Task specific adaptations in rat locomotion: runway versus horizontal ladder

Area of Science:

• Neuroscience
• Locomotion Biology
• Motor Control

Background:

• Spinal central pattern generating networks control alternating leg muscle activity and inter-limb coordination in quadrupeds.
• Brainstem reticular formation provides tonic input to activate these networks.
• Challenging locomotion, like ladder walking, requires additional context-dependent input from descending pathways, including the corticospinal and rubro-spinal tracts.

Purpose of the Study:

• To characterize adaptations in walking patterns in rats crossing a horizontal ladder.
• To investigate the role of the corticospinal tract in skilled locomotion on a horizontal ladder.

Main Methods:

• Electromyography (EMG) and kinematic analysis were used to study adult uninjured rats.
• Locomotor behavior was assessed during normal walking and while crossing a horizontal ladder.
• The effects of a dorsal column lesion, affecting the corticospinal tract, were examined.

Main Results:

• Rats exhibited altered hind limb placement on the ladder, precisely following ipsilateral forelimb placement, unlike normal walking.
• Increased hip flexion and pelvic rotation during swing phase contributed to hind limb reach.
• Electromyography showed decreased burst duration in Tibialis anterior and changes in muscle activity patterns likely due to reduced stepping frequency.
• Dorsal column lesions led to increased stepping errors and altered strategies, including reduced forelimb step length and mispositioned hind limbs.

Conclusions:

• Locomotion on a horizontal ladder involves significant adaptations in limb placement and coordination strategies.
• The corticospinal tract plays a critical role in executing precise stepping patterns and minimizing errors during challenging tasks.
• These findings highlight the neural control mechanisms underlying skilled motor behaviors in quadrupeds.