Devices to dredge memories out of the mind and make them visible are a staple of fiction from anime to Black Mirror. For decades, scientists have worked to identify a specific mechanism used to record and recall an individual memory. Is a memory preserved in a single neuron? A collection of connected neurons? Is the ‘engram’ — the permanent storage of the memory — a chemical held at a single location, a somatic change in gene expression, or an electrical state somehow preserved over time?
Much of the research has proved frustrating. Efforts to pin down the location of memories have often given what seemed to be definitive results … only to see those results evaporate in the face of additional data.
But there’s a new generation of memory research that’s progressing rapidly. Making that progress took letting go of the long-held idea that there was a dedicated part of the brain playing hard drive, acting as storage to the rest of the mind. Writing in Nature, Helen Shen recounts the research of Johns Hopkin’s researcher Janice Chen.
Memory, it turns out, is a highly distributed process, not relegated to any one region of the brain. And different types of memory involve different sets of areas. Many structures that are important for memory encoding and retrieval, such as the hippocampus, lie outside the cortex — and Lashley largely missed them. Most neuroscientists now believe that a given experience causes a subset of cells across these regions to fire, change their gene expression, form new connections, and alter the strength of existing ones — changes that collectively store a memory. Recollection, according to current theories, occurs when these neurons fire again and replay the activity patterns associated with past experience.
As an example, Chen had people watch a scene from the television series Sherlock. Then she had people recount that scene. Even though people used different words to describe what they had seen, and even though the scene — one in which a shy medical examiner tentatively flirts with Holmes while a body lies between them — made different impressions on people, Chen was able to see the same brain activity pattern behind those thoughts. Advances in brain imaging that allow researchers to track real time activity in fine detail have made these patterns easier to detect and more definitive to trace.
The work represents a dramatic departure from previous memory research, which identified more general locations and mechanisms.
Chen’s original article is also available. What neither piece makes clear is: Would Chen’s pattern-search reveal whether someone had watched Molly Hooper try to get Sherlock’s attention even if they were not recounting their impression of the scene? If it could, that would bring the research frighteningly close to the Chiclet-sized device from “Crocodile,” which like many episodes of Black Mirror, already seems not that far away. And neither Chen nor Shen indicates whether it would be possible to impose one of these patterns in the mind of someone who didn’t have the original experience, effectively inserting a memory.
In any case, research around memory and consciousness continues to be one of the most fascinating areas out there. Because of course it is. If we genuinely grasped the mechanisms of how memory works and how self arises, just that understanding would go a long way toward making us fundamentally different people.
But … for now, come on inside and see if you can make some memories about this week’s articles.
Mysterious radio sources in the news
The fantastic radio dish at Arecibo Observatory in Puerto Rico was lashed by hurricanes and temporarily without power this year, but some of the results it produced have been in the news this week in the form of “mysterious radio waves from outer space.” But in this case you can turn off your theremin and stop looking for approaching space ships. The signals are part of a class of “fast radio burts,” extraordinarily powerful, brief and enigmatic shots of radio power that are mostly one-offs. But in this case such signals have repeatedly been found coming from one point of origin.
FRB 121102—has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. ... The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses).
Put it all together, and it looks like these radio bursts may be coming from a nuetron star that’s spiraling toward death in a very massive black hole at the center of a distant galaxy. The result is an set of clashing magnetic fields of almost unbelievable power that distort, twist, bump, and throw off those radio bursts. It’s one of those Amazing Universe things that we can be glad is happening very, very far away. Oh, and it’s not aliens. Sorry.
Genetic connections between schizophrenia and lung cancer
Few genetic changes can be been neatly proscribed by a single effect. The gene that gives some cats blue eyes is also connected to deafness. Alteration of a single gene on chromosome 22 has been associated with both autism and schizophrenia — as well as hearing loss and arthritis. When a gene affects two or more seemingly unconnected features it’s called pleiotropy.
Epidemiological studies had previously suggested that there was some connection between schizophrenia and the incidence of lung cancer. But was this really a genetic connection, or something more coincidental, such as a different incidence of smoking among people who have schizophrenia? A large group, primarily from Norway (not Normay) and the United States went looking for a genetic connection.
After excluding the major histocompatibility complex region, we identified three independent loci jointly associated with schizophrenia and lung cancer. The strongest association included nicotinic acetylcholine receptors and is an established pleiotropic locus shared between lung cancer and smoking. The two other loci were independent of genetic association with smoking. Functional analysis identified downstream pleiotropic effects on epigenetics and gene-expression in lung and brain tissue. These findings suggest that genetic factors may explain partly the observed epidemiological association of lung cancer and schizophrenia.
