Figure 9.

Activation based on predicted sensory input of a closed loop rule to limit backward hyperextension in Cat E. Recorded hind limb tilt is shown in blue and the real-time predicted tilt is shown in red. The activation threshold of the rule is shown with a black horizontal dotted line. Gray vertical regions represent times within the step cycle (corresponding to the underlying state system of the controller) when a rule can activate if the threshold is exceeded (activation windows). In panel A, the prediction (red) did not exceed the threshold during the activation windows. Panel B shows that a lower threshold causes many activations of the rule. The solid vertical line marks a rule activation and subsequent state transition to swing. Due to the underlying state transition, the activation window is truncated based on sensory feedback and appears irregular across steps.