Latest Data from Large Hadron Collider Gives No Inkling of New Physics

November 16, 2012

Science

Higgs boson candidate particle, from CERN’s ATLAS

In July, physicists at the Large Hadron Collider announced the discovery of a new particle that looked like the Higgs boson. This particle was never perfect; but based on the available data, it looked exactly what the Standard Model of Particle Physics predicted the Higgs would look like.

This week, physicists working at the LHC shared more data from their Higgs projects. The LHC can’t observe the Higgs directly, but scientists can count up the number of particles that detectors observe and tease out of those that may have existed momentarily before the Higgs decayed. Any deviation in these expected numbers would indicate something happening beyond the Standard Model.

The results presented at the Hadron Collider Physics symposium in Kyoto, Japan, have all been within the Standard Model. Physicists at ATLAS and CMS have double the amount of data they had back in July and the data remains consistent with the announced findings of a Higgs-like particle.

In July, physicists found that the Higgs decayed into two photos slightly more often than it was expected to. This could possibly hint at new physics. It could also have been a statistical inconsistency that would wash away as more data becomes available.

Ranchers in the USA Are Struggling to Adapt to Climate Change

November 16, 2012

Science

Across the West, ranchers and farmers are adapting to a more unpredictable future. Image: Flickr/Echo Valley Ranch

In Boulder, Colorado, local cattle have developed immunity against the poisonous larkspur flowers that grow amongst the more edible grasses, making decisions to sell cattle a tough one. A rancher culling a herd he can’t afford to feed faces a problem restocking once economics improve, the replacements may die if they binge on the larkspur.

Replacement cattle will cost ranchers more per head as the price rises from the rock-bottom lows. The drought has made many cattle operations untenable since it has pressured ranchers to sell breeding cattle, take on more debt, or seek supplemental work off the farm. In Texas, many ranchers liquidated whole ranches.

The drought has killed off much of the natural forage on grazing pastures, forcing ranchers to buy hay, straw, and soybean supplements. Many ranchers are struggling to adapt to the new reality of climate change, or make themselves more resilient to the upcoming vicissitudes.

In a survey conducted last year in Colorado, one-quarter of respondents said they would likely leave the industry if the drought persisted into this year. The number was higher, 36%, among ranching operations that included livestock and irrigated farming. Some ranchers are retiring early, selling off their ranches, or leasing them, though not in noticeably large numbers.

Most sales are from recreation ranches owned by wealthy families, rather than working cattle ranches. Most of the third- or fourth-generation ranchers are reducing herds. US cattle inventories have sunk to their lowest since 1952 last year, according to the US Department of Agriculture.

This year’s drought is more extensive than any since the 1950s, affecting 80% of agricultural land in the US. The USDA has designated 2,186 counties in 41 states as disaster areas due to the drought. Some ranchers are diversifying, offering hunting and fishing tours, or opening event centers.

Some ranchers are trying to grow new crops, like soybeans, in an effort to cut down on chemicals that keep weeds in check. Others are trying to fill product niches of high-end local beef.

Magnetic Field Interacting with Gravity and Spin Shape Black Hole’s Environment

November 16, 2012 by Staff

Space

Version 1: A spinning black hole (at center) produces a powerful jet (white-blue) along its spin axis. While near the hole, the disk rotational axis and jet direction are aligned with the black hole spin axis. Farther away the jet deviates and eventually points along the outer disk’s rotational axis. (Credit: Jonathan McKinney, University of Maryland, and Ralf Kaehler, SLAC National Accelerator Laboratory)

A newly published study describes how astrophysicists used simulations, which follow both the rules of general relativity and the laws of magnetism, to demonstrate that gravity isn’t the sole arbiter of a spinning black hole’s behavior.

Black holes are the ultimate Bogeyman. With a well-deserved reputation as monstrous destructive machines, black holes owe their power to huge quantities of mass that warp space and time until the gravitational force they command sucks in everything – even light. No surprise that astrophysicists have long considered gravity the dominant player in shaping the accretion disks of dust and gas surrounding black holes.

But that may not be true, at least for spinning black holes. In a paper published today in Science Express, three astrophysicists focus on a different fundamental force: magnetism. In state-of-the-art simulations that follow both the rules of general relativity and the laws of magnetism, they demonstrate that gravity isn’t the sole arbiter of a spinning black hole’s behavior.

Magneto-spin alignment effect movie by Ralf Kaehler (for Science paper by McKinney, Tchekhovskoy, and Blandford 2012): The black hole spin axis, disk rotational axis, and emergent jet axis are all initially aligned. We instantly tilt the black hole spin by 90 degrees in the middle of the simulation, after which the spinning black hole (at center) reforms the powerful jet (white-blue) along the tilted black hole spin axis. The jet rams into the surrounding accretion disk (infalling hot plasma as white-red near the hole) and causes the disk to align with the black hole spin axis near the black hole. At larger distances from the black hole, the disk finally pushes back on the jet causing the jet to re-align with the outer disk rotational axis.

Version 2: Spinning black hole (at center) produces a powerful jet (white-blue) along its spin axis. The jet affects the orientation of the surrounding accretion disk (infalling hot plasma as white-red near the hole) causing the disk to align with the spin axis near the hole, but at larger distances the disk dominates the jet and the jet re-aligns with the outer disk. (Credit: Jonathan McKinney, University of Maryland, and Ralf Kaehler, SLAC National Accelerator Laboratory)

“We found that the black hole’s magnetic field interacting with its gravity and spin has an even bigger effect” than gravity alone, said first author Jonathan McKinney, who, before he became an assistant professor of physics at the University of Maryland, was a postdoctoral researcher at Stanford University and SLAC National Accelerator Laboratory, where he did much of the work for the paper.

The result, especially in the case of a black hole with a thick accretion disk, is a complex maelstrom of interacting forces: Near the black hole, spiraling magnetic fields cause the material in the accretion disk to orbit about the black hole in the same direction as the black hole’s spin. Twisting lines of magnetic force launch two jets of particles in opposite directions at close to the speed of light. These jets, called relativistic jets, initially speed away parallel to the black hole’s axis of rotation – its north and south poles. But as gravity’s grip weakens, the charged gas in the outermost regions of the accretion disk pulls at the jets, pulling them away from the black hole’s rotational axis even as the jets collide with that gas and knock it away from the black hole.

Version 3: Spinning black hole (at center) produces a powerful jet (white smoke) along its spin axis. The jet affects the orientation of the surrounding accretion disk (infalling hot plasma as purple far from the hole and yellow near the hole) causing the disk to align with the spin axis near the hole, but at larger distances the disk dominates the jet and the jet re-aligns with the outer disk. (Credit: Jonathan McKinney, University of Maryland, and Ralf Kaehler, SLAC National Accelerator Laboratory)

McKinney says the results of the simulations have direct consequences for studies of the delicate balance between how much gas a black hole can pull in from its accretion disk and how much gas it blows away with its jets. The greedier the black hole, the more gas it pulls in and the more energy is funneled to the jets, until they become so powerful they can blast the surrounding area clear – shutting down star formation in the vicinity – and, says McKinney, “The black hole stops its own growth.”

