Johns Hopkins researchers believe they may have discovered an explanation for the sleepless nights associated with restless legs syndrome (RLS), a symptom that persists even when the disruptive, overwhelming nocturnal urge to move the legs is treated successfully with medication.
Neurologists have long believed RLS is related to a dysfunction in the way the brain uses the neurotransmitter dopamine, a chemical used by brain cells to communicate and produce smooth, purposeful muscle activity and movement. Disruption of these neurochemical signals, characteristic of Parkinson's disease, frequently results in involuntary movements. Drugs that increase dopamine levels are mainstay treatments for RLS, but studies have shown they don't significantly improve sleep. An estimated 5 percent of the U.S. population has RLS.
The small new study, headed by Richard P. Allen, Ph.D., an associate professor of neurology at the Johns Hopkins University School of Medicine, used MRI to image the brain and found glutamate ? a neurotransmitter involved in arousal ? in abnormally high levels in people with RLS. The more glutamate the researchers found in the brains of those with RLS, the worse their sleep.
The findings are published in the May issue of the journalNeurology.
"We may have solved the mystery of why getting rid of patients' urge to move their legs doesn't improve their sleep," Allen says. "We may have been looking at the wrong thing all along, or we may find that both dopamine and glutamate pathways play a role in RLS."
For the study, Allen and his colleagues examined MRI images and recorded glutamate activity in the thalamus, the part of the brain involved with the regulation of consciousness, sleep and alertness. They looked at images of 28 people with RLS and 20 people without. The RLS patients included in the study had symptoms six to seven nights a week persisting for at least six months, with an average of 20 involuntary movements a night or more.
The researchers then conducted two-day sleep studies in the same individuals to measure how much rest each person was getting. In those with RLS, they found that the higher the glutamate level in the thalamus, the less sleep the subject got. They found no such association in the control group without RLS.
Previous studies have shown that even though RLS patients average less than 5.5 hours of sleep per night, they rarely report problems with excessive daytime sleepiness. Allen says the lack of daytime sleepiness is likely related to the role of glutamate, too much of which can put the brain in a state of hyperarousal ? day or night.
If confirmed, the study's results may change the way RLS is treated, Allen says, potentially erasing the sleepless nights that are the worst side effect of the condition. Dopamine-related drugs currently used in RLS do work, but many patients eventually lose the drug benefit and require ever higher doses. When the doses get too high, the medication actually can make the symptoms much worse than before treatment. Scientists don't fully understand why drugs that increase the amount of dopamine in the brain would work to calm the uncontrollable leg movement of RLS.
Allen says there are already drugs on the market, such as the anticonvulsive gabapentin enacarbil, that can reduce glutamate levels in the brain, but they have not been given as a first-line treatment for RLS patients.
RLS wreaks havoc on sleep because lying down and trying to relax activates the symptoms. Most people with RLS have difficulty falling asleep and staying asleep. Only getting up and moving around typically relieves the discomfort. The sensations range in severity from uncomfortable to irritating to painful.
"It's exciting to see something totally new in the field ? something that really makes sense for the biology of arousal and sleep," Allen says.
As more is understood about this neurobiology, the findings may not only apply to RLS, he says, but also to some forms of insomnia.
Thanks to Johns Hopkins Medicine for this article.
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Contact: Andreas Wallraff andreas.wallraff@phys.ethz.ch 41-446-337-563 ETH Zurich
Quantum mechanics, famously, is full of effects that defy our basic intuition. A fine example is the Hong-Ou-Mandel effect, which occurs when two light quanta (or, photons) arrive simultaneously at a so-called beam splitter. As its name implies, a beam splitter is a device that splits one beam of light into two, by transmitting one half of the impinging light and reflecting the other half. For a single quantum of light, a photon, this means that it has a 50-percent chance to appear on either side of the device. But when two photons arrive at the same time at the splitter, something unexpected happens: The photons then always emerge as a pair on the same side of the beam splitter, either both on one side or both on the other side. Never do the two photons exit on different sides.
