Sept 6, 2010

By SINDYA N. BHANOO

In humans, the cerebral cortex, the tissuelike outermost layer of the brain, is thought to play a critical role in creative and analytical thinking.

But just how this portion of the brain evolved has remained a mystery.
Now researchers report that something resembling a cerebral cortex exists in the marine ragworm, a small creature with ancient roots that has not changed in hundreds of millions of years. The findings appear in the journal Cell. Read a summary

'You can say that the topography is so similar that the human and worm must come from a common ancestor,' said Detlev Arendt, a researcher at the European Molecular Biology Laboratory and one of the study's authors.

To conduct their study, Dr. Arendt and his colleagues used a technique called cellular profiling to determine what genes were turned on and off in the cells of the ragworm's brain. This sort of profiling provides a molecular footprint for each cell.

Remarkably, the molecular footprint in certain parts of the ragworm's brain, known as mushroom bodies, had a very similar footprint to the cerebral cortex.
The mushroom bodies are thought to control the worm's olfactory senses, and may have helped the common ancestor of ragworms and humans to find food while crawling across the seafloor.

'Now that we have paved the way to study these mushroom bodies, we can try and understand what this brain structure is doing,' Dr. Arendt said. 'What is it capable of doing, and was it important to catching prey?'

http://www.nytimes.com/2010/09/07/science/07obbrain.html?_r=1&scp=1&sq=worm%20cerebral%20cortex&st=cse