A non-human primate model of bipedal locomotion under restrained condition allowing gait studies and single unit brain recordings.

For decades, several animal models of locomotion have allowed a better understanding of the basic physiological mechanisms of gait. However, unlike most of the mammals, the Order Primates is characterized by fundamental changes in locomotor behaviour. In particular, some primates use a specific pattern of locomotion and are able to naturally walk bipedally due possibly to a specific supra-spinal control of locomotion. These features must be taken into account when one considers to study the intrinsic properties of human gait. Thus, an experimental model of bipedal locomotion allowing precise and reproducible analysis of gait in non-human primate is still lacking. This study describes a non-human primate model of bipedal locomotion under restrained condition. We undertook a kinematic and biomechanic study in three Macaca fascicularis trained to walk bipedally on a treadmill. One of the primate was evaluated in complete head fixation. Gait visual analysis and electromyographic recordings provided pertinent description of the gait pattern. Step frequencies, step lengths, cycle and stance phase durations were correlated with Froude number (dimensionless velocity), whereas swing phase durations remained non-correlated. Gait patterns observed in our model were similar to those obtained in freely bipedal Macaca fuscata and to a lesser extend to Humans. Gait pattern was not modified by head fixation thereby allowing us to perform precise and repetitive micro electrode recordings of deep cerebral structures. Thus, the present model could provide a pertinent pre-clinical tool to study gait parameters and their neuronal control but also could be helpful to validate new therapeutics interventions.