Di seguito gli interventi pubblicati in questa sezione, in ordine cronologico.
Con il decollo avvenuto poco tempo fa della navetta Endeavour, l’era degli Shuttle volge al termine e con la missione STS 135, la cui partenza è prevista per l’inizio di luglio, il Programma Shuttle della NASA sarà definitivamente concluso.
(© NASA/Dimitri Gerondidakis)
Quali sono i motivi che hanno decretato il pensionamento dei gloriosi velivoli spaziali? Da cosa saranno sostituiti? Che ne sarà della Stazione Spaziale Internazionale e dei suoi occupanti? E quale sarà il futuro dell’esplorazione del cosmo? Ve lo spieghiamo in 7 domande e risposte.
1) Perchè gli Shuttle vengono dismessi?
Le navicelle Shuttle hanno costi di missione e manutenzione che crescono con il passare degli anni. Sono in servizio dal 1981 e il loro compito, cioè la costruzione della ISS, è praticamente terminato. La NASA vuole quindi utilizzare le risorse assorbite dal Programma Shuttle in qualcosa di nuovo.
L'idea di pensionare gli Shuttle non è comunque nuova: già nel 2003 la commissione d’inchiesta sull’incidente del Columbia concludeva il suo rapporto con la frase "È nell’interesse del paese rimpiazzare gli Shuttle il prima possibile"
2) Chi ha deciso di fermare gli Shuttle?
La decisione fu presa dal Presidente degli Stati Uniti George Bush nel 2004. Il Presidente chiese alla NASA di sviluppare un nuovo programma spaziale che portasse nuovamente l’uomo sulla Luna e magari anche su Marte.
Per raggiungere questi obiettivi l’agenzia spaziale aveva però bisogno di ingenti fondi e sospendendo il programma Shuttle si potevano liberare oltre 4 miliardi di dollari l’anno.
Lo scorso anno il Presidente Obama ha però annullato tutti i progetti lunari per concentrarsi sulla costruzione di un grande razzo in grado di portare l’uomo sugli asteroidi e su Marte.
Il trasporto di materiali e uomini da e verso la Stazione Spaziale Internazionale dovrebbe essere affidato ai vettori russi e alle future compagnie private.
3) Quando terminerà il programma Shuttle?
L’ultimo volo degli Shuttle sarà compiuto dall’Atlantis ed è programmato per luglio: porterà sulla ISS componenti elettronici e pezzi di ricambio.
4) Quali erano gli obiettivi del programma Shuttle?
Questi cargo cosmici avrebbero dovuto permettere voli spaziali sicuri ed economici, e la possibilità di lanci frequenti, addirittura settimanali.
Così non è stato: le navette si sono rivelate costose e insicure. In trent' anni di servizio, i due gravi incidenti che hanno coinvolto le navette Columbia e Challenger hanno causato la morte di 14 astronauti.
Ma gli Shuttle, a metà strada tra un tir spaziale e una gru, si sono rivelati il mezzo più idoneo per la messa in orbita e la manutenzione di grandi apparecchiature come il telescopio spaziale Hubble.
5) Che fine faranno le navicelle?
Andranno a vari musei degli States: l’Endeavour verrà esposto al California Space Center di Los Angeles, l’Atlantis rimarrà a disposizione dei visitatori del Kennedy Space Center e il Discovery andrà in un hangar della Smithsonian Institution presso l’aeroporto Dulles di Washington.
L’Enterprise, un prototipo utilizzato per alcuni voli di prova fin dalla fine degli anni ‘70, fa già bella mostra di sè nei locali del New York City's Intrepid Sea, Air and Space Museum
6) E la Stazione Spaziale Internazionale? Che ne sarà?
La ISS continuerà a funzionare almeno fino al 2020. Ora è abbastanza grande da poter ospitare 6 persone e tutti gli esperimenti e le ricerche propedeutici alla conquista di Marte.
Gli astronuauti raggiungeranno la Stazione a bordo delle capsule russe Soyouz affittate dalla NASA per questo scopo, in attesa che gli americani dispongano nuovamente di vettori spaziali propri.
