![]() The full range of the locomotor repertoire of the mouse has not yet been established. Using this paradigm, it has been shown that most quadrupeds, such as monkeys, horses, dogs, cats, and rats, display a large repertoire of locomotor gaits from walk, to pace, to trot, to gallop (Cohen and Gans, 1975 Grillner, 1975 Miller et al., 1975 Hildebrand, 1976 Dunbar, 2004 Abourachid et al., 2007 Maes and Abourachid, 2013). Conversely, asymmetrical gaits could not be described by half the cycle. A gait was defined as symmetrical when it could be described by only half the step cycle, the other half being symmetrical to the first half. asymmetrical according to their footfall pattern (Hildebrand, 1976). Historically, locomotor gaits were identified as symmetrical vs. However, less is known about the forelimbs and even less about locomotor gaits. Neonatal in vitro and adult in vivo locomotor studies using genetic manipulations (e.g., signaling cues involved in neural circuit formation or ablations of genetically identified neuronal populations) have revealed important information about the neural control of locomotion, especially the left-right alternation of the hindlimbs (Kullander et al., 2001a, b Kullander, 2003 Lanuza et al., 2004 Crone et al., 2008 Zhang et al., 2008 Rabe et al., 2009 Andersson et al., 2012 Bernhardt et al., 2012 Talpalar et al., 2013 Borgius et al., 2014). ![]() Over the last decade, advances in mouse genetics have allowed us to identify the spinal interneuronal circuits controlling muscles underlying motor and locomotor functions. Locomotion results from an interplay between biomechanical constraints of the muscles attached to the axial and appendicular skeleton and the neuronal circuit that controls these muscles. Future locomotor studies should benefit from this paradigm in assessing transgenic mice or wild-type mice with neurotraumatic injury or neurodegenerative disease affecting gait. In summary, the wild-type mouse exhibits a wider repertoire of locomotor gaits than expected. ![]() Using graph analysis, we demonstrated that transitions between gaits were predictable, not random. Surprisingly, lateral walk was less frequently observed. In contrast, lateral walk, hop, transverse gallop, rotary gallop, and half-bound were more transient and therefore considered transitional gaits (i.e., a labile state of the network from which it flows to the attractor state). Out-of-phase walk, trot, and full-bound were robust and appeared to function as attractor gaits (i.e., a state to which the network flows and stabilizes) at low, intermediate, and high speeds respectively. Instead of using the classical paradigm defining gaits according to their footfall pattern, we combined the inter-limb coupling and the duty cycle of the stance phase, thus identifying several types of gaits: lateral walk, trot, out-of-phase walk, rotary gallop, transverse gallop, hop, half-bound, and full-bound. To assess this range, young adult C57BL/6J mice were trained to walk and run on a treadmill at different locomotor speeds. ![]() Given our advances in the genetic identification of spinal and supraspinal circuits important to locomotion in the mouse, it is now important to get a better understanding of the full repertoire of gaits in the freely walking mouse. Quadrupeds exhibit a wide range of locomotor gaits. Locomotion results from an interplay between biomechanical constraints of the muscles attached to the skeleton and the neuronal circuits controlling and coordinating muscle activities.
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