Tuesday, September 29, 2009
How would you control eight legs?
It's a problem, if you are an octopus, because you have the challenge of controlling eight appendages that can assume an almost limitless number of positions. Zulio et al. (the paper has a neat video) show that the octopus brain takes a very different tack from our own. Instead of having a specific body part controlled by a specific area of the the brain (as in our brains), the control of complex, coordinated movements is consolidated into specific areas of the nervous system. They placed 35 electrodes to micro-stimulate higher motor centers (in the basal lobes)in free moving animals. Low-voltage stimulation of different areas evokes simple responses, such as a change in skin colour or small eyelid movements. Higher voltages elicit more complex responses, such as inking and jet-propelled swimming. Discrete and complex components have no central topographical organization but are distributed over wide regions. They found no stimulation site where movements of a single arm or body part could be elicited.