Cutaneous reflexes evoked during human walking are reduced when self-induced

Area of Science:

• Neuroscience
• Human Locomotion
• Motor Control

Background:

• Reflex responses are typically attenuated when self-induced, a phenomenon under-investigated quantitatively.
• Reflexes during gait are crucial for locomotion regulation, with potential cortical involvement in their modulation.
• The impact of self-triggered versus externally triggered stimuli on gait reflexes remains unclear.

Purpose of the Study:

• To quantitatively investigate differences in cutaneous reflex responses during gait when stimuli are self-induced versus computer-triggered.
• To explore the role of anticipation in modulating reflex responses during the gait cycle.

Main Methods:

• Cutaneous reflexes were elicited via sural nerve stimulation in healthy subjects across 16 gait cycle phases.
• Stimuli were either computer-triggered or self-triggered by the subjects.
• Reflex responses in various leg muscles were measured and compared between conditions.

Main Results:

• Self-generated stimuli resulted in smaller facilitatory responses and more pronounced suppressive responses in leg muscles for most subjects.
• Specific muscles like tibialis anterior (TA) showed both reduced facilitation and enhanced suppression.
• The magnitude of reflex modulation varied by muscle, with TA and peroneus longus (PL) showing significant differences.

Conclusions:

• Anticipation of self-induced reflexes reduces excitatory drive to motoneurons, potentially via presynaptic inhibition.
• These findings suggest a neural mechanism for modulating gait reflexes based on self-generated sensory input.
• The study highlights muscle-specific modulation of anticipatory influences during locomotion.