Why is brain plasticity necessary ?

Brain development is based on genetic information and from a mechanism of adaptation to the environment. However, during the gestation period, since the uterine environment is very similar in the majority of individuals, the brain seems to grow based on genetic information, so it will be developing bases of the mechanisms that will be run later, that allow interaction with the external world. The genes that determine this polarity, are called organizers genes and they are not only expressed in the nervous system, but in other tissues and organs. While the genes that direct the differentiation-specific structures known as regulatory genes because they govern not only the anatomical structure but the function of the cells (Poch, 2001).

The reasons why the distribution of structures and the development agenda are preset are not very clear, but one theory is that the nature or complexity of the functions and the genetic programming can perhaps obey physical laws that govern other natural processes. In this sense Walsh and Diller (1981) explain that the brain maturity is a progression of neural development, which is determined by two types of neurons that built the kind of connections that are established between structures. On the one hand, pyramidal neurons (called macro neurons) differ from the neurons of local type, by which the first develop much earlier, establishing early connections then it will be difficult to restore after a brain injury, apparently these neurons are genetically clip-art and are running during birth, and they are responsible for establishing the functions of lower order, for example in the case of language, sound analysis and its phonological representation; while local neurons, will enjoy a longer liberty or plasticity and will be responsible to establish new connections in more advanced developmental periods. This type of neurons will be involved in the processes of higher order, is consolidating in a more progressive way and involved in functions such as semantic processing (Tubino, 2004).

In this way, brain plasticity mechanisms may include neurochemical changes, on cortex, receivers or structures, so it’s possible to say that functional plasticity is accompanied by structural plasticity, most important among the mechanisms of functional reorganization are the unmasking, the synaptic bud, the dendritic arborization, inhibition and facilitation and modification of neurotransmitters, among others, so it admits the possibility that there are several types of neuronal plasticity, which are considered to a) the developing brain plasticity; b) plasticity of the brain in learning period and c) plasticity in the adult brain (Aguilar, 2003).

Plasticity of the brain in development

Deacon (2002) explains about the plasticity of the brain in development, that during the period of embryogenesis genes are those who will determine the distribution of the different brain tissues and will also be responsible for the coordination of the processes that later will take place in the formation of the embryo, including the basic structures of the brain; but after the birth the genetic will run other mechanisms of brain structure that will largely depend on the environment both internal and external.

 

So at the beginning of the development of the nervous system, there is an excess of neural fibers, and an important part of the development process includes the neuronal trimming of excessive connections that are not necessary and may in fact be can be harmful to normal operation. 

In fact, thought this explosion of connections as early is part of the process of plasticity during development, and this has advantages of adaptation. However if any damage occurs during the period in which there are excessive and available connections, there are more possibilities of the system to survive despite the damage that you can design a route of alternate connections that may be suitable for the repair of the damage (Avaria, 2005).

It is so accepted that there are moments or critical periods in which each of the different areas of the central nervous system has special sensitivity and responsiveness to the changes induced by the different influences, and there is enough evidence about the influence of the experience affects most the final organization of the local circuits which to the main roads, because time has already completed the topographic organization of large circuits. 

But even if there is a period of particular sensitivity to receive sensory information that ultimately is going to influence and direct the learning, so although there is a certain structural predisposition that is set from the beginning and favors a previously established connection ans its maintain, this connection depends on the strength of the neuronal signals, as no matter where come from those signals but are retained and are finally established. However, is known that the age in which the injury occurred is one of the crucial factors to take into account to predict the course of brain injuries, as it has been found in research that focal lesions before one year of age will have a worse prognosis of intellectual function that injuries of the same type after that age (Riva & Cazzaniga 1986; Woods, 1980;  Tubino, 2004).

In this sense, since plasticity is greater in the first years of life, for most of the lesions and gradually decreases with age, the learning and the recovery will be enhanced if experiences are provided or stimuli early to the individual, especially in children, since the structures nerve in the first years of life are a maturation process that continuously new synaptic connections are established and growing myelination occurs their structures, so that in response to the stimuli coming from the experience, and by means of internal biochemical processes, the infant brain is forming. 

