We all have a personal bubble, an invisible zone of privacy around our bodies. When strangers cross this boundary, it makes us feel uncomfortable. But not all of us – Daniel Kennedy from the California Institute of Technology has been studying a woman known only as SM, who lacks any sense of personal space.
SM suffers from a rare genetic disorder called Urbach-Wiethe disease, that causes parts of the brain’s temporal lobes to harden and waste away. This brain damage has completely destroyed SM’s amygdalae, a pair of small, almond-shaped structures that help us to process emotions.
Kennedy asked her to say when she felt most comfortable as a female experimenter walked towards her. On average, she preferred a distance of around a foot, about half the usual two-foot gap that 20 other normal people demanded. SM’s lack of boundaries remained whether she walked towards her partner or vice versa, whether they were looking away or at each other, and whether they started close by or far apart.
The fact that SM had a boundary at all was probably because at close distances, it’s hard to see people. She said time and time again that she was actually comfortable at any distance, and during one trial, she actually walked all the way to her partner until they were actually touching. Even when they were making direct eye contact and touching nose-to-nose, she only rated the experience as 1 on a comfort scale of 1 to 10, where 1 is perfectly comfortable and 10 is a level of discomfort that only the British can survive. When a male stranger talked to her up close, she again rated the chat as a 1 (even though he gave it a 7).
SM has been working with this group of researchers, led by Ralph Adolphs, for over a decade but her comfort didn’t stem from simply knowing her partner well. When Kennedy tested two other people who also knew the scientists equally well, but didn’t have damaged amygdalae, they were much less accommodating with their personal space than SM was. Nor did SM simply put her discomfort to heel – she knew that Kennedy was “up to something”, but so did the male stranger and that did nothing to allay his discomfort.
In fact, it was clear that SM understood the concept of personal space. She thought it was smaller than most people’s, and she said that she didn’t want to make other people too uncomfortable by standing too close to them. She estimated that people feel most comfortable about 1.5 feet apart – that’s an underestimate but it’s still larger than her own preference.
Kennedy’s experiments suggest that our sense of personal space comes from the amydgala. Indeed, when he scanned the brains of a small group of volunteers, their amygdalae were more active when someone was standing close to the scanner than when they were keeping their distance.
Kennedy thinks that the amygdala, with its pivotal role in emotional processing, governs the emotional kick we feel when people enter our personal zone. Without it, we remain unfazed by close proximity. What’s less clear is how this affect changes as we get to know people better. Why is it that friends and loved ones are allowed (or positively encouraged) to stay nearer than strangers are?
Other aspects of SM’s ability to deal with emotions are off-kilter too. For a start, she knows no fear – not in a Batman way, but in the sense that she can’t recognise the emotion in the eyes of others Way back in 1994, Adolphs’ group showed that SM can reasonably recognise the emotions in most facial expressions, but she falters when the face in question is afraid. And even though she’s a talented artist, she can’t draw a scared face, once claiming that she didn’t know what such a face would look like.
Now, Naotsugu Tsuchiya, working in Adolphs’ team, has found that SM’s knowledge of fear is a little more complicated. When asked to classify angry and fearful faces, or threatening and harmless scenes, SM did so completely normally when she had to do it quickly. Even though she felt that the scared faces were less intense than volunteers with intact amygdalae, she classified them correctly, with similar reaction times.
In a similar experiment, Tsuchiya showed SM faces that had been gradually morphed from fearful to neutral expressions. When she had unlimited time, it took much more severe expressions for her to recognise a face as fearful. But when she had to quickly pick scared faces from a set, her performances were indistinguishable from other people.
This means that the amygdala isn’t always necessary to know fear. It’s not needed for the earliest stages where our brain starts to process fearful images below the level of our consciousness. Instead, Tsuchiya suggests that after this first level of analysis is over, the amygdala helps us to use the results to make social judgments – to explicitly recognise fear for what it is and to assess the relevance of those first subconscious twinges.
Reference: Nature Neuroscience doi:10.1038/nn.2381 and 10.1038/nn.2380
More on the amygdala:
This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.
Getting excited when fish produce sperm would usually get you strange looks. But for Tomoyuki Okutsu and colleagues at the Tokyo University of Marine Science and Technology, it’s all part of a day’s work. They are trying to use one species of fish as surrogate parents for another, a technique that could help to preserve species that are headed for extinction.
