History of the brain
It is interesting to have a historical approach of the representations of the brain . We are accustomed to regard as normal that a damage on the level it brain can involve disorders on the level of other parts of the body. But this idea is however not so obvious.
During many millenia, the functions of the Cerveau were unknown, and it was believed that the mental activity had place, for example, in the Cœur. This vision, that we know today unfounded, is found in certain current expressions: “You break me the heart. ”, “To have a stony heart. ”, “To learn by heart. ”…
However, medical work of the 20th century lets think that the mental activity takes place in its center well. By various means, it was even possible to locate centers relative to various activities, even if the generalization of this approach still meets many resistances.
The brain in antiquity
Aristote saw in the brain only one species of radiator. However let us justify its error by some anatomical considerations:
the brain is indeed one of the bodies the best vascularized ones of the human body;
- moreover, exposed, the brain seems much less sensitive than the heart to mechanical stimulations.
One needed a true philosophical and scientific revolution to lead to the idea of the brain as centers Pensée philosophical S. Révolution with Plato which separates the heart in three parts of which one, immortal, is located in the head. But also scientific revolution in the knowledge of the human anatomy with Hippocrates, Hérophile and Érasistrate. The doctors accept thus little by little the idea that a damage on the level it brain can have consequences on the level of other bodies. This scientific knowledge remains however very limited. Hippocrates writes for example: “the brain is similar to a gland… white, friable like this one”. And Hérophile, although it takes part largely in the increase in the knowledge of the anatomy of the brain, remained persuaded that all the affections of the human body came exclusively from problems due to imbalances of “moods”.
The true nature of the brain and its relations with the other bodies thus is not included/understood yet. Let us keep however at the head that the anatomical knowledge of the brain largely progressed during Antiquity. It will be necessary to wait the 17th century in Europe to exceed this level of knowledge!
Later, other people, like Augustin d' Hippone, without calling into question the central character of the brain to the detriment of the heart, places well the spirit within the brain but within empty spaces whose anatomy revealed the existence within the brain: ventricles.
18th century with first half of the 20th century
At the 18th century, the neurologist François Joseph Gall emitted a theory, now exceeded, on the localization of the cerebral functions in the brain (Phrénologie). Then in first half of the 19th century, François Broussais taught this theory, after having imagined a theory on the relations between “life” and “stimulus” and on the interdependence (or “sympathies”) of the various bodies. These theories had an influence on Auguste Count, which published a cerebral table in its Système of positive policy (1851).
At the beginning of the 20th century, it appeared well quickly that there was to learn still much on the way in which the brain supervises the Langage, faculty specific to the human being. As of 1906, Sherrington (Nobel Prize in 1932) described the mechanism body-brain like a complex mechanism, controlled by retroactive loops. Feedback, wrote Sherrington, makes it possible the brain to evaluate the nature of a whole range of Stimuli and to produce the appropriate response. In same time, Santiago Ramon Cajal studied the cellular structure of the brain there. He discovered that the Neuron S transmit the nerve impulse without never touching itself. The highly-strung person] passes from one neuron to the other while crossing the Synapse using Neurotransmetteur S.
Of 1930 with 1950, Canadian Wilder Penfield made considerably evolve/move knowledge on the cerebral localizations. It carried out direct electric stimulations of the cortex (during surgical operations) and indexed méticuleusement the answers to the Stimuli. It summarized its experiments in the form of driving and sensory Homonculus.
Evolution of the representations of the brain in second half of the XXe century
What follows gives an account of the theses of Prof Dr. Michael Hagner introduced to Goettingue, the October 14th 2005 at the time of an entitled conference " Ikonophilie und Ikonophobie in der Hirnforschung"
By making a study of the illustrations of the scientific books on the brain, one notes a strong evolution during second half of the 20th century. One could say that the scientists working on the brain passed from a " icônophobie" with a " icônophilie".
Icônophobie of cyberneticsAfter the Second world war, the Cybernétique was the Paradigme dominating for the study of the brain. It was considered that the brain was equivalent to a calculating machine. One was at the beginning of the emergence of the Informatique, and much of theoretical work accumulated to show how, with basic logical operations, one could solve complex problems. By analogy it was considered that, anyhow , the brain carried out logical operations of the same type as that which one was spirit to develop for the computers. Research on the brain then will be satisfied to represent the logical circuits supposed to be subjacent with the operation of the brain. The anatomical representations absent, or are simplified. For example celebrates it book of John von Neumann, " The computer and the brain" , has as an illustration in title page a computer occupying major the part of the photograph and John von Neumann posing on with dimensions one. Or many diagrams of Neuron S connected resemble more diagrams of electronic Logique or that to histological boards . In a general way in biology, two types of representation are opposed, on the one hand physiognomical representation , and on the other hand functional representations . The cybernetics of the Années 1940 has chooses the second deliberately. Following the example Behaviorism, it is a question more of knowing what made the system rather than of knowing what is the system.
One can trace a parallel between this systematic abstraction in the representation of the brain on behalf of the cybernetic school of the Années 1940 - 50 with the general rejection of a particularistic approach in the majority of sciences of this time. In Ethnologie for example the Structuralisme with in particular Claude Lévi-Strauss dominates. Indeed the physiognomical representation (too much) was used by sciences under nationalist influence in order to put forward the superiority of such or tel. By the systematic abstraction one wants one contrary to refuse any hierarchisation, not only between human cultures, but also between living beings, even between all structures capable of logic processing of information.
Icônophilie of the cerebral imagery
Since the Années 1990 one rather attends a return of the authority of the image as scientific piece of evidence within the framework of research on the brain. Although the new methods of cerebral Imagerie require an high-tech and a complex data processing, and that thus the images obtained do not correspond to a direct observation of the phenomena, they exert nevertheless by their apparent simplicity, and their attractivity (of pretty color, sometimes even of animations…), a fascination, an intrinsic force of conviction. Consecutively the comparison computer/brain loses its force in the community of the researchers in neuroscience. It is replaced by the concepts of Car-organization, of Plasticité, Apprentissage… Ironiquement, research in data processing even tries to make computers which miment the brain. One speaks about neural networks, Artificial intelligence, computer able to learn, or quite simply about " convivialité" software and operating systems…
Nevertheless the specialists in neuroscience remain vigilant vis-a-vis this icônophilie. More and more criticisms protest against a " imagery fonctionnelle" who shows what occurs during such or such behavior/thought, but does not say anything the how is correlated a behavior with the activation of such or such cerebral surface.
A rumor amusing concerning the brain
One discovered in the interval wars which the brain was composed of more than cells gliales that of Neuron S, in a report/ratio which was estimated then from 4 to 1. It was not necessary any more so that newspapers titrate “We use only 20% of our brain to think”, which became quickly by successive deformations: “We use our brain only with 20% of its capacity”. This perdure error still in several mediums today.
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