This counterintuitive effect has been first demonstrated in 1987 by Chung K. Hong, Zhe-Yu Ou and Leonard Mandel using laser light. The experiment has been repeated many times since, but all of these demonstrations use photons in the optical range (which is the frequency range of visible light). Andreas Wallraff, a professor at the Department of Physics, and his co-workers now break out of this regime and demonstrate for the first time the Hong-Ou-Mandel effect for microwave radiation, at frequencies around 100'000 times below those of a typical laser. Even if there is no fundamental reason to believe that quantum theory would make a distinction between "microwave photons" and "optical photons", this demonstration puts this equivalence across a huge frequency range on a firm experimental footing. Moreover, the lower frequency of the microwave photons enabled a more complete characterization of the effect than has been able so far with optical photons, opening up new possibilities to characterize radiation sources. Finally, the new experiment highlights how quantum optical effects can be exploited in experiments with microwave sources, which may lead to practical applications of "microwave optics".
Microwaves bit by bit
Wallraff and his team used microwaves whose frequency is comparable to that of a common microwave oven. Their source of microwave radiation, however, couldn't have been more different from a household device. The scientists use microfabricated millimeter-sized circuits for generating microwaves that come in single photons. "We can generate individual microwave photons on demand, whenever we need one ," says Christopher Eichler, scientist in the Wallraff group. This is something that is not easily achieved with single-photon sources in the optical regime. Whereas a laser can be conveniently turned on and off, optical single-photon sources typically involve intricate processes that are much harder to control. The microwave sources have also the advantage that their frequencies can be accurately tuned, such that two independent devices produce photons at the exact same frequency. This is a prerequisite for observing the Hong-Ou-Mandel effect.
In the experiment of Wallraff and his group, the microwave photons indeed displayed the counterintuitive behavior predicted by theory. Whenever two photons reached the beam splitter at the same time, they left it in pairs. But the experiment is more than simply a repetition of the optics experiment at microwave frequencies. "As the frequency of microwave radiation is much lower than that of visible light, we were able to fully characterize the effect in all its facets. For example, we can vary the degree of how distinguishable the two photons are and can, therefore, finely control the appearance and disappearance of the effect," explains Christian Lang, a PhD student in the group of Wallraff and first author of the study. "I think it's fair to say that we have produced the so far most complete characterization of the Hong-Ou-Mandel effect," adds Wallraff. "As such, we have now an analytical tool to study microwave radiation in the quantum regime. This may be helpful to characterize non-conventional microwave sources, which are used in several quantum experiments."
Microwaves do light work
Beyond these more fundamental aspects, the findings of the ETH physicists may open up new perspectives for practical applications, too. Historically, the Hong-Ou-Mandel effect has been so important as it was one of the earliest experiments that showed how quantum mechanical effects make light do things that cannot be explained within the framework of classical physics. This then led to theoretical and experimental work on how quantum mechanics can help in computation and communication.
The new work, which shows one of the quintessential quantum optical effects with microwave photons, can be seen as a first step towards translating these findings into the regime of microwaves, which may offer unique advantages concerning how photons can be generated, manipulated, and detected. "In the longer run, this may lead to novel forms of quantum communication and quantum information processing," says Wallraff.
###
Bibliography
Lang C, Eichler C, Steffen L, Fink JM, Woolley MJ, Blais A, Wallraff A: Correlations, indistinguishability and entanglement in Hong-Ou-Mandel experiments at microwave frequencies. Nature Physics, 2013, doi: 10.1038/nphys2612
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Contact: Andreas Wallraff andreas.wallraff@phys.ethz.ch 41-446-337-563 ETH Zurich
Quantum mechanics, famously, is full of effects that defy our basic intuition. A fine example is the Hong-Ou-Mandel effect, which occurs when two light quanta (or, photons) arrive simultaneously at a so-called beam splitter. As its name implies, a beam splitter is a device that splits one beam of light into two, by transmitting one half of the impinging light and reflecting the other half. For a single quantum of light, a photon, this means that it has a 50-percent chance to appear on either side of the device. But when two photons arrive at the same time at the splitter, something unexpected happens: The photons then always emerge as a pair on the same side of the beam splitter, either both on one side or both on the other side. Never do the two photons exit on different sides.
