Saturday, August 30, 2008

hippocampus

Two inner-brain structures show signs of unusual development in autistic children and teenagers, according to a new brain-scan investigation. Louis J. Sheehan, Esquire

The imagery reveals that boys between ages 7 and 12 diagnosed with autism have larger amygdalas than neurologically healthy boys do, say David G. Amaral of the University of California, Davis and his coworkers. The amygdala is associated with emotional responses to social situations.

This finding held regardless of whether autism was accompanied by mental retardation, as often occurs. However, amygdala volume expanded markedly by age 18 in the healthy youths while remaining the same in those with autism. As a result, amygdala size ultimately wound up about equal for both groups, Amaral's team reports in the July 14 Journal of Neuroscience.

All boys with autism also displayed a larger right hippocampus than healthy boys did. Only boys whose autism was accompanied by good intellectual functioning possessed a larger left hippocampus as well. These neural differences remained during adolescence.

An enlarged hippocampus in autism may aid memory for spatial and factual information, the scientists suggest.

They used magnetic resonance imaging to study the brains of 98 participants, ages 7 to 18, who met criteria for autism with retardation, autism without retardation, Asperger syndrome (a mild form of autism), or typical development. For boys with Asperger syndrome, amygdala and hippocampus development was disturbed to a lesser extent than it was in boys with autism.

Sunday, August 24, 2008

krapina

After excavating a cache of Neandertal fossils about 100 years ago at Krapina Cave in what's now Croatia, researchers concluded that incisions on the ancient individuals' bones showed that they had been butchered and presumably eaten by their comrades. That claim has proved difficult to confirm. A new, high-tech analysis indicates that the Krapina Neandertals ritually dismembered corpses in ways that must have held symbolic meaning for the group—whether or not Neandertals ate those remains.

Neandertals apparently possessed a facility for abstract thought that has often been regarded as unique to modern Homo sapiens, says study director Jill Cook of the British Museum in London. The Krapina Neandertals lived around 130,000 years ago.http://ljsheehan.livejournal.com

"Some kind of mortuary practice that had symbolic significance was going on at Krapina," Cook suggests. Although cannibalism might also have occurred, the bodies were systematically sliced up rather than quickly butchered, in her view. "Even eating people is a complex behavior" that likely would have included ritual of some kind, the British anthropologist notes.

Cook described the new investigation last week in Milwaukee at the annual meeting of the Paleoanthropology Society.

access

She and her colleagues used digital-imaging microscopy to generate high-resolution views of stone-tool incisions on Krapina remains. Many of the more than 800 fossils, which represent nearly 80 individuals, contain such markings. The researchers digitally lifted and separated images of incisions on individual bones for closer examination.

A partial skull known as Krapina 3 provided the biggest jolt. To the researchers' surprise, it contains a pattern of regularly spaced, parallel grooves across the top of the head. "Someone sat with this skull in their lap and produced this extraordinary pattern with a stone tool," Cook says.

Krapina 3 and other skull remains exhibit marks made by slicing away the ears, removing the tongue, detaching the lower jaw, and skinning the head. Lower-body fossils contain incisions created by removing muscle from bones as well as abrasions caused by scrubbing fat and gristle off bones. Cuts on pelvic and leg bones indicate that bodies lay facedown during dismemberment.http://ljsheehan.livejournal.com

Researchers who have worked at the Krapina Cave greeted the new findings with caution. "We can't rule out some type of ritual activity at Krapina, or even cannibalism," says Fred Smith of Loyola University in Chicago. "But we can't tell for sure why these bones were processed." Many limb bones at the site were smashed open, perhaps to extract protein-rich marrow, Smith notes.

Even with digital technology, it's difficult to pinpoint incisions on the Krapina fossils, adds Milford Wolpoff of the University of Michigan in Ann Arbor. A shellac coating applied to the bones as a preservative shortly after their discovery obscures many surface features on the bones, he asserts.http://louis-j-sheehan.info

Of stone-tool marks that can be seen with digital microscopy, many resemble those on butchered-animal remains at later Stone Age sites, says Paola Villa of the University of Colorado Museum in Boulder. In her view, that raises the possibility that cannibalism, devoid of ritual, occurred at Krapina.

Studies comparing the Krapina bones with those of prehistoric game animals are under way, Cook says.Louis J. Sheehan

Friday, August 15, 2008

mutations

A gene that exerts wide-ranging effects on the brain works harder in people than it does in chimpanzees and other nonhuman primates, a DNA disparity that apparently contributed to the evolution of Homo sapiens, according to a new study.

The gene participates in production of prodynorphin, an opiumlike protein that serves as a building block for chemical messengers in the brain known as endorphins. Studies have implicated endorphins in the anticipation and experience of pain, in the formation of intimate emotional bonds with others, and in learning and memory.

All primates possess a virtually identical prodynorphin gene, say geneticist Matthew V. Rockman of Princeton University and his colleagues. However, a separate stretch of DNA regulates the extent to which the gene generates prodynorphin. This regulatory DNA displays a handful of mutations in people that must have evolved by natural selection and aided human survival, the scientists propose. The new findings appear in the December PLoS Biology.

"This is the first documented instance of a neural gene that has had its regulation shaped by natural selection during human origins," says geneticist and study coauthor Matthew W. Hahn of Indiana University in Bloomington.

Rockman's team first compared chemical sequences of prodynorphin-regulating DNA from 74 people and 32 nonhuman primates. The latter group consisted mainly of chimps but included gorillas, orangutans, baboons, and macaque monkeys.http://Louissheehan.BraveDiary.com

The people generally possessed two to four copies of the regulatory sequence, in contrast to just one copy for each nonhuman primate. Moreover, the people displayed distinctive rearrangements at five spots along the DNA sequence. A strikingly large proportion of the regulatory sequence—about 10 percent—differed between people and chimps, Hahn says.

Rockman and his coworkers also inserted copies of human and chimp regulatory sequences into human-brain cells grown in laboratory cultures. Chemical stimulation of neurons containing the human sequence yielded much more prodynorphin than did stimulation of cells containing the chimp sequence.

Finally, the scientists analyzed DNA from 510 individuals around the globe. They found that many people now living in Europe and eastern Africa possess three copies of the prodynorphin regulatory sequence, whereas people in India and China usually possess two copies of that sequence.

Changes, or mutations, in the human prodynorphin regulatory sequence must have enhanced survival over other primate species, the investigators contend, while the geographic differences that they found may have bestowed as yet unknown advantages on specific human populations. The prodynorphin-regulating gene may indeed have contributed to the evolution of people, says geneticist Sarah Tishkoff of the University of Maryland at College Park.

Geneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, regards the new study as the first convincing demonstration of a regulatory gene influencing human evolution. Until now, such evidence has been "notoriously hard to find," he says.http://Louissheehan.BraveDiary.com

Mutations of regulatory and protein-making genes acted in concert during human evolution