During this critical period, the circuits of the cerebral cortex have, as already mentioned, large capacity of plasticity, for which the absence of an adequate intake of stimuli, experiences or nutrients has important future functional consequences (Wash and Diller, 1981; Deacon, 2000; Hernandez-Muela, Mules, Mattos, 2004; Avaria, 2005).

 

Even when you know some of the factors that control the duration and the time that establishes these periods of special sensitivity, described that they relate to particular synaptogenesis, i.e., the phase in which there is hiperproducción of synapses in the cerebral cortex, but, as already explained, of these synapses will lose those neurons that do not establish any relevant connection finally will be eliminated by the system, giving rise to a phenomenon of remodeling of the brain network, so it is said that genetically predetermined development configures phases of production or synaptic outbreak (Wash and Diller, 1981).

However, there is evidence that not all the brain areas show periods of synaptogenesis and synaptic loss at the same time. In the primary visual cortex, for example there is an outbreak of synaptogenesis by 3-4 months of age with a maximum density at 4 months. But in the pre front cortex takes longer and reaches the synaptic density maximum to 3-5 years. The time course of the Elimination of synapses is also more prolonged in the frontal cortex (up to 20 years) than in the visual cortex (4 years); so, it is possible to affirm that maturation times for different brain structures are different, and the primary areas senso-motor cortical unfold before large areas of association. 

In this sense, el made that are necessary stages so that neural activity to complete development, involves the brain maturation is changed through his own stimulation and experience, providing the necessary adaptability to the brain. This scheme is probably cheaper from the biological point of view, since a model whereby the genetic control for the formation of all synapses is needed would require a incredible number of specific molecular markers and their respective genes, what a system rigid and dependent would do it. This is explained because of the extreme immaturity of the brain of the newborn, whose fragility justifies the total parental dependence of the newborn human. This emphasizes the total difference of man with respect to most of the animals, which even newborns, they are already capable of running many of its basic functions (Tubino, 2004).  

Also known that the ability to analyse and synthesize multiple sources of information, and generate different responses from the brain, which illustrates the centralized organization and brain function, there is a hierarchy in the organization in such a way that the lower segments carry out specific functions subject to the control and modulation of segments above, by which the complexity of the information processing increases progressively as the level becomes to up to the crust. But, from the periphery may cause, with certain stimuli, responses in higher levels that force the organization or the acquisition of certain functions. 

However, it has been particularly studied the early lesions that occur in the linguistic areas, which generally manage a good recovery function, but currently, there is extensive evidence that the process of recovery of functions is not able to completely eliminate the effects of the early focal lesions as in the case of the language, throughout the subsequent development of the infant, you can see difficulties in reading, writing, comprehension, articulation, fluency and/or syntax (Verger and Junque, 2000)

One possible explanation of this effect, is that all the sensory and motor regions primary brain are related from a functional point of view, by association fibers. Cortical association areas, for example, are directly connected among themselves, while the primary cortical areas are connected each other indirectly through the Association areas. Homologous areas in both hemispheres are connected through fiber inter hemispheric, mainly by the Corpus Callosum. This brain interconnectivity allows a constant interaction within each hemisphere and between both hemispheres, and in this way is intended to adapt responses globally and dynamics (Hernandez-Muela, Mules and Mattos 2004; Poch, 2001).

It is thus that the brain works in a coordinated manner and analyzes the world in a global way, for this reason, when you read something is to understand the letters that make up each word, understood the meaning of each of the words of a sentence, however, these processes are not synthesized independently, but that a general sense is given to each phrase. This is possible thanks to the coordination between each of the lobes of the brain, this is the engineering of the brain, which that allows you to interpret the world and the same design a spacecraft that learn the abc. East the working tool when it comes to learning, and modify their connections, is the final triumph of the teaching. 

It has be found at the same time, another important aspect that is modifiable during critical periods: cerebral laterality, this is expressed in three aspects: anatomical symmetry, unilateral functional differences (as the location of language, speech and analytical processing in the left hemisphere, and temporo-spatial skills, as those related to music and the emotional and humorous repertoire (right) and contralateral sensorimotor control, in this way, understand the functionality of the brain in these three aspects is essential to understand the processes that take place in the reorganization of the brain during the learning process because it is a very rich source of experiences that can benefit education (Maciques, 2004).

