A Nawaz-Modi smile and wave create a new kind of controversy

UNITED NATIONS: The meeting everybody wanted did not happen. Indian Prime Minister Narendra Modi left for home without meeting his Pakistani counterpart Nawaz Sharif.

The two leaders lived in the same hotel --- the Waldorf Astoria --- during the 70th UN General Assembly. Twice, they shared a room and used the same podium to address a summit meeting but they did not meet or talk.

Like quarrelsome neighbors forced to acknowledge each other, the two prime ministers, however, did wave and smile at each other. This happened at the UN peacekeeping summit on Monday afternoon. But even this half-friendly gesture generated another controversy: who blinked first?

“India wins again. The Pakistani prime minister was the first to wave,” claimed the Indian media while the two leaders were still in the meeting room.

“No, he did not,” shouted a journalist in the Pakistani media room at the nearby Roosevelt Hotel. And then both sides got glued to their TV screens, watching replays in slow motion to claim a point in this game of chicken.

“Does it really matter?” asked Maleeha Lodhi, Pakistan’s ambassador to the United Nations, after a half-hour “who-was-the-first” debate at an evening news briefing. “All that matters is that the two leaders waved and smiled at each other,” said Pakistan’s Foreign Secretary Aizaz Chaudhry.

This is how this ‘non-event’ happened at the Leaders’ Summit on Peacekeeping, hosted jointly by the US, Pakistan and others: Mr. Modi walked into the conference hall first and took his seat on the right side of the horseshoe table there. Mr. Sharif followed and took his seat right across Mr. Modi on the left side of the table. Both pretended not to have noticed each other.

Just minutes before the programme began, Mr. Sharif waved at Mr. Modi. Yes, he was the first to show his positive mindset, persuading the Indian leader to respond.

Mr. Modi smiled back and waved too. After a brief pause, Mr. Modi waved again to Mr. Sharif, who smiled back and nodded his head.

Now, who was the winner? Perhaps none or both, but that was not good enough for the media who continued to debate who won. Apparently handicapped by their over-zealous media, the two leaders avoided further display of affection for each other.

They made no attempt to interact. They entered the room just minutes before the summit began and took their seats. To avoid a face-to-face situation, the two leaders did not walk about to meet or greet others, as some other leaders did.

But they did clap at the end of each other’s speech.

Since Mr. Sharif was a co-host, a fact not mentioned by the Indian media, he shared the table with other hosts, US President Barack Obama, Bangladesh Prime Minister Sheikh Hasina and leaders from Rwanda and Ethiopia.

Mr. Modi sat with UN Secretary General Ban Ki-moon, Japanese Prime Minister Shinzo Abe and leaders from France and Indonesia.

The Indian and Pakistani prime ministers spent about 90 minutes in the conference room and Mr. Modi was the first to leave, immediately after addressing the summit. He did not walk up to any leader to shake hands. Mr. Sharif left the room soon after Mr. Modi.

Mr. Modi flew back to India on Monday night after concluding his two-nation tour of Ireland and the US.

Prime Minister Sharif is still in New York and will return home on Wednesday after addressing the UN General Assembly

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Why Some People Have Dangerous Food Allergies

Reporting their study data Sept. 22 in the journal Immunity, scientists at Cincinnati Children's Hospital Medical Center say their findings in mice should also provide insights into new therapeutic strategies and diagnostics for food allergies and anaphylactic shock triggered by the immune antibody IgE (immunoglobulin E).

The authors report discovery of what they call "IL-9-producing mucosal mast cells" or (MMC9 cells). The cells produce large amounts of an inflammatory immune protein called interlukin 9 (IL-9), which amplifies anaphylactic shock in response to ingested food. Prior to this study, the primary cellular source of IL-9 was unknown, according to the authors.

"Our study suggests that although you need to have some level of IgE to trigger a food allergy response, you also have to produce MMC9 cells to get a severe response and anaphylaxis," says Yui-Hsi Wang, PhD, lead investigator and a researcher in the Division of Allergy and Immunology at Cincinnati Children's. "Without these cells you will not get severe food allergies."

Set off by certain foods like peanuts, shell fish and a host of others, IgE-associated food sensitivity prompts the immune systems of some children to surge out of control. Unless there is immediate medical intervention, this can trigger a molecular chain reaction in the intestines and other organs -- leading to diarrhea, hypothermia, respiratory distress and shock.

