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Body movement and the brain

Help Book : La nature de l 'esprit Bases neurales de l’imagerie mentale THE REPRESENTING BRAIN: NEURAL CORRELATES OF MOTOR INTENTION AND IMAGERY
Motor Processes in Mental Rotation Book : Le Sens du mouvement, Alain Berthoz, 1997 Cerebral circuits for creativity Ce que pense un individu peut-il expliquer ce qu'il fait ?
Commander un ordinateur par la pensée, c'est déjà possible! Les mouvements d'un robot commandés par le cerveau d'un singe From mental power to muscle power—gaining strength How The Brain Rewires Itself

That mental imagery can play a role in the learning of movements and the improvement of motor performance is no longer questioned. Instead, the latest research is attempting to identify the determinants of efficient mental imaging. Studies have already shown that people who are better at generating mental images make faster progress in motor learning, as do people who practice a movement physically before imagining it mentally.

The concept of motor imagery extends to the sensory modalities as well. When someone has any given sensory experience, then re-imagines its later, the brain activity in the two cases will be similar in both location and intensity. Because brain activity continuously influences the body, and vice versa, any experience has a given effect on the body, and revisualizing it would generate a similar pattern of brain activity with similar effects on the endocrine system, the immune system, and so on.

Very generally speaking, visualization can therefore be regarded as a form of autosuggestion or self-hypnosis which, by generating emotions, may have a beneficial physiological effect on the body. Much remains unknown about the precise mechanisms of this interaction, but numerous studies of visualization have demonstrated its actual physiological effects.


The most elaborate processes in human psychic activity are made possible by mental entities that can be substituted for real objects. Until the late 1970s, it was thought that all information, regardless of sensory modality, produced a mental representation in the brain that was independent of this modality. Since it was thought that this representation was merely an epiphenomenon, mental images were not considered to play any functional role in the development of thought and action. But subsequent experiments have shown that mental imagery lies at the very heart of individuals' psychic lives. Indeed, it interacts with all the other major cognitive systems, such as visual perception, language, and memory.

But most important, research on mental imagery has shown that the processes for actually producing a movement and for representing it mentally are identical. Various experimental approaches have been used to show, for example, that the mental representation of an action seems to be based on the same mechanisms as the motor preparation for it.

With mental chronometry, for example, it has been shown that visual mental images preserve the spatial and structural characteristics of the of the object or scene that they represent. For example, it has been shown that the visual travel time between two points in a mental image of an object is proportional to the distance between these two points on the actual object. In another example, if you ask subjects either to pronounce or to imagine pronouncing the alphabet or a series of whole numbers as quickly as possible, the times for actually pronouncing these sequences and for imagining pronouncing them are similar.

Parsons's experiments on mental rotation of objects led to the same conclusion: the time it takes to rotate an object mentally is proportional to the number of degrees of rotation performed. For example, suppose that subjects are shown a photo of a hand and are asked to decide whether it is a left hand or a right one. They will take just as much time to make this decision as to actually rotate their hand into the position shown in the photo.The constant in the results of mental chronometry experiments is thus the striking similarity in the durations of actual actions and of actions represented mentally.

Researchers have also found some physiological indicators whose activation resulted solely from mental imaging of actions. For example, a group of researchers measured how physical training and training by mental imaging affected the strength of finger muscles. Physical training increased finger muscle strength by 30%, but mental imaging alone still increased it by 22%! Since the subjects did not make any muscle contractions during their mental imagery training, the observed changes did not come from the peripheral motor system but actually came from the activation of circuits in the central motor system.

Here is yet another example. When subjects were asked to imagine walking or running at various speeds on a treadmill, their heart rate and total ventilation increased in proportion to the speed imagined in the course of this mental exercise, even though their oxygen consumption remained steady.

To determine whether the two objects in each pair are the same, the subjects must rotate and compare them mentally.


Areas of the brain activated by mental rotation of objects
Source: University of Melbourne
Neuroimaging and Informatics

According to the theory for which Swedish neurobiologist David Ingvar coined the clever term "future memory", the parietal cortex is capable of producing internal models of movements to be performed, prior to any processing in the premotor and motor cortexes. According to this theory, the brain is constantly simulating movements, only some of which are eventually externalized. This theory could provide a conceptual foundation for the mental training done by athletes and musicians, as well as for re-education through motor imagery.

Source: Todd Siler

Link : Le cerveau, machine à produire une "mémoire du futur"

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