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Mars rover's sampling campaign begins

Science

After months of spaceflight, an 8-minute plunge to the surface of Mars, and weeks of exploration, NASA's Perseverance rover is beginning its primary scientific task: drilling out finger-size cores of martian rock for return to Earth. If all goes well, the first drilling sample will be collected from Jezero crater, a former lakebed, by early August. Perseverance has operated well since its February landing, and it recently tested its rock storage system, using its robotic arm to stow a sampling tube into its guts. There the empty tube was imaged and then sealed for storage. “The great news is that it all worked perfectly,” says Jennifer Trosper, Perseverance's project manager at NASA's Jet Propulsion Laboratory. “We are ready to sample.” Now, 1 kilometer south of its landing site, Perseverance has reached an array of what its operating team calls paver stones—flat, white, dust-coated rocks found throughout much of the floor of Jezero crater. Here, on what is believed to be the most ancient terrain in the crater, nearly 4 billion years old, the team will direct the rover to drill and collect its sample, targeting a rock that is average in chemistry, mineralogy, and texture. The chalk-size core will be stored in an ultraclean metallic tube, one of 38 samples the rover will eventually collect, with about 30 of those likely to be returned to Earth by later missions. It will reside in the rover's belly until it is deposited in a cache on the surface near the crater's rim a year and a half from now. Whether the paver stone landscape was deposited by the lake or formed by volcanic flows isn't clear. But if it is volcanic, it might have trapped radioactive elements that a lab on Earth could analyze to determine accurate dates for the lake's existence. The drill operators don't know what to expect because the rocks are covered with sand grains and pebbles, along with some sort of purplish coating, says Ken Farley, the mission's project scientist and a geologist at the California Institute of Technology. But before drilling into the pavers, the rover will unleash one instrument that could help answer this puzzle: an abrasion bit mounted at the end of its 2-meter-long arm. After grinding into the rock, the arm will blow compressed gas to clear away the grit, giving a clear glimpse of the underlying rock. The rover can then use its arm-mounted camera and laser and x-ray probes to probe its structure and mineralogy. “I'm pretty confident we will be able to answer this question,” Farley says. Perseverance has already spotted other tantalizing sites to explore and sample in Jezero crater. In the ancient delta to its west that is the rover's destination next year, its cameras have revealed distinctive layered deposits that show the lake was high, quiet, and stable for a long time, Farley says. Above those layers lie 1-meter-wide smooth boulders that could only have been carried by floodwater later in the lake's history. This suggests the lake could have seen distinct phases in its life, which fits with a larger picture of the planet's history in which lakes were common billions of years ago, then gave way to periodic floods after the climate cooled, Farley says. A long-lived lake might have also provided the nutrients and habitat to fuel life, says Kennda Lynch, an astrobiologist at the Lunar and Planetary Institute who is unaffiliated with the mission. “This is great. I feel more confident we chose the right place to go.” Samples and measurements from Perseverance's next target, Séítah, a region of sand dunes and ridges to its west that the car-size rover has skirted past, could test that picture. Seen from orbit to be rich in olivine, a volcanic mineral, and carbonates, which can form when olivine is exposed to water and carbon dioxide, Séítah has unexpectedly complex geology, including layered terrain that might preserve signs of past life or patterns of water flow. But the rover can't drive into it without getting stuck in the dunes, so the Perseverance team devised an incursion from above and behind to access its secrets. First, the rover's miniature Ingenuity helicopter, in its ninth flight earlier this month, scouted across Séètah in a 625-meter journey, breaking records for flight duration and speed before landing on the other side of the dunes. The helicopter photographed the intersection of Séètah with the paver unit that Perseverance is now exploring—a boundary that could reveal whether the pavers continue beneath Séitah's dunes, an important fact if a volcanic date is found. And it also scouted fractures that could hold evidence of whether ancient subsurface habitats existed in Jezero. Meanwhile, from afar, Perseverance has spied fine layering in Séítah's ridges, including a prominent 40-meter-tall plateau dubbed Kodiak that, in all likelihood, marks the delta's incursion into the lakebed. Such layers could be caused by mudstones, which smother and preserve life on Earth. But the layers could have a volcanic origin, as well—and so the rover will loop south around Séètah later this year, nudging into a flat space where it can safely sample and tease out that story. Once the Séítah campaign is done, Perseverance will backtrack all the way north to its landing site, “putting the pedal to the metal,” Trosper says. From there it will continue north then west on a safe route to the looming cliff of the main delta—and the life-trapping muds entombed within it.