About 40 percent of children have some IgE-associated food sensitivity, but only 8 percent of the 40 percent develop the severe food reactions that can lead to anaphylactic shock, according to Wang.

"Unfortunately the best medical intervention for these allergies remains avoiding the foods that cause them," he said. "We don't know why some patients develop such a strong response and why some don't. This is where we as basic scientists are coming in to see if we can use mouse models to learn this, because mice are very much like humans."

Wang and his colleagues suspect that some people are wired genetically to have higher or lower susceptibility to severe IgE-related allergic reactions. Still, it also remains unknown exactly how genetics contributes to these molecular chain reactions.

Just as people with food allergies have different degrees of susceptibility, so do mice. To account for this, the researchers conducted their study in several distinct strains of genetically bred mice. They gave the mice an egg white protein called ovalbumin to trigger allergic reactions and study biological reactions in the animals.

They observed that after allergic sensitization, some mouse strains generated large populations of MMC9 cells while other strains did not. Mice that did not produce MMC9 cells exhibited only minor allergic responses. Mice that produced intestinal MMC9 cells all had severe allergic reactions, regardless of whether they had low or high levels of IgE.

Wang and his colleagues report that production of MMC9 cells required the presence of type-2 CD4+ T helper immune cells and the proteins interlukin-4 and STAT6. By producing significant amounts of IL-9, the MMC9 cells caused mastocytosis and the production of mast cells, which may migrate out of the intestines to other organs as they secrete histamines and other molecules that cause anaphylaxis.

To verify that MMC9 cells were fueling severe allergic reactions in the mice, the researchers treated the mice with an antibody (anti-Fc RImAb), which eliminated the cells and decreased food allergy symptoms. When MMC9 cells were transferred back into the same mice, the animals resumed exhibiting food allergy symptoms.

Researchers next conducted tests to see if their identification of MMC9 cells was relevant to the development of human food allergies. Analyzing small intestine biopsy samples from food allergy patients (who gave authorized consent) the scientists looked for molecular signatures of MMC9 cells. They found significantly increased expression of the Il9 genetic transcript and other related transcripts in the samples of food allergy patients, suggesting a possible connection.

Wang said the researchers are now trying to find the human equivalent (orthologue) of the MMC9 cells they found in their mouse models. One goal the researchers have is to identify that cell and its biological mediators to see if it possible to develop a biomarker that might allow development of a blood test for food allergies. Eventually, Wang said, the team wants to develop a blood test that would allow clinicians to determine which patients are at higher risk for severe food allergies, and to find improved treatments for food allergy.

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Security Tools for Software Developers

"Our work is focused on understanding the developers who are trying to identify security vulnerabilities in their code, and how they use (or don't use) tools that can help them find those vulnerabilities," says Murphy-Hill, an associate professor of computer science at NC State University. "The one thing that ties all of our work together is that we want to help give programmers the best possible tools and help them use those tools effectively."

In the first of three related papers being presented next week at the Symposium on the Foundations of Software Engineering, a team of computer science and psychology researchers from NC State and Microsoft Research surveyed more than 250 developers on their experiences with security tools. The goal was to determine what influences a developer's use of these tools -- and the findings were somewhat surprising.

For one thing, developers who said they worked on products in which security was important were not much more likely to use security tools than other programmers.

Instead, "the two things that were most strongly associated with using security tools were peer influence and corporate culture," Murphy-Hill says. Specifically, people who said they had seen what others do with security tools, and people whose bosses expected them to use security tools, were most likely to take advantage of the tools.

"This research gives software development companies and managers information they can use to effectively influence the adoption of security tools by developers," Murphy-Hill says.

But these tools aren't completely accurate. For example, they can tell programmers there's a problem where no problem actually exists. And the tools aren't always user-friendly. In short, the characteristics of the tools themselves can affect whether programmers choose to use them.

To shed light on how security tools support developers in diagnosing potential vulnerabilities, Murphy-Hill's team and collaborators from the University of North Carolina at Charlotte devised a separate study, effectively asking: do tools give developers the information they need to determine if there's a real problem and how to fix it?

In this study, the researchers gave 10 developers of varying backgrounds a specific security tool and a substantial chunk of open-source code to examine. The code contained known security vulnerabilities, which were identified by the security tool. Each of the study participants was asked to use the tool, inspect the source code, and say whether each security notification from the tool was real and how they would address the vulnerabilities.

"In many cases, the tool presented multiple possible fixes for a problem, but didn't give programmers much information about the relevant advantages and disadvantages of each fix," Murphy-Hill says. "We found that this made it difficult for programmers to select the best course of action."