According to their simulations, the boost in energy provided by all the forces interacting around a black hole, including the magnetic force, makes a black hole even better at blasting its surroundings clear than currently thought. “Based on our study we’re saying there are some aspects of the feedback mechanism that we don’t understand,” McKinney said, and this remains a major unsolved problem in astrophysics.

Soon, though, the work of McKinney and his colleagues, Alexander Tchekhovskoy of Princeton and Roger Blandford, director of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC and Stanford, may be confirmed by actual observation. A globe-spanning array of telescopes all acting as one called the Event Horizon Telescope has been making its first close-up observations of black holes – with some help, said McKinney, from their simulations. “Any interpretations are still very preliminary,” he added, but the possibility that their ideas soon might face a direct test is exciting.

Source: Lori Ann White, SLAC National Accelerator Laboratory

Images: Jonathan McKinney, University of Maryland, and Ralf Kaehler, SLAC National Accelerator Laboratory

BrainGate Neural Interface System Allows People with Paralysis to Control Robotic Arms

May 16, 2012

Technology

A 58-year-old woman, paralyzed by a stroke for almost 15 years, uses her thoughts to control a robotic arm, grasp a bottle of coffee, serve herself a drink, and return the bottle to the table.

Advances in brain-computer interfaces, restorative neurotechnology, and assistive robot technology have led to a new study that reports, while using the BrainGate neural interface system, two people with tetraplegia were able to reach for and grasp objects in three-dimensional space using robotic arms that they controlled directly with brain activity.

Providence, Rhode Island (Brown University) — On April 12, 2011, nearly 15 years after she became paralyzed and unable to speak, a woman controlled a robotic arm by thinking about moving her arm and hand to lift a bottle of coffee to her mouth and take a drink. That achievement is one of the advances in brain-computer interfaces, restorative neurotechnology, and assistive robot technology described in the May 17 edition of the journal Nature by the BrainGate2 collaboration of researchers at the Department of Veterans Affairs, Brown University, Massachusetts General Hospital, Harvard Medical School, and the German Aerospace Center (DLR).

A 58-year-old woman (“S3”) and a 66-year-old man (“T2”) participated in the study. They had each been paralyzed by a brainstem stroke years earlier which left them with no functional control of their limbs. In the research, the participants used neural activity to directly control two different robotic arms, one developed by the DLR Institute of Robotics and Mechatronics and the other by DEKA Research and Development Corp., to perform reaching and grasping tasks across a broad three-dimensional space. The BrainGate2 pilot clinical trial employs the investigational BrainGate system initially developed at Brown University, in which a baby aspirin-sized device with a grid of 96 tiny electrodes is implanted in the motor cortex — a part of the brain that is involved in voluntary movement. The electrodes are close enough to individual neurons to record the neural activity associated with intended movement. An external computer translates the pattern of impulses across a population of neurons into commands to operate assistive devices, such as the DLR and DEKA robot arms used in the study now reported in Nature.

BrainGate participants have previously demonstrated neurally based two-dimensional point-and-click control of a cursor on a computer screen and rudimentary control of simple robotic devices.

The study represents the first demonstration and the first peer-reviewed report of people with tetraplegia using brain signals to control a robotic arm in three-dimensional space to complete a task usually performed by their arm. Specifically, S3 and T2 controlled the arms to reach for and grasp foam targets that were placed in front of them using flexible supports. In addition, S3 used the DLR robot to pick up a bottle of coffee, bring it to her mouth, issue a command to tip it, drink through a straw, and return the bottle to the table. Her BrainGate-enabled, robotic-arm control during the drinking task required a combination of two-dimensional movements across a table top plus a “grasp” command to either grasp and lift or tilt the robotic hand.

“Our goal in this research is to develop technology that will restore independence and mobility for people with paralysis or limb loss,” said lead author Dr. Leigh Hochberg, a neuroengineer and critical care neurologist who holds appointments at the Department of Veterans Affairs, Brown University, Massachusetts General Hospital, and Harvard. He is the sponsor-investigator for the BrainGate2 pilot clinical trial. “We have much more work to do, but the encouraging progress of this research is demonstrated not only in the reach-and-grasp data, but even more so in S3’s smile when she served herself coffee of her own volition for the first time in almost 15 years.”

Even after nearly 15 years, a part of the brain essentially “disconnected” from its original target by a brainstem stroke was still able to direct the complex, multidimensional movement of an external arm.

Partial funding for this work comes from the VA, which is committed to improving the lives of injured veterans. “VA is honored to have played a role in this exciting and promising area of research,” said VA Secretary Eric Shinseki. “Today’s announcement represents a great step forward toward improving the quality of life for veterans and others who have either lost limbs or are paralyzed.”

Hochberg adds that even after nearly 15 years, a part of the brain essentially “disconnected” from its original target by a brainstem stroke was still able to direct the complex, multidimensional movement of an external arm — in this case, a robotic limb. The researchers also noted that S3 was able to perform the tasks more than five years after the investigational BrainGate electrode array was implanted. This sets a new benchmark for how long implanted brain-computer interface electrodes have remained viable and provided useful command signals.

John Donoghue, the VA and Brown neuroscientist who pioneered BrainGate more than a decade ago and who is co-senior author of the study, said the paper shows how far the field of brain-computer interfaces has come since the first demonstrations of computer control with BrainGate.

“This paper reports an important advance by rigorously demonstrating in more than one participant that precise three-dimensional neural control of robot arms is not only possible, but also repeatable,” said Donoghue, who directs the Brown Institute for Brain Science. “We’ve moved significantly closer to returning everyday functions, like serving yourself a sip of coffee, usually performed effortlessly by the arm and hand, for people who are unable to move their own limbs. We are also encouraged to see useful control more than five years after implant of the BrainGate array in one of our participants. This work is a critical step toward realizing the long-term goal of creating a neurotechnology that will restore movement, control, and independence to people with paralysis or limb loss.”

In the research, the robots acted as a substitute for each participant’s paralyzed arm. The robotic arms responded to the participants’ intent to move as they imagined reaching for each foam target. The robot hand grasped the target when the participants imagined a hand squeeze. Because the diameter of the targets was more than half the width of the robot hand openings, the task required the participants to exert precise control. (Videos of these actions are available on the Nature website.)

In 158 trials over four days, S3 was able to touch the target within an allotted time in 48.8 percent of the cases using the DLR robotic arm and hand and 69.2 percent of the cases with the DEKA arm and hand, which has the wider grasp. In 45 trials using the DEKA arm, T2 touched the target 95.6 percent of the time. Of the successful touches, S3 grasped the target 43.6 percent of the time with the DLR arm and 66.7 percent of the time with the DEKA arm. T2’s grasp succeeded 62.2 percent of the time.

T2 performed the session in this study on his fourth day of interacting with the arm; the prior three sessions were focused on system development. Using his eyes to indicate each letter, he later described his control of the arm: “I just imagined moving my own arm and the [DEKA] arm moved where I wanted it to go.”

