemblies helps us better understand neural wiring, and may one day be useful in the development of drugs to treat spinal cord or brain injuries.”
In a developing nervous system, the signaling molecule, Netrin-1, identified by Rockefeller University Professor Marc Tessier-Lavigne and colleagues, can guide neurons by attracting or repulsing them. In the case of axons that cross from one side to the other, extended by so-called commissural neurons, Netrin-1 attracts them toward the middle.
With a technique that uses X-rays to visualize the structure of crystalized proteins, research scientist Kai Xu and colleagues in Nikolov’s laboratory revealed that Netrin-1 has two separate binding sites on opposite ends, enabling it to simultaneously bind to different receptors. This may explain how Netrin-1, which is an important axon-guiding molecule, can affect in different ways neurons that express different combinations of receptors, Nikolov says.
For some time, scientists have known commissural neurons used the receptor molecule DCC to detect Netrin-1. Neogenin has a structure similar to DCC, and this research, described today in Science, confirms neogenin too acts as a sensing molecule for commissural neurons in mammals.
In experiments that complemented the structural work, conducted by Nicolas Renier and Zhuhao Wu in Tessier-Lavigne’s lab, the researchers confirmed that, like DCC, neogenin senses Netrin-1 for the growing commissural neurons in mice.
These neurons are part of the system by which one side of the brain controls movement on the opposite side of the body. As a result, a mutation in the gene responsible for DCC interferes with this coordination, causing congenital mirror movement disorder. People with this disorder cannot move one side of the body in isolation; for example, a right-handed wave is mirrored by a similar gesture by the left hand.
The work also has implications for understanding why DCC, neogenin and other cell-surface receptors come in slightly different forms, called splice isoforms. The structural research revealed these isoforms bind differently to Netrin-1. However, it is not yet clear what this means for neuron wiring, Nikolov says.
“With this structural knowledge, and with the identification of an additional receptor involved in axon guidance in the spinal cord, we are gaining deeper insight into the mechanisms through which neurons make connections that produce a functioning nervous system, as well as the dysfunction that arises from miswiring of connections” says Tessier-Lavigne.
(Source: newswire.rockefeller.edu)
Unprecedented detail of intact neuronal receptor offers blueprint for drug developers
Biologists at Cold Spring Harbor Laboratory (CSHL) report today that they have succeeded in obtaining an unprecedented view of a type of brain-cell receptor that is implicated in a range of neurological illnesses, including Alzheimer’s disease, Parkinson’s disease, depression, schizophrenia, autism, and ischemic injuries associated with stroke.
The team’s atomic-level picture of the intact NMDA (N-methyl, D-aspartate) receptor should serve as template and guide for the design of therapeutic compounds.
The NMDA receptor is a massive multi-subunit complex that integrates both chemical and electrical signals in the brain to allow neurons to communicate with one another. These conversations form the basis of memory, learning, and thought, and critically mediate brain development. The receptor’s function is tightly regulated: both increased and decreased NMDA activities are associated with neurological diseases.
Despite the importance of NMDA receptor function, scientists have struggled to understand how it is controlled. In work published today in Science, CSHL Associate Professor Hiro Furukawa and Erkan Karakas, Ph.D., a postdoctoral investigator, use a type of molecular photography known as X-ray crystallography to determine the structure of the intact receptor. Their work identifies numerous interactions between the four subunits of the receptor and offers new insight into how the complex is regulated.
“Previously, our group and others have crystallized individual subunits of the receptor – just fragments – but that simply was not enough,” says Furukawa. “To understand how this complex functions you need to see it all together, fully assembled.”
For such a large complex, this was a challenging task. Using an exhaustive array of protein purification methods, Furukawa and Karakas were able to isolate the intact receptor. Their crystal structure reveals that the receptor looks much like a hot air balloon. “The ‘basket’ is what we call the transmembrane domain. It forms an ion channel that allows electrical signals to propagate through the neuron,” explains Furukawa.
An ion channel is like a gate in the neuronal membrane. Ions, small electrically charged atoms, are unable to pass through the cell membrane. When the ion channel “gate” is closed, ions congregate outside the cell, creating an electrical potential across the cell membrane.
When the ion channel “gate” opens, ions flow in and out of the cell through the channel pores. This generates an electrical current that sums up to create pulses that rapidly propagate through the neuron. But the current can’t jump from one neuron to the next. Rather, the electrical pulse triggers the release of chemical messengers, called neurotransmitters. These molecules traverse the distance between the neurons and bind to receptors, such as the NMDA receptor, on the surface of neighboring cells. There, they act much like a key, unlocking ion channels within the receptor and propelling the electrical signal across another neuron and, ultimately, across the brain.