Human-wildlife conflict under climate change

Science

Human-wildlife conflict—defined here as direct interactions between humans and wildlife with adverse outcomes—costs the global economy billions of dollars annually, threatens human lives and livelihoods, and is a leading cause of biodiversity loss ([ 1 ][1]). These clashes largely stem from the co-occurrence of humans and wildlife seeking limited resources in shared landscapes and often has unforeseen consequences. For example, large carnivore species like leopards may prey upon livestock and disrupt human livelihoods, leading to retaliatory killings that can drive wildlife decline, zoonotic disease outbreaks, and child labor practices ([ 2 ][2]). As dire as these conflicts have been, climate change is intensifying human-wildlife conflict by exacerbating resource scarcity and forcing people and wildlife to share increasingly crowded spaces. Consequently, human-wildlife conflict is rising in frequency and severity, but the complex connections among climate dynamics, ecological dynamics, and social dynamics contributing to the heightened conflict have yet to be fully appreciated. ![Figure][3] Warming temperatures have driven animals to human-dominated areas in search of food. Increased attacks on livestock can spur retaliatory killing of predators. A sheep corral in the Himalayas is covered with wire to protect against attacks from snow leopards. PHOTO: NICK GARBUTT/MINDEN PICTURES Both extreme climate events and directional climate change have the potential to alter the dynamics of human-wildlife conflict. Acute climate events can cause rapid changes in resource availability that drive strong behavioral and spatial responses in animals and people, leading to increased co-occurrence and competition. In terrestrial systems, droughts in particular have intensified some of the most visible conflicts. For example, from 1986 to 1988, a severe drought in India brought about by an extreme El Niño led to a sharp decline in vegetation productivity; loss of food drove elephants to new human-dominated areas, which led to rapid increases in crop damage and fatal attacks on people ([ 3 ][4]). The same drought event in India saw a marked increase in livestock losses to lions, and human fatalities from lion attacks rose by more than 600% in one region to 6.7 deaths per year following the drought ([ 3 ][4]). More recently in 2018, a prolonged drought in Botswana saw some of the highest incidences of livestock depredations by large carnivores on record, compounding drought-induced food and economic insecurity in agricultural and pastoral communities ([ 4 ][5]). Similar connections between climate events and conflicts are occurring in marine systems. For instance, anomalously warm water temperatures off the South African coast drove changes in prey availability that displaced great white sharks into areas of high human use; the increase in spatial overlap between people and sharks led to a nearly fourfold increase in shark attacks within a single year ([ 5 ][6]). A similar increase in spatial overlap that resulted in heightened conflict occurred in 2014 to 2016 off the US West Coast, when an intense marine heat wave drove changes in both large-whale distributions and fisheries management, leading to an unprecedented number of whale entanglements in fishing gear ([ 6 ][7]). Not only did these entanglements cause high rates of whale mortality, but subsequent management restrictions have threatened millions of dollars in lost fishery revenue. Although extreme climate events often create dramatic conflicts, long-term warming is also producing conflicts with interconnected consequences for people and wildlife. In a notable example, over a 30-year period in Canada's Hudson Bay, human–polar bear conflicts involving property damage, life-threatening encounters, or bear killings have more than tripled as sea ice has declined and polar bears have spent more time on land ([ 7 ][8]). In the Himalayas, warming-induced vegetation changes at high elevations have driven the bharal or blue sheep to lower elevations, where they forage on crops, which affects the livelihoods of local subsistence agricultural producers. Simultaneously, the redistribution of bharal has also drawn their primary predator, snow leopards, to lower elevations, leading to increased livestock depredation and retaliatory killing of leopards ([ 8 ][9]). In other examples, crop foraging ([ 9 ][10]), livestock depredation ([ 10 ][11]) or competition ([ 11 ][12]), and human-wildlife encounters ([ 12 ][13]) are inversely correlated with interannual rainfall as a result of reduced food and water availability, and declining rainfall trends in parts of the globe continue to create more frequent and intense conflicts ([ 13 ][14]). Even as climate change restricts resource availability in many contexts, climate-driven expansion of the human footprint further forces people and animals to share spaces and can create new conflicts—for example, agricultural expansion into previously unproductive or inaccessible areas is significantly associated with rises in human-wildlife conflict ([ 9 ][10]). By investigating the interrelated consequences of climate change on wildlife and human populations, we can better anticipate undesired outcomes and identify how human interventions can mitigate cascading ecological and social dynamics. Climate impacts on human-wildlife conflict do not act in isolation—among other factors, socioeconomic drivers such as land-use change and demographic processes such as rising human populations or changes in predator and prey populations play major roles in determining the frequency, scale, and distribution of conflicts ([ 1 ][1]). Thus, illuminating and ultimately addressing the interconnections between climate change and human-wildlife conflict requires a coupled socioecological systems approach, drawing from fields as diverse as ecology, global change biology, human demography, political science, public policy, history, and economics. Although the impact of climate change on human-wildlife conflict has arguably received relatively little research attention, governmental bodies are increasingly recognizing