References:

 Aguilar, F. (2003) Plasticidad cerebral: parte 1. Rev Med IMSS. 41(1) 55-64.

Avaria, M. A. (2005)  Aspectos biológicos del desarrollo psicomotor.  Rev. Ped. Elec. [en línea] Vol 2, N° 1.

Deacon, T. (2000) Evolutionary perspectivas on language and brain plasticity. Cognitive science. 28 (1) 34- 39.

Hernández-Muela, S., Mulas, F. y  Mattos, L. (2004) Plasticidad neuronal funcional Rev Neurol. 38 (Supl 1): S58-S68.

Maciques (2004)  Plasticidad Neuronal. Revista de neurología. 2 (3) 13-17.

Poch, M.L. (2001) Neurobiología del desarrollo temprano. Contextos educativos. 4. 79-94.

Tubino, M. (2004) Plasticidad y evolución: papel de la interacción cerebro – entorno. Revista de estudios neurolingüsticos.Vol. 2, número 1. 21-39

Verquer, K. & Junqué, C. (2000) Recuperación de las lesiones cerebrales en la infancia: polémica en torno a la plasticidad cerebral. Rev Logop Fon Audiol. XX(3):151-157.

Walsh, T. M. & Diller, K. C. (1981) Neurolinguistic considerations on the optimum age of second language learning. En. K.C. Diller (Ed) Universal in language learning aptitude USA. Rowley: Newbury House Publishers.

Woods, B. (1980) The restricted effects of right hemisphere lesions after age one: Wechsler test data. Neuropsychology. 18: 65-70.

Brain plasticity: history of the concept

The term plasticity was introduced in 1890 by the American psychologist William James, in which described the natural modificability of human behavior. Although in the last years of the 19th century, Santiago Ramón y Cajal proposed that these behavioral modifications would surely have a anatomical substrate, attributable to the brain, and those changes of variable duration in synaptic function which arise with origin in external stimuli affecting learning, are modificable by this plasticity. Thus Lugaro and Ramón y Cajal deduced it almost at the same, with different variations of ideas, both explained that learning involves functional plastic changes in the properties of the neurons or their interconnections.

From this perspective, learning may be the result of a morphological change among the interconnections of nerve cells, similar to the phenomena that occur during the formation of synapses in the embryonic life, however, after Cajal’s death, it was adopted a rigid way of looking at the adult central nervous system and it was accepted the idea that once finished its development, anatomy of the brain remained unchanged, except for the degenerative processes (cited in Nieto, 2003). 

Since then, the concept of synaptic plasticity has come developed mainly in studies related to memory and learning.  

However, even after years evidence about the capacity of our brain to change its functions and to compensate some damage, the importance of this role has come to be appreciated only recently, since studies brain in late 19th century and early 20th focused on the identification of areas of specific performance which gave the idea of a brain that governs its functions in specific areas and thus the widespread idea in the psychology of learning must be obtained in specific periods of time. 

Some persons believe, this was thanks to Paul Broca, who in the mid-19th century, identified a certain area in the left frontal lobe-related to language, which was the starting point for the neurosciences focused strictly on localizations of processes. Since then, many others continued describing specific brain areas with specialized functions, such as Broadmann; who described them but with more and more improved of morphological techniques, architectural and neurochemical studies, researchers discovered more details of the brain structure and functional connections.

The enormous complexity of the brain may have contributed to the conceptual rigidity that  was developed in those years, since its organization was known within a whole, the anatomists had to sectorize such knowledge. This motivated to Broadmann to divide the cortex into 52 regions, and descriptions made by constituents showed them separate, and this gave another reason to believe in concept of a rigid, strictly divided brain. This, coupled with studies of connectivity and the absence of concrete evidence of regeneration in the brain (in contrast to organs like the liver which has the capability of mitotic cell duplication), led to believe that it was a body divided in compartments, not malleable (not plastic) and with little ability to recovery after injury, so few Anatomists, physiologists or clinical projected a concept of dynamic adaptability of the brain (Aguilar, 2003b; Poch, 2001, Aguilar, 2005).