7) Quanto costa mandare un uomo nello spazio?
Con le capsule Soyouz il costo del traporto di un astronauta da e per la Stazione Spaziale Internazionale si aggirerà sui 50 milioni di euro. Una cifra mostruosa, ma comunque inferiore a quella di un volo dello Shuttle. Nei prossimi 2 - 3 anni saranno pronti anche i primi vettori spaziali privati e i costi dei biglietti per la ISS potrebbero scendere.
La NASA infatti, all’inizio del 2011, ha affidato a Space X, Boeing, Blu Origin e Sierra Nevada, una commessa da oltre 200 milioni di euro per la progettazione di un missile e una capsula in grado di portare uomini sulla ISS.
It has long been thought that, even though light has electric and magnetic components, the effects of the magnetic field are so weak that they could effectively be ignored. Now researchers at the University of Michigan (U-M) have discovered that under the right conditions, a light field can generate magnetic effects that are 100 million times stronger than previously expected. The researchers say the discovery paves the way for the creation of an "optical battery" that could harness power from the sun without the use of solar cells.
Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics, and his colleagues found that if light focused to an intensity of 10 million watts per square centimeter (W/cm2) is traveling through a material that does not conduct electricity, such as glass, the light field can generate magnetic effects with the strength equivalent to a strong electric effect.
"This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation," Rand said. "In solar cells, the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source."
William Fisher, a doctoral student in applied physics at U-M, says that a previously undetected brand of "optical rectification" is what makes this possible. In traditional optical rectification, light's electric field causes a pulling apart of the positive and negative charges in a material, which sets up a voltage similar to that in a battery. This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry, but Rand and Fisher found that light's magnetic field can also create optical rectification in other types of materials, under the right circumstances.
"It turns out that the magnetic field starts curving the electrons into a C-shape and they move forward a little each time," Fisher said. "That C-shape of charge motion generates both an electric dipole and a magnetic dipole. If we can set up many of these in a row in a long fiber, we can make a huge voltage and by extracting that voltage, we can use it as a power source."
Although the light must be focused through a non-conductive material to an intensity of 10 million W/cm2, which is much higher than the roughly 0.136 W/cm2 intensity of sunlight on its own, the researchers are looking for new materials that would work at lower intensities.
"In our most recent paper, we show that incoherent light like sunlight is theoretically almost as effective in producing charge separation as laser light is," Fisher said.
The researchers predict that with improved materials, they could achieve 10 percent efficiency, which is comparable to today's commercial-grade solar cells. They add that, because their technique doesn't require the extensive semiconductor processing required for traditional solar cells, it could also make solar power much cheaper.
"All we would need are lenses to focus the light and a fiber to guide it. Glass works for both. It's already made in bulk, and it doesn't require as much processing. Transparent ceramics might be even better," said Fisher.
Over the summer, the researchers will first work on harnessing power with laser light, and then sunlight.
The researcher's paper is titled, "Optically-induced charge separation and terahertz emission in unbiased dielectrics," and the University of Michigan is pursuing a patent for the technology.
Italy is again at a crossroads about freedom and quality of its media. On July 6, Italy's telecommunication regulator, AGCOM, will decide how long will let the public debate about the new enforcement tools to fight copyright infringement the Agency is introducing. The law, introduced by the present government, generally requires AGCOM to adopt anti-piracy tools, but the AGCOM proposal gives the Authority itself the power to remove content from Italian websites or to block access to foreign websites accused by copyright holders to break their rights. There will be no need to go through a regular trial, no judge will be involved in the decision making. Accused sites will have only 5 days to explain their position and their right to defend themselves will be quite limited.
The issue has generated very polarized reactions.
Strong approvers have been some publishers associations such as TV producers (APT), film (ANICA), music (FIMI). But they limit their support to new rules that are able to suppress only those sites that do business selling intellectual property that they don't own, while explicitly excluding from the desired effects of the new regulations all private blogs, sites, platforms, search engines and other operators whose business is not piracy.
