Connecting brains to robots: an artificial animal for the study of learning in vertebrate nervous systems

We have developed an artificial animal, consisting of the brain of a lamprey (a primitive vertebrate) controlling a small mobile robot. The mobile robot acts as an artificial body, which delivers sensory information to the brain through its light sensors, and is controlled by command signals generated by the brain itself. As the behaviors resulting from the interaction with the external environment are specified by the structure and operation of the neural circuitry, this system provides a unified context for investigating the behavioral, computational and neurobiological mechanisms underlying sensorimotor adaptation. In this paper, we provide a detailed description of the system and report on a number of experiments in which we have analyzed the behavior of the animal in response to a light stimulus. Most preparations generated stable and repeatable behaviors; different preparations showed different behaviors, with a slight preference for moving toward the light source. The observed behaviors were consistent with those predicted by the measured input/output responses of the neural circuitry. In addition, we observed long-term behavioral changes taking place in response to repeated tonic optical stimulation on one side of the animal. Our results suggest that the system may be used as a new experimental paxadigm for investigating the computational properties of synaptic plasticity in the context of sensorimotor adaptation.