Figure 2.

Schematic of connections between simulated spinal populations. Motor neuron (MN)-vastus lateralis (VL), MN-vastus medialis (VM), MN-rectus femoris (RF), MN-semitendinosus (ST), and MN-biceps femoris (BF) populations are identified as diamonds although all populations consist of exponential integrate-and-fire neurons. The Extensor and Flexor Interneuron Populations allow both outgoing excitatory and inhibitory connections. All populations receive a background level of input producing a baseline activity. Parameters for the network connectivity are provided in Table 1. The InhibRF population is used to offset the level of bias given to the MN-RF population. Afferent Input senFlInt and senExtInt control the balance of input to the flexor and extensor interneuron populations, respectively, which influences the agonist/antagonist bias. Afferent Input senInhRF represents an additional input, activated to reproduce the change in activity of RF in position 2. Connections that exist in other models but that are not required to produce the observed synergies have been omitted. For example, direct afferent inputs to motor neuron populations. The relative strengths of each connection are not shown but can be found in the connectivity parameters (Table 1).