The study used two advanced robotic arms: the DLR Light-Weight Robot III with DLR five-fingered hand and the DEKA Arm System. The DLR LWR-III, which is designed to assist in recreating actions like the human arm and hand and to interact with human users, could be valuable as an assistive robotic device for people with various disabilities. Patrick van der Smagt, head of bionics and assistive robotics at DLR, director of biomimetic robotics and machine learning labs at DLR and the Technische Universität München, and a co-senior author on the paper said: “This is what we were hoping for with this arm. We wanted to create an arm that could be used intuitively by varying forms of control. The arm is already in use by numerous research labs around the world who use its unique interaction and safety capabilities. This is a compelling demonstration of the potential utility of the arm by a person with paralysis.”

DEKA Research and Development developed the DEKA Arm System for amputees, through funding from the United States Defense Advanced Research Projects Agency (DARPA). Dean Kamen, founder of DEKA said, “One of our dreams for the Luke Arm [as the DEKA Arm System is known informally] since its inception has been to provide a limb that could be operated not only by external sensors, but also by more directly thought-driven control. We’re pleased about these results and for the continued research being done by the group at the VA, Brown and MGH.” The research is aimed at learning how the DEKA arm might be controlled directly from the brain, potentially allowing amputees to more naturally control this prosthetic limb.

The BrainGate2 Neural Interface System. An implanted microelectrode array, first used more than a decade ago, detects brain signals which can be translated by a computer into machine instructions, allowing control of robotic devices by thought.

Over the last two years, VA has been conducting an optimization study of the DEKA prosthetic arm at several sites, with the cooperation of veterans and active duty service members who have lost an arm. Feedback from the study is helping DEKA engineers to refine the artificial arm’s design and function. “Brain-computer interfaces, such as BrainGate, have the potential to provide an unprecedented level of functional control over prosthetic arms of the future,” said Joel Kupersmith, M.D., VA chief research and development officer. “This innovation is an example of federal collaboration at its finest.”

Story Landis, director of the National Institute of Neurological Disorders and Stroke, which funded the work in part, noted: “This technology was made possible by decades of investment and research into how the brain controls movement. It’s been thrilling to see the technology evolve from studies of basic neurophysiology and move into clinical trials, where it is showing significant promise for people with brain injuries and disorders.”

In addition to Hochberg, Donoghue, and van der Smagt, other authors on the paper are Daniel Bacher, Beata Jarosiewicz, Nicolas Masse, John Simeral, Joern Vogel, Sami Haddadin, Jie Liu, and Sydney Cash.

Source: David Orenstein, Brown University

Images: Brown University

Record Numbers of Gray Whales Spotted Off California Coast

January 2, 2012

Science

According to Whale watchers, migrating gray whales are swimming through Southern California waters in record numbers this winter and amazing all who see them. Whale watchers at Point Vicente in Rancho Palos Verdes have recorded over 163 sightings in December, which is a new record. It is the most that they have seen at that location in 28 years and is generating a lot of excitement in the whale watching community.
In contrast, last year at this time, they recorded a total of 26 of the gray whales. The previous record of 133 occurred back in 1996. It looks like a good sign that whale populations are flourishing. Over 20,000 gray whales migrate each year from the arctic to Baja California. Once there, the females give birth, then migrate back north for the spring.
Next year’s numbers will be very telling should they be high again and then we can almost certainly say that their numbers are rising. However if they go back to being low, we will have to figure out how to interpret the discrepancies.

Adult White Killer Whale Spotted in the Wild for the First Time

April 24, 2012

Biology

There have been sightings of white whales sporadically over the last few decades, but the only white killer whales (Orcinus orca) were young, including one with a rare genetic condition that died in a Canadian aquarium in 1972.
A group of Russian scientists and students on a research cruise off Kamchatka made the sightings of an adult O. orca. The only two other white orcas seen in Russia were young, but this time, researchers are sure it’s an adult they’ve spotted. The dorsal fin measured two meters in height, implying that it’s at least 16 years old. The fin was somewhat ragged, so it could even be older.

Male killer whales can live up to 50 or 60 years, though 30 is the median life expectancy. They mature at the age of 15. The researchers have called him Iceberg and he seems fully socialized with this pod. The cause of the unusual pigmentation is not yet known. It could be the Chediak-Higashi syndrome, but researchers hope to get a closer look at Iceberg to see his eye color.

O. orca have a complex social structure, including matrilineal family clans, pods consisting of several families, and much larger super-pods.

Crowdsourcing Experiment Aims To Decode Whale Song

November 30, 2011

Science

The race is on to decode whale song and you can help. A global crowdsourcing experiment may finally be what is needed to unlock the mystery of just what whale song is all about.
Any “Citizen Scientists” who are interested can study about 15,000 recordings of calls by pilot whales and killer whales around the planet. Hopefully we can learn some new phrases, meanings and dialects. The Whale Project was launched today by Scientific American and the online citizen science organization The Zooniverse.
If you are interested, just visit whale.fm where you will be able to study and then compare sound wave patterns of calls made by whales in different pods and families around the world via spectrogram. The idea is to identify identical or similar sound wave patterns, and don’t worry, you will be able to play back each sound as you study it. Each sound recording is linked to a specific location in the sea, so scientists know which calls come from which specific families of whales and where.
Why not just use computers? It turns out that people are better at spotting similarities in complex spectrograms. The human brain excels at comparing images. Every matched group of sounds will be compared with the whales’ location and activities that the whales were involved in. They are hoping to discover a dialect at the least and if they get very lucky, perhaps different kinds of messages.

Neuroscientists Decode Correlation Between Sound and Brain Activity

January 31, 2012

Biology

An X-ray CT scan of the head of one of the volunteers, showing electrodes distributed over the brain’s temporal lobe, where sounds are processed.

