Figure 2.

Muscle and neural network properties of the Oropod. A: proprioceptive receptors of the Oropod muscle. In this report, we focus exclusively on the Ia-MN synapse indicated in red; other afferent and interneuronal elements are depicted in gray. B: illustration of the neural network design of the Oropod. The Ia afferent from each muscle synapses initially onto the βMNs controlling all four muscles (both extra- and intrafusal muscle fibers). Limbs and muscles are drawn as in Fig. 1, A–C. C: in the top is an example of a twitch APG with 100% amplitude and 50-ms duration; the black line shows the internal square pulse into the APG and the light gray area shows the output range when fed through the one-dimensional Kalman filter with the gain range 0.5–0.8. It is the output that is injected into the MN synapse. Below are all 16 possible binary permutations of the phasic APG output and hence βMN activation (but note that in the actual simulations both the amplitudes and unitary durations were also varied). Name of each permutation is indicated along the x axis. Gray backgrounds indicate permutations used to generate Figs. 5 and 7. APG, activity pattern generator; Ia, primary afferent; MN, motoneuron.