The Gamma Motor Neuron System
The sheer volitional element in the function of the muscular system is governed by the alpha neuron system. The flow and grace of muscular action is governed by the gamma neuron system
The alpha system comprises what is generally thought of as the voluntary motor system. It carries out the conscious instrumental intent of the person, and for that reason monopolizes the intention of mainstream physiology. Alpha neurons are responsible for the force of contraction, but movement controlled by the alpha system alone is jerky.
The gamma motor system is associated with muscle spindles and golgi complexes which are the tension control system of the muscle, and the proprioceptive and kinesthetic systems for the body. The gamma system both sets resting muscle tone and importantly adjusts dynamically muscle tension during instrumental contraction by interacting with the alpha system. This both smooths out and 'corrects' movement, allowing for 'fine motor control.'
It is the gamma system that is connected to the limbic and autonomic systems. That is, the gamma system provides the emotional aspect of movement. For instance, fright or embarrassment will make movements choppy or awkward. Sympathetic shift also causes poor motor control and clumsiness. Most clumsiness is caused by a lack of harmony between alpha and gamma systems due to suppression and neuro-muscular development being limited by early environmental negation
Where the feeling state of the body is both open and salutary, movements are graceful, and this is the contribution of the gamma system. Grace is not just an observational phenomenon, but a biological act. That is, gamma qualities of movement not only convey feeling but actually discharge the tension of emotion.
Neurogenic Tremors: Trembling is a phenomenon in which the gamma system discharges. It may happen involuntarily and is healthy if it does. But trembling can be induced by exercises that couple partial stretch with partial muscle fatigue ('stress positions') Most Lowenian (or 'bio-energetic') exercises have as an objective, inducing trembling through stress positions, and David Bercelli's Trauma Releasing Exercises® is an efficient sequence of such exercises intended to maximize the possibility of trembling. Voluntary shaking does not have the therapeutic effect of trembling because it is not driven by the gamma neurons.
Dance is an activity that, while it employs (like all movement) the alpha system, its whole purpose in working the gamma system. There is no instrumental objective of the movement, it is for pleasure. Ballet is a well-known example, but in the arts, Duncan dance is perhaps the epitome of this. In popular dance, Latin dances such as the samba are an example.
Psycho-motor learning relies on the sensory feedback through the muscle spindles and gamma system. Alpha dominated movement is also usually performed at full contraction which defeats sensitivity. That is why clumsiness does not yield to mere practice. In fact, sheer repetition of alpha dominated movements reinforces clumsiness. This is because overly willed and desperate 'flung' movements undermine the gamma system more. Our culture is increasingly relying on pushbutton technology which depends on instrumental intent and the quality of execution is almost irrelevant. This is possibly both a response to, and an accelerant toward, gamma impoverishment.
A poorly functioning gamma system is both caused by and results in muscle shortening. (although truly overly lengthened muscles also disable it) That is why stretching muscles is an essential element in all restorative bodywork. Professional dancers, who, as mentioned above, make their living putting emotional expression into movement, are known to be avid stretchers. As a remedial undertaking, moving very slowly is also necessary to encourage gamma participation. Penmanship practice used to be employed as gamma training for children, but fell out of use, perhaps because as average muscle tension increased among children generally over the last century, it became only a source of frustration and failure, and not pleasure as it had in earlier times.
Last updated 12-5-16