[TN-Bird] Article about birds having "minds of their own."
- From: Dthomp2669@xxxxxxx
- To: Dthomp2669@xxxxxxx
- Date: Wed, 2 Feb 2005 07:45:17 EST
Here is an interesting "birdy" article that I hope you will all enjoy and,
hopefully, will not think it to be too "off message" for me to have posted.
Dee Thompson
Nashville, TN
February 1, 2005
Minds of Their Own: Birds Gain Respect
By SANDRA BLAKESLEE
irdbrain has long been a colloquial term of ridicule. The common notion is
that birds' brains are simple, or so scientists thought and taught for many
years. But that notion has increasingly been called into question as crows and
parrots, among other birds, have shown what appears to be behavior as
intelligent
as that of chimpanzees.
The clash of simple brain and complex behavior has led some neuroscientists
to create a new map of the avian brain.
Today, in the journal Nature Neuroscience Reviews, an international group of
avian experts is issuing what amounts to a manifesto. Nearly everything
written in anatomy textbooks about the brains of birds is wrong, they say. The
avian
brain is as complex, flexible and inventive as any mammalian brain, they
argue, and it is time to adopt a more accurate nomenclature that reflects a new
understanding of the anatomies of bird and mammal brains.
"Names have a powerful influence on the experiments we do and the way we
think," said Dr. Erich D. Jarvis, a neuroscientist at Duke University and a
leader
of the Avian Brain Nomenclature Consortium. "Old terminology has hindered
scientific progress."
The consortium of 29 scientists from six countries met for seven years to
develop new, more accurate names for structures in both avian and mammalian
brains. For example, the bird's seat of intelligence or its higher brain is now
termed the pallium.
"The correction of terms is a great advance," said Dr. Jon Kaas, a leading
expert in neuroanatomy at Vanderbilt University in Nashville who did not
participate in the consortium. "It's hard to get scientists to agree about
anything."
Scientists have come to agree that birds are indeed smart, but those who
study avian intelligence differ on how birds got that way. Experts, including
those in the consortium, are split into two warring camps. One holds that
birds'
brains make the same kinds of internal connections as do mammalian brains and
that intelligence in both groups arises from these connections. The other holds
that bird intelligence evolved through expanding an old part of the mammal
brain and using it in new ways, and it questions how developed that
intelligence
is.
"There are still puzzles to be solved," said Dr. Peter Marler, a leading
authority on bird behavior at the University of California, Davis, who is not
part
of the consortium. But the realization that one can study mammal brains by
using bird brains, he said, "is a revolution."
"I think that birds are going to replace the white rat as the favored subject
for studying functional neuroanatomy," he added.
The reanalysis of avian brains gives new credibility to many behaviors that
seem odd coming from presumably dumb birds. Crows not only make hooks and
spears of small sticks to carry on foraging expeditions, some have learned to
put
walnuts on roads for cars to crack. African gray parrots not only talk, they
have a sense of humor and make up new words. Baby songbirds babble like human
infants, using the left sides of their brains.
Avian brains got their bad reputation a century ago from the German
neurobiologist Ludwig Edinger, known as the father of comparative anatomy.
Edinger
believed that evolution was linear, Dr. Jarvis said. Brains evolved like
geologic
strata. Layer upon layer, the brains evolved from old to new, from fish to
amphibians to reptiles to birds to mammals. By Edinger's standards, fish were
the
least intelligent. Humans, created in God's image, were the most intelligent.
Edinger cut up all kinds of vertebrate brains, noting similarities and
differences, Dr. Jarvis said.
In mammals, the bottom third of the brain contained neurons organized in
clusters. The top two-thirds of the brain, called the neocortex, consisted of a
flat sheet of cells with six layers. This new brain, the seat of higher
intelligence, lay over the old brain, the seat of instinctual behaviors.
In humans, the neocortex grew so immense that it was forced to assume folds
and fissures, so as to fit inside the skull.
Birds' brains, in contrast, were composed entirely of clusters. Edinger
concluded that without a six-layered cortex, birds could not possibly be
intelligent. Rather, their brains were fully dedicated to instinctual
behaviors.
This view persisted through the 20th century and is still found in most
biology textbooks, said Dr. Harvey Karten, a neuroscientist at the University
of
California, San Diego, and a member of the consortium, whose research has long
challenged the classic view.