this phenomenon and developing forward-looking policies to explicitly incorporate climate into the management of certain conflicts ([ 3 ][4], [ 4 ][5]). For example, the state of California in the US recently implemented a Risk Assessment and Mitigation Program that assimilates climatic, oceanographic, biological, and economic indices to inform dynamic fisheries management to reduce the risk of whale entanglements ([ 6 ][7]). Knowledge of climate impacts on human-wildlife conflict can also aid long-term planning efforts and public outreach. For instance, livestock compensation programs, one of the most widely implemented tools to mitigate human-carnivore conflict, could plan funding allocations to anticipate higher spending in years with anomalous climate conditions. Furthermore, given early warning from climate predictions or emerging efforts to predict human-wildlife conflicts using artificial intelligence ([ 14 ][15]), governments or nongovernmental organizations can educate and warn the public about possible increased interactions with wildlife ([ 12 ][13]). As climate change continues to drive both increased climate variability and directional change ([ 15 ][16]), climate-driven human-wildlife conflict can be expected to be a recurring challenge. To protect wildlife and humans alike, it is vital that a diverse body of research and institutions considers the role of a changing climate in shaping the complex socioecological dynamics of conflict. 1. [↵][17]1. P. J. Nyhus , Annu. Rev. Environ. Resour. 41, 143 (2016). [OpenUrl][18] 2. [↵][19]1. J. Terborgh, 2. J. A. Estes 1. J. S. Brashares, 2. L. R. Prugh, 3. C. J. Stoner, 4. C. W. Epps , in Trophic Cascades, J. Terborgh, J. A. Estes, Eds. (Island Press, 2010), pp. 221–240. 3. [↵][20]1. J. R. Bhatt, 2. A. Das, 3. K. Shanker , Eds., Biodiversity and Climate Change: An Indian Perspective (Ministry of Environment, Forest and Climate Change, Government of India, New Delhi, 2018), pp. 1–138. 4. [↵][21]Botswana Vulnerability Assessment Committee, (Botswana Ministry of Local Government and Rural Development, 2019); . 5. [↵][22]1. B. K. Chapman, 2. D. McPhee , Ocean Coast. Manage. 133, 72 (2016). [OpenUrl][23] 6. [↵][24]1. J. A. Santora et al ., Nat. Commun. 11, 536 (2020). [OpenUrl][25] 7. [↵][26]1. L. Towns et al ., Polar Biol. 32, 1529 (2009). [OpenUrl][27][CrossRef][28] 8. [↵][29]1. A. Aryal et al ., Theor. Appl. Climatol. 115, 517 (2013). [OpenUrl][30] 9. [↵][31]1. J. M. Mukeka, 2. J. O. Ogutu, 3. E. Kanga, 4. E. Røskaft , Glob. Ecol. Conserv. 18, e00620 (2019). [OpenUrl][32] 10. [↵][33]1. M. Schiess-Meier, 2. S. Ramsauer, 3. T. Gabanapelo, 4. B. Konig , J. Wildl. Manage. 71, 1267 (2007). [OpenUrl][34] 11. [↵][35]1. S. P. Vargas et al ., Oryx 55, 275 (2021). [OpenUrl][36] 12. [↵][37]1. C. S. Zack et al ., Wildl. Soc. Bull. 31, 517 (2003). [OpenUrl][38] 13. [↵][39]1. J. M. Mukeka et al ., Hum. Wildl. Interact. 14, 255 (2020). [OpenUrl][40] 14. [↵][41]1. P. Variyar , Can Artificial Intelligence Predict Human-Wildlife Conflict? (Wildlife Conservation Trust, 2021); [www.wildlifeconservationtrust.org/can-artificial-intelligence-predict-human-wildlife-conflict/][42]. 15. [↵][43]1. D. Coumou, 2. S. Rahmstorf , Nat. Clim. Chang. 2, 491 (2012). [OpenUrl][44] Acknowledgments: I thank K. Gaynor, A. McInturff, E. Pikitch, and J. Samhouri for valuable discussions and comments. [1]: #ref-1 [2]: #ref-2 [3]: pending:yes [4]: #ref-3 [5]: #ref-4 [6]: #ref-5 [7]: #ref-6 [8]: #ref-7 [9]: #ref-8 [10]: #ref-9 [11]: #ref-10 [12]: #ref-11 [13]: #ref-12 [14]: #ref-13 [15]: #ref-14 [16]: #ref-15 [17]: #xref-ref-1-1 "View reference 1 in text" [18]: {openurl}?query=rft.jtitle%253DAnnu.%2BRev.%2BEnviron.%2BResour.%26rft.volume%253D41%26rft.spage%253D143%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [19]: #xref-ref-2-1 "View reference 2 in text" [20]: #xref-ref-3-1 "View reference 3 in text" [21]: #xref-ref-4-1 "View reference 4 in text" [22]: #xref-ref-5-1 "View reference 5 in text" [23]: {openurl}?query=rft.jtitle%253DOcean%2BCoast.%2BManage.%26rft.volume%253D133%26rft.spage%253D72%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [24]: #xref-ref-6-1 "View reference 6 in text" [25]: {openurl}?query=rft.jtitle%253DNat.%2BCommun.%26rft.volume%253D11%26rft.spage%253D536%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [26]: #xref-ref-7-1 "View reference 7 in text" [27]: {openurl}?query=rft.jtitle%253DPolar%2BBiol.%26rft.volume%253D32%26rft.spage%253D1529%26rft_id%253Dinfo%253Adoi%252F10.1007%252Fs00300-009-0653-y%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [28]: /lookup/external-ref?access_num=10.1007/s00300-009-0653-y&link_type=DOI [29]: #xref-ref-8-1 "View reference 8 in text" [30]: {openurl}?query=rft.jtitle%253DTheor.%2BAppl.%2BClimatol.%26rft.volume%253D115%26rft.spage%253D517%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [31]: #xref-ref-9-1 "View reference 9 in text" [32]: {openurl}?query=rft.jtitle%253DGlob.%2BEcol.%2BConserv.%26rft.volume%253D18%26rft.spage%253D00620e%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [33]: #xref-ref-10-1 "View reference 10 in text" [34]: {openurl}?query=rft.jtitle%253DJ.%2BWildl.%2BManage.%26rft.volume%253D71%26rft.spage%253D1267%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [35]: #xref-ref-11-1 "View reference 11 in text" [36]: {openurl}?query=rft.jtitle%253DOryx%26rft.volume%253D55%26rft.spage%253D275%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [37]: #xref-ref-12-1 "View reference 12 in text" [38]: {openurl}?query=rft.jtitle%253DWildl.%2BSoc.%2BBull.%26rft.volume%253D31%26rft.spage%253D517%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [39]: #xref-ref-13-1 "View reference 13 in text" [40]: {openurl}?query=rft.jtitle%253DHum.%2BWildl.%2BInteract.%26rft.volume%253D14%26rft.spage%253D255%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [41]: #xref-ref-14-1 "View reference 14 in text" [42]: http://www.wildlifeconservationtrust.org/can-artificial-intelligence-predict-human-wildlife-conflict/ [43]: #xref-ref-15-1 "View reference 15 in text" [44]: {openurl}?query=rft.jtitle%253DNat.%2BClim.%2BChang.%26rft.volume%253D2%26rft.spage%253D491%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx


