Maintenance of Lateral Stability During Standing and Walking in the Cat

Abstract

During free behaviors animals often experience lateral forces, such as collisions with obstacles or interactions with other animals. We studied postural reactions to lateral pulses of force (pushes) in the cat during standing and walking. During standing, a push applied to the hip region caused a lateral deviation of the caudal trunk, followed by a return to the initial position. The corrective hindlimb electromyographic (EMG) pattern included an initial wave of excitation in most extensors of the hindlimb contralateral to push and inhibition of those in the ipsilateral limb. In cats walking on a treadmill with only hindlimbs, application of force also caused lateral deviation of the caudal trunk, with subsequent return to the initial position. The type of corrective movement depended on the pulse timing relative to the step cycle. If the force was applied at the end of the stance phase of one of the limbs or during its swing phase, a lateral component appeared in the swing trajectory of this limb. The corrective step was directed either inward (when the corrective limb was ipsilateral to force application) or outward (when it was contralateral). The EMG pattern in the corrective limb was characterized by considerable modification of the hip abductor and adductor activity in the perturbed step. Thus the basic mechanisms for balance control in these two forms of behavior are different. They perform a redistribution of muscle activity between symmetrical limbs (in standing) and a reconfiguration of the base of support during a corrective lateral step (in walking).

Balance responses to lateral perturbations in human treadmill walking

“…This effect is brought about by a shortening of contralateral swing time, as double stance time is not shortened. A shortening of stride time of a similar magnitude was reported in cats (Karayannidou et al, 2009), but to our knowledge it has not been reported before for human walking.…”

“…In a related experiment in cats pushed while walking on a treadmill (Karayannidou et al, 2009), very similar results were found: inward or outward stepping responses, dependent on the phase of the perturbation. In agreement with the present study, a single correction step was sufficient to restore balance.…”

Task dependent activity of motor unit populations in feline ankle extensor muscles

“…The cat has been used in a wide range of studies of locomotor biomechanics, muscle mechanics, physiology and neural control and is, therefore, a historically well-defined animal model. Recordings of myoelectric signals from feline muscles have revealed co-ordinated patterns of activation between groups of whole muscles and how these patterns change in response to different locomotor conditions (Walmsley et al, 1978;Hodgson, 1983;Pierotti et al, 1989;Carlson-Kuhta et al, 1998;Kaya et al, 2003;Gregor et al, 2001;Gregor et al, 2006) and mechanical perturbations (Gorassini et al, 1994;Torres-Oviedo et al, 2006;Karayannidou et al, 2009). The cat model has also been used extensively in studies related to the organisation of spinal reflexes and sensory feedback, and their role in the control of locomotion (Gorassini et al, 1994;Gossard, 1996;Donelan and Pearson, 2004;Maas et al, 2007;Maas et al, 2010;Ross and Nichols, 2009).…”

Integration of posture and rhythmic motion controls in quadrupedal dynamic walking using phase modulations based on leg loading/unloading

“…These include for example the stepping reflex, which adjusts the touchdown angle of the swinging legs using vestibular information. In animals, a similar mechanism contributes to the stabilization of the posture in the frontal plane via hip abduction and adduction movements (Misiaszek 2006;Karayannidou et al 2009). We intend to consider this issue in the future and investigate the relative contributions of the phase-modulations-based and stepping-reflex-based stabilization mechanisms in more detail.…”

“…Quadrupedal mammals usually have long and narrow bodies and contralateral legs are never simultaneously in the swing phase during walking. Therefore, posture in the sagittal plane is easy to stabilize, and the main issue is to control the posture in the frontal plane, that is, to stabilize the rolling motion of the body (Karayannidou et al 2009). In the author's former studies (Fukuoka et al 2003;Kimura and Fukuoka 2004;Kimura et al 2007), adaptive walking on irregular terrain with the mammal-like quadruped robot Tekken was realized in the medium-speed range (Fr ∈ [0.3, 0.7]), using a biologically-inspired control system based on a Central Pattern Generator (CPG) associated with a set of reflexes.…”