refers According to the latest findings of brain research instead of brain development between the genes and the environment in a fluctuating exchange. Therefore would be both the perspective of a pure biological determinism, and the views of the people in terms of a "Tabula - Rasa," which only characterized by its (social) environment is wrong. Wolf Singer tried this with the following example to illustrate:
"It is likely that our genetic make-up for the last 30 - 40,000 years ago, only slightly, if at all, changed added. (...) This also means that a baby would inhabiting caves stone age parents are like us, if it were raised from birth in our society, perhaps micrograph study ...
other hand, would our children, they would be the then entrusted to become so as their children. We do not know very much about these people. But it is certain that they must have differed dramatically from us and mainly with respect to higher mental skills and cognitive abilities such as language and abstract reasoning. This shows how obsolete the current over-emphasis on genetic determinism. "(Singer 2001 p.2)
Even the neurobiologist Gerald Huether is similar to Singer believes that human development between these two factors treats. He describes the human brain as a " social product ", which is optimized at birth for the design of social processes. In his view, are all areas in which the human brain differs from its closest animal relatives, and are seen as specifically human, areas that are fully formed until after birth. According to Huether innate none of the culture-specific services is. (See Huether 2006 p.42)
This finding is from an educational point of view of a not to underestimate the relevance, since it implies how important education and socialization for the development of man. But before I continue that thought, I would like to represent the process of brain development in its various stages. To this end, I first explain the processes of neurogenesis, migration and differentiation, then the important issue of cell loss and reduction of synapses, and the sensitive or critical periods of brain development.
neurogenesis, migration and differentiation
neurogenesis
about the ninth day after fertilization, the embryonic tissue differentiated into two types, known as the ectoderm and endoderm. From the ectoderm caused the skin, the sense organs and the entire nervous system. Previously, however, is a third type of tissue, called the mesoderm, from which develop connective tissue, bones and muscles. From the ectoderm and mesoderm meeting of
formed in the third week of pregnancy, the neural plate, which is the first neural developed until they finally enfügt the neural tube, Together
. On the wall of the neural tube begins from then on cell division, resulting in the 250000-500000 nerve cells per minute. Here, glial cells and neurons develop from the same stem cells, but the two cell types, which depend on the location of cell division. A cell that was once as differentiated neuron loss, while the ability to divide. (See tree ann 2007 p.74 / This led to the neuro-scientific dogma that the nerve cells when they die, could no longer be replaced. However, this could more recently, by the neuroscientist Fred Gage be invalidated. He found that develop in mammals in the adult olfactory bulb and hippocampus resistant to new neurons.)
is worth noting that even at this time, a development in between off-exchange Environment and genes takes place. Genes are always embedded in their specific environment ever. According to Wolf Singer, it is the environment that initiates the readout of genetic information. The development of the nervous system, like the whole person, occurs always in a dialogue between genome and environment. This shows how obsolete, the claim is that the man is completely determined genetically. (See
Singer 2004 p.2)
migration
After the cells caused in this way, they work to the place where they are to work later. The glial cells are the nerve cells as "signposts" along which neurons migrate to their final destination. Reached their destination, a nerve cell, it combines with other neurons along the glial cells of the so-called "pillars" and forms the basis for subsequent functional units. From this point, the differentiation starts at a specific cell type. Subsequent neurons have to migrate through this already incurred through cell layers and form the outer wall of a new cell layer. The brain matures, therefore, from the inside out. While still make the cells on the migration, the axons begin to sprout. This process can repeat the brain at any späterenZeitpunkt and thus initiate the Axonenwachstum always, if circumstances so require. The focus of the migration takes place prenatally. (See Baumann 2007 P.75)
differentiation
parallel to the growth of dendrites form synapses. Only with the emergence of the first synapse in the seventh week of pregnancy can occur in the brain communicate. This process provides the basis for all learning processes. Synapses formed for life and are able to change their structure and thus the type of communication. There are apparently two waves, in which specially trained many synapses be. The first phase, referred to as synaptogenesis begins prenatally and continues throughout the entire pregnancy. In some areas, such as the frontal cortex, even over the first year out. The second phase occurs in early adolescence, in which there is an overproduction of synapses and dendrites, but over the following years reduced again. (Ibid. p.76)
cell death and synapse reduction
The human infant comes with many more neurons and synaptic connections to the world as it actually takes to functional Schaltkre ise to develop information development. ( see Stern / Grabner 2007 p. 62) This surplus neurons is reduced in the course of human development into adulthood by about half of the original neurons, so that those neurons that survive the development, are also those which are actually used. In much greater extent, these processes are also for dendrites and synapses, however, begins the destruction of dendrites and synapse much later in the development, from about the age of two, and extends at least to the early adulthood. ( see Baumann 2007 p. 78ff)
this run two processes simultaneously. On the one hand, the formation of new synapses and on the other side of the downfall of those synapses that are not used regularly. Through these processes the developing brain gets the ideal opportunity to adapt to its ever-specific environment. It found of cell death and synapse reduction in the course of human development throughout the brain, but not everywhere at the same time instead. About this process in his search for Wolf Singer in the brain only about a third of all part of synaptic connections is preserved. This means that the "architecture" of the brain to a high degree of environmental factors and is dependent on experience. ( see Singer 2004, p. 4)
H ieraus can conclude that the man in the early childhood faster and more flexible can learn, because the brain can react in this age the most flexible to new experiences and it is clear from these findings, the recommendation that children as early as possible to promote educational, eg by a specific foreign language teaching or a mathematical ECI.