Huge protein structure database could transform biology

Science

Earlier this month, two groups unveiled the culmination of years of work by computer scientists, biologists, and physicists: advanced modeling programs that can predict the precise 3D atomic structures of proteins. Last week, the biggest payoff of that work arrived. One team used its newly minted artificial intelligence (AI) programs to solve the structures of 350,000 proteins from humans and 20 model organisms, such as Escherichia coli bacteria, yeast, and fruit flies, all mainstays of biological research. In the coming months, the group says it plans to expand its efforts to all cataloged proteins—some 100 million molecules. “It's pretty overwhelming,” says John Moult, a protein folding expert at the University of Maryland, Shady Grove, who runs a biennial competition called the Critical Assessment of protein Structure Prediction (CASP). Moult says structural biologists have dreamed for decades that accurate computer models would one day augment slow, painstaking experimental methods, such as x-ray crystallography, that map protein shapes with extreme precision. “I never thought the dream would come true,” Moult says. The computer model, called AlphaFold, is the work of researchers at DeepMind, a U.K. AI company owned by Alphabet, the parent company of Google. In fall of 2020, AlphaFold swept the CASP competition, tallying a median accuracy score of 92.4 out of 100 for its predicted structures, well ahead of the next closest competitor ( Science , 4 December 2020, p. [1144][1]). But because DeepMind researchers didn't reveal AlphaFold's underlying computer code, other teams were left frustrated, unable to build on the progress. That began to change this month ( Science , 16 July, p. [262][2]). On 15 July, researchers led by Minkyung Baek and David Baker at the University of Washington, Seattle, reported online in Science that they had created a competing system: a highly accurate protein structure prediction program called RoseTTAFold, which they released publicly. The same day, Nature rushed out details of AlphaFold in a paper by DeepMind researchers led by Demis Hassabis and John Jumper. Both programs use AI to spot folding patterns in vast databases of solved protein structures. The programs compute the most likely structure of unknown proteins by applying those patterns and also considering basic physical and biological rules governing how neighboring amino acids in a protein interact. In their paper, Baek and Baker used RoseTTAFold to create a structure database of hundreds of G-protein coupled receptors, a class of common drug targets. Now, DeepMind researchers report in Nature that they have amassed 350,000 predicted structures—more than twice as many as experimenters have solved in many decades of work. AlphaFold's structures for which the researchers say they have high confidence cover nearly 44% of all human proteins. AlphaFold determined that many of the remaining human proteins were “disordered,” meaning their shape doesn't adopt a single structure. Such disordered proteins may ultimately adopt a structure when they bind to a protein partner, Baker says. They may also naturally adopt multiple conformations, says David Agard, a structural biologist at the University of California, San Francisco. A database of DeepMind's new protein predictions, assembled with collaborators at the European Molecular Biology Laboratory (EMBL), is freely accessible online. “It's fantastic they have made this available,” Baker says. “It will really increase the pace of research.” Because the 3D structure of a protein largely dictates its function, the DeepMind library is apt to help biologists sort out how thousands of unknown proteins do their jobs. “We at EMBL believe this will be transformative to understanding how life works,” says the lab's director general, Edith Heard. “This will be one of the most important data sets since the mapping of the human genome,” adds Ewan Birney, director of EMBL's European Bioinformatics Institute. DeepMind collaborators say that by making it possible to quickly assess how a change in a protein's sequence alters its structure and function, AlphaFold has already spurred the development of novel enzymes for breaking down plastic waste. It has also prompted efforts to better target parasitic diseases. The impacts aren't likely to stop there. The predictions will help experimentalists who solve structures, Baek says. Data from x-ray crystallography and cryo–electron microscopy experiments can be difficult to interpret, Baek and others say, and having a model can help pinpoint the correct structure. “In the short term, it will boost structure determination efforts,” she predicts. “And over time it will also slowly replace [experimental] structural determination efforts.” If that happens, structural biologists won't find themselves out of work. Baker notes that both experimental and computational scientists are already beginning to turn their efforts to the more complex challenge of understanding exactly which proteins interact with one another and what molecular changes happen during these interactions. The new tools will “reset the field,” Baker says. “It's a very exciting time.” [1]: http://www.sciencemag.org/content/370/6521/1144 [2]: http://www.sciencemag.org/content/373/6552/262


Linked Weyl surfaces and Weyl arcs in photonic metamaterials

Science

In condensed-matter systems, the band structure of a material has often been equated with functionality. However, consideration of the topology of the band structure now provides a route to developing a functionality that goes far beyond the expected properties of the materials. Using electromagnetic metamaterials as building blocks, Ma et al. realized a five-dimensional generalization of a topological Weyl semimetal. Along with the three real momentum dimensions, these included two bi-anisotropy material parameters as synthetic dimensions to demonstrate both linked Weyl surfaces and Yang monopoles. The metamaterial platform provides a powerful route to explore the exotic physics associated with higher-order topological phenomena. Science , abi7803, this issue p. [572][1] Generalization of the concept of band topology from lower-dimensional to higher-dimensional ( n > 3) physical systems is expected to introduce new bulk and boundary topological effects. However, theoretically predicted topological singularities in five-dimensional systems—Weyl surfaces and Yang monopoles—have either not been demonstrated in realistic physical systems or are limited to purely synthetic dimensions. We constructed a system possessing Yang monopoles and Weyl surfaces based on metamaterials with engineered electromagnetic properties, leading to the observation of several intriguing bulk and surface phenomena, such as linking of Weyl surfaces and surface Weyl arcs, via selected three-dimensional subspaces. The demonstrated photonic Weyl surfaces and Weyl arcs leverage the concept of higher-dimension topology to control the propagation of electromagnetic waves in artificially engineered photonic media. [1]: /lookup/doi/10.1126/science.abi7803


Plant PIEZO homologs modulate vacuole morphology during tip growth

Science

Piezo sensors in animal cells are localized in the cell membrane and transduce mechanical signals. The cell membrane of plant cells, unlike that of animal cells, is usually plastered up against a stiff cell wall and does not have much mobility. Much of the cell's volume is accounted for by a large central vacuole, the membrane of which, the tonoplast, is not so mechanically constrained. Radin et al. studied how and where plant cells use Piezo sensors. Plant homologs of the animal mechanosensitive channels are not found in the plasma membrane but rather in the tonoplast. In both moss and the small flowering plant Arabidopsis , mutations in plant Piezo sensors altered vacuolar morphology and growth patterns in tip-growing cells. Science , abe6310, this issue p. [586][1] In animals, PIEZOs are plasma membrane–localized cation channels involved in diverse mechanosensory processes. We investigated PIEZO function in tip-growing cells in the moss Physcomitrium patens and the flowering plant Arabidopsis thaliana . Pp PIEZO1 and Pp PIEZO2 redundantly contribute to the normal growth, size, and cytoplasmic calcium oscillations of caulonemal cells. Both Pp PIEZO1 and Pp PIEZO2 localized to vacuolar membranes. Loss-of-function, gain-of-function, and overexpression mutants revealed that moss PIEZO homologs promote increased complexity of vacuolar membranes through tubulation, internalization, and/or fission. Arabidopsis PIEZO1 also localized to the tonoplast and is required for vacuole tubulation in the tips of pollen tubes. We propose that in plant cells the tonoplast has more freedom of movement than the plasma membrane, making it a more effective location for mechanosensory proteins. [1]: /lookup/doi/10.1126/science.abe6310