Currently is kind of a simple accept that an adult 30 years old knows much more than a child of 10 years old, and at 70 years old someone knows more than during 20’s, because the cognitive development process goes hand in hand with developing brain in particular the development of adapted neural networks that allow respond to the environment, and all this depends on the genetic information which is endowed to each individual as well as from the mechanisms of adaptation of the environment, so these days, such assertions become searchable thanks to the study of the process called neuroplasticity or brain plasticity (Tubino, 2004 and Ginarte, 2007).

However, it was not until some years later that this concept of neuroplasticity was defined by Gollini (1981) and Kaplan (1983) as a potential of nervous system to change (although it has observed this same capacity in other systems such as the endocrine, respiratory and skeletal muscle). This capacity can modify behavior and allow the adaptation to the environment patterns of conduct, so this ability of central nervous system allows it to never be finished and always change and adjusting as result of the interaction of factors genetic and cultural, but also it’s know that this ability decreases as neurons specialize (Bergado cited in Ginarte, 2007; Poch, 2001).

 

Defined more broadly, plasticity is the functional adaptation of the central nervous system to minimize the effects of the structural or physiological alterations, regardless of the original cause. This is possible thanks to the faculty of the nervous system to experience structural-functional changes detonated by influences endogenous (internal) or exogenous (external), which can occur at any time of life. Some researchers explain that this includes learning in its entirety; more specifically, there is evidence of morphological changes such as neuronal branching after learn a new skill. 

 While another group of experts, with a more intermediate position, considered it as adaptive capacity of the central nervous system to modify its own structural and functional organization, since plasticity mechanisms may include neurochemical changes,  at the parenquima, receivers or structures. Likewise, functional plasticity is accompanied by a structural plasticity, since there is also evidence of cooperation between brain areas (Aguilar, 2003b).

In the same way, it has been observed that there is also a great ability to communicate between neuron-glia, which collaborates on brain plasticity (either by creating new connections or removal and cleaning of the existing) (Aguilar, 2003a, b).

 

In response, it should be recalled that major cellular kinds of nervous tissue are the neurons and glial cells. Neurons, cells that are highly specialized in quick, message reception and transmission have a small body and multiple branches that cover an extensive area, allowing you to optimize your intercom, making them malleable to the needs of the cerebral environment (Nieto, 2003).

It is thus that the synaptic strength can be altered in the different periods of development and range from milliseconds to months. 

The cellular mechanisms of these changes are transitional modifications of neurotransmission and in longer alterations, changes in gene expression, so it can be said that there is a continuous renovation of the organization and neuronal maturation (Aguilar, 2003a; Aguilar, 2003b; Castroviejo, 1996; Poch, 2001).

References: 

Aguilar, F. (2003 a) Plasticidad cerebral: parte 2. Rev Med IMSS. 41 (2) 133-142.

Aguilar, F. (2003 b) Plasticidad cerebral: parte 1. Rev Med IMSS. 41(1) 55-64.

Aguilar, F. (2005) Razones biológicas de la plasticidad cerebral y la restauración neurológica. Revista Plasticidad y Restauración Neurológica. Vol. 4 Num.1. 5-6.

Castroviejo, P. (1996) Plasticidad cerebral. Revista de Neurología 24 (135) 1361-1366.

Ginarte, Y. (2007) La neuroplasticidad como base biológica de la rehabilitación cognitiva. Geroinfo. Vol. 2. No. 1. 31-38

Gollin. E. S. (1981) Developmental and plasticity: behavioral and biological aspects of variation in developmental. New York. Academic Press.

Kaplan, B. A. (1983) Developmental psychology: historical and philosophical learning. New Jersey. Elrbaum Hillsdale.

Nieto, M. (2003) Plasticidad neural. Mente y cerebro. O3. 72-80.

Poch, M.L. (2001) Neurobiología del desarrollo temprano. Contextos educativos. 4. 79-94.

