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Sunday, Aug. 14, 2011
Delving into 'white matter'
By ROWAN HOOPER
Last week I watched "Rise of the Planet of the Apes," a new film about superintelligent chimps that bust out of captivity and rampage across San Francisco in a bid for freedom.
After that — of which more in a moment — I came across a new paper by Kyoto University's famed primatologist, Tetsuro Matsuzawa.
Matsuzawa's work is always fascinating. He has been working on the Ai project at Kyoto since 1978, a study on the memory and language ability of a female chimp named Ai. The project is one of the world's longest-running lab-based inquiries into chimpanzee intelligence.
By a happy coincidence, given that I'd just watched a film about smart chimps, this latest paper turns out to be the first to track the development of the chimpanzee brain over time — and to compare it with what happens in humans.
First a bit about the movie. In it, a well-meaning scientist (played by James Franco) is working on a treatment for Alzheimer's disease, and he tests a drug he's developed on chimps in a medical research facility.
He finds that it works remarkably well — and delivers a massive boost in intelligence for the treated chimps. But will it work on humans with dementia?
Alzheimer's, it hardly needs saying, is a devastating disease. Not only does it prevent the formation of new memories, but it then causes the loss of language ability and of long-term, distant memories. It is also big business.
Research has suggested that worldwide by 2050 one person in 85 will suffer from the disease. In countries with aging populations, such as Japan, it is already a significant social problem, and it will only get worse.
Clearly, a biomedical company that can find a cure or treatment for Alzheimer's will stand to make a lot of money.
In "Rise of the Planet of the Apes," Franco's gene-therapy treatment is used to make the brain grow new neurons. This suddenly gives chimps the brain power of humans. Handily, too, the chimps that have been treated with the drug also develop beautiful green eyes, so it is easy to tell the smart ones from the regular dumb ones.
Matsuzawa in Kyoto doesn't have a smart drug for chimpanzees, but he's now performed brain scans on three growing chimps from the age of 6 months to 6 years, which is when chimps reach pre-puberty.
In both chimpanzees and humans, there are portions of the brain that become critical later in life but are immature at birth. But Matsuzawa's brain scans show that baby chimps don't undergo the explosive growth in "white matter" in the brain that human children do. His work is published in the journal Current Biology (DOI 10.1016/j.cub.2011.07.019).
So what is white matter and why is it important?
The brain is made of neurons: about 86 billion of them. A neuron has a central "body" and long spindly "arms," or axons, that connect to other neurons. The cell body is gray and the axons are white. In fact, the axons are covered in a fatty insulating substance called myelin, and it is this that gives them their pale-white color.
Although they are individually microscopic, there are lots and lots of axons in the brain: A young man's head contains about 176,000 km of them.
"One of the most marked evolutionary changes underlying human-specific cognitive traits is a greatly enlarged prefrontal cortex," said Matsuzawa. "It is also one of the latest-developing brain regions of the cerebrum," he noted in reference to this large frontal lobe where the "higher," executive powers of the brain are located and where we reason, and decide, and plan future movement.
In other words, both chimps and humans are born with underdeveloped frontal cortexes, and these develop as we grow up. Matsuzawa suggests that this developmental delay may provide an extended period of flexibility, allowing both humans and chimps to develop complex social interactions, knowledge and skills that are shaped by life experiences.
Or as Matsuzawa puts it, more dryly: "Both humans and chimpanzees need to render their neural network and brain function more susceptible to the influence of postnatal experience."
Both chimps and humans enjoy close relationships between infants and adults. However, Matsuzawa's team found in their brain scans of chimps at different ages that their prefrontal cortex doesn't expand as much as in humans. The greater expansion of this region in the human brain may contribute to the development of language, complex social interaction and other abilities that are unique to us.
Matsuzawa says his group is interested in exploring when, over the course of evolutionary time, this feature of brain development evolved.
His team also hopes to explore the comparison between human and chimpanzee brains into young adulthood, noting that the chimps they've studied have entered late puberty at 11 years of age.
We already know quite a lot about that mysterious and (for parents) infuriating period when human children enter puberty and the teenage years — soon we will understand the equivalent period in chimps.
I've never visited Matsuzawa's lab in Kyoto, but from what I've seen, the chimps appear to be happy, and they are certainly well cared for — pampered, even. It is anyway not a lab where invasive experiments are carried out on chimps. That's all quite different from the inhuman, prison-like conditions depicted in "Rise of the Planet of the Apes."
The film has a vital message: that we should respect and care for our closest animal relatives better than we currently do. But it delivers that message with a distinct lack of subtlety (though I enjoyed it more than Tim Burton's 2001 "Planet of the Apes," which I reviewed for the JT; see search.japantimes.co.jp/cgi-bin/fe20010725a1.html)
Scientists, too, are not all as dumb as those in the film, and even multinational drug corporations aren't as evil as depicted.
Meanwhile, during a Q&A session after a screening of the movie in London, Andy Serkis, who plays the chimp leader, Caesar, was asked if — despite the computer-generated imagery — he recognizes himself when he sees Caesar. "Absolutely," he replied. "When I look at Caesar I see myself."
That's what makes chimpanzees so fascinating: the fact that we can see so much evidence of the roots of human behavior in what they do.
Rowan Hooper (@rowhoop on Twitter) is the News Editor of New Scientist magazine. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is "Hito wa Ima mo Shinka Shiteru" ("The Evolving Human"). "Rise of the Planet of the Apes" opens on Oct. 7 in Toho Cinemas.