This counterintuitive effect has been first demonstrated in 1987 by Chung K. Hong, Zhe-Yu Ou and Leonard Mandel using laser light. The experiment has been repeated many times since, but all of these demonstrations use photons in the optical range (which is the frequency range of visible light). Andreas Wallraff, a professor at the Department of Physics, and his co-workers now break out of this regime and demonstrate for the first time the Hong-Ou-Mandel effect for microwave radiation, at frequencies around 100'000 times below those of a typical laser. Even if there is no fundamental reason to believe that quantum theory would make a distinction between "microwave photons" and "optical photons", this demonstration puts this equivalence across a huge frequency range on a firm experimental footing. Moreover, the lower frequency of the microwave photons enabled a more complete characterization of the effect than has been able so far with optical photons, opening up new possibilities to characterize radiation sources. Finally, the new experiment highlights how quantum optical effects can be exploited in experiments with microwave sources, which may lead to practical applications of "microwave optics".
Microwaves bit by bit
Wallraff and his team used microwaves whose frequency is comparable to that of a common microwave oven. Their source of microwave radiation, however, couldn't have been more different from a household device. The scientists use microfabricated millimeter-sized circuits for generating microwaves that come in single photons. "We can generate individual microwave photons on demand, whenever we need one ," says Christopher Eichler, scientist in the Wallraff group. This is something that is not easily achieved with single-photon sources in the optical regime. Whereas a laser can be conveniently turned on and off, optical single-photon sources typically involve intricate processes that are much harder to control. The microwave sources have also the advantage that their frequencies can be accurately tuned, such that two independent devices produce photons at the exact same frequency. This is a prerequisite for observing the Hong-Ou-Mandel effect.
In the experiment of Wallraff and his group, the microwave photons indeed displayed the counterintuitive behavior predicted by theory. Whenever two photons reached the beam splitter at the same time, they left it in pairs. But the experiment is more than simply a repetition of the optics experiment at microwave frequencies. "As the frequency of microwave radiation is much lower than that of visible light, we were able to fully characterize the effect in all its facets. For example, we can vary the degree of how distinguishable the two photons are and can, therefore, finely control the appearance and disappearance of the effect," explains Christian Lang, a PhD student in the group of Wallraff and first author of the study. "I think it's fair to say that we have produced the so far most complete characterization of the Hong-Ou-Mandel effect," adds Wallraff. "As such, we have now an analytical tool to study microwave radiation in the quantum regime. This may be helpful to characterize non-conventional microwave sources, which are used in several quantum experiments."
Microwaves do light work
Beyond these more fundamental aspects, the findings of the ETH physicists may open up new perspectives for practical applications, too. Historically, the Hong-Ou-Mandel effect has been so important as it was one of the earliest experiments that showed how quantum mechanical effects make light do things that cannot be explained within the framework of classical physics. This then led to theoretical and experimental work on how quantum mechanics can help in computation and communication.
The new work, which shows one of the quintessential quantum optical effects with microwave photons, can be seen as a first step towards translating these findings into the regime of microwaves, which may offer unique advantages concerning how photons can be generated, manipulated, and detected. "In the longer run, this may lead to novel forms of quantum communication and quantum information processing," says Wallraff.