Critics include groups like Agora Digitale and Altroconsumo, personalities such as Stefano Rodotà - former European data protection commissioner and very respected jurist - and scholars such as Juan Carlos De Martin - one of Nexa founders and fellow at Harvard's Berkman Center - and many others. They think that the AGCOM proposal is worded in a way that enables the Authority to shut down any site, including those that are not in the piracy business and are focused on gathering and analysing the news, without granting a real right to defense.
In many past cases, copyright trials have shown different controversial interpretations about, for example, the freedom of the press and the fair use of some copyrighted content. For sure, copyright is not always a matter that can be decided through simple administrative solutions. Without recourse to the courts in these matters, unilateral decisions are likely.
In a country that has allowed some of the weirdest irregularities in the media system for a western democracy, with a Prime Minister personally owning three of the seven major national television networks and controlling the three public networks through his political power, the regulation of the internet seems to be a fundamental subject for any local democratic development. The Economist has covered some of the consequences, while showing how television was used by the government to silence the issues at stake in the recent referendums. As a matter of fact, the government has lost those referendums and many experts considered this setback as a victory for new social media and the internet.
There are not many news about this subject in English. Who reads Italian can take a look at Juan Carlos De Martin piece published by la Stampa. AGCOM's head Calabrò's answer. And many other links at the end of previous posts. Vocal opposition to the AGCOM decision is growing on the Italian network: LatoSinistro, EsserePrimisuGoogle, IsolaCassintegrati, ValigiaBlu, DoppioCieco, MatteoPlatone, Ciwati, LucaNicotra, YesPolitica, Semioblog, Gilioli, Nichilista, DamianoZito, Avaaz, MinimaAcademica, PiccoloSocrate, Ilmiopaesealtrove, Pozzallo, Pasteris, Perdukistan, GuidoVetere. And many more...
FIMI (association of music publishers) has circulated a mail about Obama's administration support to AGCOM, quoting this Us document: "The United States encourages Italy to ensure that the AGCOM regulations are swiftly promulgated and implemented, that these regulations create an effective mechanism against copyright piracy over the Internet, and that they address all types of piracy that takes place online."
Source: blog.debiase.com - Author: Luca De Biase (An Italian journalist writes about perspective, a notion that Italy sort of invented and then forgot. Because the future is the consequence of what we do today. Subjects: knowledge economy and happiness, social media and information ecology, value and vision.)
A study of Israeli new spapers indicates that both religious and secular newspapers are using their ability to select and present information to divide groups of Israeli citizens, said Matt Evans, a ssistant professor, political science.
"The media has immense power to influence people by the way they frame information," said Evans. "Instead of working to heal differences, they are actually exacerbating the social cleavages."
Journalists frame information by determining what articles they publish, where articles are placed in the paper and how the articles are written. They can also use photos and artwork to frame the information, said Evans, who reported his findings in the current issue of the Middle East Journal.
Evans said media framing is often unintentional.
"I do not think the media are being used to deliberately divide people," said Evans. "Rather there is a downward spiral as each side makes its case to its core audience."
According to Evans, media framing in Israeli newspapers is largely aimed at separating secular and religious Jewish communities. Newspapers run by the ultra-orthodox Haredim, such as Yated Ne'eman and HaModia, provide more obvious examples of how media framing divides people.
Since most Haredi avoid secular media, the newspapers are the primary news sources for the group's members. However, the Haredi press typically omits stories about religious public officials involved in crimes or scandals. Haredi reporters also use such phrases as "wonderful boys" or "brilliant young men," to sarcastically describe secular political figures.
Secular newspapers use more subtle media framing techniques to divide groups, according to Evans. For example, secular newspapers use pictures of conservatively clad Haredi five times more than moderate modern orthodox community members, even though the majority of orthodox citizens are modern orthodox. Evans said that the portrayal of religious citizens as Haredi plays on fears that orthodox citizens are threatening to exert political influence. Secular citizens fear change in the neighborhood standards, such as closing stores on the Sabbath.