The tool would also give developers multiple notifications that seemed to be related to each other -- but the notifications didn't give developers information on exactly how the problems related to each other.

"This can be confusing for programmers, and lead to problems if developers don't fully understand how various problems are related to each other or how potential fixes might affect the overall code," Murphy-Hill says.

"More research is needed to really flesh these findings out -- we need to expand this study to incorporate more programmers and more security tools," Murphy-Hill says. "But overall, we're hoping that this and related work can help programmers create more effective tools for use by the software development community."

One concept that Murphy-Hill and colleagues from NC State propose in a third paper is the idea of "bespoke" tools. The basic idea is to create tools that developers use -- including security tools -- that are capable of evolving over time as they are used, adapting to each programmer's particular areas of expertise.

"For example, programmers with expertise in addressing security vulnerabilities won't need a security tool that offers extensive information on all of the potential fixes for a given vulnerability -- wading through that might slow them down," Murphy-Hill says. "So a bespoke tool might learn to offer only basic information about potential fixes for them. But the tool could also recognize that it needs to leave in that additional information for less security-savvy programmers, who may need it to make informed decisions."

These bespoke tools could learn about a programmer's strengths through both the programmer's interactions with the tool and by analyzing the programmer's code itself, Murphy-Hill says.

The Symposium on the Foundations of Software Engineering is being held Aug. 30 to Sept. 4 in Bergamo, Italy. Lead author of "Quantifying Developers' Adoption of Security Tools" is Jim Witschey, a former computer science graduate student at NC State. The paper was co-authored by Olga Zielinska, Allaire Welk, Murphy-Hill, and Chris Mayhorn of NC State and Thomas Zimmerman of Microsoft Research. Lead author of "Questions Developers Ask While Diagnosing Potential Security Vulnerabilities with Static Analysis," is Justin Smith, a Ph.D. student at NC State. The paper was co-authored by Brittany Johnson and Murphy-Hill of NC State and Bill Chu and Heather Richter Lipford of UNC-Charlotte. Johnson is also lead author of "Bespoke Tools: Adapted to the Concepts Developers Know." Co-authors are Rahul Pandita, Murphy-Hill and Sarah Heckman of NC State.

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First optical Rectenna-- Combined Rectifier and Antenna -- Converts light to DC Current

Based on multiwall carbon nanotubes and tiny rectifiers fabricated onto them, the optical rectennas could provide a new technology for photodetectors that would operate without the need for cooling, energy harvesters that would convert waste heat to electricity -- and ultimately for a new way to efficiently capture solar energy.

In the new devices, developed by engineers at the Georgia Institute of Technology, the carbon nanotubes act as antennas to capture light from the sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.

Billions of rectennas in an array can produce significant current, though the efficiency of the devices demonstrated so far remains below one percent. The researchers hope to boost that output through optimization techniques, and believe that a rectenna with commercial potential may be available within a year.

"We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way" said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. "As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture."

The research, supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center and the Army Research Office (ARO), is scheduled to be reported September 28 in the journal Nature Nanotechnology.

Developed in the 1960s and 1970s, rectennas have operated at wavelengths as short as ten microns, but for more than 40 years researchers have been attempting to make devices at optical wavelengths. There were many challenges: making the antennas small enough to couple optical wavelengths, and fabricating a matching rectifier diode small enough and able to operate fast enough to capture the electromagnetic wave oscillations. But the potential of high efficiency and low cost kept scientists working on the technology.

"The physics and the scientific concepts have been out there," said Cola. "Now was the perfect time to try some new things and make a device work, thanks to advances in fabrication technology."

Using metallic multiwall carbon nanotubes and nanoscale fabrication techniques, Cola and collaborators Asha Sharma, Virendra Singh and Thomas Bougher constructed devices that utilize the wave nature of light rather than its particle nature. They also used a long series of tests -- and more than a thousand devices -- to verify measurements of both current and voltage to confirm the existence of rectenna functions that had been predicted theoretically. The devices operated at a range of temperatures from 5 to 77 degrees Celsius.

Fabricating the rectennas begins with growing forests of vertically-aligned carbon nanotubes on a conductive substrate. Using atomic layer chemical vapor deposition, the nanotubes are coated with an aluminum oxide material to insulate them. Finally, physical vapor deposition is used to deposit optically-transparent thin layers of calcium then aluminum metals atop the nanotube forest. The difference of work functions between the nanotubes and the calcium provides a potential of about two electron volts, enough to drive electrons out of the carbon nanotube antennas when they are excited by light.

