Organization of voluntary movement -1

A voluntary movement is characterized by the intention of performing it and despite it is slower is much less limited and stereotyped than reflex movements; Voluntary movements can be performed to different level of proficiency by different individual and the ability of executing them is clearly influenced by learning.  What do we mean by learning and do we have a recipe to learn effectively?

Very often when we attend a gym course or a swimming class we are instructed to move in a certain way but we can obtain very similar results performing actions that to a trained eye are very different. Voluntary movements are largely dependent on the motor cortex, this is a region of our brain that we can imagine as a dynamic (plastic) map of our body with each part extending accordingly with the functional role of the limb represented (i.e. the thumb is huge compared to the torso) and adjacent region in our body close to each other; a notable exception are the genitalia (close to the feet) and my guess is that this is related to the foetal position where they are actually close together.

A closer look reveals that the border between these regions are not only
dynamic (e.g. remapping of phantom limbs on other parts of the body) but also not so well defined, a stimulation of the map corresponding to the region of the feelers in rats once the feelers were disconnected after few hours started to produce movements in the anterior limb; either the interpretation of this study is not easy it is possible that the face
map also has some connections with the anterior legs and the removal of the link with the feelers can facilitate such connection.

Another aspect that is extremely interesting in a Feldenkrais perspective is that if two similar actions are performed with different forces (e.g. grabbing a ball) some neurons in the motor cortex decrease their discharge with increasing the force, whereas they discharge when fine control is required.

We learn in Feldenkrais classes to do less during the learning process, i.e. reduce the amplitude and force of the movements, Feldenkrais discussed this in term of the Weber-Fechner law, that Stevens modified in 1953, the idea of the law is that reducing the amplitude of the stimulus we can appreciate more subtle differences and hence learn.

The more modern approach seems to implicate that besides the aspects related to the Weber-Fechner law a small movement is qualitatively different from a large movement not only with respect to the increasing our sensitivity and possibility of learning but also in term of the cortex areas activated.

Interestingly this also poses a problem as learning through small/slow movements might not be completely effective to correct the large/fast ones if the areas activated are different but probably the overlap areas are large enough to have an important influence.

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Published by

albo09

I am a condensed matter physicist and a beamline scientist. I am fascinated by recent developments in neurosciences. I practised the Feldenkrais method for more than fifteen years and I think that he developed an unsurpassed practical understanding of organic learning processes. A blog is the perfect way to share my thoughts and learn from others.

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