A fast link between face perception and memory in the temporal pole

Science

Explicit semantic information in the brain is generated by gradually stripping off the specific context in which the item is embedded. A particularly striking example of such explicit representations are face-specific neurons. Landi et al. report the properties of neurons in a small region of the monkey anterior temporal cortex that respond to the sight of familiar faces. These cells respond to the internal features of familiar faces but not unknown faces. Some of these responses are very highly selective, reliably responding to only one face out of a vast number of other stimuli. These findings will advance our understanding about where and how semantic memories are stored in the brain. Science , abi6671, this issue p. [581][1] The question of how the brain recognizes the faces of familiar individuals has been important throughout the history of neuroscience. Cells linking visual processing to person memory have been proposed but not found. Here, we report the discovery of such cells through recordings from an area in the macaque temporal pole identified with functional magnetic resonance imaging. These cells responded to faces that were personally familiar. They responded nonlinearly to stepwise changes in face visibility and detail and holistically to face parts, reflecting key signatures of familiar face recognition. They discriminated between familiar identities, as fast as a general face identity area. The discovery of these cells establishes a new pathway for the fast recognition of familiar individuals. [1]: /lookup/doi/10.1126/science.abi6671


Retinal waves prime visual motion detection by simulating future optic flow

Science

As a mouse runs forward across the forest floor, the scenery that it passes flows backwards. Ge et al. show that the developing mouse retina practices in advance for what the eyes must later process as the mouse moves. Spontaneous waves of retinal activity flow in the same pattern as would be produced days later by actual movement through the environment. This patterned, spontaneous activity refines the responsiveness of cells in the brain's superior colliculus, which receives neural signals from the retina to process directional information. Science , abd0830, this issue p. [eabd0830][1] ### INTRODUCTION Fundamental circuit features of the mouse visual system emerge before the onset of vision, allowing the mouse to perceive objects and detect visual motion immediately upon eye opening. How the mouse visual system achieves self-organization by the time of eye opening without structured external sensory input is not well understood. In the absence of sensory drive, the developing retina generates spontaneous activity in the form of propagating waves. Past work has shown that spontaneous retinal waves provide the correlated activity necessary to refine the development of gross topographic maps in downstream visual areas, such as retinotopy and eye-specific segregation, but it is unclear whether waves also convey information that instructs the development of higher-order visual response properties, such as direction selectivity, at eye opening. ### RATIONALE Spontaneous retinal waves exhibit stereotyped changing spatiotemporal patterns throughout development. To characterize the spatiotemporal properties of waves during development, we used one-photon wide-field calcium imaging of retinal axons projecting to the superior colliculus in awake neonatal mice. We identified a consistent propagation bias that occurred during a transient developmental window shortly before eye opening. Using quantitative analysis, we investigated whether the directionally biased retinal waves conveyed ethological information relevant to future visual inputs. To understand the origin of directional retinal waves, we used pharmacological, optogenetic, and genetic strategies to identify the retinal circuitry underlying the propagation bias. Finally, to evaluate the role of directional retinal waves in visual system development, we used pharmacological and genetic strategies to chronically manipulate wave directionality and used two-photon calcium imaging to measure responses to visual motion in the midbrain superior colliculus immediately after eye opening. ### RESULTS We found that spontaneous retinal waves in mice exhibit a distinct propagation bias in the temporal-to-nasal direction during a transient window of development (postnatal day 8 to day 11). The spatial geometry of directional wave flow aligns strongly with the optic flow pattern generated by forward self-motion, a dominant natural optic flow pattern after eye opening. We identified an intrinsic asymmetry in the retinal circuit that enforced the wave propagation bias involving the same circuit elements necessary for motion detection in the adult retina, specifically asymmetric inhibition from starburst amacrine cells through γ-aminobutyric acid type A (GABAA) receptors. Finally, manipulation of directional retinal waves, through either the chronic delivery of gabazine to block GABAergic inhibition or the starburst amacrine cell–specific mutation of the FRMD7 gene, impaired the development of responses to visual motion in superior colliculus neurons downstream of the retina. ### CONCLUSION Our results show that spontaneous activity in the developing retina prior to vision onset is structured to convey essential information for the development of visual response properties before the onset of visual experience. Spontaneous retinal waves simulate future optic flow patterns produced by forward motion through space, due to an asymmetric retinal circuit that has an evolutionarily conserved link with motion detection circuitry in the mature retina. Furthermore, the ethologically relevant information relayed by directional retinal waves enhances the development of higher-order visual function in the downstream visual system prior to eye opening. These findings provide insight into the activity-dependent mechanisms that regulate the self-organization of brain circuits before sensory experience begins. ![Figure][2] Origin and function of directional retinal waves. ( A ) Imaging of retinal axon activity reveals a propagation bias in spontaneous retinal waves (scale bar, 500 μm). ( B ) Cartoon depiction of wave flow vectors projected onto visual space. Vectors (black arrows) align with the optic flow pattern (red arrows) generated by forward self-motion. ( C ) Asymmetric GABAergic inhibition in the retina mediates wave directionality. ( D ) Developmental manipulation of wave directionality disrupts direction-selective responses in downstream superior colliculus neurons at eye opening. The ability to perceive and respond to environmental stimuli emerges in the absence of sensory experience. Spontaneous retinal activity prior to eye opening guides the refinement of retinotopy and eye-specific segregation in mammals, but its role in the development of higher-order visual response properties remains unclear. Here, we describe a transient window in neonatal mouse development during which the spatial propagation of spontaneous retinal waves resembles the optic flow pattern generated by forward self-motion. We show that wave directionality requires the same circuit components that form the adult direction-selective retinal circuit and that chronic disruption of wave directionality alters the development of direction-selective responses of superior colliculus neurons. These data demonstrate how the developing visual system patterns spontaneous activity to simulate ethologically relevant features of the external world and thereby instruct self-organization. [1]: /lookup/doi/10.1126/science.abd0830 [2]: pending:yes


