DISTRIBUTED-PROCESSING ON THE BASIS OF PARALLEL AND ANTAGONISTIC PATHWAYS SIMULATION OF THE FEMUR-TIBIA CONTROL-SYSTEM IN THE STICK INSECT

In inactive stick insects, sensory information from the femoral chordo tonal organ (fCO) about position and movement of the femur-tibia joint is transferred via local nonspiking interneurons onto extensor and fl exor tibiae motoneurons. Information is processed by the interaction o f antagonistic parallel pathways at two levels: (1) at the input side of the nonspiking interneurons and (2) at the input side of the motone urons. We tested by a combination of physiological experiments and com puter simulation whether the known network topology and the properties of its elements are sufficient to explain the generation of the motor output in response to passive joint movements, that is resistance ref lexes. In reinvestigating the quantitative characteristics of interneu ronal pathways we identified 10 distinct types of nonspiking interneur ons. Synaptic inputs from fCO afferents onto these interneurons are di rect excitatory and indirect inhibitory. These connections were invest igated with respect to position and velocity signals from the fCO. The results were introduced in the network simulation. The motor output o f the simulation has the same characteristics as the real system, even when particular types of interneurons were removed in the simulation and the real system.