UC Berkeley neuroscientists are hoping to be able to hear the unsaid words of patients in the near future. While conducting their research, they were able to decode the electrical activity in the brain’s temporal lobe as a person listens to normal conversation, which in turn allowed them to predict the words the person had heard solely from the temporal lobe activity. By understanding the correlation between sound and brain activity, neuroscientists hope to use this technology to help people that have damage to their speech mechanisms.
BERKELEY — Neuroscientists may one day be able to hear the imagined speech of a patient unable to speak due to stroke or paralysis, according to University of California, Berkeley, researchers.
These scientists have succeeded in decoding electrical activity in the brain’s temporal lobe – the seat of the auditory system – as a person listens to normal conversation. Based on this correlation between sound and brain activity, they then were able to predict the words the person had heard solely from the temporal lobe activity.
“This research is based on sounds a person actually hears, but to use it for reconstructing imagined conversations, these principles would have to apply to someone’s internal verbalizations,” cautioned first author Brian N. Pasley, a post-doctoral researcher in the center. “There is some evidence that hearing the sound and imagining the sound activate similar areas of the brain. If you can understand the relationship well enough between the brain recordings and sound, you could either synthesize the actual sound a person is thinking, or just write out the words with a type of interface device.”
“This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig’s disease and can’t speak,” said co-author Robert Knight, a UC Berkeley professor of psychology and neuroscience. “If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit.”
In addition to the potential for expanding the communication ability of the severely disabled, he noted, the research also “is telling us a lot about how the brain in normal people represents and processes speech sounds.”
Pasley and his colleagues at UC Berkeley, UC San Francisco, University of Maryland and The Johns Hopkins University report their findings Jan. 31 in the open-access journal PLoS Biology.
Help from epilepsy patients
They enlisted the help of people undergoing brain surgery to determine the location of intractable seizures so that the area can be removed in a second surgery. Neurosurgeons typically cut a hole in the skull and safely place electrodes on the brain surface or cortex – in this case, up to 256 electrodes covering the temporal lobe – to record activity over a period of a week to pinpoint the seizures. For this study, 15 neurosurgical patients volunteered to participate.
Pasley visited each person in the hospital to record the brain activity detected by the electrodes as they heard 5-10 minutes of conversation. Pasley used this data to reconstruct and play back the sounds the patients heard. He was able to do this because there is evidence that the brain breaks down sound into its component acoustic frequencies – for example, between a low of about 1 Hertz (cycles per second) to a high of about 8,000 Hertz –that are important for speech sounds.
Pasley tested two different computational models to match spoken sounds to the pattern of activity in the electrodes. The patients then heard a single word, and Pasley used the models to predict the word based on electrode recordings.
“We are looking at which cortical sites are increasing activity at particular acoustic frequencies, and from that, we map back to the sound,” Pasley said. He compared the technique to a pianist who knows the sounds of the keys so well that she can look at the keys another pianist is playing in a sound-proof room and “hear” the music, much as Ludwig van Beethoven was able to “hear” his compositions despite being deaf.
The better of the two methods was able to reproduce a sound close enough to the original word for Pasley and his fellow researchers to correctly guess the word.
“We think we would be more accurate with an hour of listening and recording and then repeating the word many times,” Pasley said. But because any realistic device would need to accurately identify words heard the first time, he decided to test the models using only a single trial.
“This research is a major step toward understanding what features of speech are represented in the human brain” Knight said. “Brian’s analysis can reproduce the sound the patient heard, and you can actually recognize the word, although not at a perfect level.”
Knight predicts that this success can be extended to imagined, internal verbalizations, because scientific studies have shown that when people are asked to imagine speaking a word, similar brain regions are activated as when the person actually utters the word.
“With neuroprosthetics, people have shown that it’s possible to control movement with brain activity,” Knight said. “But that work, while not easy, is relatively simple compared to reconstructing language. This experiment takes that earlier work to a whole new level.”
Based on earlier work with ferrets
The current research builds on work by other researchers about how animals encode sounds in the brain’s auditory cortex. In fact, some researchers, including the study’s coauthors at the University of Maryland, have been able to guess the words ferrets were read by scientists based on recordings from the brain, even though the ferrets were unable to understand the words.
The ultimate goal of the UC Berkeley study was to explore how the human brain encodes speech and determine which aspects of speech are most important for understanding.
“At some point, the brain has to extract away all that auditory information and just map it onto a word, since we can understand speech and words regardless of how they sound,” Pasley said. “The big question is, What is the most meaningful unit of speech? A syllable, a phone, a phoneme? We can test these hypotheses using the data we get from these recordings.”
Coauthors of the study are electrical engineers Stephen V. David, Nima Mesgarani and Shihab A. Shamma of the University of Maryland; Adeen Flinker of UC Berkeley’s Helen Wills Neuroscience Institute; and neurologist Nathan E. Crone of The Johns Hopkins University in Baltimore, Md. The work was done principally in the labs of Robert Knight at UC Berkeley and Edward Chang, a neurosurgeon at UCSF.
Source: Robert Sanders, UC Berkeley
Image: Adeen Flinker, UC Berkeley
Chang and Knight are members of the Center for Neural Engineering and Prostheses, a joint UC Berkeley/UCSF group focused on using brain activity to develop neural prostheses for motor and speech disorders in disabling neurological disorders.

Neuroscientists Predict Which Parts of the Fusiform Gyrus are Face-Selective

January 7, 2012

Science

Neuroscientists know a lot about the functionality of our brain cells and recently they furthered that knowledge with a new discovery. By tracing the interaction between the fusiform gyrus, the brain region responsible for face recognition, and using diffusion-weighted imaging, researchers may be able to better understand face-recognition impairments.
For more than a decade, neuroscientists have known that many of the cells in a brain region called the fusiform gyrus specialize in recognizing faces. However, those cells don’t act alone: They need to communicate with several other parts of the brain. By tracing those connections, MIT neuroscientists have now shown that they can accurately predict which parts of the fusiform gyrus are face-selective.
The study, which appeared in the Dec. 25 issue of the journal Nature Neuroscience, is the first to link a brain region’s connectivity with its function. No two people have the exact same fusiform gyrus structure, but using connectivity patterns, the researchers can now accurately predict which parts of an individual’s fusiform gyrus are involved in face recognition.
This work goes a step beyond previous studies that have used magnetic resonance imaging (MRI) to locate the regions that are involved in particular functions. “Rather than just mapping the brain, what we’re doing now is adding on to that a description of function with respect to connectivity,” says David Osher, a lead author of the paper and a graduate student in the lab of John Gabrieli, the Grover Hermann Professor of Health Sciences and Technology and Cognitive Neuroscience and a member of MIT’s McGovern Institute for Brain Research.
Using this approach, scientists may be able to learn more about the face-recognition impairments often seen in autism and prosopagnosia, a disorder often caused by stroke. This method could also be used to determine relationships between structure and function in other parts of the brain.
To map the brain’s connectivity patterns, the researchers used a technique called diffusion-weighted imaging, which is based on MRI. A magnetic field applied to the brain of the person in the scanner causes water in the brain to flow in the same direction. However, wherever there are axons — the long cellular extensions that connect a neuron to other brain regions — water is forced to flow along the axon, rather than crossing it. This is because axons are coated in a fatty material called myelin, which is impervious to water.
By applying the magnetic field in many different directions and observing which way the water flows, the researchers can identify the locations of axons and determine which brain regions they are connecting.
“For every measurable unit of the brain at this level, we have a description of how it connects with every other region, and with what strength it connects with every other region,” says Zeynep Saygin, a lead author of the paper and a graduate student who is advised by Gabrieli and Rebecca Saxe, senior author of the paper and associate professor of brain and cognitive sciences.
Gabrieli is also an author of the paper, along with Kami Koldewyn, a postdoc in MIT professor Nancy Kanwisher’s lab, and Gretchen Reynolds, a former technical assistant in Gabrieli’s lab.
Making connections
The researchers found that certain patches of the fusiform gyrus were strongly connected to brain regions also known to be involved in face recognition, including the superior and inferior temporal cortices. Those fusiform gyrus patches were also most active when the subjects were performing face-recognition tasks.
Based on the results in one group of subjects, the researchers created a model that predicts function in the fusiform gyrus based solely on the observed connectivity patterns. In a second group of subjects, they found that the model successfully predicted which patches of the fusiform gyrus would respond to faces.
“This is the first time we’ve had direct evidence of this relationship between function and connectivity, even though you certainly would have assumed that was going to be true,” says Saxe, who is also an associate member of the McGovern Institute. “One thing this paper does is demonstrate that the tools we have are sufficient to see something that we strongly believed had to be there, but that we didn’t know we’d be able to see.”
The other regions connected to the fusiform gyrus are believed to be involved in higher-level visual processing. One surprise was that some parts of the fusiform gyrus connect to a part of the brain called the cerebellar cortex, which is not thought to be part of the traditional vision-processing pathway. That area has not been studied very thoroughly, but a few studies have suggested that it might have a role in face recognition, Osher says.
Now that the researchers have an accurate model to predict function of fusiform gyrus cells based solely on their connectivity, they could use the model to study the brains of patients, such as severely autistic children, who can’t lie down in an MRI scanner long enough to participate in a series of face-recognition tasks. That is one of the most important aspects of the study, says Michael Beauchamp, an associate professor of neurobiology at the University of Texas Medical School.
“Functional MRI is the best tool we have for looking at human brain function, but it’s not suitable for all patient groups, especially children or older people with cognitive disabilities,” says Beauchamp, who was not involved in this study.
The MIT researchers are now expanding their connectivity studies into other brain regions and other visual functions, such as recognizing objects and scenes, as well as faces. They hope that such studies will also help to reveal some of the mechanisms of how information is processed at each point as it flows through the brain.

