Scientists create detailed map of dinosaur brain
Scientists have created a detailed map
of the dinosaur brain for the first
time and found that the ancient beasts
had the faculties for complex
behaviour, and perhaps made sounds
to communicate with one another.
The map provides an
unprecedented view of the makeup of
the dinosaur brain and a glimpse
back in time at what the creatures
might have been capable of during
their reign on Earth millions of years
ago.
"In the popular mind, dinosaurs
may be underrated in the complexity
of their behaviour," said Erich Jarvis,
who led the study at Duke University
in North Carolina.
Soft tissues are not preserved in
fossils, so researchers have had to
infer the details of dinosaur brains
from the faint impressions the organs
leave on the insides of fossilised
skulls. These "endocasts" give a sense
of the size and shape of the outermost
brain parts, but leave no clues about
the brain's deeper structures.
But now researchers have pieced
together the innermost regions of the
dinosaur brain, including six areas
that are specialised for complex
behaviour such as processing visual
information and learning and
making sounds.
Among other skills, the extinct
beasts had sufficient brain
complexity to communicate with
sounds, Jarvis said. "But did it really
happen? That we do not know."
To recreate the dinosaur brain,
the US researchers first studied the
brains of alligators and birds.
Alligators came from a lineage that
predated many dinosaurs, while the
first birds evolved afterwards. On
that basis, Jarvis and his colleague
Chun-Chun Chen argue that the
dinosaur brain should have evolved
to be somewhere in between.
The researchers drew up detailed
maps of alligator and bird brains
using a recently developed procedure
that relies on gene activity varying
across different parts of the brain.
Though some genes are switched on
in the brain all the time, others are
activated only momentarily when
something happens. This is the case
for auditory regions of the brain,
where genes are switched on in
response to sounds.
To map the auditory regions of
the brain, Jarvis quietened the
animals down in a darkened room
and then played bird songs to birds
and alligator grunts to alligators. He
then swiftly removed their brains,
froze them, sliced them, and looked at
the genes that had switched on in
different regions.
The genetic information allowed
Jarvis to make high-precision maps of
bird and alligator brains, which
showed the various regions and their
organisation. To get the structure of
the dinosaur brain he simply merged
the two, and shaped the map to
dinosaur brain proportions, which
Chen worked out from the endocasts
from Tyrannosaurus rex , an
Allosaurus and the early bird
Archaeopteryx.
The map of the dinosaur brain
contained six regions, including one
called the mesopallium involved in
complex processing. "It suggests that
the dinosaur brain had the capacity
for complex sensory motor
processing, just like we see in birds
and alligators," said Jarvis.
But while song birds learn tunes
and sing them, Jarvis said, it was
impossible to know whether
dinosaurs were capable of a similar
form of "vocal learning".
"We don't have any evidence that
there was a dinosaur out there that
did this, that shared vocal learning
with songbirds. But all the brain
subdivisions to support vocal
learning are there, so I'd argue the
capacity to evolve vocal learning did
exist in dinosaurs," he said. Jarvis
described the study at the Society for
Neuroscience meeting in San Diego .
"Because birds and alligators
have this large cortex, it suggests that
dinosaurs probably had a pretty big
cortex too and were capable of pretty
sophisticated behaviours," said
Michale Fee , who studies bird brains
at MIT.
"It's very unlikely that we're
ever going to find a dinosaur brain
preserved anywhere, so the details
are always going to have to be
inferred. As we understand brain
evolution better we'll be able to make
sharper speculations about what
dinosaur brains might have looked
like. But actually nailing it with real
data is going to be hard," he said.