Okutsu works on salmonids, a group of fish that includes salmon and trout. Many members of this tasty clan have suffered greatly from over-fishing in the last few decades, and their populations are dwindling their way to extinction.
If stocks fall below a critical level, they may need a jump-start. One strategy is to freeze some eggs to be fertilised artificially, in the way that many human eggs are in fertility clinics. But it’s much harder for fish eggs – they are large and have lots of fat, which makes them difficult to freeze effectively.
Okutsu’s group have hit on a more effective solution. They use transplanted sexual stem cells to turn another species of fish into surrogate parents for the endangered ones.
When sportsmen use rackets or bats, their best bet is to hit a ball on the “sweet spot”, the point where various forces balance out to deliver powerful blows with only very small forces on the wielder’s wrist. Engineers have the right tools and models to work out where this spot lies on their instruments. Now, palaeontologists have used the same techniques to study biological hammers that adorn the tails of giant prehistoric armadillos called glyptodonts.
At first glance, glyptodonts have little in common with the likes of Andy Murray and Roger Federer. These armoured beasts lived in the Americas several million years ago and the largest of them weighed up to two tons. Much like their modern armadillo relatives, they were clad in large suits of bony armour. Their long tails were similarly protected by bony rings and in some species, they were topped with large clubs, or spiky weapons that resembled medieval morning stars.
Uruguayan scientist Rudemar Ernesto Blanco was set about studying the tail clubs of the most formidable of the glyptodonts, by using the same approaches used to analyse sports tools. The analogy is particularly appropriate for species like Doedicurus, where the rings at the end of the tail were completely fused, meaning that the animal’s rear end was defended by a single metre-long piece of solid bone – a biological hammer, indeed.
When wielding this weapon, whether against a predator or a fellow glyptodont, it would be in the animal’s interest to strike at the sweet spot of its own tail to reduce the forces acting on the part of the tail where the bony tip met the more flexible base. Otherwise, it might have risked severe strain and damage. To find the locations of these spots, Blanco applied sports modelling techniques to the tails of nine species of glyptodonts.
Gravity affects not just our bodies and our behaviours, but our very thoughts. That’s the fascinating conclusion of a new study which shows that simply holding a heavy object can affect the way we think. A simple heavy clipboard can makes issues seem weightier – when holding one, volunteers think of situations as more important and they invest more mental effort in dealing with abstract issues.
In a variety of languages, from English to Dutch to Chinese, importance is often described by words pertaining to weight. We speak of ‘heavy news, ‘weighty matters’ and ‘light entertainment’. We weigh up the value of evidence, we lend weight to arguments with facts, and our opinions carry weight if we wield influence and authority. These are more than just quirks of language – they reflect real links that our minds make between weight and importance.
Nils Jostmann from the University of Amsterdam demonstrated the link between weight and importance through a quartet of experiments. In each one, a different set of volunteers held a clipboard that either weighed 1.5 pounds or 2.3 pounds.
The extra 0.8 pounds were enough to make volunteers think that a foreign currency was worth more money. Forty volunteers were asked to guess the conversion rates between euros and six other currencies, indicating their estimate by marking a straight line. Those who held the heavier clipboard valued the currencies more generously, even though a separate questionnaire showed that they felt the same about the euro.
Money, of course, does have its own weight, so for his next trick, Jostmann wanted to stay entirely within the abstract realm. He considered justice – an area that is free of weight but hardly free of importance. Jostmann showed 50 volunteers a scenario where a university committee was denying students the opportunity to voice their opinions on a study grant. It was a potentially weighty issue, but more so to the students who held the heavy clipboard. They felt it was more important that the university listened to the students’ opinions.
Since late 2006, honeybees in Europe and North America have been mysteriously disappearing. Once abuzz with activity, hives suddenly turned into honeycombed Marie Celestes. They still had plentiful supplies of honey, pollen and youngsters but the adult workers vanished with no traces of their bodies. The phenomenon has been dubbed colony collapse disorder (CCD). In the first winter when it struck, US hive populations crashed by 23% and in the next winter, they fell again by a further 36%.
Eager to avert the economic catastrophe that a bee-less world, scientists have been trying to find the cause behind the collapse. Amid wackier explanations like mobile phone radiation and GM crops, the leading theories include sensitivity to pesticides, attacks by the vampiric Varroa mite or a parasitic fungus called Nosema, infections by various viruses, or combinations of these threats.