News at a glance

Science

SCI COMMUN### Astronomy The Hubble Space Telescope ended a monthlong hiatus on 16 July when operators successfully switched a failed control system to backup devices. The trouble started on 13 June when Hubble's payload computer, which controls its instruments, halted, and the main spacecraft computer put all the astronomical instruments in safe mode. Operators were unable to restart the payload computer, and switching memory modules—which they initially thought were at fault—didn't wake the telescope. They tested and ruled out problems in other devices before zeroing in on a power control unit. NASA called in retired staff to help devise a fix for the 31-year-old telescope, which involved remotely switching to a spare power control unit and other backup hardware for managing the instruments and their data. The agency practiced and checked the repair on the ground for 2 weeks before executing it. After powering up all the hardware, Hubble returned to work on 17 July, and has already beamed back new images. NASA says it expects Hubble to continue for many years. ### Conservation A new automated alert system can help veterinarians get a jump on investigating disease outbreaks and disasters afflicting wildlife. Researchers at the University of California, Davis, and colleagues used a machine learning algorithm to scan case reports of sick and dead wildlife submitted to a database by wildlife clinics and rehabilitation centers in the United States and other countries. The researchers used data from 3081 reports filed from California to train the algorithm to detect patterns of species suffering common symptoms. The software is designed to identify unusual events in one of 12 clinical categories, such as mass starvation or an oil spill. The algorithm assigned the correct category to 83% of cases examined, including ones from an outbreak of neurological disease in California brown pelicans (above) and red-throated loons, the research team reported last week in the Proceedings of the Royal Society B . The system could help wildlife officials more quickly detect developing problems and confirm specific causes. ### Public health Reflecting another toll of the coronavirus pandemic, 23 million children missed routine vaccinations in 2020, the most since 2009 and 19% more than in 2019, the World Health Organization (WHO) and UNICEF said last week. As many as 17 million didn't receive any childhood vaccine at all. The pandemic led to closures or cutbacks at vaccination clinics and lockdowns that prevented parents and their children from reaching them, the groups reported. In addition, 57 mass vaccination campaigns for non–COVID-19 diseases in 66 countries were postponed. Childhood vaccination rates decreased across all WHO regions, with the Southeast Asian and eastern Mediterranean regions particularly affected. In India, more than 3 million children missed a first dose of the diphtheria, tetanus, and pertussis vaccine, more than double the number in 2019. “We [are] leaving children at risk from devastating but preventable diseases like measles, polio, or meningitis,” says WHO Director-General Tedros Adhanom Ghebreyesus. ### Climate policy As part of the run-up to the U.N. climate summit in November, the European Union and China announced last week plans to follow through on commitments to curb their carbon emissions. The European proposal, which must be approved by the bloc's member states, would steeply increase the price of carbon dioxide (CO2) emissions; eliminate new gas-powered cars by 2035; require 38% of all energy to come from renewables by 2030, up from a previous goal of 32%; and impose tariffs on goods from countries that have not acted on climate change. (Democratic lawmakers in the United States proposed a similar tariff this week.) Meanwhile, China on 16 July launched a carbon trading scheme for power plants that instantly created the world's largest carbon market, triple the European Union's in size. China's plan incentivizes plants to lower CO2 emissions by allowing more efficient facilities to sell some of their reductions to less efficient ones. Although some observers call the plan weak because it covers a relatively small portion of China's emissions, it could be expanded to eventually incorporate three-fourths of the country's emissions from all sources. ### Public health When temperatures soar, workers and their employers need to take heed: Hot weather led to 20,000 more injuries annually in California between 2001 and 2018, according to a novel analysis of 11 million workers compensation claims. Economist Jisung Park at the University of California, Los Angeles, and colleagues classified work-related injuries by ZIP code and looked up local temperatures on the day each was recorded. They found increases of between 5% and 15% in claims, depending on the temperature and occupation, compared with those filed on a typical cooler day, defined as a temperature of 16°C. Few were attributed directly to heat, but the injuries connected to higher temperatures—such as falls and mishandling equipment—may have resulted because the heat made workers woozy, the researchers reported to Congress last week and in a preprint on the SSRN server. But mitigation may be possible: Heat-related injury claims declined after 2005, when California began to require shade, water, and breaks for outdoor workers—in industries such as construction, utilities, and farming—whenever temperature exceeded 35°C. ### Research integrity Both the United Kingdom and the United States last week announced new high-level bodies to provide guidance on research integrity—but both lack the powers that many whistleblowers say are critical, such as independently investigating complaints of wrongdoing and pulling grant funding from institutions that fail to conduct misconduct probes properly. The umbrella funding body UK Research and Innovation (UKRI) launched the Committee on Research Integrity, which plans to operate for 3 years and accelerate existing projects in this area. The U.S. National Academies of Sciences, Engineering, and Medicine (NASEM) unveiled the Strategic Council for Research Excellence, Integrity, and Trust, which will have members from the U.S. National Institutes of Health and National Science Foundation. Unlike UKRI, NASEM does not fund researchers, so it cannot set policies on how to handle misconduct allegations. But it could promote integrity in other ways—for instance by pushing for a central repository for researchers to report their financial conflicts of interest, says Marcia McNutt, president of the National Academy of Sciences and an ex officio member of the new panel. ### Microbiology Sifting through DNA in the mud of her backyard, a geomicrobiologist discovered what may be the longest known extrachromosomal sequence, which includes genes from a variety of microbes—prompting her son to propose naming it after Star Trek 's Borg, cybernetic aliens that assimilate humans. Jill Banfield of the University of California, Berkeley, was searching for viruses that infect archaea, a type of microbe often found in places devoid of oxygen. The 1-million-base-pair strand of DNA contains genes known to help archaea metabolize methane, suggesting the fragment might exist inside the microbes but outside their normal chromosome, the research team wrote in a preprint posted on 10 July on the bioRxiv server. Scanning a public microbial DNA database, the authors identified 23 possible Borgs, with many of the same characteristics, in other U.S. locations. The Borgs' role remains murky, but they may provide another example of DNA that can hop between an organism's chromosomes or between organisms, helping species adapt to changes in their environment.


