Abstract

A variety of human and animal postural tasks are commonly used to describe the different strategies used to cope with a perturbation of the base of support. Rodent research on posture is generally limited to tasks which test dexterity and coordination more than posture per se. We designed a novel task in which a conditioning stimulus tone was coupled to a platform drop in order to entrain anticipatory postural behaviour. Rats were conditioned using delay-conditioning, which consisted of a 2 s stimulus tone coupled to the drop of a moveable platform. The platform was fitted with a force plate built with a clear acrylic sheet and 4 load cells. This force plate measured ground reaction forces which were used to calculate center of pressure (CoP), CoP displacement, CoP excursion and CoP variability. Video of the animal behaviour was recorded from underneath the platform and used to calculate the orientation of the animal. It was found that trained rats increased their CoP displacement, CoP excursion and CoP variability in response to the stimulus tone, before the platform drop. Trained animals consistently moved toward the back of the platform upon hearing the tone, indicating acquisition of the desired conditioned response, and understanding of the parameters of the task. There were no training-related changes to orientation variables, but the animals demonstrated a preference for facing the interior of the platform. This is the first step in describing rat behaviour in an anticipatory behaviour paradigm.