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Thursday, 6 September, 2001, 18:29 GMT 19:29 UK
Octopus arms do the thinking
Octopus, PA
Octopus arms are highly manoeuvrable
By BBC News Online's Ivan Noble

Reaching for something can sometimes be tricky for humans, but for the octopus, it is a much trickier task.


German Sumbre and colleagues
Octopus arms are so flexible that they have an enormous number of degrees of freedom, compared with our restrictive elbow and wrist arrangement.

Israeli scientists trying to work out how the octopus manages to keep control of so many flexible limbs think they have the answer.

The octopus, it seems, has some of its intelligence actually inside in its arms.

Embedded program

"The basic motor program for voluntary movement is embedded within the neural circuitry of the arm itself," German Sumbre, Binyamin Hochner and colleagues write in the journal Science.

Octopus arm sequence, Science
Reaching out: An octopus arm
Image: Science

The team, based at the Hebrew University of Jerusalem and the Weizmann Institute of Science, was able to make an octopus arm move realistically even when it was disconnected from the octopus's brain.

The researchers applied a series of electrical pulses to an octopus arm, making it flail outwards with a bend travelling out along the arm as it moved.

This characteristic movement is the same as that made by a healthy, living octopus.

Independent thinking

The implication is that an octopus moves its arms simply by sending a "move" command from its brain to its arm and telling it how far to move.

The arm does the rest, controlling its own movement as it extends.

"There appears to be an underlying motor program... which does not require continuous central control," the researchers write.

Each arm is controlled by an elaborate nervous system consisting of around 50 million neurons.

The neurons are organised as a nerve cord and nerve fibre tracts running along the opposite side of the arm to the octopus's suckers.

The BBC's Julian Siddle reports
"They use tiny electrical signals to stimulate the nerve tissue in the arm"
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