Proximity and single-molecule energetics

Science

Probing single molecules in their nanoenvironment can reveal site-specific phenomena that would be obscured by ensemble-averaging experiments on macroscopic populations of molecules. Particularly in the past decade, major technological breakthroughs in scanning probe microscopy (SPM) have led to unprecedented spatial resolution and versatility and enabled the interrogation of molecular conformation, bond order, molecular orbitals, charge states, spins, phonons, and intermolecular interactions. On page 452 of this issue, Peng et al. ([ 1 ][1]) use SPM to directly measure the triplet lifetime of an individual pentacene molecule and demonstrate its dependence on interactions with nearby oxygen molecules with atomic precision. In addition to allowing the local tuning and probing of spin-spin interactions between molecules, this study represents a notable advance in the single-molecule regime and provides insights into many macroscopic behaviors and related applications in catalysis, energy-conversion materials, or biological systems. Single-molecule studies have benefited from the high resolution achieved with well-defined functionalized probes, especially with carbon monoxide–terminated atomic force microscopy (AFM) tips ([ 2 ][2]). The versatility and applicability of AFM have also been enhanced by biasing the tip with gate voltages and supporting molecules on insulating substrates. In this configuration, the conductive AFM tip serves as an atomically controlled charge injector with single-charge sensitivity. Such electrical addressing of electronic states of single molecules ([ 3 ][3]) allows for the study of charge distribution and transport in single-molecule devices, organic electronics, and photovoltaics. Beyond steady-state spectroscopy, excited-state dynamics of single molecules can be measured by using an ultrashort and high-intensity electric (voltage) or optical (laser) pulse (the “pump”) to excite the sample. After a nonequilibrium state is generated, a second weaker pulse (the “probe”) monitors the change of the excited state. By varying the time delay between the two pulses, the temporal evolution of the excited state can be mapped out. Peng et al. used the electronic pump-probe approach in AFM to measure the lifetime of the excited triplet state of an individual pentacene molecule with atomic precision (see the figure). They observed strong quenching of the triplet lifetime by co-adsorbed molecular oxygen (O2). The electronic energy-transfer processes had an intriguing dependence on the arrangement of surrounding O2 molecules, which they controlled by atomic manipulation with the tip. Spin-relaxation measurements of single molecules in space with atomic resolution provide insights into their local interactions with each other, as well as with their nanoenvironment. Such information could be useful for spin-based quantum-information storage or quantum computing ([ 4 ][4]). Given the radiative relaxation of excited states, SPM-coupled optical spectroscopy provides a powerful tool to perform spatially and energy-resolved spectroscopic studies of single molecules. Specifically, site-resolved excitations of molecules can be induced by highly localized scanning tunnel microscopy (STM) current, and the resulting luminescence, which carries information that describes excited states, can be probed by integrated optical detection systems. This approach revealed redox state–dependent excitation of single molecules and intermolecular excitonic coupling interactions with atomic-scale spatial precision ([ 5 ][5], [ 6 ][6]). A study of electroluminescence demonstrated selective triplet formation by manipulating electron spin inside a molecule ([ 7 ][7]), which could provide a route to interrogate quantum spintronics and organic electronics at the single-molecule level. Besides tunneling electrons, the interaction of photons with molecules can provide valuable structural information and chemical identification through measurements of absorption, emission, or scattering of light. In particular, by confining laser light at the atomic-scale SPM junction and taking advantage of plasmon-enhanced Raman scattering, tip-enhanced Raman spectroscopy can overcome the diffraction limit of conventional optical spectroscopy and thereby achieve submolecular chemical spatial resolution ([ 8 ][8]). Such capability provides in-depth insights into single-molecule chemistry and site-specific chemical effects at the spatial limit ([ 9 ][9]). ![Figure][10] Atomically addressing excited single molecules The effect of nearby oxygen molecules on the lifetimes (τ) of triplet states T x , T y , and T z or T1 decaying to the singlet state S of individual pentacene molecules has been probed on an insulating salt surface. GRAPHIC: V. ALTOUNIAN/ SCIENCE Most excited states induced by photon absorption are incredibly short-lived (on the order of picoseconds to femtoseconds), so time-resolved optical STM techniques have been developed with ultrafast lasers. For example, pump-probe terahertz laser pulses were used to induce state-selective ultrafast STM tunneling currents through a single molecule. This approach allowed the molecular orbital structure and vibrations to be measured directly on the femtosecond time scale ([ 10 ][11]). Optical STM further showed the capability to explore photon and field-driven tunneling with angstrom-scale spatial resolution and attosecond temporal resolution. This experimental platform can be used to study quasiparticle dynamics in superconductor and two-dimensional materials with exceptional resolutions ([ 11 ][12]). Single-molecule studies could open avenues to access extremely transient states and chemical heterogeneity, suc h as the vibration of atoms within a molecule, the precession of a spin, ultrashort-lived complex reaction intermediates, and some key stochastic processes of reactions in chemistry and biology. For example, the study of Peng et al. relates to the reactivity of electronic excited states of organic molecules to O2 (and thus air). These processes can affect various natural photochemical and photophysical processes undergoing excitation by sunligh that can lead to transformation, degradation, or aging ([ 12 ][13]). The insightful descriptions of molecular conformation, dynamics, and function provided by spatially resolved single-molecule studies could inform complex and emergent behaviors of populations of molecules or even cells. 1. [↵][14]1. J. Peng et al ., Science 373, 452 (2021). [OpenUrl][15][Abstract/FREE Full Text][16] 2. [↵][17]1. L. Gross, 2. F. Mohn, 3. N. Moll, 4. P. Liljeroth, 5. G. Meyer , Science 325, 1110 (2009). [OpenUrl][18][Abstract/FREE Full Text][19] 3. [↵][20]1. S. Fatayer et al ., Nat. Nanotechnol. 13, 376 (2018). [OpenUrl][21][CrossRef][22][PubMed][23] 4. [↵][24]1. M. N. Leuenberger, 2. D. Loss , Nature 410, 789 (2001). [OpenUrl][25][CrossRef][26][PubMed][27] 5. [↵][28]1. Y. Zhang et al ., Nature 531, 623 (2016). [OpenUrl][29][CrossRef][30][PubMed][31] 6. [↵][32]1. B. Doppagne et al ., Science 361, 251 (2018). [OpenUrl][33][Abstract/FREE Full Text][34] 7. [↵][35]1. K. Kimura et al ., Nature 570, 210 (2019). [OpenUrl][36][CrossRef][37][PubMed][38] 8. [↵][39]1. J. Lee, 2. K. T. Crampton, 3. N. Tallarida, 4. V. A. Apkarian , Nature 568, 78 (2019). [OpenUrl][40][CrossRef][41][PubMed][42] 9. [↵][43]1. S. Mahapatra, 2. L. Li, 3. J. F. Schultz, 4. N. Jiang , J. Chem. Phys. 153, 010902 (2020). [OpenUrl][44] 10. [↵][45]1. T. L. Cocker, 2. D. Peller, 3. P. Yu, 4. J. Repp, 5. R. Huber , Nature 539, 263 (2016). [OpenUrl][46][CrossRef][47][PubMed][48] 11. [↵][49]1. M. Garg, 2. K. Kern , Science 367, 411 (2020). [OpenUrl][50][Abstract/FREE Full Text][51] 12. [↵][52]1. P. R. Ogilby , Chem. Soc. Rev. 39, 3181 (2010). [OpenUrl][53][CrossRef][54][PubMed][55] Acknowledgments: We acknowledge support from the National Science Foundation (CHE-1944796). 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{openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DDoppagne%26rft.auinit1%253DB.%26rft.volume%253D361%26rft.issue%253D6399%26rft.spage%253D251%26rft.epage%253D255%26rft.atitle%253DElectrofluorochromism%2Bat%2Bthe%2Bsingle-molecule%2Blevel%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.aat1603%26rft_id%253Dinfo%253Apmid%252F30026221%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [34]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzNjEvNjM5OS8yNTEiO3M6NDoiYXRvbSI7czoyMjoiL3NjaS8zNzMvNjU1My8zOTIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [35]: #xref-ref-7-1 "View reference 7 in text" [36]: 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Brain signals 'speak for person with paralysis