So, yes. As if schizophrenia isn’t godawful enough on its own, it also seems to have a genetic connection with a higher incidence of lung cancer.
Online citizen science finds multi-planet system
A web site called Exoplanet Explorers offers anyone the opportunity to look through data collected from the Kepler Space telescope, searching for the cyclical changes in light levels that represent planets orbiting distant suns. By correlating the input of dozens, or hundreds of users, the site was able to locate and confirm that K2-138 has five planets, most of which seem to fall into the rocky “superearth” category.
A system of at least five exoplanets has been discovered by citizen scientists through a project called Exoplanet Explorers, part of the online platform Zooniverse, using data from NASA's Kepler space telescope. This is the first multi-planet system discovered entirely through crowdsourcing. A study describing the system has been accepted for publication in The Astronomical Journal.
One of the people looking at that data was (blows casually on his knuckles) ... me. The discovery of these planets around K2-138 happened in connection with Zooniverse being featured on a television program in Australia, but I’m very hopeful that soon we’re going to work out a means of throwing them a brand new horde of researchers … people from this site. Stand by for details.
Your tastebuds and the Sonic hedgehog protein
I’ll make no bones about it. I’m putting in this article mostly because the idea that researchers actually named something the Sonic hedgehog protein (Shh) amuses me. But it’s also here because tastebuds turn out to be something of a mystery sense.
The maintenance of taste sensory organs in the tongue was shown 140 years ago to depend on innervation from distant ganglion neurons, but the underlying mechanism has remained unknown. Here, we show that Sonic hedgehog (Shh), which encodes a secreted protein signal, is expressed in these sensory neurons, and that experimental ablation of neuronal Shh expression causes loss of taste receptor cells (TRCs).
Sonic hedgehog protein is, of course, the product of the Sonic hedgehog gene. And if you think that’s funny, “Sonic” is just one of a family of genes in the hedgehog family, which also includes desert hedgehog and Indian hedgehog. You can probably blame the name on the fact that all these genes were discovered in 1980.
Many drugs used in chemotherapy affect the hedgehog genes, so the reason that cancer patients lose their sense of taste is that Sonic can no longer race along their tongues to maintain their tastebuds, Now try to think about that without involving animated hedgehogs. I dare you.
Another control dial for body fat
Until now, the only known regulator for body weight has been the leptin system. In really, really short form — the hormone ghrelin makes you feel hungry while the hormone leptin makes you feel full. Many studies have shown that people can develop a reduced sensitivity to leptin, making them feel constantly hungry.
But this big team of Swedish researchers suggests there may be a second control mechanism affecting body weight in another way.
The results demonstrate that there is a body weight homeostat that regulates fat mass independently of leptin. As the body weight-reducing effect of increased loading was dependent on osteocytes, we propose that there is a sensor for body weight in the long bones of the lower extremities acting as “body scales.” This is part of a body weight homeostat, “gravitostat,” that keeps body weight and body fat mass constant.
In tests, the researchers loaded down mice with weights. Rather than eating more to make up for the extra effort of walking around with that mass, the mice ate less, suggesting that there was a system that sensed the weight and signaled “stop eating, fat mouse.” But this sentence from the paper …
We propose that increased body weight activates a sensor dependent on osteocytes of the weight-bearing bones.
would seem to fall firmly in the “gee, I think you may be jumping to conclusions” category. Still, I propose we all wear heavy coats this week and report back on whether it made us feel fuller.
Red-dwarf planets can hold on to their atmospheres
There are a lot of red dwarf stars out there. A lot. So the discovery that the red dwarf star TRAPPIST-1 has at least eight planets was very exciting. Even more exciting is that, when it comes to temperature range, three of these planets exist in what should be the “habitable zone” around the star, where water could exist as a liquid.
But there have been several concerns about the possibility of whether a planet around such a small star could host life. The star is smaller and cooler, and the close orbits of the inner planets mean they’re almost certainly tidally-locked, with one side snared in permanent day and the far side in endless night. Other questions have popped up on everything from how tidal forces affect the interiors of these plants to whether or not they can maintain a magnetic field.
But a US team has good news about one feature.
The presence of an atmosphere over sufficiently long timescales is widely perceived as one of the most prominent criteria associated with planetary surface habitability. … We conclude that the outer planets of the TRAPPIST-1 system are capable of retaining their atmospheres over billion-year timescales.
Still, when it comes to this specific system, that might not be enough. TRAPPIST-1 is a lot older than our sun, maybe twice as old. So even if conditions had been great for a billion years or more … that could have been billions of years ago.
Really good news on pollution that needs to be repeated
“Organic aerosols” sounds like it could be a term used by perfume manufacturers. So instead think “tiny particles of soot.” Tiny particles of soot that cause cancer, asthma, and a dozen other major causes of death.