The “balloon” portion of the receptor that Furukawa describes is found outside the cell. This is the region that binds to neurotransmitters. The structure of the assembled multi-subunit receptor complex, including the elusive ion channel, helps to explain some of the existing data about how NMDA receptors function. “We are able to see how one domain on the exterior side of the receptor directly regulates the ion channel within the membrane,” says Furukawa. “Our structure shows why this particular domain, called the amino terminal domain, is important for the activity of the NMDA receptor, but not for other related receptors.”
This information will be critical as scientists work to develop drugs that control the NMDA receptor. “Our structure defines the interfaces where multiple subunits and domains contact one another,” says Furukawa. “In the future, these will guide the design of therapeutic compounds to treat a wide range of devastating neurological diseases.”
Outgrowing emotional egocentricity
Children are more egocentric than adults. Scientists from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig have demonstrated for the first time that children are also worse at putting themselves in other people’s emotional shoes. According to the researchers, the supramarginal gyrus region of the brain must be sufficiently developed in children for them to be able to overcome their egocentric take on the world.
When little Philip rejoices at winning the prize in a game, it is almost impossible for him to understand that his best friend Tom, who has just lost, is not as jubilant. The opposite also applies. “Children are simply more egocentric,” says Nikolaus Steinbeis, a researcher at the Leipzig-based Max Planck Institute, summing up the general hypothesis.
Egocentrism refers to the inability to differentiate between one’s own point of view and that of other people. Egocentric people consider themselves to be the centre of all activity and assess all events and circumstances from this perspective. They project their own ideas, fears and desires onto the environment and others.
Up to now, all that the research in this area had to offer was a few theoretical ideas and studies on the development of cognitive perspective-taking. The question concerning egocentrism in connection with people’s emotional states and the development of this phenomenon over the course of childhood had been largely ignored. “We currently know very little about how emotional egocentrism is expressed in childhood and about the neuronal and cognitive processes on which this is based,” explains Steinbeis.
In order to compare the emotional states of different age groups, Steinbeis used an innovative game involving monetary rewards and punishments. “Earlier studies have shown that similarly strong emotional states can be triggered in both children and adults using such rewards and punishments. Children take as much delight as adults in monetary rewards and they are just as frustrated by losses,” he says.
During the game, two people competed against each other without, however, being able to see each other. Equipped with a computer screen and keyboard, the test subjects were asked to demonstrate their reaction speed. The participants were informed by the screen as to whether they or their opponents could rejoice in victory or despair in defeat. They were then asked to estimate the emotions experienced by their opponents. Of principal interest was how strongly the players’ own results influenced their assessments of their opponents’ emotional state. For example, if, due to their own status as a winner, a participant assessed their counterpart as being happy, despite the fact that the latter had just lost the game, this indicated that the winner was egocentrically projecting their own state onto the opponent.
The results of the study reveal that adults found it easy to overcome this tendency, whereas children between the ages of 6 and 13 tended to be guided by their own emotions when assessing those of others. The ability to assess the emotions of our counterparts independently of our own emotional state improves with age. “In general, the older a child is, the better he or she will be able to put itself in the emotional position of another person,” says Steinbeis, explaining the study findings.
In addition, the scientists measured the activity of different regions of the brain in MRI scanners and discovered a region that plays a crucial role in our ability to overcome our own feelings. The right supramarginal gyrus is a region of the temporoparietal junction, which is generally necessary for overcoming one’s own point of view. It is strongly linked with other brain regions like the anterior insula, which is exclusively responsible for enabling us to identify with other people’s emotional states. “This means that, with the right supramarginal gyrus, we have located a region which mainly functions in enabling us to overcome our own feelings,” says Steinbeis. Moreover, the scientists established that, with increasing age, the cortical thickness of the nerve fibres in this area declines. This suggests that the nerve fibres are more active as we get older.
Emotional egocentrism plays a major role in many conflicts, as the inability to overcome egocentric thinking leads to inappropriate social behaviour. People affected by this condition experience rejection, which has been shown to have a negative impact on health and development. Scientists would therefore like to understand the reasons for socially detrimental behaviour and develop options for targeted intervention.
Research shows why ketamine is an effective antidepressant but memantine is not
Ketamine is a fast-acting antidepressant. However, it can create symptoms that mimic psychosis. Therefore, doctors don’t give it to depressed patients. Memantine, a similar drug, does not have psychotomimetic effects, but it also does not appear to alleviate depression. Lisa M. Monteggia of the University of Texas Southwestern Medical Center and her colleagues have determined that these drugs have different effects on neurotransmitter pathways. In particular, ketamine promotes the expression of neurotrophic factors but memantine doesn’t. The research appears in the Proceedings of the National Academy of Sciences.