Newspapers are important sources of news in Israel. Most Israelis read two or more newspapers on the weekend and in a 1995 survey on Israeli newspaper readership, 88 percent of the Jewish respondents read a daily paper, according to Evans. Israel is the only country in the Middle East that has a free press, according to the Global Press Freedom Rankings.
Evans said the use of media framing to divide groups is a global problem.
"The power the media is using to divide people isn't just found in Israel, and it's not just being used to exacerbate the differences between secular and religious groups," Evans said. "In the United States, for instance, you can see how MSNBC, on the left, and Fox News, on the right, frame coverage to change how we see Republicans and Democrats."
Provided by Pennsylvania State University.
I risultati di un recente studio condotto tra i ghiacci dell’Antartide attribuiscono un nuovo e inquietante ruolo agli oceani, che per colpa del riscaldamento delle loro acque si trasformerebbero in enormi e potenti amplificatori dell’effetto serra.
Gli oceani catturano circa il 30% della CO2 prodotta dalle attività umane (30 miliardi di tonnellate l’anno secondo l’ONU) e la nascondono nelle loro profondità. Questo sequestro naturale dell’anidride carbonica contribuisce a contenere il surriscaldamento globale del pianeta e i suoi effetti.
Lo stoccaggio oceanico della CO2 non è però permanente: secondo gli studi ha una durata compresa tra i 400 e i 1300 anni, al termine dei quali viene di nuovo rilasciata nell’atmosfera.
Ma qualcosa in questo meccanismo sembra essersi inceppato: il progressivo aumento delle temperature avrebbe infatti velocizzato il processo e gli oceani avrebbero cominciato a rilasciare le loro scorte di CO2 dopo soli 2 secoli, aumentando così la quantità totale di gas serra nell’atmosfera.
Ma quanta fretta, dove corri...
Tas van Ommen della Australian Antarctic Division di Hobart ha analizzato delle bolle di CO2 intrappolate nei ghiacci di Siple e Byrd, nell’Antartico Occidentale, le ha datate e la confrontate con i ati sulle temperature medie di quello stesso periodo.
Lo scienziato ha scoperto che all’aumento delle temperature segue regolarmente un incremento nelle emissioni di CO2 oceanica e che l’intervallo di tempo tra il sequestro e il rilascio del gas sta diventando inferiore ai 200 anni.
Ma in che modo l’aumento delle temperature influenza le emissioni di CO2? "Pensate a una bottiglia di Coca Cola: aumentando la temperatura, l’andiride carbonica disciolta nel liquido sale verso la superficie e fugge" ha spiegato Ommen ai media. Non solo: l’aumento delle temperature favorisce il rimescolamento delle acque profonde e la salita verso la superficie delle bolle di gas.
Ommen ha presentato i dati del suo studio alla conferenza sul clima Greenhouse 2011 che si è tenuta a Cairns, in Australia, nei giorni scorsi ma ha ammesso che prima di poterli applicare alla situazione attuale per trarre conclusioni sull’evoluzione del clima del pianeta occorreranno ancora attente verifiche.
They also believe rescue attempts are futile as billions more euros will be paid to bail out Greece.
A poll by German newspaper, the Frankfurter Allgemeine, found 71 per cent had “doubt,” “no trust” or thought there is “no future” for the euro. Only 19 per cent expressed “confidence” in it.
Sixty eight per cent said they did not think the emergency bail out of Greece would work.
A separate poll last week showed more than half of Germans thought that Greece should be thrown out of the euro.
Rumours are also rife in Germany that Deutsche Mark bank notes are being printed again in preparation for ditching the euro.
It is said Germany’s central bank, the Bundesbank, has been ordered to print marks as part of contingency plans to leave Europe’s single currency.
This would be an extraordinary step for Germany and would deepen the growing divide between Europe’s leading states.
Since its introduction in 1999, the euro has had a tough time trying to win over a sceptical German public, who saw the mark – one of the world’s most stable currencies – as a symbol of post-war prosperity, second only to the US dollar as the reserve option for investors.