In operation, oscillating waves of light pass through the transparent calcium-aluminum electrode and interact with the nanotubes. The metal-insulator-metal junctions at the nanotube tips serve as rectifiers switching on and off at femtosecond intervals, allowing electrons generated by the antenna to flow one way into the top electrode. Ultra-low capacitance, on the order of a few attofarads, enables the 10-nanometer diameter diode to operate at these exceptional frequencies.

"A rectenna is basically an antenna coupled to a diode, but when you move into the optical spectrum, that usually means a nanoscale antenna coupled to a metal-insulator-metal diode," Cola explained. "The closer you can get the antenna to the diode, the more efficient it is. So the ideal structure uses the antenna as one of the metals in the diode -- which is the structure we made."

The rectennas fabricated by Cola's group are grown on rigid substrates, but the goal is to grow them on a foil or other material that would produce flexible solar cells or photodetectors.

Cola sees the rectennas built so far as simple proof of principle. He has ideas for how to improve the efficiency by changing the materials, opening the carbon nanotubes to allow multiple conduction channels, and reducing resistance in the structures.

"We think we can reduce the resistance by several orders of magnitude just by improving the fabrication of our device structures," he said. "Based on what others have done and what the theory is showing us, I believe that these devices could get to greater than 40 percent efficiency."

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Tips for Simple Hair Styling at Home

Beauty attracts everybody. Hair is beauty of women, it attracts everybody. But if hair is beautifully pin up they look more beautiful. Healthy hairs are more beautifully styled so special care should be devoted towards your hair in order to style hair properly. Here are some easy, simple and fast tips and tricks for your hair to style them.

About Your Hair Type:

It is most important thing to know about the hair type of your hair. Hair styling depends upon the health of your hair so use the products that are good for your hair. You can determine that what type of hair you are having like thick, medium and fine. Hair can be wavy, straight, curly, and kinky. After determining the texture and type of your hairs choose the products accordingly. A good hair cut will also add beauty to your hair and as well as to your face.

Quick Hairstyles Tips

Quick Hairstyles Tips

Hair Styling Tips:

Twist hair:

Divide the hair into two sections. Twist the hair from one side than from other side and pin up hair with bobby pins.

Double Side braids:

Side braids is simple styling of hair but looks very nice. Braids small section of hair and pin up it at the side. Take another small section of hair from little below than braid it and pin up it with the previous braid.

Simple side braid:

Part hair on one side. Pull hair to one side and braid it. Secure hair band at the end. Braid will ready.

Quick and simple styling:

• After curling your hair part them on both sides. Brush them than put two bobby pins on both side of your hair.

• Part hair in the middle .Divide them in two equal sections. Twist hair from one side than pin up. Repeat this with other side and pin up simple style will be ready.

• Curl your hair. Divide this into equal parts. Twist them and pin it up. Simple but attractive style is ready.

Messy side pony:

Bring hair in front, the small ones. Take rest of hair at one side and tie them with rubber band in the shape of pony. The messier, the better. It will look good.

French braid:

Divide the hair into two sections. French braid the first section. Repeat this to second section also and then pin it up together.

Braid bun:

Braid your straight hairs .Tuck in end and secure with bobby pins.

Low ponytail:

Part the hair in middle. Pull back into low ponytail and secure. It will suit on all faces.

Vintage curls:

These curls are very simple. Divide the hair in to small sections. Curl them until all head is curled. Twist curls together with your fingers. They will look natural and you will look beautiful.

Small twists in to bun:

Start with hair partition twist one back and pin up with the bobby pin. Then pull the rest of your hair into low messy bun .Pull some hairs from the bun to give a messy look, it will look beautiful.

Three mini twists:

Divide hair into three equal sections. Start with the middle section twist it until it coils into tiny bun. Repeat it with other two other section.

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Barcelona Deserve more Credit from Fans

MADRID: Barcelona boss Luis Enrique launched a staunch defense of his players after they came from behind without the injured Lionel Messi to beat Bayer Leverkusen 2-1 on Tuesday.

Goals in the last 10 minutes from Sergi Roberto and Luis Suarez propelled the European champions to the top of Champions League Group F after Kyriakos Papadopoulos had headed the visitors into a deserved half-time lead.