Brain Oscillations Reveal We Experience the World in Rapid Snapshots

May 14, 2012

Biology

Neuroscientists from the University of Glasgow have demonstrated that our brains experience the world in discrete snapshots determined by the cycles of brain rhythms. While studying a brain rhythm associated with visual cortex, they used a “simple trick” to affect and “reset” the oscillations of this rhythm.
It has long been suspected that humans do not experience the world continuously, but rather in rapid snapshots.
Now, researchers at the University of Glasgow have demonstrated this is indeed the case. Just as the body goes through a 24-hour sleep-wake cycle controlled by a circadian clock, brain function undergoes such cyclic activity – albeit at a much faster rate.
Professor Gregor Thut of the Institute of Neuroscience and Psychology, said: “Rhythms are intrinsic to biological systems. The circadian rhythm, with its very slow periodicity of sleep and wake cycles every 24 hours has an obvious, periodic effect on bodily functions.
“Brain oscillations – the recurrent neural activity that we see in the brain – also show periodicity but cycle at much faster speeds. What we wanted to know was whether brain function was affected in a cyclic manner by these rapid oscillations.”
The researchers studied a prominent brain rhythm associated with visual cortex functioning that cycles at a rate of 10 times per second (10Hz).
They used a ‘simple trick’ to affect the oscillations of this rhythm which was presenting a brief sound to ‘reset’ the oscillation.
Testing subsequent visual perception, by using transcranial magnetic stimulation of visual cortex, revealed a cyclic pattern at the very rapid rate of brain oscillations, in time with the underlying brainwaves.
Prof Thut said: “Rhythmicity therefore is indeed omnipresent not only in brain activity but also brain function. For perception, this means that despite experiencing the world as a continuum, we do not sample our world continuously but in discrete snapshots determined by the cycles of brain rhythms.”
The research, ‘Sounds reset rhythms of visual cortex and corresponding human visual perception’ is published in the journal Current Biology.

MIT Neuroscientists Research Brain Activity Related to Face Recognition

January 9, 2012

Science

How does the human brain recognize faces and distinguish between genuine faces and objects that resemble faces? A new study by Professor Pawan Sinha at MIT and his colleagues indicates that looked at brain activity indicates that both hemispheres are involved in this decision.
Objects that resemble faces are everywhere. Whether it’s New Hampshire’s erstwhile granite “Old Man of the Mountain,” or Jesus’ face on a tortilla, our brains are adept at locating images that look like faces. However, the normal human brain is almost never fooled into thinking such objects actually are human faces.
“You can tell that it has some ‘faceness’ to it, but on the other hand, you’re not misled into believing that it is a genuine face,” says Pawan Sinha, professor of brain and cognitive sciences at MIT.
A new study from Sinha and his colleagues reveals the brain activity that underlies our ability to make that distinction. On the left side of the brain, the fusiform gyrus — an area long associated with face recognition — carefully calculates how “facelike” an image is. The right fusiform gyrus then appears to use that information to make a quick, categorical decision of whether the object is, indeed, a face.
This distribution of labor is one of the first known examples of the left and right sides of the brain taking on different roles in high-level visual-processing tasks, Sinha says, although hemispheric differences have been seen in other brain functions, most notably language and spatial perception.
Lead author of the paper, published Jan. 4 in the Proceedings of the Royal Society B, is Ming Meng, a former postdoc in Sinha’s lab and now an assistant professor at Dartmouth College. Other authors are Tharian Cherian ’09 and Gaurav Singal, who recently earned an MD from the Harvard-MIT Division of Health Sciences and Technology and is now a resident at Massachusetts General Hospital.
Face versus nonface
Many earlier studies have shown that neurons in the fusiform gyrus, located on the brain’s underside, respond preferentially to faces. Sinha and his students set out to investigate how that brain region decides what is and is not a face, particularly in cases where an object greatly resembles a face.
To help them do that, the researchers created a continuum of images ranging from those that look nothing like faces to genuine faces. They found images that very closely resemble faces by examining photographs that machine vision systems had falsely tagged as faces. Human observers then rated how facelike each of the images were by doing a series of one-to-one comparisons; the results of those comparisons allowed the researchers to rank the images by how much they resembled a face.
The research team then used functional magnetic resonance imaging (fMRI) to scan the brains of research subjects as they categorized the images. Unexpectedly, the scientists found different activity patterns on each side of the brain: On the right side, activation patterns within the fusiform gyrus remained quite consistent for all genuine face images, but changed dramatically for all nonface images, no matter how much they resembled a face. This suggests that the right side of the brain is involved in making the categorical declaration of whether an image is a face or not.
Meanwhile, in the analogous region on the left side of the brain, activity patterns changed gradually as images became more facelike, and there was no clear divide between faces and nonfaces. From this, the researchers concluded that the left side of the brain is ranking images on a scale of how facelike they are, but not assigning them to one category or another.
“From the computational perspective, one speculation one can make is that the left does the initial heavy lifting,” Sinha says. “It tries to determine how facelike is a pattern, without making the final decision on whether I’m going to call it a face.”
Key to the research was imaging-analysis technology that allowed the scientists to look at patterns of activity across the fusiform gyrus.
“This is a relatively recent innovation — looking at the pattern of activation as opposed to overall activation,” says Thomas Busey, associate professor of psychological and brain sciences at Indiana University, who was not involved in this research. “Anytime you have a measure that replicates and correlates with human behavior, that seems to be a pretty compelling story.”
Timing is instructive
The researchers found that activation in the left side of the fusiform gyrus preceded that of the right side by a couple of seconds, supporting the hypothesis that the left side does its job first and then passes information on to the right side.
Sinha says that given the sluggishness of fMRI signals (which rely on blood-flow changes), the timing does not yet constitute definitive evidence, “but it’s a very interesting possibility because it begins to tease apart this monolithic notion of face processing. It’s now beginning to get at what the constituents are of that overall face-processing system.”
The researchers hope to obtain more solid evidence of temporal relationships between the two hemispheres with studies using electroencephalography (EEG) or magnetoencephalography (MEG), two technologies that offer a much more precise view of the timing of brain activity. They also hope to discover how and when the right and left sides of the fusiform gyrus develop these independent functions by studying blind children who have their sight restored at a young age. Many such children have been treated by Project Prakash, an effort initiated by Sinha to find and treat blind children in India.

