Feed the Tiger: a Method Fo Jaw Stretch Reflexes

The human jaw stretch reflex is a short-latency excitatory response of the jaw closing muscles to a rapidly imposed downward stretch of the mandible. Typically, the jaw stretch reflex has been evoked in children by using a hand-held reflex hammer. Understanding the development of the jaw stretch reflex has been hindered due to lack of experimental control of stimulus magnitude, motoneuron pool excitability, and activation of cutaneous mechanoreceptors in the lower face. A new methodology is presented involving closed-loop control of parameters of stimulus displacement, real-time biofeedback of jaw-closer muscle performance, and minimization of effects from activation of extraneous mechanoreceptors. Special consideration was given to developing a task that could be understood and easily performed by young children. To that end, an oscilloscope and a picture of an animal were used to create a “video game” played with the mouth. This strategy proved to be highly successful in obtaining reliable jaw-stretch reflexes in children as young as 5 years of age.