In 2007, US scientists thought they had revealed the main villain in the piece, by showing that the an imported virus – Israeli acute paralysis virus (IAPV)- was strongly linked to empty hives. But since then, another group showed that IAPV arrived in the US many years before the first signs of CCD were reported. Other related viruses have also been linked to CCD hives, including Kashmir bee virus (KBV) and deformed wing virus (DWV).
To pare down these potential culprits, Reed Johnson from the University of Illinois compared the genetic activity of bees from over 120 colonies, including some affected by CCD and healthy ones that were sampled before the vanishing began. He looked at their digestive systems – one of the most places where infections and environmental toxins would start wreaking havoc.
The analysis didn’t offer any simple answers, but Johnson found some evidence to suggest that CCD bees have problems with producing proteins. In animal cells, proteins are manufactured in molecular factories called ribosomes. These factories assemble proteins by translating instructions encoded within molecules of RNA. Ribosomes themselves are partially built form a special type of RNA known as rRNA. And when Johnson looked at the guts of CCD bees, he found unusually high levels of fragmented rRNA.
This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science. There’s been more work on CCD since, but I’m reposting this mainly because of some interesting follow-up research that will I will post about tomorrow.
In 2006, American and European beekeepers started noticing a strange and worrying trend – their bees were disappearing. Their hives, usually abuzz with activity, were emptying. There were no traces of the workers or their corpses either in or around the ghost hives, which still contained larvae and plentiful stores of food. It seemed that entire colonies of bees had apparently chosen not to be.
The cause of the aptly named ‘Colony Collapse Disorder’, or CCD, has been hotly debated over the last year. Fingers were pointed at a myriad of suspects including vampiric mites, pesticides, electromagnetic radiation, GM crops, climate change and poor beekeeping practices. And as usual, some people denied that there was a problem at all.
But a large team of US scientists led by Diana Cox-Foster and Ian Lipkin have used modern genomics to reveal a new villain in this entomological whodunnit – a virus called Israeli Acute Paralysis Virus or IAPV. By and large, the team found that where there was IAPV, there was CCD. The virus and the affliction were so stongly connected that Cox-Foster and Lipkin estimated that a hive infected with IAPV had a 96% chance of suffering from CCD. Once infected, the chances of a colony collapsing shot up by 65 times.
Viruses and bacteria often act as parasites, infecting a host, reproducing at its expense and causing disease and death. But not always – sometimes, their infections are positively beneficial and on rare occasions, they can actually defend their hosts from parasitism rather than playing the role themselves.
In the body of one species of aphid, a bacterium and a virus have formed a unlikely partnership to defend their host from a lethal wasp called Aphidius ervi. The wasp turns aphids into living larders for its larvae, laying eggs inside unfortunate animals that are eventually eaten from the inside out. But the pea aphid (Acyrthosiphon pisum) has a defence – some individuals are infected by guardian bacteria (Hamiltonella defensa) that save their host by somehow killing the developing wasp larvae.
H.defensa can be passed down from mother to daughter or even sexually transmitted. Infection rates go up dramatically when aphids are threatened by parasitic wasps. But not all strains are the same; some provide substantially more protection than others and Kerry Oliver from the University of Georgia has found out why.
H.defensa‘s is only defensive when it itself is infected by a virus – a bacteriophage called APSE (or “A.pisum secondary endosymbiont” in full). APSE produces toxins that are suspected to target the tissues of animals, such as those of invading wasp grubs. The phage infects the bacteria, which in turn infect the aphids – it’s this initial step that protects against the wasps.
During chase scenes, movie protagonists often make their getaway by releasing a decoy to cover their escape or distract their pursuer. But this tactic isn’t reserved for action heroes. Some deep-sea animals also evade their predators by releasing decoys – glowing ones.
Karen Osborn from the Scripps Institute of Oceanography has discovered seven new species of closely related marine worms (annelids) that use this trick. Four of these pack up to four pairs of “bombs” near their heads – simple, fluid-filled globes that the worms can detach at will. When released, the “bombs” give off an intense light that lasts for several seconds.
The worms were collected from the Pacific Ocean by remote-controlled submarines. Unfortunately, the small size of the bombs and the low resolution of the sub’s cameras meant that Osborn was never able to film the worms actually releasing their glowing payload in their natural environment (although she did capture some great videos; see bottom of post).
Nonetheless, the specimens she recovered would indeed launch one or two bombs, when they were prodded on any part of their body. If she prodded them further, they would release more bombs, until they ran out. The fact that some worms also carried much smaller globes suggests that they can regenerate them once their supply is exhausted.