"Birdbrain" No Longer Means "Stupid," Asserts Scientific Consortium
Dennis Meredith
Duke University | 1/31/2005
http://news.mc.duke.edu/news/article.php?id=8401
DURHAM, N.C. -- An international consortium of 29 neuroscientists has
proposed a drastic renaming of the structures of the bird brain to
correctly portray birds as more comparable to mammals in their
cognitive ability. The scientists assert that the century-old
traditional nomenclature is outdated and does not reflect new
molecular, genetic and behavioral studies that reveal the brainpower
of birds.
For example, they identified behavioral studies demonstrating that
pigeons can discriminate cubist from impressionistic styles of
painting; that crows can make useful tools and pass on their skills
to other birds, and that parrots can not only learn human words but
use them to communicate with humans.
The researchers emphasize that the old view of evolution as
progressive and linear is outdated, pointing out that so-
called "primitive" animals such as birds evolved some 50 to 100
million years after mammals.
The Avian Brain Nomenclature Consortium published a report on the
rationale for the proposed revised nomenclature in the February 2005
issue of Nature Reviews Neuroscience. A technical report detailing
the revisions was published in the May 2004 issue of the Journal of
Comparative Neurology. The consortium's efforts were supported by the
National Institutes of Health and the National Science Foundation,
including the NSF's Waterman Award for young researchers to the
Nature Reviews Neuroscience paper's first author, Duke University
Medical Center neurobiologist Erich Jarvis.
"We believe that names have a powerful influence on the experiments
we do and the way in which we think," wrote the consortium members in
their paper. "For this reason, and in the light of new evidence about
the function and evolution of the vertebrate brain, the international
consortium of neuroscientists has reconsidered the traditional 100-
year-old terminology that is used to describe the avian cerebrum.
"Our current understanding of the avian brain -- in particular the
neocortex-like cognitive functions of the avian pallium -- requires a
new terminology that better reflects these functions and the
homologies between avian and mammalian brains."
The consortium members asserted that the old terminology -- which
implied that the avian brain was more primitive than the mammalian
brain -- has hindered scientific understanding. They concluded
that "The inaccurate evolution-based terminology for the vertebrate
brain that was used throughout the twentieth century became a severe
impediment to the communication of scientific discoveries and the
generation of new insights."
The consortium's revision of the nomenclature for avian brains is
aimed at replacing the century-old system developed in the 19th
century by Ludwig Edinger, considered the father of comparative
neuroanatomy. Edinger's system was based on the then-common practice
of combining Darwin's recent theory of evolution and Aristotle's old
concept that there exists a natural "scale" of creatures from lowest
to highest. The result were the views that evolution was progressive
from organisms with "lower" intelligence to those with "higher"
intelligence and that evolution had a purpose -- the generation of
humans.
The resulting nomenclature used prefixes such as palaeo- ("oldest")
and archi- ("archaic") to designate structures in the avian brain and
neo- ("new") to designate supposedly new structures, particularly in
the mammalian brain.
"According to this theory, the avian cerebrum is almost entirely
composed of basal ganglia, the basal ganglia is involved only in
instinctive behavior, and the malleable behavior that is thought to
typify mammals exclusively requires the so-called neocortex," wrote
the researchers.
However, said Jarvis, "We have to get rid of the idea that mammals --
and humans in particular -- are the pinnacle of evolution. We have to
stop using words like 'lower vertebrates' and 'higher vertebrates.'
We also have to understand that evolution is not linear, but an
intricate branching process. So, we can't automatically expect to
track a structure in the human brain back to other current vertebrate
species."
According to Jarvis, new research "debunks the theory that the brain
evolved in stages, like the laying down of geological sediments layer
by layer. There is no evidence to show that there was a primordial
brain structure to which so-called higher brain structures were
systematically added."
In the Nature Reviews Neuroscience paper, the authors described
studies by other researchers and their own studies demonstrating that
the so-called "primitive" regions of avian brains were actually
sophisticated processing regions homologous to those in mammals.