Chancellor Angela Merkel now faces her biggest crisis. The opposition is speculating her government may fall as Germans become more vocal in their opposition to bailing out Greece.
If a new development from labs at MIT pans out as expected, someday the entire surface area of a building’s windows could be used to generate electricity — without interfering with the ability to see through them.
Richard Lunt, one of the researchers who developed the new transparent solar cell, demonstrates its transparency using a prototype cell. Photo: Geoffrey Supran
The key technology is a photovoltaic cell based on organic molecules, which harnesses the energy of infrared light while allowing visible light to pass through. Coated onto a pane of standard window glass, it could provide power for lights and other devices, and would lower installation costs by taking advantage of existing window structures.
These days, anywhere from half to two-thirds of the cost of a traditional, thin-film solar-power system comes from those installation costs, and up to half of the cost of the panels themselves is for the glass and structural parts, said Vladimir Bulovi?, professor of electrical engineering in the Department of Electrical Engineering and Computer Science. But the transparent photovoltaic system he developed with Richard Lunt, a postdoctoral researcher in the Research Laboratory of Electronics, could eliminate many of those associated costs, they say.
A paper by Bulovi? and Lunt describing their new system has been published online in the journal Applied Physics Letters, and will appear in a forthcoming issue of the print edition.
Previous attempts to create transparent solar cells have either had extremely low efficiency (less than 1 percent of incoming solar radiation is converted to electricity), or have blocked too much light to be practical for use in windows. But the MIT researchers were able to find a specific chemical formulation for their cells that, when combined with partially infrared-reflective coatings, gives both high visible-light transparency and much better efficiency than earlier versions — comparable to that of non-transparent organic photovoltaic cells.
A prototype of the MIT researchers' transparent solar cell is seen on top of a promotional item for MIT's 150th anniversary celebrations. Photo: Geoffrey Supran
In a new building, or one where windows are being replaced anyway, adding the transparent solar cell material to the glass would be a relatively small incremental cost, since the cost of the glass, frames and installation would all be the same with or without the solar component, the researchers say, although it is too early in the process to be able to estimate actual costs. And with modern double-pane windows, the photovoltaic material could be coated on one of the inner surfaces, where it would be completely protected from weather or window washing. Only wiring connections to the window and a voltage controller would be needed to complete the system in a home.
In addition, much of the cost of existing solar panels comes from the glass substrate that the cells are placed on, and from the handling of that glass in the factory. Again, much of that cost would not apply if the process were made part of an existing window-manufacturing operation. Overall, Bulovi? says, “a large fraction of the cost could be eliminated” compared to today’s solar installations.
This will not be the ultimate solution to all the nation’s energy needs, Bulovi? says, but rather it is part of “a family of solutions” for producing power without greenhouse-gas emissions. “It’s attractive, because it can be added to things already being deployed,” rather than requiring land and infrastructure for a whole new system.
Fine-tuning the cells
The work is still at a very early stage, Bulovi? cautions. So far, they have achieved an efficiency of 1.7 percent in the prototype solar cells, but they expect that with further development they should be able to reach 12 percent, making it comparable to existing commercial solar panels. “It will be a challenge to get there,” Lunt says, “but it’s a question of excitonic engineering,” requiring optimization of the composition and configuration of the photovoltaic materials.
The researchers expect that after further development in the lab followed by work on manufacturability, the technology could become a practical commercial product within a decade. In addition to being suitable for coating directly on glass in the manufacture of new windows, the material might also be coated onto flexible material that could then be rolled onto existing windows, Lunt says.
Using the window surfaces of existing buildings could provide much more surface area for solar power than traditional solar panels, Bulovi? says. In mornings and evenings, with the sun low in the sky, the sides of big-city buildings are brightly illuminated, he says, and that vertical “footprint” of potential light-harvesting area could produce a significant amount of power.
