The Stomatogastric Nervous System as a Model for Studying Sensorimotor Interactions in Real-Time Closed-Loop Conditions

The perception of proprioceptive signals that report the internal state of the body is one of the essential tasks of the nervous system and helps to continuously adapt body movements to changing circumstances. Despite the impact of proprioceptive feedback on motor activity it has rarely been studied in conditions in which motor output and sensory activity interact as they do in behaving animals, i.e., in closed-loop conditions. The interaction of motor and sensory activities, however, can create emergent properties that may govern the functional characteristics of the system. We here demonstrate a method to use a well-characterized model system for central pattern generation, the stomatogastric nervous system, for studying these properties in vitro. We created a real-time computer model of a single-cell muscle tendon organ in the gastric mill of the crab foregut that uses intracellular current injections to control the activity of the biological proprioceptor. The resulting motor output of a gastric mill motor neuron is then recorded intracellularly and fed into a simple muscle model consisting of a series of low-pass filters. The muscle output is used to activate a one-dimensional Hodgkin–Huxley type model of the muscle tendon organ in real-time, allowing closed-loop conditions. Model properties were either hand tuned to achieve the best match with data from semi-intact muscle preparations, or an exhaustive search was performed to determine the best set of parameters. We report the real-time capabilities of our models, its performance and its interaction with the biological motor system

Charakterisierung intrinsischer Eigenschaften eines Propriozeptors und deren Beitrag zur sensorischen Informationsverarbeitung

Interaction with the environment is an important part of animal behavior. Sensory feedback provides necessary information for the body to generate an adequate behavior. The cellular properties and their importance for sensory feedback, however, are often unclear. The stomatogastric nervous system of the crab, Cancer pagurus, is a model system to investigate the basics of neuronal information processing on the cellular level. Two central pattern generators (CPGs) are located in the stomatogastric ganglion and generate two motor patterns: the pyloric rhythm is responsible for food filtering, while the gastric mill rhythm (GMR) drives the movement of internal teeth during chewing. The underlying CPGs have been characterized on both, cellular and network levels. They are under modulatory control of higher centers and receive information from multiple sense organs. The latter, often single neurons, can be studied with intracellular recordings. In this work I investigated the functional impact of cellular properties of a proprioceptor (the anterior gastric receptor) on the motor output. My thesis shows that cellular properties of sense organs have a strong influence on sensory actions and that they can even add additional functions to the sense organ, for example that of an interneuron