Postural perturbation does not reset stepping rhythm in humans, but brief intermission does

Area of Science:

• Neuroscience
• Human Motor Control
• Biomechanics

Background:

• The rhythm generator is hypothesized to maintain periodic motor output during temporary pattern generator inactivation.
• Understanding rhythm maintenance is crucial for explaining continuous movement despite brief interruptions.

Purpose of the Study:

• To test if the human rhythm generator maintains stepping rhythm during brief cessations of motor output.
• To investigate whether step rhythm resets after an interruptive event.

Main Methods:

• Healthy participants performed stepping tasks on a translating platform.
• Two conditions were tested: continuous stepping (non-stop session) and stepping with a brief pause (stop session).
• Step timing and side were analyzed after a postural perturbation.

Main Results:

• In the non-stop session, stepping rhythm was generally maintained, indicating postural perturbations do not disrupt rhythm-keeping.
• In the stop session, step rhythm was reset after the intermission, with steps occurring at random timing.
• The side of the first step post-intermission was random, further supporting rhythm reset.

Conclusions:

• The findings contradict the hypothesis that the rhythm generator maintains activity during brief pattern generator inactivation.
• Step rhythm is reset after a brief intermission of stepping.
• Rhythm-keeping activity appears to be inactivated by interruptive events during periodic motor activity.