Tapping into rhythm generation circuitry in humans during simulated weightlessness conditions

Frontiers in Systems Neuroscience, 2015 · DOI: 10.3389/fnsys.2015.00014 · Published: February 18, 2015

Simple Explanation

The article reviews the ability to produce rhythmic activity, which is important for generating and controlling movement. It discusses how this rhythm-generating capacity of the spinal cord is being studied, especially for helping people with spinal cord injuries. The review focuses on how reducing external resistance, like with body weight support, can help reveal the spinal cord's ability to create rhythmic movements. This can be useful for understanding and improving rehabilitation strategies. The review examines experiments where people perform 'air-stepping' in simulated weightlessness to study the spinal cord's rhythm-generating circuits. This model allows for easier investigation of these circuits without interference from body weight and balance control.

Study Duration

Not specified

Participants

Healthy subjects and SCI patients

Evidence Level

Review Article

Key Findings

1
Tonic central and peripheral sensory inputs can activate the spinal CPG circuitry in healthy humans, leading to stepping-like movements.
2
Automatic, alternating movements of the legs can be initiated by upper limb movements during hand-walking, indicating a functional coupling between arm and leg CPGs.
3
Epidural stimulation of the spinal cord in SCI patients can produce rhythmic EMG activities and stepping-like movements, which are facilitated by leg suspension.

Research Summary

This review explores the role of rhythm generation circuitry in humans, particularly its relevance to locomotion and rehabilitation after spinal cord or brain injuries. It highlights the significance of the spinal cord's central pattern generator (CPG) and its interaction with supraspinal inputs and sensory feedback. The article emphasizes the facilitatory effect of simulated weightlessness on rhythmogenesis, which allows for a clearer assessment of the CPG circuits and their potential for gait recovery. Techniques like air-stepping and spinal cord stimulation are discussed in the context of activating these circuits. The review also examines the importance of supraspinal motor areas in human walking and how their engagement can benefit gait recovery. It concludes by advocating for the development of CPG-modulating therapies and techniques to augment function in disabled individuals.

Practical Implications

Rehabilitation Strategies

The findings can inform the development of more effective gait rehabilitation strategies for individuals with spinal cord and brain injuries by targeting the spinal CPG circuitry.

Assessment Tools

Simulated weightlessness and air-stepping can be used as valuable tools for assessing the state of the CPG circuits and evaluating new medications for gait recovery.

Spinal Cord Stimulation

The combination of spinal cord stimulation and simulated weightlessness may enhance the utility of CPG-modulating therapies, leading to improved outcomes for disabled individuals.

Study Limitations

1
Limited evidence of the efﬁcacy of treadmill interventions with body weight support in some injured populations.
2
The complex nature of the control of locomotion, compensatory strategies, and plasticity of neuronal networks.
3
Difficulty in investigating impairments in the CPG functioning due to interference with the ongoing task of body weight and balance control.

Your Feedback

Was this summary helpful?

Back to Neurology