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October 19, 2009

A Multi-Armed Approach to Brain Evolution



by Greg Miller

Did you know that an octopus brain has more than 50 lobes and about as many neurons (100 million) as a mouse's brain? And that's not counting the smaller brains in each arm and the tiny brains (okay, ganglia) devoted to each sucker? Neither did I, until I spent the morning visiting with Cliff Ragsdale and his postdoc Shuichi Shigeno at the University of Chicago.

Ragsdale and Shigeno think octopuses may have much to teach us about brain evolution. In size and complexity, the octopus brain rivals that of many vertebrate species. But it's put together much, much differently. "This is as far from the vertebrate design as we can get in a successful, living animal," Ragsdale says.

That raises interesting questions about whether the neural circuits that control movement, memory, and other functions in an octopus brain work the same way as do the analogous circuits in other animals. To investigate, Shigeno has been using molecular methods to examine the anatomy, neurochemistry, and developmental genetics of the octopus brain. He presented some of his preliminary findings yesterday at the Society for Neuroscience meeting in Chicago, and I'll post a longer discussion of this work (and more cool photos) later this week over on our Origins blog. Stay tuned.