Does an octapus have 8 brains? asked:
Does an octopus have one motor cortex with 8 sections, one for each arm, or just one brain to control them all?
We put this question to professor Scott Hooper, of the University of Ohio
A 2001 article in Science by Sumbre, Gutfreund, Fiorito, Flash, and Hochner has the answer. Octopus arms contain a very large number of neurons. To show that these neurons generate arm movements, Sumbre and her co-workers amputated octopus arms and then electrically stimulated nerves in the arms that normally carry information to the arms from the brain. This stimulation induced normal arm movement and, importantly, in many cases the movements did not begin until after the stimulation had ended. These experiments thus showed that signals from the brain trigger arm movements (they give the command to move), but it is the peripheral nervous systems (one in each arm) that calculate how to actually make the movements.