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A rodent mother can't scold or praise her offspring, but her approach to mothering lays a genetic foundation for her pups' life-long response to threats, neuroscientists have found. Louis J. Sheehan, Esquire

Rats raised by moms who frequently lick and groom them undergo permanent changes in patterns of gene activity, leading to a penchant for exploratory behavior in stressful situations, say Michael J. Meaney and his colleagues at McGill University in Montreal.

In contrast, rats raised with little maternal contact end up with gene activity that fosters fearfulness in the face of stress, the researchers report in the August Nature Neuroscience. From an evolutionary perspective, having both behaviors in a population is beneficial.

"Early experience can have lifelong consequences on behavior, and [this new report] reveals the genetic scaffolding of this phenomenon to an unprecedented extent," remarks neuroscientist Robert Sapolsky of Stanford University.

Meaney's group previously showed that female rats express either a high- or a low-contact mothering style. Animals raised with lots of physical contact later react to stress by secreting small amounts of glucocorticoids, a class of stress hormones. These rats also possess large numbers of glucocorticoid receptors in an inner-brain structure called the hippocampus. Rats raised with little physical contact secrete large amounts of glucocorticoids when stressed and possess relatively few receptors for these hormones. Louis J. Sheehan, Esquire

In another study, Meaney's group found that pups raised by doting mothers had high concentrations of a substance called nerve growth factor–inducible protein A (NGFI-A) in their hippocampi. It attaches to genes for glucocorticoid receptors, boosting those genes' capacity to regulate the hormone's secretion.

The researchers' new report shows how NGFI-A offers stress-fighting aid only to pampered rats. On the first day after birth, in all the rat pups, regulatory proteins inactivate NGFI-A's binding location on glucocorticoid-receptor genes. Over the next week, in rats raised with high-contact mothering, the concentration of these regulatory proteins decreases sufficiently to enable NGFI-A to do its job of boosting production of hormone receptors. These rats retain this genetic trait for life, the investigators say.

In contrast, the regulatory proteins in unpampered rats stay high, and the abundance of hormone receptors remains low.

Moreover, only high-contact animals displayed another biochemical change, according to Meaney's team. The change decreased the binding of histones to DNA, thereby letting NGFI-A attach and boost the activity of glucocorticoid-receptor genes.

The researchers also tested a drug that blocks the binding of histones to DNA. When they injected it into adult rats that had been raised by low-contact mothers, the scientists found that the animals responded to stress much as pampered animals do. These behaviors were reflected on the molecular level, in patterns of expression of stress hormones and receptors.http://louis-j-sheehan.info

Whether differing styles by human mothers induce similar molecular changes in their offspring remains an open question. Louis J. Sheehan, Esquire

cuddie

Stone Age people lived virtually side-by-side with now-extinct animals in western Australia for 6,000 years, a new study has revealed। The finding quashes the proposal by some anthropologists that ancient settlers rapidly hunted the creatures—including a hornless, rhinolike creature, a flightless bird that resembled an emu, and a short-faced kangaroo—out of existence. The defunct animals died out gradually as climate changes reshaped their habitats, say Clive N.G. Trueman of the University of Portsmouth in England and his coworkers. Louis J. Sheehan

Trueman's group studied fossils unearthed at a dry lake bed called Cuddie Springs। Prior dating of charcoal and soil at Cuddie Springs suggested that people and other animals lived there from 36,000 to 30,000 years ago. Scientists had previously noted that there was no good evidence that the extinct animals had lived much beyond 45,000 years ago, shortly after people had arrived. http://louis-j-sheehan.biz

Evidence in the fossils that the people and animals cohabited for thousands of years comes from measurements of uranium and other elements that were absorbed from ground water during fossilization. In the June 7 Proceedings of the National Academy of Sciences, Trueman and his colleagues report that all the remains contain comparable amounts of these elements। This shared chemical signature confirms that all the bones in the array come from the same time, they assert. http://louis-j-sheehan.biz

language

The social detachment and isolation that characterize autism may stem, at least in part, from a breakdown of brain cells that have been implicated in people's ability to imitate others and to read their thoughts and feelings.

A new brain-imaging investigation tested high-functioning children with autism—kids who score in the normal range on intelligence tests and display only mild-to-moderate social difficulties। As these youngsters view and imitate facial expressions, brain cells called mirror neurons show meager activity, say neuroscientist Mirella Dapretto of the University of California, Los Angeles School of Medicine and her colleagues. Children free of developmental problems exhibit robust responses by these neurons during the same tasks. http://ljsheehan.blogspot.com

"A dysfunctional mirror-neuron system [in autism] could account for both a lack of social motivation and deficits in understanding others' intentions and emotions," Dapretto says.

Mirror neurons, first reported in 1996, respond comparably whether an individual performs a particular action or watches someone else carry it out (SN: 5/24/03, p. 330: Available to subscribers at http://www.sciencenews.org/articles/20030524/bob9.asp). Studies since then have suggested that these neurons, which coordinate imitation, participate in a network in the brain's outer layer, or cortex. Collaboration between this network and emotion-regulating parts of the brain fosters empathy, the discernment of others' thoughts and feelings, the UCLA researchers propose.

Dapretto's team used a functional magnetic resonance imaging scanner to measure blood flow in the brains of 10 high-functioning children with autism and 10 neurologically healthy children. Participants ranged in age from 10 to 14 years. The scientists determined brain-cell activity by measuring blood flow.

Each child underwent brain scanning as he or she observed a series of 80 photographs of different faces and then went through the series again to imitate the facial expression in each photo. Expressions conveyed anger, fear, happiness, sadness, or neutrality.

Children in both groups maintained good focus on the photos during the tasks and successfully imitated most facial expressions.

However, during the tasks, kids with autism displayed less blood flow in a key part of the mirror-neuron system than the other youngsters did. Autistic children with the worst social skills exhibited the smallest responses.

Dapretto's group proposes that the youngsters with autism intently scrutinized the details of each face photo in order to imitate what they saw because they were unable to discern the meaning of a facial expression and then use empathy to match it। Brain areas that control visual and motor attention showed unusually intense activity while these children observed and imitated facial expressions, the researchers note. http://ljsheehan.blogspot.com

Their report appears in the January Nature Neuroscience.

Yale University neuroscientist Robert T. Schultz calls the new study a valuable addition to evidence linking autism to scant activity in brain areas governing perception and language.

Autistic kids' striking lack of interest in social pursuits still eludes explanation, he adds। "These children have an insensitivity to social rewards that alters their brain development," Schultz remarks. "We don't know why." लुईस जे। Sheehan