Tubino, M. (2004) Plasticidad y evolución: papel de la interacción cerebro – entorno. Revista de estudios neurolingüsticos. Vol. 2, número 1. 21-39

When the theory brings into play the love

Daniel is a Russian physicist ready to conquer the world with his ideas, but in the midst of publications filled with Greek letters and numbers, he has failed to atract a beautiful girl’s love of the lab at the other side of the campus. That girl that walks around with the sweetest smile and when she meets Daniel in the cafeteria, smiles even more broadly, knowing that he is a foreigner so she does not want to say something wrong... that girl who ... does she make him sweat?... perhaps so much that he has even asked her name...

 

Town was suffering the third winter storm of the season that evening, so Daniel went into the library, hiding as it was his habit to expect bad things to pass, it was his refuge for everything and everyone. 

He had been studying game theory during a while, especially from Nash’s perspective, and he was determined to publish an article about this topic, applying a proposal from economic and biological models. Although there is a lot of articles written on the subject, he wanted to innovate, he wanted to find something that no one else had seen, however he had to find  that something, there was no doubt he was going to find it there, or perhaps here... maybe in this journal... maybe...

He began to move from one side to another around 300 magazines on the table when one of them slid...... when he bent down to lift it without paying attention to the environment, he saw a hand taking his magazine. He was ready to shout do not touch my magazine, when his eyes followed a hand, and then an arm and then a shoulder... he came up to the neck and two brown eyes met with his blue eyes.

The smile was expanded as always... but this time she modulated carefully her words:

-Hey!, I found this!... What are reading?, she said.

-I'm reading Nash’s theory... He said as doubting whether those words came from his voice or if he was listening to through his headphones, he took them off to be able to distinguish between his voice and the music he was hearing, and they fell to the floor.

She hurried to help him to lift them up and while she did it put attention into the magazines on the table and reached to read one of them: game theory and their applications in biological models...

When she concluded reading, she gave him the headphones and then she stretched out her hand: 

-My name is Kathleen, Kat... I study nanotechnology applied to biological models, and try to explain evolutionary patterns... I see that you understand math... my advisor says that my proposal has no future... perhaps you can help me?... huh?, what do I say?, I’m sure you are very busy...

When she dropped his hand, he took it back and he said almost in a whisper:

-My name is Daniel... Dan... and yes!, in fact I want to design a model of application with game theory to economic and evolutionary models, although this  has been done before... I want to find a specific area that allows me to innovate a bit.

She moved a chair beside her and then more magazines fell, but this time he rose and offered her his chair,  he began cleaned the table a little and decided to talk about what he knew and loved so much with her... 

- Please,  sit down Kat, I think  I can explain you from mathematics how species have evolvied, however, remember that maths are only models that represent the reality.

-The science is that, isn't it? Kat, said smiling.

-Yes, yes... it is true... just explain the reality...

- What I know about game theory, is that studies the sharing of profits and therefore decision making among the players, if an entity can understand that it can win or lose during an exchange, it makes decisions based on its experience. I believe the same applies to biological models, as if we believe that species should take into account information from the environment and predators to survive, then they must apply decision-making on environmental responses.

Daniel further opened the eyes and arched eyebrows...

 -Exactly!, that's the idea... Game theory is much related to economic theory, where a zero-sum game is a mathematical representation of a situation in which a participant gains or loses profits and utility is exactly balanced by the gain or loss of the participant, as opposed to a non-zero sum game where both profits and losses are added to a situation in which players interact. To sum game zero resolves le with the Minimax theorem that is closely related to the theory of the Nash equilibrium.

-     I couldn’t understand that, could you explain it to me?, but used simple words, please.

-    It is a conceptual solution to the non-cooperative games that include two or more players, in which it is assumed that it is possible to know the balance of strategies of each player  since has something to gain by changing if strategy during the game.

-    It sounds complicated...

-    It is not, in fact it can be ridiculously simple: maybe if we try to understand biological systems... look, we will assume that you have a bee and a butterfly trying to obtain pollen from two flowers... do you work with biological systems at this level?, or perhaps... microbes, bacteria... 