###
Bibliography
Lang C, Eichler C, Steffen L, Fink JM, Woolley MJ, Blais A, Wallraff A: Correlations, indistinguishability and entanglement in Hong-Ou-Mandel experiments at microwave frequencies. Nature Physics, 2013, doi: 10.1038/nphys2612
[ | E-mail | Share ]
?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Nick Porto and his partner Kevin Atkins were attacked near Madison Square Garden on Sunday after they had enjoyed an afternoon brunch, DNA Info's Matthew Katz reports:
The pair were assaulted on Eighth Avenue, between West 34th and West 35th Street about 5 p.m., cops said ? as the Indiana Pacers played the Knicks on Sunday.
Police said could not say whether the attack was a hate crime, as it was still under investigation, but Porto, who was left with a broken nose and severe headaches, said there was no doubt in his mind...
...Porto said that he and Atkins, 22, were walking arm-in-arm down Eighth Avenue after a leisurely brunch when a group of men he said were in their early-to-mid 20s and wearing Knicks jerseys started shouting slurs at the couple.
"They called us f----ts," said Porto, a clothing designer. "They made fun of my jeans ? I made the jeans myself, for that day."
When Porto turned around asked why they were shouting at him, the group of men knocked the pair to the ground and began to violently kick and punch them, he said.
Their attackers are unlikely to be identified, police say, as there were so many people in the area wearing Knicks jerseys. Atkins suffered a broken right wrist and lost his bag with iPad and cell phone in the attack.
LOS ANGELES (TheWrap.com) - Bad boys, bad boys, whatcha gonna do? Move to Spike TV, apparently.
Reality TV institution "Cops" is pulling up stakes and moving to Spike TV after 25 seasons on Fox, Spike TV president Kevin Kay said Monday. New episodes of "Cops" will begin airing in September, in the same Saturdays at 8 p.m. timeslot where it has enthralled dateless schadenfreude junkies for more than two decades.
In addition to airing new episodes of "Cops," Spike TV will also have access to a portion of the series' 900-episode library.
"After 25 seasons with Fox, we are delighted to find our new home with the Spike family where we previously aired 'Undercover Stings,'" "Cops" creator John Langley said. "And we are doubly pleased that our 'Cops' timeslot remains Saturday nights for our fans. It may be bold to say, but we are looking for yet another record-breaking run with Spike!"
Admit it; you're already humming the theme song, aren't you?
The mayor of Boston says it c appears the two suspects in Monday's Boston Marathon bombing acted alone.
"All of the information that I have they acted alone," Thomas Menino said during an appearance on ABC's "This Week with George Stephanopoulos" Sunday.
However, he added that it was not clear if they would be able to question the suspects about the possibility of outside help.
"The older brother's dead now. We have the second one at Beth Israel Hospital in very serious condition," he said "And we don't know if we'll ever be able to question the individual."
So far the FBI has only named two people in relation to the attack. Both suspects,?Dzhokhar and Tamerlan Tsarnaev, had family ties to Chechnya, an area of Russia known for Islamic insurgency. The older suspect, Tamerlan, took a six-month-long trip to nearby Dagestan last year that is being investigated.
However, no other groups or individuals have been linked to Monday's bombing. A website affiliated with rebels from the North Caucasus region has disavowed the attack with a note saying "Caucasus fighters are not waging any military activities against the United States of America."
Menino said that another individual was taken into custody after the discovery of a pipe bomb, but this was not related to Monday's bombing.
Alongside its developer model, HTC now has an unlocked One for the rest of us. The fetching 4.7-inch 1080p device is in stock at HTC's US store with 32GB of storage and the same powerhouse specs we saw earlier: 1.7Ghz quad-core CPU, 2GB of RAM, 4-megapixel "UltraPixel" cam and Android 4.1.2 with Sense 5. You'll also get a SIM-unlocked model, but unlike the 64GB equipped, $650 developer edition, it won't come with a liberated bootloader -- though it'll cost a touch less at $575. So, if you've been biding your time for a carrier-free version of the svelte aluminum-bodied handset, you can place your order at the source.'s
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The pair were assaulted on Eighth Avenue, between West 34th and West 35th Street about 5 p.m., cops said ? as the Indiana Pacers played the Knicks on Sunday.