Max Shtein, associate professor of materials science and engineering at the University of Michigan, says, “This work demonstrates a useful effect, and is based on very sound science and engineering.” But he adds that “it is but one of the many other methods by which a similar functionality could be achieved,” and says the biggest uncertainty at this point is that because they are so new, “the lifetime of organic PV cells is a bit of an unknown at this point, though there is some hope.”
In addition, Shtein says, “The potential of this technology is good if projected far into the future,” but only if the efficiency can be improved as the researchers expect it can.
As added benefits, the manufacturing process for the MIT researchers' solar cells could be more environmentally friendly, because it does not require the energy-intensive processes used to create silicon solar cells. The MIT process of fabricating solar cells keeps the glass panes at ordinary room temperature, Bulovi? noted. Installations of the new system would also block much of the heating effect of sunlight streaming through the windows, potentially cutting down on air conditioning needs within a building.
The research was funded by the Center for Excitonics, an Energy Frontier Research Center funded by the U.S. Department of Energy.
For many years the only way to fight fire was water. Come the 20'th century and special foams and powders which are somewhat more effective but are used in a fundamentally similar fashion - hose, bucket or pressurized container and drench. But now a team of Harvard scientists were able to demonstrate a new way of fighting fires - using a powerful blast of electric current.
During a recent meeting of the American Chemical Society the scientists described a way of extinguishing fire using 600-watt amplifier which directs the electrical current into a beam. The scientists went on to demonstrate how they extinguish a foot high flame using the device time and time again from a distance.
How this magic is done is apparently not well understood at this point and several factors might go into play here. However it seems that carbon particles which are created during the combustion process can be easily charged and from this point on they respond to electrical fields in ways which are not fully understood but can cause the flame to lose its stability.
Researchers believe that with further research they can reduce the amount of power needed to perform this kind of trick to several dozen watts and reduce the size of the device to a backpack unit or even a hand held device.
This kind of technology can open a completely new area in firefighting and although it is still many years before we can even dream of extinguishing forest fires with electrical power (if this task is even possible) smaller fires in closed buildings might benefit from such a technology.
Researchers have achieved a breakthrough in quantum communications and computing using a teleporter and a paradoxical cat.
The breakthrough is the first-ever transfer, or teleportation, of a particular complex set of quantum information from one point to another, opening the way for high-speed, high-fidelity transmission of large volumes of information, such as quantum encryption keys, via quantum communications networks.
Beam me up ... the teleporter in the lab of Professor Akira Furusawa at the University of Tokyo
The research was published in the April edition of the journal Science.
Teleportation – the transfer of quantum information from one location to another using normal, "classical" communications - is one of the fundamental quantum communication techniques.
The cat in the equation was not a living, breathing feline but rather "wave packets" of light representing the famous "thought experiment" known as Schrodinger’s Cat. Schrodinger’s Cat was a paradox proposed by early 20th century physicist Erwin Schrodinger to describe the situation in which normal, "classical" objects can exist in a quantum "superposition" - having two states at once.
Professor Elanor Huntington, in the School of Engineering and Information Technology at UNSW's Canberra campus at the Australian Defence Force Academy (ADFA), was part of a team led by University of Tokyo researchers. She said the team’s achievement was another step towards building a super-powerful quantum computer and transmitting quantum information.
"One of the limitations of high-speed quantum communication at present is that some detail is lost during the teleportation process. It’s the Star Trek equivalent of beaming the crew down to a planet and having their organs disappear or materialise in the wrong place. We’re talking about information but the principle is the same – it allows us to guarantee the integrity of transmission.
"Just about any quantum technology relies on quantum teleportation. The value of this discovery is that it allows us, for the first time, to quickly and reliably move quantum information around. This information can be carried by light, and it’s a powerful way to represent and process information. Previous attempts to transmit were either very slow or the information might be changed. This process means we will be able to move blocks of quantum information around within a computer or across a network, just as we do now with existing computer technologies.
"If we can do this, we can do just about any form of communication needed for any quantum technology."
The experiments were conducted on a machine known as "the teleporter" in the laboratory of Professor Akira Furusawa in the Department of Applied Physics in the University of Tokyo.