Science

A man unable to speak after a stroke has produced sentences through a system that reads electrical signals from speech production areas of his brain, researchers report this week. The approach has previously been used in nondisabled volunteers to reconstruct spoken or imagined sentences. But this first demonstration in a person who is paralyzed “tackles really the main issue that was left to be tackled—bringing this to the patients that really need it,” says Christian Herff, a computer scientist at Maastricht University who was not involved in the new work. The participant had a stroke more than a decade ago that left him with anarthria—an inability to control the muscles involved in speech. Because his limbs are also paralyzed, he communicates by selecting letters on a screen using small movements of his head, producing roughly five words per minute. To enable faster, more natural communication, neurosurgeon Edward Chang of the University of California, San Francisco, tested an approach that uses a computational model known as a deep-learning algorithm to interpret patterns of brain activity in the sensorimotor cortex, a brain region involved in producing speech ( Science , 4 January 2019, p. [14][1]). The approach has so far been tested in volunteers who have electrodes surgically implanted for nonresearch reasons such as to monitor epileptic seizures. In the new study, Chang's team temporarily removed a portion of the participant's skull and laid a thin sheet of electrodes smaller than a credit card directly over his sensorimotor cortex. To “train” a computer algorithm to associate brain activity patterns with the onset of speech and with particular words, the team needed reliable information about what the man intended to say and when. So the researchers repeatedly presented one of 50 words on a screen and asked the man to attempt to say it on cue. Once the algorithm was trained with data from the individual word task, the man tried to read sentences built from the same set of 50 words, such as “Bring my glasses, please.” To improve the algorithm's guesses, the researchers added a processing component called a natural language model, which uses common word sequences to predict the likely next word in a sentence. With that approach, the system only got about 25% of the words in a sentence wrong, they report this week in The New England Journal of Medicine . That's “pretty impressive,” says Stephanie Riès-Cornou, a neuroscientist at San Diego State University. (The error rate for chance performance would be 92%.) Because the brain reorganizes over time, it wasn't clear that speech production areas would give interpretable signals after more than 10 years of anarthria, notes Anne-Lise Giraud, a neuroscientist at the University of Geneva. The signals' preservation “is surprising,” she says. And Herff says the team made a “gigantic” step by generating sentences as the man was attempting to speak rather than from previously recorded brain data, as most studies have done. With the new approach, the man could produce sentences at a rate of up to 18 words per minute, Chang says. That's roughly comparable to the speed achieved with another brain-computer interface, described in Nature in May. That system decoded individual letters from activity in a brain area responsible for planning hand movements while a person who was paralyzed imagined handwriting. These speeds are still far from the 120 to 180 words per minute typical of conversational English, Riès-Cornou notes, but they far exceed what the participant can achieve with his head-controlled device. The system isn't ready for use in everyday life, Chang notes. Future improvements will include expanding its repertoire of words and making it wireless, so the user isn't tethered to a computer roughly the size of a minifridge. [1]: http://www.sciencemag.org/content/363/6422/14