How are stretch reflexes modulated during voluntary movement?

How did the bodies of animals, including ours, become such fine-tuned movement machines? How vertebrates coordinate the eternal tug-o-war between involuntary reflexes and seamless voluntary movements is a mystery that Francisco Valero-Cuevas' Lab in USC Alfred E. Mann Department of Biomedical Engineering, set out to understand. The Lab's newest computational paper published in the Proceedings of the National Academy of Sciences adds to the thought leadership about the processing of sensory information and control of reflexes during voluntary movements—with implications as to how its disruption could give rise to motor disorders in neurological conditions like stroke, cerebral palsy , and Parkinson's disease.

Do you remember the pediatrician tapping your knee to see if you had a strong involuntary knee-jerk reaction? This was to test the stretch reflexes in your spinal cord, which resist muscle stretching to give you muscle tone to hold your body up against gravity for example, fast corrections after tripping. So, how exactly those reflexes are modulated or inhibited to allow smooth, voluntary movement has been debated since Charles Scott Sherrington's foundational work in the 1880s (yes, the 1880s). This new work cuts directly into critical debates about how the ancient spinal cord and the relatively new human brain interact to produce smooth movements and how some neurological conditions disrupt this fine balance and produce slow, inaccurate, jerky, etc.

movements in neuro.