Deciphering the novel principles of the octopus neuromuscular systems control using a bottom-up approach
Abstract
Soft robotics is a booming field that has attracted significant research interest in the last decade, due to the potential of soft r obots to interact with real-world environments, where a myriad of factors can change in an unpredictable manner at any given time.Th e octopus is an outstanding example of complex multi-functional behavior in a soft bodied animal. With its long flexible arms and hi ghly developed brain, the octopus has been an excellent source of inspiration for soft robots at least for the last 10 years. Still, there are some unresolved issues, such as the motor control mechanisms, that dramatically interfere with translating the features o f this unique flexible body into an artificial robotic model. Some of these basic issues are how the brain governs the arms, what ty pe of information it sends and how it is being decoded to translate into precise movement along the flexible arms.In a recent study, we analyzed the special properties of the neuromuscular system of the arm and our findings led to these four distinct working assum ptions: 1. Every muscle cell in the octopus arm is able to perform various types of contraction to generate a skeletal-like suppor t (by stiffening) or to generate movements by length change (shortening/elongation). 2. The muscle cell contraction is triggered and controlled by three types of motor neuronal inputs which determine the stiffening/contraction kinetics. 3. The neural excitation ro le in muscle contraction control is far more important than in most other muscle cell types. 4. The arms have largely autonomous con trol. The brain produces behavior by running a series of programs embedded in the arms themselves. Based on the above working hypoth esis, we propose a bottom up approach to decipher the organization of the control system via the following four objectives.1) Morpho logically characterizing the somatotopic representation of motor neurons (MN) at various stations of the control hierarchy (from arm peripheral nervous system (PNS) to the brain).2) Functional investigation of the motor command organization by stimulation of d ifferent portions of the arm PNS, and monitoring the input at the arm muscles.3) Monitoring the input to the muscle cells and MN.4) The Holy Grail experiment: look for brain sites that independently activate different patterns of motor neuron pool recruitments and motion by the recruitment of different motor neuron pools.This will be achieved through several methodologies. We will use brain im plemented neurologger to monitor neural activity from freely moving octopus to reveal the central versus peripheral levels of contro l. To map the sensory-motor pathways between brain and arms we will employ fluorescent lipophilic carbocyanine dyes that have the ad vantage of progressing along the neurites from the injection site without spreading to neighbor neurons on their way. Last, through electrophysiology techniques, we will generate specific command in the arm central and peripheral nervous system to activate arm mus cles and we will reveal how the central systems command and modulate the final motor action.Providing this level of detail will esta blish the building blocks allowing to design and incorporating biological data in computational frameworks that will eventually driv e animal biomechanics in soft robotic structures. This represents a clear advancement in the soft robotic field, especially if done in parallel with the design and construction of robotic artefacts based on soft deformable materials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 22, 2021
- Source ID
- N000142112516
Entities
People
- Letizia Zullo
Organizations
- Istituto Italiano di Tecnologia
- Office of Naval Research
- United States Navy