surtout que curieusement, ça semble aussi avoir des effets nocifs (à forte dose toujours et cette fois que sur les rats) sur le fonctionnement hépatique et sur l'absorption de fer :-o

ouais 'fin bon, les rats ils ont que de l'infusion de menthe assez concentrée à boire pendant 30 jours et les humains sont dans une zone où ils consomment quotidiennement plusieurs verres d'infusion à la menthe/ thé à la menthe par jour
avec une théière par ci par là, z'allez pas en mourir!

private ralerie: et après c'est moi qui suis binaire!

Rose-scented sleep improves memory
Bursts of scent during the night can help solidify learning.
Kerri Smith

It's often said that optimistic people look at the world through rose-tinted spectacles. Now it seems that rose-tinted smells can have benefits too.

Taking a whiff of rose scent while learning a task and then being exposed to the same smell during sleep helps memories to set, researchers have found. The discovery could see students frantically spraying themselves with perfume before exams — although the effect is tricky to replicate at home.

Jan Born of the University of Lübeck and his colleagues exposed people to the smell of roses one evening while they learned the locations of various picture cards laid in a square. Half of them were then given the same odour to smell as they slept, while the other half had an odour-free night. When they were tested the next day, those who'd had a rosy sleep remembered 97% of the locations — without the roses this figure was 86%.

The team's findings, published in Science1, supports theories about how memories are solidified in the brain during sleep.

Researchers think that a part of the brain called the hippocampus is like the scratch-pad of memory, where we put new things that have been experienced or learned until they can be filed for long-term storage. During sleep, these memories are 'reactivated' and transferred to the cortex.

Odours are known to have a potent effect on the hippocampus. Born and his team speculated that an odour could thus help to trigger the 'reactivation' process during sleep, making permanent memory storage more efficient. Their tests support this theory. "By experimentally inducing it, we can show that reactivation enhances memory," says Born.

On again, off again

But simply sleeping in a rose-scented room won't necessarily do the trick, because the timing of odour exposure is crucial.

Revising what you have to learn and then getting a good night's shut-eye might prove infinitely more practical.

Volunteers in the study had to be exposed during so-called slow-wave sleep, when the hippocampus is triggered into replaying memories. Passing roses under the nose during lighter, REM (rapid eye movement) sleep, when most dreams occur, had no effect on memory.

But because people get used to odours very quickly, the odour had to be turned on and off at the right times to get the memory effect.

You might think that a whiff of roses the following day, while being tested, would help the volunteers remember the card locations. But the researchers found that this didn't improve the volunteers' scores — though Born doesn't rule it out. The same mechanisms are involved in securing memory during sleep and when awake, he says — the difference is that the hippocampus is more sensitive when its owner is sleeping.

Don't do this at home
It's hard to tell the difference between slow-wave and other types of sleep without being hooked up to a brain scanner, making it a difficult technique to perfect at home. "It's difficult to imagine that we can create a machine that can improve memory during sleep," says Philippe Peigneux, a sleep researcher at the Brussels Free University in Belgium. For students, simply revising what you have to learn and then getting a good night's shut-eye might prove infinitely more practical.


The smell trick is useful only for certain types of learning. It won't be useful for remembering the skills needed for playing the piano or riding a bike, for example, because these activity-related memories don't rely on the hippocampus.

But the finding might provide a friendlier way to improve memory than other suggested techniques, says Born.

Born's group published a study in Nature last year that showed an increase in memory when people's brains were stimulated with a mild electric current2. "Everyone's afraid of shocking the brain," he says. "Odour presentation is a much 'softer' method."

'Semi-identical' twins discovered
Hermaphrodite reveals previously unknown type of twinning.
John Whitfield

Researchers have discovered a pair of twins who are identical through their mother's side, but share only half their genes on their father's side.

The 'semi-identical' twins are the result of two sperm cells fusing with a single egg — a previously unreported way for twins to come about, say the team that made the finding. The twins are chimaeras, meaning that their cells are not genetically uniform. Each sperm has contributed genes to each child.

"Their similarity is somewhere between identical and fraternal twins," says geneticist Vivienne Souter, of the Banner Good Samaritan Medical Center in Phoenix, Arizona. "It makes me wonder whether the current classification of twins is an oversimplification."

Such twins are probably very rare. Their existence and discovery relies on three unusual, and possibly unlinked, events: first, that an egg fertilized by two sperm develops into a viable embryo; second, that this embryo splits to form twins; and third, that the children come to the attention of science.

"There's value in understanding that this can happen, but it's extremely unlikely that we'll ever see another case," says Charles Boklage, an expert on twinning who works at Eastern Carolina University in Greenville, North Carolina.

Souter and her colleagues investigated the twins' genetic makeup because one was born with ambiguous genitalia. This twin turned out to be a 'true hermaphrodite', with both ovarian and testicular tissue. The other twin is anatomically male.

Genetic tests revealed that each twin contained some 'female' cells with two X chromosomes, and some 'male' cells with an X and a Y. The proportion of each type varies from tissue to tissue in each twin, the researchers report in Human Genetics1.

The babies, now toddlers, were conceived and born normally, and each twin's growth and mental abilities appear normal.

Just the two of us

Fraternal twins are formed when two eggs meet two sperm in the womb. Each is fertilized independently, and each becomes an embryo. With identical twins, one egg is fertilized by one sperm, and the embryo splits at some later stage to become two.

Occasionally, two sperm are known to fertilize a single egg; this 'double fertilization' is thought to happen in about 1% of human conceptions. An embryo created this way doesn't usually survive, but a few cases are known to have made it — these children are chimaeras of cells with X and Y chromosomes.

"The number of these cases is very small, but before they were reported, most people would have said this could never happen," says geneticist David Bonthron of the University of Leeds, UK.

The new case seems to be a sub-type of double fertilization that involves the extra step of twinning. There are two possible ways this could have happened. The first possibility is that an egg cell divided, without separating, and each cell was then fertilized with a single sperm. The genes could have then been muddled up before the egg fully separated. But egg division before fertilization is thought to be extremely rare, says Souter.

The second, more likely scenario is that two sperm cells fused with a single egg, creating an embryo with three sets of chromosomes. Then, perhaps at the embryo's two-cell stage, one cell would have shed the chromosomes from one sperm, and the other cell the other sperm's genes.

Curiosities

It had been previously predicted that this might happen. Biologist Michael Golubovsky, for example, now at the University of California, Berkeley, suggested in 2003 that twins intermediate between identical and fraternal might result from double fertilizations. The new discovery confirms his theory.

"There are a lot of unclear situations in the genetics of twins and twinning," Golubovsky says. "We need to keep our eyes open for other unusual scenarios."

"Whether these things are academic curiosities, or whether we've overlooked something significant is hard to say," says Bonthron. "A lot of what we know about fertilization is deductive, because we can't observe these events in humans."

http://news.bbc.co.uk/2/hi/health/6517137.stm

Un avis là dessus, les biologistes ?

C'est pas de la bio mais il me semblait que c'était le thread le plus approprié.

C'est quoi cette discrimination ? Les informaticiens ne sont pas des scientifiques, peut-être ?

Et, de façon complètement subjective, j'ai estimé qu'un rapport sur l'état de la science aurait plus tendance à intéresser les rares biologistes que les nombreux informaticiens :razz2: