Control of Octopus Arm Extension by a Peripheral Motor Program

TLDR

Octopus arm movements are guided by a nervous system that issues motor commands to direct the arm toward targets, yet the arm’s ability to move in any direction with virtually infinite degrees of freedom makes its control exceptionally complex. We demonstrate that severed octopus arms can extend mechanically or electrically with kinematics nearly identical to normal, indicating that a peripheral motor program embedded in the arm’s circuitry simplifies control of this highly redundant appendage.

Abstract

For goal-directed arm movements, the nervous system generates a sequence of motor commands that bring the arm toward the target. Control of the octopus arm is especially complex because the arm can be moved in any direction, with a virtually infinite number of degrees of freedom. Here we show that arm extensions can be evoked mechanically or electrically in arms whose connection with the brain has been severed. These extensions show kinematic features that are almost identical to normal behavior, suggesting that the basic motor program for voluntary movement is embedded within the neural circuitry of the arm itself. Such peripheral motor programs represent considerable simplification in the motor control of this highly redundant appendage.