“Decision making, emotional processing, empathy, and theory of mind all appear to be involved in understanding sarcasm,” says lead researcher Simone Shamay-Tsoory, a neuropsychologist at the Rambam Medical Center in Haifa, Israel.

Previous research has shown that people with damage in the prefrontal cortex (PFC) have difficulty understanding non-verbal aspects of language like tone, says Richard Delmonico, a neuropsychologist at the University of California at Davis, US.

Researchers studied 25 participants with damage to their prefrontal lobes, 16 participants with damage in the posterior lobes, and 17 healthy controls. They assessed people’s ability to understand someone else’s emotional state by testing how well they could recognise different facial expressions and tone of voice.

To determine if participants understood sarcasm, researchers read a sarcastic and non-sarcastic version of a story and asked participants what the speaker meant in each situation. They also tested ‘theory of mind’ – the ability to understand another person’s frame of mind – by determining if people could recognise when a story contained a “social faux-pas”.

Series of events

Shamay-Tsoory and colleagues found that people with prefrontal damage had trouble recognising sarcasm, while people with damage in posterior brain areas were unaffected. People with damage in the right hemisphere and the prefrontal lobe also had problems understanding the emotional cues involved in processing sarcasm, such as tone of voice or theory of mind, which correlated with their ability to understand sarcasm.

Based on the findings, Shamay-Tsoory suggests that understanding sarcasm requires a series of events – the brain’s language areas interpret the literal meaning of a statement, the right hemisphere and frontal lobes process the emotional context, while the prefrontal cortex integrates the two.

The research could help doctors distinguish between different types of neurodegenerative diseases, such as frontotemporal dementia and Alzheimer’s disease, says David Salmon, a neuroscientist at the University of California at San Diego, US. Doctors may also be able to give families a better idea of what kind of problems to expect from brain-damaged or diseased patients.

Journal reference: Neuropsychology (vol 19, p 288)

Previous screening tests have shown the prions that cause BSE are found only in specific organs, such as the brain and intestines. “So the assumption has been that other parts are safe to eat,” says Adriano Aguzzi, at the University Hospital of Zurich, Switzerland, who led the new research.

“People in countries with BSE still eat steak because the authorities say if you stay away from the brain and lymphoid tissue, you should be safe,” he told żěè¶ĚĘÓƵ. However, the experiments to find out where BSE prions lurk in cattle incubating the disease have been done in otherwise healthy animals, he says: “If you have a sick cow, these rules may no longer apply.”

The US and UK agencies responsible for BSE testing say the findings do not warrant any immediate changes to existing regulations, but say they plan to review the new research in depth.

Infectivity can vary between species, says Danny Matthews, at the UK Department for Environment, Food and Rural Affairs, so the results need to be replicated in cattle. The officials also claim that inflamed tissue can be identified and removed from carcasses along with specified risk organs.

Prion bioreactor

However, if the findings of Aguzzi’s team translate to cattle, changes may be needed. Current European surveillance programs test the central nervous system of slaughtered cattle for signs of infection, on the assumption that even animals incubating the disease poses no risk to consumers until prions show up in the brain.

But if inflamed organs are infected with prions earlier than brain tissue – as preliminary results from Aguzzi’s lab suggest – animals whose brains test negative for BSE could still be carrying dangerous levels of prions in other organs, and those could end up in food.

In their new study, the researchers tested mice with five different inflammatory diseases of the kidney, pancreas and liver. They found that in all cases, chronic inflammation caused a build up of prion proteins in organs that are normally prion-free.

“The organ transforms itself into a bioreactor for prions,” says Aguzzi. For example, diabetic mice injected with prions end up with a pancreas full of the misfolded protein, while the organ is unaffected in healthy mice.

Immune reaction

While inflammation does affect where prions accumulate, it does not make animals more susceptible to brain infection or affect how quickly the disease makes the animals sick. The team now plans to carry out similar experiments with farm animals.

The scientists are not sure why inflamed organs become more vulnerable to prions, but suspect it may be connected to the immune reaction. When an organ is inflamed, the immune system produces blood cells called lymphocytes to help battle the disease.

These cells produce a substance called lymphotoxin, which Aguzzi says may trigger a reaction that turns a normal cell into one capable of replicating prions. His lab has found that mice lacking the lymphotoxin receptor lack prion disease in inflamed organs.