Those studies, which included tracing of neural pathways and
behavioral studies, showed that such avian brain regions carried out
sensory processing, motor control and sensorimotor learning just as
did the mammalian neocortex. Also, wrote the scientists, molecular
studies have shown that the avian and mammalian brain regions are
comparable in their genetic and biochemical machinery. The neocortex
and related areas in the mammalian brain are derived from a region in
the embryonic cerebrum called the pallium, which means mantle or
covering. Edinger thought, however, that most of this region in the
bird cerebrum was part of the basal ganglia. Accordingly, he gave
them names that ended in the basal ganglia term "-striatum", a
practice he also employed in naming the parts of the mammalian basal
ganglia.
As a result of the recent studies, the consortium has recommended
such changes as renaming the avian brain region called
the "archistriatum" as the "arcopallium," (arched pallium); and
renaming the region that includes part of the true basal ganglia in
birds, the "palaeostriatum primitivum" and the "ventral
palaeostriatum" which sits below the pallium as the "pallidum"
(pallidal or pale domain).
The consortium's work began in 1997 and was organized by Jarvis,
Anton Reiner of the University of Tennessee Health Science Center in
Memphis, Martin Wild of the University of Auckland in New Zealand,
and other neurobiologists, dubbing themselves the ThinkTank. Jarvis
recalled that "there were people in the field of avian neurobiology
who knew the real structures behind these names and knew the names
were wrong. And as a member of the younger generation of
neurobiologists, I just felt that it was against my conscience to
continue to use terminology that I knew was wrong and would mislead
scientists."
For example, said Jarvis, researchers not familiar with the growing
body of scientific literature demonstrating the sophistication of the
avian brain could not understand how birds could exhibit
sophisticated cognitive abilities with brains that held only what the
nomenclature designated as the equivalent of the human basal ganglia.
The result of the scientists' objections led to a seven-year effort,
which steadily recruited new participants. This effort culminated in
an intensive international scientific forum at Duke in 2002, in which
the new nomenclature was developed.
"We knew that we were doing something that may have an impact, not
only on the immediate conduct of research in neuroscience, but on
neuroscience for the next hundred years," said Jarvis. "And, this
nomenclature will help people understand that evolution has created
more than one way to generate complex behavior -- the mammal way and
the bird way. And they're comparable to one another. In fact, some
birds have evolved cognitive abilities that are far more complex than
in many mammals."
Besides Jarvis, other co-authors of the paper were
-- Onur G�nt�rk�n, Ruhr-Universit�t Bochum, Germany,
-- Laura Bruce, Creighton University School of Medicine,
-- Andr�s Csillag, Semmelweis University, Hungary,
-- Harvey Karten, University of California San Diego,
-- Wayne Kuenzel, University of Arkansas
-- Loreta Medina, University of Murcia, Spain,
-- George Paxinos, Prince of Wales Medical Research Institute,
Australia,
-- David J. Perkel, University of Washington,
-- Toru Shimizu, University of South Florida,
-- Georg Striedter, University of California at Irvine,
-- Martin Wild, University of Auckland, New Zealand,
-- Gregory F. Ball, Johns Hopkins University,
-- Jennifer Dugas-Ford, University of Chicago,
-- Sarah Durand, CUNY-LaGuardia,
-- Gerald Hough, Rowan University,
-- Scott Husband, University of South Florida,
-- Lubica Kubikova, Duke University Medical Center,
-- Diane Lee, California State University Long Beach,
-- Claudio Mello, Oregon Health & Science University,
-- Alice Powers, St. John's University,
-- Connie Siang, Duke University Medical Center,
-- Tom Smulders, University of Newcastle, United Kingdom,
-- Kazuhiro Wada, Duke University Medical Center,
-- Stephanie White, University of California, Los Angeles,
-- Keiko Yamamoto, University of Tennessee Health Science Center,
-- Jing Yu, Duke University Medical Center,
-- Anton Reiner, University of Tennessee Health Science Center,
-- Ann Butler, George Mason University
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