Interlimb coordination during stepping in the cat: in-phase stepping and gait transitions

Area of Science:

• Neuroscience
• Biomechanics
• Animal Locomotion

Background:

• Coordinated limb movement is crucial for locomotion.
• Understanding interlimb coordination in quadrupedal animals provides insights into neural control mechanisms.

Purpose of the Study:

• To analyze the coordination patterns of all four limbs in cats during steady-state in-phase stepping and during transitions to/from alternate stepping.
• To investigate the nature (gradual vs. abrupt) of phase changes in interlimb coordination during gait transitions.

Main Methods:

• Electromyographic (EMG) activity from extensor muscles in each limb of 12 adult cats was analyzed during overground stepping.
• Temporal spacing and phase relationships between step cycles of different limb pairs were calculated.
• Coordination patterns were identified based on the frequency of phase values and defined steady-state conditions.

Main Results:

• Distinct coordination patterns were observed between forelimb-forelimb and forelimb-hindlimb pairs during steady-state stepping.
• Transitions to and from alternate stepping involved both gradual and abrupt phase changes.
• Forelimb-forelimb and forelimb-hindlimb phase changes were predominantly gradual, while hindlimb-hindlimb changes were nearly always abrupt.
• When one limb pair exhibited abrupt phase changes, the other pair's changes were gradual.

Conclusions:

• Four-limb coordination during in-phase stepping adheres to a few discernible patterns, though variability suggests complex neural circuitry.
• The predominantly gradual nature of gait transitions supports a state-dependent model of interlimb control.
• The type of transition is influenced by the strength of neural coupling among all four limbs at the initiation of the transition.