Australian scientists use imaging to map the brain of the extinct Tasmanian tiger
Study shows it’s possible to reconstruct pathways in brains that are more than a century old
By Kim Arlington
Eighty years after the last Tasmanian tiger died, scientists have used imaging techniques to map the marsupial’s brain for the first time.
The Tasmanian tiger, or thylacine, was elusive before its extinction and its behaviour in the wild was never scientifically documented.
But a reconstruction of its brain architecture and neural networks suggests it had more cortex devoted to action planning and possibly even decision making than its closest living relative, the Tasmanian devil.
The findings, published in PLOS ONE on Thursday, are consistent with the tiger’s more complex ecological role as a predator, while the devil survives mainly by scavenging.
The thylacine once ranged over the Australian continent but by the time Europeans arrived was found only in Tasmania.
The carnivorous marsupial was blamed for the destruction of livestock and in 1830 a bounty was put its head. From 1888 the Tasmanian government offered £1 for each animal killed, paying 2184 bounties before it ended the scheme in 1909.
The last known Tasmanian tiger died in Hobart Zoo in 1936, two months after the species was listed as a protected animal. The thylacine was officially declared extinct in 1986.
Only four specimens of the animal’s brain exist. Researchers Gregory Berns and the University of NSW’s Kenneth Ashwell used magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) to scan two of the preserved specimens.
One, from a thylacine that died in 1905, was held by the Smithsonian Institution, while the Australian Museum lent a brain from a Tasmanian tiger that died in the 1930s.
MRI scans reveal information about the architecture of a brain, or gray matter, while DTI provides information about the connective pathways, known as white matter.
The study showed it was possible to reconstruct white matter pathways in brains more than 100 years old.
“We now have the technology available to make use of the treasure trove of museum collections around the world,” said Professor Berns, a neuroscientist at Emory University in the US and the study’s lead author.
Professor Berns is pioneering the use of a form of DTI to digitally reconstruct the neural networks of animals using preserved brain specimens from zoological and museum collections. He has also launched the Brain Ark, a digital archive to help researchers explore questions about brain evolution.
“We are living in a time when much of the planet’s megafauna is at risk for extinction,” he said. “It’s important to gather as much data as we can before many of these animals disappear.”
Professor Ashwell, a neuroscientist and anatomist, said MRI imaging of the preserved brains of rare, endangered and extinct species was “an exciting innovation in the study of brain evolution”.
“It holds lots of potential because just about any species where there’s a brain preserved in a museum, we can now start to make some detailed structural studies,” he said.
“It will allow us to track pathways and study functional connections that could never be analysed [with] older experimental techniques. We can see how those brain circuits have evolved over time, how they differ from modern animals and get some idea about how old they might be.”
Professor Ashwell, who is an expert on the brain evolution of marsupials and monotremes, said the imaging technique “also avoids the ethical and conservation problems of doing experiments on rare and endangered animals”.