Locomotor behavior and control in human and non-human primates: comparisons with cats and dogs

For many years the cat has been the accepted mammalian model for investigations on the neural control of locomotion. The results from such studies, and also similar studies on dogs, have been assumed to represent the typical mammalian condition. The primary purpose of this review is to evaluate this assumption relative to human and non-human primates. A second purpose is to acquaint investigators of mammalian locomotor behavior and control with the large amount of data available on this topic for non-human primates. The analysis shows that non-human primates are different from carnivores in footfall patterns, gaits, gait transitions, relative stride length, limb angular excursions, weight support, mechanisms of propulsion, spinal vs. supraspinal control of stepping, and possible EMG patterns. Humans exhibit more similarities with other primates than with cats or dogs, but also appear to be unique in many ways. Thus, it is clear that extrapolations of results based on cat or dog experiments may not be applicable to non-human or human primates. Furthermore, although non-human primates unquestionably make a better experimental model than cats or dogs for understanding human locomotor control mechanisms, exactly how much better remains to be determined.