Exposure to atmospheric particulate matter (PM) exacerbates respiratory and cardiovascular conditions and is a leading source of premature mortality globally. Organic aerosol contributes a significant fraction of PM in the United States.
So what’s the good news?
Here, using surface observations between 1990 and 2012, we show that organic carbon has declined dramatically across the entire United States by 25–50%; accounting for more than 30% of the US-wide decline in PM. The decline is in contrast with the increasing organic aerosol due to wildfires and no clear trend in biogenic emissions.
Despite more frequent wildfires, despite every other natural source of such aerosols, these tiny floating death threats declined by 30 percent in the space of just over a decade. That’s #$@%ing amazing. How did it happen?
By developing a carbonaceous emissions database for the United States, we show that at least two-thirds of the decline in organic aerosol can be explained by changes in anthropogenic emissions, primarily from vehicle emissions and residential fuel burning.
Cleaner cars, cleaner power. And what did it gain us?
We estimate that the decrease in anthropogenic organic aerosol is responsible for averting 180,000 (117,000–389,000) premature deaths between 1990 and 2012.
Look at that number again: 180,000 Americans are alive today because of better fuel economy, because of cleaner diesel fuel, because of a cleaner mix of power sources, because of less fuel oil use, because of … all of that. When Donald Trump, or anyone else, suggests that we’re being “strangled” by regulations, come Right. Back. Here. Because the truth is exactly the opposite. We’re being saved by regulations. Tens of thousands of Americans are only alive because of regulations.
And every attempt to loosen those regulations is nothing short of murder.
Fracking as a long term threat to groundwater
When thinking about how fracking potentially affects groundwater sources, it’s tempting to consider them a problem for the few years that the well is operating. But the potential damage can go on for decades.
We show that the methane chemistry in shallow groundwater overlying the site of a catastrophic underground blowout continues to be impacted 50 y later.
Importantly, this was a blowout that occurred at depth, but which was propagated into more shallow water sources likely using the well as a vector.
Little brothers stand a better chance of being gay
This isn’t new research, but it continues to be kind of amazing: For a man, the more older brothers you have, the better the chance that you will be gay. Is that something baked in at birth? Is it an effect of nurture? Is it a somatic genetic change that occurs over time?
Twenty years ago, Ray Blanchard and Anthony Bogaert demonstrated that the probability of a boy growing up to be gay increases for each older brother born to the same mother, the so-called fraternal birth order (FBO) effect. Their first investigation indicated that each older brother increased the probability of being gay by about 33%. This startling phenomenon was confirmed in multiple studies based on independent populations totaling over 10,000 subjects, and a meta-analysis indicated that between 15% and 29% of gay men owe their sexual orientation to this effect.
That’s a genuinely jaw-dropping statement. Something like a quarter of gay men are gay men because they had older brothers. Why is that? There’s been a lot of speculation, but it seems like we may be getting closer to an answer. There is a strange mechanism that seems to, with each birth, make mothers have an increasing immune response to male embryos. This effect in turn affects the development of the embryo’s nervous system.
This study provides the first data-based explanation for the FBO effect and adds a significant chapter to growing evidence indicating that sexual orientation is heavily influenced by prenatal biological mechanisms rather than by unidentified factors in socialization.
It’s nature, not nurture. But it’s another demonstration that the mechanisms involved in something as subtle as sexual orientation are a lot more complex than just having a “gay gene.”
Japan gets ready to attack the Standard Model
Oh, Standard Model, we depend on you for … pretty much everything. And yet, you are so darn messy. So many particles. So many ugly inequalities. And yet test after test keeps proving you true, leaving me so few remaining opportunities to build that time machine, pocket warp drive, or Green Lantern ring. I love-hate you, Standard Model.
Which is why I’m not so secretly pulling for a series of upcoming experiments in Japan to produce some nonstandard results.
The collider feeding the Belle II experiment will squeeze particles into a tight beam just 50 nanometres across, an advance that will lead to a collision rate 40 times higher than that achieved by its KEK predecessor. This will help it to explore reams of recently discovered exotic particles made up of four or five quarks, known as tetraquarks and pentaquarks, respectively, and allow it to scour rare b-quark decays for any as-yet unknown preferences towards producing matter over antimatter. It will enable physicists to explore intriguing signs of physics beyond the standard model, a theory which has been verified repeatedly by experiments since the 1970s, but which fails to account for gravity or a host of mysteries, such as why there is so much more matter than antimatter.
I’ll settle for headlines proclaiming either “This provides a means to create unlimited cheap power in a way that can’t be turned into a bomb!” or “Scientists expect portals into the multiverse to be easily constructed.”
Is that too much to ask?