-    Sounds like a cute example with bees and butterflies, please explain this and then maybe we can apply to spores...

-    Daniel looked at her very happy... well... I’ll explain it with butterflies... There are two flowers and one butterfly and one bee are trying to obtain the maximum pollen, if Butterfly makes it first movement, it can take all the pollen and thus the bee lost, and if the bee makes a first movement, butterfly lost, but both want to profit, so it is important to take a decision on the action and you can see it in simple way with a picture like this:

	Bee takes pollen from a flower	Bee tries to take two flower
The butterfly takes pollen from a flower	Maximum common benefit	Bee gains and butterfly loses
Butterfly tries to take the pollen from two flowers	Butterfly gains and bee loses	Maximum common prejudice

- Crap!, it sounds so easy that even I can understand that, but surely there are a lot of numbers and things involved as I can see in your magazines.

-    I don’t understand it if I see it that way, but let me give you another example to see if I understood... Kat and Dan can learn from each other, and they both make decisions ... then if I do a matrix would be this:

	Kat speaks with Dan	Kat does not speak with Dan
Dan speaks with Kat	Maximum common benefit	Kat goes home
Dan does not speak with Kat	Dan finishes his readings	Maximum common prejudice

-    Yes, more or less like that, but both must have the same level of profit, in this case the gain is different, you would have gone home and I would have read 2 or 3 magazines. 

-I want to study chaotic fluctuations in phenotypic frequency, specifically in those cases where it is necessary the adequacy of a heterozygote based on the measure of a recessive parent the next generation, which I think, is the measure of the adequacy of the homozygotes and heterozygotes would therefore have a destructive effect on the homozygotes and themselves, although to a lesser extent about themselves. This because if a behavior is associated with a low to reply to the environment and high fertility fitness gets a chaotic fluctuation.

Daniel's eyes were opened so much that his glasses were on ready to falling, when he could finally talk, began to mambling few words and then coughed a little to clarify his own ideas...

-Kat... I think that no doubt we both can gain from this talk, there are at least two possible explanations, even it would be possible to make predictions... I can apply my mathematical theories to everything you said,  however, the truth is  I did not understand a half of what you just said, but we can sit down and explain every thing with pears and apples, but I believe that we both would receive profits from all this and it is possible to balance our profits no doubt...

-  I want to know if it is possible to find patterns of adaptation and survival in living populations...

-    Have you ever read about the life of Conway game?

-     Yes, I do!, actually… that what gave me this idea, but I don't understand enough about math,  mmmm but I think that what you just explained and Conway model can help me a lot, now all are algorithms to create stable patterns, as the analysis of the databases, everything is math is our everyday lives, everything is about looking for patterns!.

-   Yes it is, yes... of course... I think you just increase our chances of achieving our dreams...Yes... can I invite a coffee?, I only need to ... collect all these magazines... and... I think it’s not snowing anymore... I can take you in my car, or do you have a car?

-    Let me help you with this… No, I do not have a car, only my bike, but I can leave it on campus, and I come tomorrow on the bus. Climatic variables, increases the probability of accidents as drivers change their behavior patterns...

-    Yes, it is true... well... we can put your bike in my car... I have a porta-bike that I use on weekends... well... only when there is no snow, because as you say... There are changes of patterns in the drivers... Yes... ohm... then if you put your bike in my car, can I take you home?... after coffee, of course...

-  Let me think... If I say yes, then we both get gains, then I should not take the bus tomorrow, and you know where to find me... but in such a case, there will be probably other decisions that each player goes, isn't it?

-    Yes, Yes... the pattern can be exponential... sure!

-    Yes, I figured that... can it become a chaotic fluctuation... the pattern could meet different conditions and therefore... change... evolve...

-    Yes, yes... it's true... yes...

-   Cool!, it seems that mathematics are not so complex!.!

-    No, no... they are not... they can explain many things and as you say... we apply them more and more everyday... I worked applying all this to economic models and I an algorithm to Google, so it seems that it can read your mind when you type something...

-    Amazing!... have you explained biological models?

-    No, but... apparently... I'm about to do it... If you allow it to me!.

Alma Dzib Goodin