myelination
About 100 years ago occupied the German neurologist Paul Flechsig with the phenomenon of size and weight gain of the brain after birth. He found out from tests on the brains of deceased children, the size of the brain increase is mainly due to the increase in the thickness of fiber connections between the neurons. The reason for the thickening of the fibers is known as the myelin sheath. (See Spitzer 2002, p. 229)
The myelin sheath consists of white cells and serves as a sheath of axons for much faster transmission of information in the brain. It begins after the migration, namely after the neuron has found its destination and has already taken the axon initial contact with dendrites of other cells. (See Baumann 2007 p. 81)
After Manfred Spitzer leads the insulation of nerve fibers with myelin (and therefore their increase in thickness) to increase the speed of nerve transmission to up to 110 meters per second. Without myelin, the speed is just three meters per second. The fact that cortical areas are on a rapid exchange with each other need is that an area, the connecting fibers are not myelinated, very little can contribute to information processing. (See Spitzer 2002, p. 230)
The interesting thing about the progressive myelination, is that it ensures that a developing human being can only learn certain things at a certain time. It replaces what are essentially the "teacher".
According to Manfred Spitzer after the birth of the first myelinated primary sensory and motor areas, ie areas that look for the primary processing of hearing, and touch are responsible, and be used to perform movements. This allows the infant take their first experience, do not process the information, however, very deep. Thereafter, secondary areas and myelinated until around the time of puberty around the compounds of the highest myelinated cortical areas in the frontal brain and go to "online". From the late maturation of the frontal lobe Spitzer therefore concludes, that ethics education, because the topics are represented in the frontal lobe, should be introduced no earlier than the seventh grade, because younger students might not have the brain areas that they need to deal with the ethics lessons. (ibid. p. 359)
Those in humans than other primates, strongly delayed brain maturation has long been interpreted as a disadvantage, stood but in hindsight is an asset, as it ensures that people initially with simple structures and learn with the progressive myelination and more complex structures . After Spitzer was via computer-simulated neural - networks, to which we investigated how a network learns grammatical rules, be shown that the only way a network in general can learn more complex structures. If the brain from birth to be "open" for all that flows to stimuli, it would ultimately be overloaded, with no or only very slowly learning. Accordingly, says the brain researcher Spitzer, that the progressive myelination of the brain, the biological correlate to educational wisdom that one should always learn from easy to difficult, be. (See Spitzer 2002, p. 231ff)
phase-sensitive and critical in brain development
After Sabine Pauen one speaks generally of a critical or sensitive period of learning, when experience in a given age have a dominating effect for all other life. 133 After Stern, a distinction between critical and sensitive periods, depending on the degree of expression in relation to the age dependence and the irreversibility of the phase. From a critical phase is called only when certain developmental problems at a later date can not catch up (see Pauen 2006. time window of brain and behavioral development: fad or class siker , in: Hermann (ed.) 2006 p. 33)
These phases are caused by genetically determined developmental mechanisms that but need a specific external stimulus to expire. As you have heard about in the item "cell death and synapse reduction", held in the brain, a permanent conversion process, which at certain stages but is more active than others. Over-production and selection of synapses is not in any brain region at one time and at the same rate and intensity. Thus, for example in the occipital lobe, which is responsible for visual perception, achieved the highest density of synapses in the first months of life, in the frontal lobe, however, is the growth between the third and sixth year at the highest. Hence, the brain researchers, that are particularly susceptible in these phases the brain for specific learning experiences, chosen because at this time for the relevant synapses and structured. Conversely, the brain researcher, one would expect that at later stages of missed learning experiences could no longer be remedied because the synapses, which by not - use would no longer be needed, would be reduced. Since it would not come again to such an overproduction of synapses in the relevant area, could the missed learning achievements and experiences and not or can not be made up completely.
An example of a critical phase is the development of visual perception: the past, newborns often suffer from infections of their eyes, which she contracted at birth. The consequences were clouding of the cornea or lens, whereby the children became blind and could see only vague differences in brightness. When it was possible to transplant corneas and lenses, the hopes were high that the children would learn again to see normally, but did not. The children did have functioning eyes, but remained blind, because the brain with the information they got could not do anything. The critical phase in which the visual system becomes evident in humans, was skipped and could not be made up. (See Singer 2004, p. 4)
sensitive and phases are critical for the education of a high interest. Thus it is entirely of relevance to know when a person can learn something, and when the time window, in that he can learn it closes again. So you could probably figure out in the near future with the help of brain research, when the ideal time has come to learn certain mathematical and linguistic skills. In this way, a kind incurred neurobiological curriculum that aligns directly to the development of the brain. Second, many parents and educators are worried that they miss a sensitive or critical phase and so the child can take forever to get to certain things or to acquire certain skills.
After Spitzer this concern to be unfounded: the human Brain is actively looking out from his environment what it needs for its optimal development. It is such a universal appeal that they should appear in any "normal" environment. (See Stern / Grabner including 2007 p. 10)
According to Spitzer targeted promotion or particularly strong attractive environments seem rather counterproductive, since the risk of over-exposure of the brain too big sei.v (gl Spitzer 2002, p. 234 )
The school education in the near future, a curriculum is available that would have been in brain development and the sensitive-or . critical phases directed, but is expected not be expected. The entire visible from me literature on this subject contained only secure data on sensitive or critical stages of visual perception, language development and individual motor skills. For other skills are at best guesses.
So my dear ladies and gentlemen. That's it for today. In the next article we go further in depth of the brain ... You will be surprised.
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