Overground locomotion in intact rats: interlimb coordination, support patterns and support phases duration

The interlimb coordination during overground locomotion was analysed in int act rats, using the method of contact electrodes (Gorska et al. 1998). It w as found that in animals moving with a speed ranging from 10 to 78 cm/s (st ep cycles 685 to 215 ms, respectively) the interlimb coordination was chara cterized by homologous phase shifts close to 0.5 and much shorter diagonal than lateral phase shifts. These features corresponded to symmetrical gait with diagonal sequence and diagonal couplets (Hildebrandt 1976). Shortening the step cycle changed the gait from a walking trot (duty factor >0.5) int o a running trot (duty factor <0.5). Correspondingly, the support patterns in the four-legged step cycles, i.e., the sequence of phases of support on various limbs changed: the support on diagonal limbs persisted but the thre e-limb support was replaced by one-limb support and the support on homolate ral limbs by phases of flight. For each phase of support the relationship b etween its absolute and relative durations and the step cycle duration is b eing described. The paper explains the variability of support patterns desc ribed in the literature. The picture of locomotion obtained in intact rats will be used as a template for studying locomotor control deficits after CN S lesions.