Journal reference: Science (DOI: 10.1126/science.1106460)

Rats have an exquisitely sensitive sense of smell and can crawl just about anywhere. This combination makes them ideal candidates for sniffing out buried survivors. For that, the animals need to be taught to home in on people, and they must also signal their position to rescuers on the surface.

In a project funded by DARPA, the Pentagon’s research arm, Linda and Ray Hermer-Vazquez of the University of Florida in Gainesville have worked out a way to achieve this.

First the researchers identified the neural signals rats generate when they have found a scent that they are looking for. “When a dog is sniffing a bomb, he makes a unique movement that the handler recognises,” says John Chapin, a neuroscientist at the State University of New York in Brooklyn who is collaborating on the project. “Instead of the rat making a conditioned response, we pick up the response immediately from the brain.”

Pleasurable sensations

Each rat has electrodes implanted in three areas of the brain: the olfactory cortex, where the brain processes odour signals; the motor cortex, where the brain plans its next move; and the reward centre, which when stimulated gives the rat a pleasurable sensation.

The electrodes, each consisting of an array of up to 32 stainless steel wires 75 micrometres in diameter, are permanently implanted in the brain and can give accurate signals for up to nine months.

The researchers trained the rats to search for human odour by stimulating the reward centre when it found its target smell. Once the rats were trained, they were set to forage for the target smell, while electrodes recorded their neural activity patterns.

This allowed researchers to identify the brainwave patterns associated with finding that smell. They were also able to train the rats to sniff out the explosives TNT and RDX – key after terrorist attacks that may leave buildings harbouring unexploded bombs.

High-frequency activity

“There are two neural events that we believe are hallmarks of the ‘aha!’ moment for the rat,” says Linda Hermer-Vazquez. These are high-frequency activity in one subset of neurons, and decreased activity in two other areas, she says.

Signals from the rat’s brain will be relayed to a radio transmitter pack strapped to the animal’s back, which Chapin is developing. Rescuers will be able to follow the rat’s position by tracking these signals. They are also developing software that will recognise the “aha!” moment when the rat has found its target, so rescuers will know where to start digging. The team hope to create a working system within nine months.

Other teams looking at ways to seek people trapped under debris have designed wheeled, tracked or even snake-like robots that can slither into wrecked buildings (żěè¶ĚĘÓƵ print edition, 10 November 2001).

But rats have several advantages. “Artificial noses don’t work well when there are other smells around,” says Christiane Linster, an olfaction expert at Cornell University in New York. “Rats are good at that.” Rats are also adept at navigating over unexpected obstacles, and of course they do not need an electricity supply.

Rescue teams welcome the idea. “It would be absolutely fantastic,” says Julie Ryan of International Rescue Corps in Scotland, which flies rescuers to disaster zones around the world. “A rat could get into areas and spaces we couldn’t get to. And a rat would try to get out if it didn’t feel safe.”

Linguist Amy Perfors of the Massachusetts Institute of Technology in Boston, US, placed photos with fake names on a website called “Hot or Not”, which allows viewers to rank strangers’ photos for attractiveness.

She found that men labelled with names including “front vowels,” such as the “aaa” sound in Matt were rated as more attractive by website viewers than photos labelled with “back vowel” names, such as the “aw” sound in Paul. The opposite was true for women’s names.

While most linguists agree that there is no inherent relationship between the sound of a word and its meaning, there is some evidence to the contrary, says Perfors. Front vowels, those produced in the front of the mouth, are often perceived as smaller than back vowels, those produced in the back of the mouth.

It may seem counterintuitive that men named with the smaller-sounding front vowel are rated as more attractive. But other studies have shown that men with slightly feminine features are considered more desirable, says Perfors. “Maybe women are subconsciously looking for more sensitive or gentle men,” she says.

Persistent association

But having too feminine a name could backfire for men – as those labelled with women’s names were rated least attractive. However, having a man’s name – such as Bob – had no negative effect on a woman’s attractiveness to website viewers.

“No one knows why people make these associations with front and back vowel sounds,” says Lera Boroditsky, a psychologist at Stanford. It may be that some words with these sounds have created a persistent association, she says.

“This is a very clever example of how to use the tremendous resources of the web,” adds Boroditsky.

And while the effects were robust, an attractive name cannot completely compensate for a face that is more frog than prince. “An attractive person with a bad vowel name is still more attractive than an unattractive person with a good vowel name,” says Perfors.

The study results were presented at the Cognitive Science Society meeting in Chicago, US on 7 August.