Friday, November 27, 2009

BIGGER NOT NECESSARILY BETTER, WHEN IT COMES TO BRAINS

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Tiny insects could be as intelligent as much bigger animals, despite only having a brain the size of a pinhead, say scientists at Queen Mary, University of London.

"Animals with bigger brains are not necessarily more intelligent," according to Lars Chittka, Professor of Sensory and Behavioural Ecology at Queen Mary's Research Centre for Psychology and University of Cambridge colleague, Jeremy Niven. This begs the important question: what are they for?

Research repeatedly shows how insects are capable of some intelligent behaviours scientists previously thought was unique to larger animals. Honeybees, for example, can count, categorise similar objects like dogs or human faces, understand 'same' and 'different', and differentiate between shapes that are symmetrical and asymmetrical.

"We know that body size is the single best way to predict an animal's brain size," explains Chittka, writing in the journal Current Biology, today. "However, contrary to popular belief, we can't say that brain size predicts their capacity for intelligent behaviour."

Differences in brain size between animals is extreme: a whale’s brain can weigh up to 9 kg (with over 200 billion nerve cells), and human brains vary between 1.25 kg and 1.45 kg (with an estimated 85 billion nerve cells). A honeybee’s brain weighs only 1 milligram and contains fewer than a million nerve cells.

While some increases in brain size do affect an animal's capability for intelligent behaviour, many size differences only exist in a specific brain region. This is often seen in animals with highly developed senses (like sight or hearing) or an ability to make very precise movements. The size increase allows the brain to function in greater detail, finer resolution, higher sensitivity or greater precision: in other words, more of the same.

Research suggests that bigger animals may need bigger brains simply because there is more to control - for example they need to move bigger muscles and therefore need more and bigger nerves to move them.

Chittka says: "In bigger brains we often don't find more complexity, just an endless repetition of the same neural circuits over and over. This might add detail to remembered images or sounds, but not add any degree of complexity. To use a computer analogy, bigger brains might in many cases be bigger hard drives, not necessarily better processors."

This must mean that much 'advanced' thinking can actually be done with very limited neuron numbers. Computer modelling shows that even consciousness can be generated with very small neural circuits, which could in theory easily fit into an insect brain.

In fact, the models suggest that counting could be achieved with only a few hundred nerve cells and only a few thousand could be enough to generate consciousness. Engineers hope that this kind of research will lead to smarter computing with the ability to recognise human facial expressions and emotions.

(Photo: Queen Mary, UL)

Queen Mary, University of London

HEART DISEASE FOUND IN EGYPTIAN MUMMIES

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Hardening of the arteries has been detected in Egyptian mummies, some as old as 3,500 years, suggesting that the factors causing heart attack and stroke are not only modern ones; they afflicted ancient people, too.

"Atherosclerosis is ubiquitous among modern day humans and, despite differences in ancient and modern lifestyles, we found that it was rather common in ancient Egyptians of high socioeconomic status living as much as three millennia ago," says UC Irvine clinical professor of cardiology Dr. Gregory Thomas, a co-principal investigator on the study. "The findings suggest that we may have to look beyond modern risk factors to fully understand the disease."

The nameplate of the Pharaoh Merenptah (c. 1213-1203 BC) in the Museum of Egyptian Antiquities reads that, when he died at approximately age 60, he was afflicted with atherosclerosis, arthritis, and dental decay. Intrigued that atherosclerosis may have been widespread among ancient Egyptians, Thomas and a team of U.S. and Egyptian cardiologists, joined by experts in Egyptology and preservation, selected 20 mummies on display and in the basement of the Museum of Egyptian Antiquities for scanning on a Siemens 6 slice CT scanner during the week of Feb. 8, 2009.

The mummies underwent whole body scanning with special attention to the cardiovascular system. The researchers found that 9 of the 16 mummies who had identifiable arteries or hearts left in their bodies after the mummification process had calcification either clearly seen in the wall of the artery or in the path were the artery should have been. Some mummies had calcification in up to 6 different arteries.

Using skeletal analysis, the Egyptology and preservationist team was able to estimate the age at death for all the mummies and the names and occupations in the majority. Of the mummies who had died when they were older than 45, 7 of 8 had calcification and thus atherosclerosis while only 2 of 8 of those dying at an earlier age had calcification. Atherosclerosis did not spare women; vascular calcifications were observed in both male and female mummies.

The most ancient Egyptian afflicted with atherosclerosis was Lady Rai, who lived to an estimated age of 30 to 40 years around 1530 BC and had been the nursemaid to Queen Ahmose Nefertiri. To put this in context, Lady Rai lived about 300 years prior to the time of Moses and 200 prior to King Tutankhamun (Tut).

In those mummies whose identities could be determined, all were of high socioeconomic status, generally serving in the court of the Pharaoh or as priests or priestess. While the diet of any one mummy could not be determined, eating meat in the form of cattle, ducks and geese was not uncommon during these times.

"While we do not know whether atherosclerosis caused the demise of any of the mummies in the study, we can confirm that the disease was present in many," Thomas says.

(Photo: Dr. Michael Miyamoto / UC San Diego)

UC Irvine

RIGHT-HANDED CHIMPANZEES PROVIDE CLUES TO THE ORIGIN OF HUMAN LANGUAGE

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Most of the linguistic functions in humans are controlled by the left cerebral hemisphere. A study of captive chimpanzees at the Yerkes National Primate Research Center (Atlanta, Georgia), reported in the January 2010 issue of Elsevier's Cortex, suggests that this "hemispheric lateralization" for language may have its evolutionary roots in the gestural communication of our common ancestors.

A large majority of the chimpanzees in the study showed a significant bias towards right-handed gestures when communicating, which may reflect a similar dominance of the left hemisphere for communication in chimpanzees as that seen for language functions in humans.

A team of researchers, supervised by Prof. William D. Hopkins of Agnes Scott College (Decatur, Georgia), studied hand-use in 70 captive chimpanzees over a period of 10 months, recording a variety of communicative gestures specific to chimpanzees. These included 'arm threat', 'extend arm' or 'hand-slap' gestures produced in different social contexts, such as attention-getting interactions, shared excitation, threat, aggression, greeting, reconciliation or invitations for grooming or for play. The gestures were directed at the human observers, as well as toward other chimpanzees.

"The degree of predominance of the right hand for gestures is one of the most pronounced we have ever found in chimpanzees in comparison to other non-communicative manual actions. We already found such manual biases in this species for pointing gestures exclusively directed to humans. These additional data clearly showed that right-handedness for gestures is not specifically associated to interactions with humans, but generalizes to intraspecific communication", notes Prof. Hopkins.

The French co-authors, Dr. Adrien Meguerditchian and Prof. Jacques Vauclair, from the Aix-Marseille University (Aix-en-Provence, France), also point out that "this finding provides additional support to the idea that speech evolved initially from a gestural communicative system in our ancestors. Moreover, gestural communication in apes shares some key features with human language, such as intentionality, referential properties and flexibility of learning and use".

Elsevier's Cortex

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