Fig. 7. Plots of responses and encoding of load and muscle forces in stick insect femoral campaniform sensilla.

A. and B. Cumulative plots of sensory discharges to forces applied in the plane of the CTr joint in the direction of joint flexion (levation) and in a posterior direction perpendicular to the joint plane. Intense discharges were elicited both in a posterior direction and in the plane of the CTr joint. C. Encoding of load – Plot of the mean sensory firing frequencies to forces applied as ramp and hold functions to forces in the joint plane (flexion) and perpendicular to the plane. The femoral sensilla effectively encode force magnitude in the plane of the coxo-trochanteral joint and in a posterior direction perpendicular to the plane. D. Encoding of muscle force – Responses to depressor muscle forces were obtained by applying forces to the pin in the trochanter that were resisted in the distal femur by the force probe. The mean discharge frequency effectively encoded the muscle forces.