There is a bird way and a mammal way to create intelligence, Dr. Karten said.
One uses clusters. One uses flat sheet cells in six layers. Each exploits the
basic design of having a lower brain and a higher brain with mutual
connections.
In the 1960's, Dr. Karten carried out experiments using new techniques to
trace brain wiring and identify the paths taken by various brain chemicals. In
humans, a chemical called dopamine is found mostly in lower brain areas, called
basal ganglia, which consist of clusters.
Using the same tracing techniques in birds, Dr. Karten found that dopamine
also projected primarily to lower clusters and no higher. Later studies show
numerous similarities between clusters in the mammalian brain and lower
clusters
in the avian brain. Experts now agree that the two regions are evolutionarily
older structures that lie underneath a newer mantle.
Where the experts divide is on the question of the upper clusters in a bird's
brain. Agreed, they are not primitive basal ganglia. But where did they come
from? How did they evolve? What is their function?
Dr. Karten and others in the consortium think these clusters are directly
analogous to layers in the mammalian brain. They migrate from similar embryonic
precursors and perform the same functions.
For example, in mammals, sensory information - sights, sounds, touch - flows
through a lower brain region called the thalamus and enters the cortex at the
fourth layer in the six-layered cortex.
In birds, sensory information flows through the thalamus and enters specific
clusters that are functionally equivalent to the fourth layer. In this view,
other clusters perform functions done by different layers in the mammal brain.
A second group, including Dr. Georg Striedter of the University of
California, Irvine, a consortium member, believes that upper clusters in the
avian brain
are an elaboration of two mammalian structures - the claustrum and the
amygdala. In this view, these structures look alike in bird and mammal embryos.
But
in birds they grow to enormous proportions and have evolved entirely new ways
to support intelligence.
In mammals, the amygdala is involved in emotional systems, Dr. Striedter
said. "But birds use it for integrating information," he said. "It's not
emotional
anymore."
Meanwhile, examples of brilliance in birds continue to flow from fields and
laboratories worldwide.
Dr. Nathan Emery and Dr. Nicola Clayton at the University of Cambridge in
England study comparisons between apes and corvids - crows, jays, ravens and
jackdaws. Relative to its body size, the crow brain is the same size as the
chimpanzee brain.
Everyone knows apes use simple tools like twigs, Dr. Emery said, selecting
different ones for different purposes. But New Caledonian crows create more
complex tools with their beaks and feet. They trim and sculpture twigs to
fashion
hooks for fetching food. They make spears out of barbed leaves, probing under
leaf detritus for prey.
In a laboratory, when a crow named Betty was given metal wires of various
lengths and a four-inch vertical pipe with food at the bottom, she chose a
four-inch wire, made a hook and retrieved the food.
Apes and corvids are highly social. One explanation for intelligence is that
it evolved to process and use social information - who is allied with whom,
who is related to whom and how to use this information for deception. They also
remember.
Clark nutcrackers can hide up to 30,000 seeds and recover them up to six
months later.
Nutcrackers also hide and steal. If they see another bird watching them as
they cache food, they return later, alone, to hide the food again. Some
scientists believe this shows a rudimentary theory of mind - understanding that
another bird has intentions and beliefs.
Magpies, at an earlier age than any other creature tested, develop an
understanding of the fact that when an object disappears behind a curtain, it
has not
vanished.
At a university campus in Japan, carrion crows line up patiently at the curb
waiting for a traffic light to turn red. When cars stop, they hop into the
crosswalk, place walnuts from nearby trees onto the road and hop back to the
curb. After the light changes and cars run over the nuts, the crows wait until
it
is safe and hop back out for the food.
Pigeons can memorize up to 725 different visual patterns, and are capable of
what looks like deception. Pigeons will pretend to have found a food source,
lead other birds to it and then sneak back to the true source.
Parrots, some researchers report, can converse with humans, invent syntax and
teach other parrots what they know. Researchers have claimed that Alex, an
African gray, can grasp important aspects of number, color concepts, the
difference between presence and absence, and physical properties of objects
like
their shapes and materials. He can sound out letters the same way a child does.
Like mammals, some birds are naturally smarter than others, Dr. Jarvis said.
But given their range of behaviors, birds are extraordinarily flexible in
their intelligence quotients. "They're right up there with hominids," he said.
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