Researchers have identified a "critical period" during which new nerve cells in adult brains have the same capacity to learn as those in developing brains. The finding in mice, reported in this week's Neuron, provides the promise of therapies that may one day limit or perhaps even reverse the damage of neurodegenerative diseases such as multiple sclerosis and Parkinson's.

Scientists first observed neurogenesis - the creation of new neurons in the adult brain - in animal brains in the 1960s but did not find evidence of it in humans until the late 1990s, says senior study author Hongjun Song, an assistant professor of neurology at the Johns Hopkins University School of Medicine in Baltimore.

Four people have tested positive for bird flu linked to a low-risk strain found in chickens which died on a farm in north Wales, as samples were being taken Saturday from another farm in the area.

Doctor Christianne Glossop, chief veterinary officer for Wales, has said that the chickens at the first farm died from the H7N2 low pathogenic avian influenza strain, not the most virulent H5N1 strain.

The Health Protection Agency (HPA) "confirmed infections in four" of the samples taken from nine people who were associated with the infected or dead birds and reported flu-like symptoms, its chief executive Pat Troop said.

"These test results confirm that human infection with the avian flu virus has occurred. The cases so far have been associated with the infected birds," Troop said.

The World Health Organisation (WHO) has announced that three children outside Vietnam have died after receiving vaccinations from two batches of hepatitis B vaccine produced by Korea's LG company.

FEDERAL Health Minister Tony Abbott and health authorities have urged parents not to panic over reports that dozens of teenage girls have been sickened by a new cervical cancer vaccine.

Event Reports Obtained from FDA Detail 1,637 Adverse Reactions to Gardasil

Judicial Watch, the public interest group that investigates and prosecutes government corruption, today released documents obtained from the U.S. Food and Drug Administration (FDA) under the provisions of the Freedom of Information Act, detailing 1,637 reports of adverse reactions to the vaccination for human papillomavirus (HPV), Gardasil. Three deaths were related to the vaccine. One physician's assistant reported that a female patient "died of a blood clot three hours after getting the Gardasil vaccine." Two other reports, on girls 12 and 19, reported deaths relating to heart problems and/or blood clotting.

An outbreak of mumps in eastern Canada appears to have spread to Manitoba.

Public health officials have confirmed two reported cases of mumps in Winnipeg, both in people in their 20s. Neither has been hospitalized.

Exposure to toxic materials in the womb can cause health problems later in life, an international panel declares.

In a strongly worded declaration, many of the world's leading environmental scientists warned Thursday that exposure to common chemicals makes babies more likely to develop an array of health problems later in life, including diabetes, attention deficit disorders, prostate cancer, fertility problems, thyroid disorders and even obesity.

At four months, babies can tell whether a speaker has switched to a different language from visual cues alone, according to a University of British Columbia study.

Researcher Whitney Weikum found that infants are able to discern when a different language is spoken by watching the shapes and rhythm of the speaker's mouth and face movements.

The findings suggest that older infants, raised in a monolingual environment, no longer need this facility. However, babies growing up in a bilingual environment advantageously maintain the discrimination abilities needed for separating and learning multiple languages.

In a paper to be published in the May 25 issue of the journal Science, Weikum explores whether babies use visual speech information to tell the difference between someone speaking their native language(s) and an unfamiliar language. Weikum is a UBC Neuroscience doctoral student working with Canada Research Chair and Psychology Prof. Janet Werker.

The researchers tested three groups of infants - ages four, six and eight months - from monolingual English homes and two groups of infants - ages six and eight months - from bilingual homes. They showed each group silent video clips of three bilingual French-English speakers, who recited sentences first in English or French, and then switched to the other language.

A popular stereotype that boys are better at mathematics than girls undermines girls' math performance because it causes worrying that erodes the mental resources needed for problem solving, new research at the University of Chicago shows.

The scholars found that the worrying undermines women's working memory. Working memory is a short-term memory system involved in the control, regulation and active maintenance of limited information needed immediately to deal with problems at hand.

They also showed for the first time that this threat to performance caused by stereotyping can also hinder success in other academic areas because mental abilities do not immediately rebound after being compromised by mathematics anxiety.

"This may mean that if a girl takes a verbal portion of a standardized test after taking the mathematics portion, she may not do as well on the verbal portion as she might do if she had not been recently struggling with math-related worries and anxiety," said Sian Beilock, Assistant Professor in Psychology and lead investigator in the study.

"Likewise, our work suggests that if a girl has a mathematics class first thing in the morning and experiences math-related worries in this class, these worries may carry implications for her performance in the class she attends next," she added.

The results of the study appear in the paper "Stereotype Threat and Working Memory: Mechanisms, Alleviation, and Spill Over," published in the current issue of the Journal of Experimental Psychology: General. Co-authors are Robert Rydell, a postdoctoral researcher in psychology at the University of California, Santa Barbara and Allen McConnell, University Distinguished Professor of Psychology at Miami University.

The use of 12 tone intervals in the music of many human cultures is rooted in the physics of how our vocal anatomy produces speech, according to researchers at the Duke University Center for Cognitive Neuroscience.

The particular notes used in music sound right to our ears because of the way our vocal apparatus makes the sounds used in all human languages, said Dale Purves, the George Barth Geller Professor for Research in Neurobiology.

It's not something one can hear directly, but when the sounds of speech are looked at with a spectrum analyzer, the relationships between the various frequencies that a speaker uses to make vowel sounds correspond neatly with the relationships between notes of the 12-tone chromatic scale of music, Purves said.

The work appeared online May 24 in the Proceedings of the National Academy of Sciences. (Download at http://www.pnas.org/cgi/reprint/0703140104v1)

Purves and co-authors Deborah Ross and Jonathan Choi tested their idea by recording native English and Mandarin Chinese speakers uttering vowel sounds in both single words and a series of short monologues. They then compared the vocal frequency ratios to the numerical ratios that define notes in music.