Human Stretch Reflex Example

This video was produced for our paper on the AnimatLab system. We demonstrated a simple human stretch reflex and pain avoidance circuit. First the arm is raised using a step excitatory command. This produces a new equilibrium position for the arm, but it is quite slow. Next, we use a tri-phasic command to move the arm quickly and smoothly to its target position. After that we again use a tri-phasic command, but we without gamma co-activation. This causes the arm to think that its motion is not planned, so it fights against the movement causing it to be jerky and slow. Next, we have the arm move again, but put a blocker in its way that it can potentially overcome, but since we have disabled feedback it is not able to produce enough extra force to move the blocker out of the way. We then do this again, but keep the feedback intact. This time it overcomes the obstacle and reaches it target position. Finally, we move the arm up, but put a pointed object in its path. Touch sensitive receptive fields detect the contact and cause the withdrawl of the hand from the stimulus. The biomechanical project for this video is also available for download.