Psychadelic Chemicals Subdue Brain Activity Instead of Expanding It

January 23, 2012

Science

While it’s colloquially believed that psychedelic drugs, such as magic mushrooms, have the capacity to expand the minds of its users, researchers have actually shown that the hallucinogenic chemical induces widespread decreases in brain activity.
The recent study was published in the Proceedings of the National Academy of Sciences, and it shows that psilocybin, which has been revered for centuries to induce mystical experiences, has actually the therapeutic potential to treat a variety of psychiatric conditions. The drug activates serotonin receptors, but the way this happens in reality is poorly understood.
David Nutt, a neuropsychopharmacologist at the Imperial College London, and his colleagues used functional magnetic resonance imaging to monitor the changes in brain activity during the transition in states when a patient ingests the drug.
The most significant decreases were observed in the medial prefrontal cortex, and the anterior and posterior cingulate cortices. The scans showed a reduction in functional connectivity between these areas, so that their normal synchronous activity became desynchronized. The stronger the drug, the larger the decrease.
The mPFC, PCC, and thalamus act as connector hubs that have a pivotal role in the way that information is coordinated throughout the brain, which is what accounts for hallucinations, since the drugs induce a state of unconstrained cognition.
Since depression involves hyperactivity in the mPFC, it’s possible that a reduction in activity in the mPFC could alleviate some of the symptoms.
However Nutt’s findings contradict some earlier ones, which had reported activation in these areas of the brain, not a deactivation. Keith Laws, a neuropsychologist at the University of Hertfordshire states that the deactivation of the mPFC and PCC could be linked to the anxiety and anticipation of pleasant and unpleasant experiences. The lab situation could have been stressful for the patients, which suggests that there should be a much larger subject pool before more exact conclusions can be drawn.

Researchers Study the Effects of Psilocybin in Magic Mushrooms on Brain Activity

January 24, 2012

Science

A recent study shows how psilocybin, the active ingredient in magic mushrooms, effects brain activity. 30 healthy volunteers underwent MRIs while having psilocybin in their blood and researchers found that psilocybin actually caused activity to decrease in the medial prefrontal cortex, the posterior cingulate cortex, reduced blood flow in the hypothalamus, while participants recalled their recollections as being more vivid after taking psilocybin compared with a placebo.
Brain scans of people under the influence of the psilocybin, the active ingredient in magic mushrooms, have given scientists the most detailed picture to date of how psychedelic drugs work. The findings of two studies being published in scientific journals this week identify areas of the brain where activity is suppressed by psilocybin and suggest that it helps people to experience memories more vividly.
In the first study, published today in Proceedings of the National Academy of Sciences (PNAS), 30 healthy volunteers had psilocybin infused into their blood while inside magnetic resonance imaging (MRI) scanners, which measure changes in brain activity. The scans showed that activity decreased in “hub” regions of the brain – areas that are especially well-connected with other areas.
The second study, due to be published online by the British Journal of Psychiatry on Thursday, found that psilocybin enhanced volunteers’ recollections of personal memories, which the researchers suggest could make it useful as an adjunct to psychotherapy.
Professor David Nutt, from the Department of Medicine at Imperial College London, the senior author of both studies, said: “Psychedelics are thought of as ‘mind-expanding’ drugs so it has commonly been assumed that they work by increasing brain activity, but surprisingly, we found that psilocybin actually caused activity to decrease in areas that have the densest connections with other areas. These hubs constrain our experience of the world and keep it orderly. We now know that deactivating these regions leads to a state in which the world is experienced as strange.”
The intensity of the effects reported by the participants, including visions of geometric patterns, unusual bodily sensations and altered sense of space and time, correlated with a decrease in oxygenation and blood flow in certain parts of the brain.
The function of these areas, the medial prefrontal cortex (mPFC) and the posterior cingulate cortex (PCC), is the subject of debate among neuroscientists, but the PCC is proposed to have a role in consciousness and self-identity. The mPFC is known to be hyperactive in depression, so psilocybin’s action on this area could be responsible for some antidepressant effects that have been reported. Similarly, psilocybin reduced blood flow in the hypothalamus, where blood flow is increased during cluster headaches, perhaps explaining why some sufferers have said symptoms improved under psilocybin.

Psilocybin decreased brain activity in the medial prefrontal cortex and posterior cingulate cortex.

In the British Journal of Psychiatry study 10 volunteers viewed written cues that prompted them to think about memories associated with strong positive emotions while inside the brain scanner. The participants rated their recollections as being more vivid after taking psilocybin compared with a placebo, and with psilocybin there was increased activity in areas of the brain that process vision and other sensory information.
Participants were also asked to rate changes in their emotional wellbeing two weeks after taking the psilocybin and placebo. Their ratings of memory vividness under the drug showed a significant positive correlation with their wellbeing two weeks afterwards. In a previous study of 12 people in 2011, researchers found that people with anxiety who were given a single psilocybin treatment had decreased depression scores six months later.
Dr Robin Carhart-Harris, from the Department of Medicine at Imperial College London, the first author of both papers, said: “Psilocybin was used extensively in psychotherapy in the 1950s, but the biological rationale for its use has not been properly investigated until now. Our findings support the idea that psilocybin facilitates access to personal memories and emotions.
“Previous studies have suggested that psilocybin can improve people’s sense of emotional wellbeing and even reduce depression in people with anxiety. This is consistent with our finding that psilocybin decreases mPFC activity, as many effective depression treatments do. The effects need to be investigated further, and ours was only a small study, but we are interested in exploring psilocybin’s potential as a therapeutic tool.”
The researchers acknowledged that because the participants in this study had volunteered after having previous experience of psychedelics, they may have held prior assumptions about the drugs which could have contributed to the positive memory rating and the reports of improved wellbeing in the follow-up.
Functional MRI measures brain activity indirectly by mapping blood flow or the oxygen levels in the blood. When an area becomes more active, it uses more glucose, but generates energy in rapid chemical reactions that do not use oxygen. Consequently, blood flow increases but oxygen consumption does not, resulting in a higher concentration of oxygen in blood in the local veins.
In the PNAS study, the volunteers were split into two groups, each studied using a different type of fMRI: 15 were scanned using arterial spin labelling (ASL) perfusion fMRI, which measures blood flow, and 15 using blood-oxygen level-dependent (BOLD) fMRI. The two modalities produced similar results, strongly suggesting that the observed effects were genuine.
The studies were carried out with a Home Office licence for storing and handling a schedule 1 drug and were approved by NHS research ethics committees. All the volunteers were mentally and physically healthy and had taken hal l ucinogenic drugs previously without any adverse response. The research involved scientists from Imperial, the University of Bristol and Cardiff University and was funded by the Beckley Foundation, the Neuropsychoanalysis Foundation, Multidisciplinary Association for Psychedelic Studies, and the Heffter Research Institute.