“It was a difficult night. It was our second game without Leo Messi, the second game without our best player, an irreplaceable player, and it is the second game the team has won,” said Enrique.

“I am very happy for what the players have achieved. They turned around a very difficult game. We can be more precise, but no one can say Barca relax and don't give everything.”

Despite Messi's absence, the Camp Nou crowd was less than patient as boos rang out at the half-time whistle.

Enrique pleaded for more understanding from the club's supporters at a difficult time with a host of young players drafted in to cover a mounting injury crisis.

“I think this team deserves more credit for what they have won recently and how they carry themselves.

“They try until the last minute and if then they deserve to be booed then fine, but we are much stronger in the delicate moments if they support us.

“At 2-1 we didn't need their support; we needed it a 0-1.

“I would like the few people that do boo not to do it because we hear them and we need the support of everyone,” pleaded the Barca boss.

Injury toll

On top of Messi and Brazilian international Rafinha, Barca is set to be without Andres Iniesta for a month after he pulled up with a hamstring injury after an hour.

“It is very sad news for us because he is a fundamental player for us as everyone knows,” added Enrique.

“These are hurdles in our way that we have to overcome and I have confidence in the players that will come in.”

A hectic pre-season tour and three early season clashes with Sevilla and Athletic Bilbao in the UEFA and Spanish Super Cup respectively have been blamed for Barca's raft of injuries.

However, defender Javier Mascherano called on those like Roberto and Munir El Haddadi, who made a significant impact from the bench against Leverkusen, to take their chance in the first team.

“Obviously we are in a difficult situation with a number of important players that are injured.

“That is football and that is why we have a squad to keep going in these moments.

“It is not just 11 or 12 players that win competitions, there are reserves behind and now some of those that wouldn't have had so many minutes will get their chance.

“It is an unusual season. You always have these injuries throughout the season, but after the more serious injuries for Rafinha and Leo is it much more worrying that Andres is now injured too.

“Those of us that are fit need to keep going and know that whilst we win games there is less time left until those important players return,” said the Argentine international.

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137 fresh dengue cases in Rawalpindi take total to 934

RAWALPINDI: At least 137 fresh cases of dengue fever were registered on Thursday in three government-run hospitals of Rawalpindi, taking the reported tally of the mosquito-borne viral disease reported within one month to 934.

Out of the 137 cases, 76 were registered at Holy Family Hospital (HFH), 55 at Benazir Bhutto Hospital (BBH) and six at District Headquarters (DHQ) Hospital.

No data is available from private medical facilities in the city.

All the patients at the government-run hospitals arrived from 70 city union councils and 20 wards of Rawalpindi and Chaklala Cantonment Board.

BBH Medical Superintendent Dr. Asif Qadir Mir told Dawn that during the past 24 hours, 55 dengue patients arrived on Thursday while at least 35 had arrived on Wednesday night.

“A total of 90 patients arrived, however 76 patients were tested dengue positive and the report of dengue serology of the remaining patients are awaiting,” said Dr. Tahir Sharif of Holy Family Hospital.

He said that the hospital had sufficient beds to accommodate more patients in the evening while 26 dengue patients were discharged on Thursday after provision of treatment.

A lady died of the disease at the facility on September 26.

“Six new dengue patients were brought to the hospital and total 25 dengue patients admitted in the hospital,” said a doctor at DHQ hospital's dengue ward.

The alarming rise in dengue cases prompted Chief Minister Punjab Shahbaz Sharif to form an inquiry committee yesterday.

The committee will also apprise the Punjab government about the irregularities and negligence of relevant departments in the anti-dengue drive.

According to the report published in Dawn newspaper yesterday, Shahbaz Sharif had asked the provincial chief secretary and adviser on health to stay in the city and supervise the campaign against the disease.

Presiding over a meeting through video link from Lahore, the chief minister reprimanded heads of departments and institutions concerned and officers of the administration for their poor performance.

Meanwhile, the local administration declared 22 union councils of the garrison city as sensitive and initiated a fumigation drive in the city.

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Facebook effect: Research Shows Comments about Candidates have Impact on Potential Voters

That influence occurred even though the research participants weren't Facebook friends or even acquaintances of the commenters. In fact, the commenters -- like the candidate himself -- didn't even exist.

The research team, consisting of faculty and students from the departments of Communication and of Political Science and International Relations, created a Facebook page for a fictitious candidate using general and nonpartisan "information" about him.