Professor Huntington, who leads a research program for the Centre for Quantum Computation and Communication, developed the high-speed communication part of the teleporter at UNSW’s Canberra campus with PhD student James Webb.
Scientists have moved a step closer to being able to develop a computer model of the brain after developing a technique to map both the connections and functions of nerve cells in the brain together for the first time.
A new area of research is emerging in the neuroscience known as 'connectomics'. With parallels to genomics, which maps the our genetic make-up, connectomics aims to map the brain's connections (known as 'synapses'). By mapping these connections -- and hence how information flows through the circuits of the brain -- scientists hope to understand how perceptions, sensations and thoughts are generated in the brain and how these functions go wrong in diseases such as Alzheimer's disease, schizophrenia and stroke.
Mapping the brain's connections is no trivial task, however: there are estimated to be one hundred billion nerve cells ('neurons') in the brain, each connected to thousands of other nerve cells -- making an estimated 150 trillion synapses. Dr Tom Mrsic-Flogel, a Wellcome Trust Research Career Development Fellow at UCL (University College London), has been leading a team of researchers trying to make sense of this complexity.
"How do we figure out how the brain's neural circuitry works?" he asks. "We first need to understand the function of each neuron and find out to which other brain cells it connects. If we can find a way of mapping the connections between nerve cells of certain functions, we will then be in a position to begin developing a computer model to explain how the complex dynamics of neural networks generate thoughts, sensations and movements."
Nerve cells in different areas of the brain perform different functions. Dr Mrsic-Flogel and colleagues focus on the visual cortex, which processes information from the eye. For example, some neurons in this part of the brain specialise in detecting the edges in images; some will activate upon detection of a horizontal edge, others by a vertical edge. Higher up in visual hierarchy, some neurons respond to more complex visual features such as faces: lesions to this area of the brain can prevent people from being able to recognise faces, even though they can recognise individual features such as eyes and the nose, as was famously described in the book The Man Who Mistook Wife for a Hat by Oliver Sachs.
In a study published online April 10 in the journal Nature, the team at UCL describe a technique developed in mice which enables them to combine information about the function of neurons together with details of their synaptic connections.
The researchers looked into the visual cortex of the mouse brain, which contains thousands of neurons and millions of different connections. Using high resolution imaging, they were able to detect which of these neurons responded to a particular stimulus, for example a horizontal edge.
Taking a slice of the same tissue, the researchers then applied small currents to a subset of neurons in turn to see which other neurons responded -- and hence which of these were synaptically connected. By repeating this technique many times, the researchers were able to trace the function and connectivity of hundreds of nerve cells in visual cortex.
The study has resolved the debate about whether local connections between neurons are random -- in other words, whether nerve cells connect sporadically, independent of function -- or whether they are ordered, for example constrained by the properties of the neuron in terms of how it responds to particular stimuli. The researchers showed that neurons which responded very similarly to visual stimuli, such as those which respond to edges of the same orientation, tend to connect to each other much more than those that prefer different orientations.
Using this technique, the researchers hope to begin generating a wiring diagram of a brain area with a particular behavioural function, such as the visual cortex. This knowledge is important for understanding the repertoire of computations carried out by neurons embedded in these highly complex circuits. The technique should also help reveal the functional circuit wiring of regions that underpin touch, hearing and movement.
"We are beginning to untangle the complexity of the brain," says Dr Mrsic-Flogel. "Once we understand the function and connectivity of nerve cells spanning different layers of the brain, we can begin to develop a computer simulation of how this remarkable organ works. But it will take many years of concerted efforts amongst scientists and massive computer processing power before it can be realised."
The research was supported by the Wellcome Trust, the European Research Council, the European Molecular Biology Organisation, the Medical Research Council, the Overseas Research Students Award Scheme and UCL.
"The brain is an immensely complex organ and understanding its inner workings is one of science's ultimate goals," says Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust. "This important study presents neuroscientists with one of the key tools that will help them begin to navigate and survey the landscape of the brain."
Source: Science Daily