Researchers Study the Link Between Hyperactivity in the Brain and Depression

February 29, 2012

Biology

Maps showing the difference in the strength of brain connections between depressed subjects (left) and controls (right). Depressed subjects show much stronger connections, as evidenced by red colors in their maps.

Researchers at UCLA have shown that people with depression have increased connections among most brain areas. While studying the functional connections of the brain in 121 adults diagnosed with MDD, they found that the depressed subjects showed increased synchronization across all frequencies of electrical activity, indicating dysfunction in many different brain networks.
Most of us know what it means when it’s said that someone is depressed. But commonly, true clinical depression brings with it a number of other symptoms. These can include anxiety, poor attention and concentration, memory issues, and sleep disturbances.
Traditionally, depression researchers have sought to identify the individual brain areas responsible for causing these symptoms. But the combination of so many symptoms suggested to UCLA researchers that the multiple symptoms of depression may be linked to a malfunction involving brain networks — the connections that link different brain regions.
Now, for the first time, these UCLA researchers have shown that people with depression have increased connections among most brain areas. Indeed, their brains are widely hyperconnected. The report, published this week in the online journal PLoS One, sheds new light on the brain dysfunction that causes depression and its wide array of symptoms.
“The brain must be able to regulate its connections to function properly,” said the study’s first author, Dr. Andrew Leuchter, a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA. “The brain must be able to first synchronize, and then later desynchronize, different areas in order to react, regulate mood, learn and solve problems.”
The depressed brain, Leuchter said, maintains its ability to form functional connections but loses the ability to turn these connections off.
“This inability to control how brain areas work together may help explain some of the symptoms in depression,” he said.
In the study, the largest of its kind, the researchers studied the functional connections of the brain in 121 adults diagnosed with major depressive disorder, or MDD. They measured the synchronization of electrical signals from the brain — brain waves — to study networks among the different brain regions.
While some previous studies have hinted at abnormal patterns of connections in MDD, the UCLA team used a new method called “weighted network analysis” to examine overall brain connections. They found that the depressed subjects showed increased synchronization across all frequencies of electrical activity, indicating dysfunction in many different brain networks.
Brain rhythms in some of these networks regulate the release of serotonin and other brain chemicals that help control mood, said Leuchter, who is also the director of UCLA’s Laboratory of Brain, Behavior, and Pharmacology and chair of the UCLA Academic Senate.
“The area of the brain that showed the greatest degree of abnormal connections was the prefrontal cortex, which is heavily involved in regulating mood and solving problems,” he said. “When brain systems lose their flexibility in controlling connections, they may not be able to adapt to change.
“So an important question is, to what extent do abnormal rhythms drive the abnormal brain chemistry that we see in depression? We have known for some time that antidepressant medications alter the electrical rhythms of the brain at the same time that levels of brain chemicals like serotonin are changing. It is possible that a primary effect of antidepressant treatment is to ‘repair’ the brain’s electrical connections and that normalizing brain connectivity is a key step in recovery from depression. That will be the next step in our research.”
Other authors of the study include Dr. Ian A. Cook, Aimee M. Hunter, Chaochao Cai and Steve Horvath, all of UCLA. Funding for the study was provided by the National Institutes of Health, Lilly Research Laboratories and Pfizer Pharmaceuticals. The authors report no conflict of interest.

GATA1 Plays a Role in the Loss of Connections between Neurons and in Symptoms of Depression

August 13, 2012

Biology

Expression of a single gene dramatically decreases synaptic connections between brain cells. Yale scientists believe this may explain why people suffering from chronic stress and depression suffer loss of brain volume.

A new study by Yale University scientists found that GATA1 represses the expression of several genes that are necessary for the formation of synaptic connections between brain cells and that GATA1 may play a role in symptoms of depression.
Major depression or chronic stress can cause the loss of brain volume, a condition that contributes to both emotional and cognitive impairment. Now a team of researchers led by Yale scientists has discovered one reason why this occurs — a single genetic switch that triggers loss of brain connections in humans and depression in animal models.
The findings, reported in the Aug. 12 issue of the journal Nature Medicine, show that the genetic switch known as a transcription factor represses the expression of several genes that are necessary for the formation of synaptic connections between brain cells, which in turn could contribute to loss of brain mass in the prefrontal cortex.
“We wanted to test the idea that stress causes a loss of brain synapses in humans,” said senior author Ronald Duman, the Elizabeth Mears and House Jameson Professor of Psychiatry and professor of neurobiology and of pharmacology. “We show that circuits normally involved in emotion, as well as cognition, are disrupted when this single transcription factor is activated.”
The research team analyzed tissue of depressed and non-depressed patients donated from a brain bank and looked for different patterns of gene activation. The brains of patients who had been depressed exhibited lower levels of expression in genes that are required for the function and structure of brain synapses. Lead author and postdoctoral researcher H.J. Kang discovered that at least five of these genes could be regulated by a single transcription factor called GATA1. When the transcription factor was activated, rodents exhibited depressive-like symptoms, suggesting GATA1 plays a role not only in the loss of connections between neurons but also in symptoms of depression.
Duman theorizes that genetic variations in GATA1 may one day help identify people at high risk for major depression or sensitivity to stress.
“We hope that by enhancing synaptic connections, either with novel medications or behavioral therapy, we can develop more effective antidepressant therapies,” Duman said.
The study was funded by the National Institutes of Health and the Connecticut Department of Mental Health and Addiction Services.
Other Yale authors of the paper are Bhavya Voleti, Pawel Licznerski, Ashley Lepack, and Mounira Banasr.

Synchronized Brain Oscillations Crucial for Short-Term Memory

Neuroscientists Discover that Drosophila Orb2 Plays Role in Long-Term Memory

January 27, 2012

Biology

Upon stimulation, Orb2 (shown in yellow) forms amyloid-like oligomers (shown in red), which are an essential ingredient for the formation of long-term memory.