Delawareans selected as a test group were sent an online survey, asking them to look at the page and then rate their impressions of the candidate. Some of the recipients saw a page with two fictitious supportive comments, while others saw two challenging comments.

"A social media campaign is practically obligatory for candidates today, and the key to social media is that it's interactive; it's not one-way like traditional political advertising," said Paul R. Brewer, professor of communication and of political science and international relations and director of UD's Center for Political Communication (CPC). "We wanted to test this interactivity between the candidate and citizens."

The research, published in the Journal of Experimental Political Science, found that those who saw positive comments or "likes" had a more favorable perception of the candidate and were more likely to support him, while those who saw the negative comments had more unfavorable perceptions.

Whether the candidate responded to the comments had no effect on how he was perceived.

"This showed that people trust comments from their peers more than they trust self-generated comments from the candidate," Brewer said. "It's the idea that what other people say about you is genuine, perhaps unlike what you say about yourself. So comments from some random person on the Internet do shape citizens' perceptions."

Calling the study a first step in researching the effect of social media interactivity in political campaigns, Brewer said that it may have been easier to influence viewers looking at the "blank slate" of a fictitious candidate rather than at a real candidate with whom they may already be familiar. He also noted that the survey group was asked to look at the Facebook page, while in real campaigns, citizens decide for themselves whether to check out a candidate on social media.

Still, Brewer said, "I was surprised that no one had done this kind of study before, at least not in published research. Campaigns invest heavily in social media, and this is something that will play out in 2016."

Campaigns already sometimes try to influence social media by removing negative comments from their pages or encouraging staffers and supporters to post positive comments. This is nothing new, Brewer said, recalling a pre-social-media campaign in which he worked as an intern and was instructed to write positive letters to the editor at newspapers.

"Candidates have long used carefully orchestrated social cues, from endorsements to photo opportunities to stage-managed public events, in their efforts to persuade voters that they are riding a wave of popular support," the researchers concluded in their journal article. "The increasing use of [social networking sites] by voters provides candidates and other actors with new tools for projecting images of popularity or unpopularity in ways that may carry electoral consequences."

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How the Brain Encodes Time and Place

This circuit, which connects the hippocampus and a region of the cortex known as entorhinal cortex, separates location and timing into two streams of information. The researchers also identified two populations of neurons in the entorhinal cortex that convey this information, dubbed "ocean cells" and "island cells."

Previous models of memory had suggested that the hippocampus, a brain structure critical for memory formation, separates timing and context information. However, the new study shows that this information is split even before it reaches the hippocampus.

"It suggests that there is a dichotomy of function upstream of the hippocampus," says Chen Sun, an MIT graduate student in brain and cognitive sciences and one of the lead authors of the paper, which appears in the Sept. 23 issue of Neuron. "There is one pathway that feeds temporal information into the hippocampus, and another that feeds contextual representations to the hippocampus."

The paper's other lead author is MIT postdoc Takashi Kitamura. The senior author is Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and director of the RIKEN-MIT Center for Neural Circuit Genetics at MIT's Picower Institute for Learning and Memory. Other authors are Picower Institute technical assistant Jared Martin, Stanford University graduate student Lacey Kitch, and Mark Schnitzer, an associate professor of biology and applied physics at Stanford.

When and where

Located just outside the hippocampus, the entorhinal cortex relays sensory information from other cortical areas to the hippocampus, where memories are formed. Tonegawa and colleagues identified island and ocean cells a few years ago, and have been working since then to discover their functions.

In 2014, Tonegawa's lab reported that island cells, which form small clusters surrounded by ocean cells, are needed for the brain to form memories linking two events that occur in rapid succession. In the new Neuron study, the team found that ocean cells are required to create representations of a location where an event took place.

"Ocean cells are important for contextual representations," Sun says. "When you're in the library, when you're crossing the street, when you're on the subway, you have different memories associated with each of these contexts."

To discover these functions, the researchers labeled the two cell populations with a fluorescent molecule that lights up when it binds to calcium -- an indication that the neuron is firing. This allowed them to determine which cells were active during tasks requiring mice to discriminate between two different environments, or to link two events in time.

The researchers also used a technique called optogenetics, which allows them to control neuron activity using light, to investigate how the mice's behavior changed when either island cells or ocean cells were silenced.

When they blocked ocean cell activity, the animals were no longer able to associate a certain environment with fear after receiving a foot shock there. Manipulating the island cells, meanwhile, allowed the researchers to lengthen or shorten the time gap between events that could be linked in the mice's memory.

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