While studying fruit flies, neuroscientists at the Stowers Institute for Medical Research discovered a major clue in how synapses stay strong and keep long-term memories alive. Their research hints that oligomers play a larger role in the brain than previously thought and that self-sustaining populations of oligomers located at synapses may be the key to long-term memory. The scientists hope that their findings help future researchers further understand disease-causing oligomers like Alzheimer’s and Parkinson’s disease.
KANSAS CITY, MO – Memories in our brains are maintained by connections between neurons called “synapses”. But how do these synapses stay strong and keep memories alive for decades? Neuroscientists at the Stowers Institute for Medical Research have discovered a major clue from a study in fruit flies: Hardy, self-copying clusters or oligomers of a synapse protein are an essential ingredient for the formation of long-term memory.
The finding supports a surprising new theory about memory, and may have a profound impact on explaining other oligomer-linked functions and diseases in the brain, including Alzheimer’s disease and prion diseases.
“Self-sustaining populations of oligomers located at synapses may be the key to the long-term synaptic changes that underlie memory; in fact, our finding hints that oligomers play a wider role in the brain than has been thought,” says Kausik Si, Ph.D., an associate investigator at the Stowers Institute, and senior author of the new study, which is published in the January 27, 2012 online issue of the journal Cell.
Si’s investigations in this area began nearly a decade ago during his doctoral research in the Columbia University laboratory of Nobel-winning neuroscientist Eric Kandel. He found that in the sea slug Aplysia californica, which has long been favored by neuroscientists for memory experiments because of its large, easily-studied neurons, a synapse-maintenance protein known as CPEB (Cytoplasmic Polyadenylation Element Binding protein) has an unexpected property.
A portion of the structure is self-complementary and—much like empty egg cartons—can easily stack up with other copies of itself. CPEB thus exists in neurons partly in the form of oligomers, which increase in number when neuronal synapses strengthen. These oligomers have a hardy resistance to ordinary solvents, and within neurons may be much more stable than single-copy “monomers” of CPEB. They also seem to actively sustain their population by serving as templates for the formation of new oligomers from free monomers in the vicinity.
CPEB-like proteins exist in all animals, and in brain cells they play a key role in maintaining the production of other synapse-strengthening proteins. Studies by Si and others in the past few years have hinted that CPEB’s tendency to oligomerize is not merely incidental, but is indeed essential to its ability to stabilize longer-term memory. “What we’ve lacked till now are experiments showing this conclusively,” Si says.
In the new study, Si and his colleagues examined a Drosophila fruit fly CPEB protein known as Orb2. Like its counterpart in Aplysia, it forms oligomers within neurons. “We found that these Orb2 oligomers become more numerous in neurons whose synapses are stimulated, and that this increase in oligomers happens near synapses,” says lead author Amitabha Majumdar, Ph.D., a postdoctoral researcher in Si’s lab.
The key was to show that the disruption of Orb2 oligomerization on its own impairs Orb2’s function in stabilizing memory. Majumdar was able to do this by generating an Orb2 mutant that lacks the normal ability to oligomerize yet maintains a near-normal concentration in neurons. Fruit flies carrying this mutant form of Orb2 lost their ability to form long-term memories. “For the first 24 hours after a memory-forming stimulus, the memory was there, but by 48 hours it was gone, whereas in flies with normal Orb2 the memory persisted,” Majumdar says.
Si and his team are now following up with experiments to determine for how long Orb2 oligomers are needed to keep a memory alive. “We suspect that they need to be continuously present, because they are self-sustaining in a way that Orb2 monomers are not,” says Si.
The team’s research also suggests some intriguing possibilities for other areas of neuroscience. This study revealed that Orb2 proteins in the Drosophila nervous system come in a rare, highly oligomerization-prone form (Orb2A) and a much more common, much less oligomerization-prone form (Orb2B). “The rare form seems to be the one that is regulated, and it seems to act like a seed for the initial oligomerization, which pulls in copies of the more abundant form,” Si says. “This may turn out to be a basic pattern for functional oligomers.”
The findings may help scientists understand disease-causing oligomers too. Alzheimer’s, Parkinson’s and Huntington’s disease, as well as prion diseases such as Creutzfeldt-Jakob disease, all involve the spread in the brain of apparently toxic oligomers of various proteins. One such protein, strongly implicated in Alzheimer’s disease, is amyloid beta; like Orb2 it comes in two forms, the highly oligomerizing amyloid-beta-42 and the relatively inert amyloid-beta-40. Si’s work hints at the possibility that oligomer-linked diseases are relatively common in the brain because the brain evolved to be relatively hospitable to CPEB proteins and other functional oligomers, and thus has fewer mechanisms for keeping rogue oligomers under control.
Other researchers who contributed to the work include Wanda Colón Cesario, Erica White-Grindely, Huoqin Jian, Fangzhen Ren, Mohammed ‘Repon’ Khan, Liying Li, Edward Man-Lik Choi, Kasthuri Kannan, Feng Li, Jay Unruh and Brian Slaughter at the Stowers Institute for Medical Research in Kansas City, Missouri.

Brain Oscillations Reveal We Experience the World in Rapid Snapshots

Synchronized Brain Oscillations Crucial for Short-Term Memory

February 3, 2012

Biology

A monkey has to carry out a classic memory task: the animal is shown two consecutive images and then has to indicate whether the second image was the same as the first one.

Scientists from the Max Planck Institute of Biological Cybernetics are studying how different brain regions cooperate during memory. While testing monkeys with images for visual stimulation, they recorded electrical activity both in a visual area and in the frontal part of the brain. Their research states that brain activity showed strong oscillations in the theta-band and that these oscillations synchronized their activity temporarily.
Holding information within one’s memory for a short while is a seemingly simple and everyday task. We use our short-term memory when remembering a new telephone number if there is nothing to write at hand, or to find the beautiful dress inside the store that we were just admiring in the shopping window. Yet, despite the apparent simplicity of these actions, short-term memory is a complex cognitive act that entails the participation of multiple brain regions. However, whether and how different brain regions cooperate during memory has remained elusive. A group of researchers from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany have now come closer to answering this question. They discovered that oscillations between different brain regions are crucial in visually remembering things over a short period of time.
It has long been known that brain regions in the frontal part of the brain are involved in short-term memory, while processing of visual information occurs primarily at the back of the brain. However, to successfully remember visual information over a short period of time, these distant regions need to coordinate and integrate information.
To better understand how this occurs, scientists from the Max Planck Institute of Biological Cybernetics in the department of Nikos Logothetis recorded electrical activity both in a visual area and in the frontal part of the brain in monkeys. The scientists showed the animals identical or different images within short intervals while recording their brain activity. The animals then had to indicate whether the second image was the same as the first one.
The scientists observed that, in each of the two brain regions, brain activity showed strong oscillations in a certain set of frequencies called the theta-band. Importantly, these oscillations did not occur independently of each other, but synchronized their activity temporarily: “It is as if you have two revolving doors in each of the two areas. During working memory, they get in sync, thereby allowing information to pass through them much more efficiently than if they were out of sync,” explains Stefanie Liebe, the first author of the study, conducted in the team of Gregor Rainer in cooperation with Gregor Hörzer from the Technical University Graz. The more synchronized the activity was, the better could the animals remember the initial image. Thus, the authors were able to establish a direct relationship between what they observed in the brain and the performance of the animal.

In each of the two brain regions (IPF and V4) brain activity shows strong oscillations in a certain set of frequencies called the theta-band.

The study highlights how synchronized brain oscillations are important for the communication and interaction of different brain regions. Almost all multi-faceted cognitive acts, such as visual recognition, arise from a complex interplay of specialized and distributed neural networks. How relationships between such distributed sites are established and how they contribute to represent and communicate information about external and internal events in order to attain a coherent percept or memory is still poorly understood.