Adult brain and neuro-plasticity

As I have been sharing in other posts, plastic capacity of young brains has been tirelessly studied, but what does happen with the neuroplasticity of the adult brain?, are brain structures modifiable?. 

 It is known that there are critical periods which depend on the explosion of neural connections and they decay during lifetime, however, new research show a different vision, and now is said that is never too late to make a brain learn new tricks. 

   

  For example, according to preliminary studies in the laboratory of Michael Merzenich of the University of California at San Francisco, who is a pioneer in the understanding of plasticity, memory in pre senile individuals can, with the help of training, be dramatically rejuvenated, and his studies show that plasticity has no limits. Some times even if areas of the cortex, e.g. Broca's area are destroyed by a stroke, a brain attack or a brain tumor, patient is likely to recover function once moved the circuit affected by others who may have other capabilities (Shreeve2005).

Something remarkable both neurogenesis, synaptogenesis is the direct relationship between increased mental activity and physical exercise, which suggests that people could reduce the risk of neural diseases and thereby help to repair brain processes choosing mental challenges and a physically active life, that’s the reason a majority of researches are running environmental stimulation as an important part of the recovering process, demonstrating that the environment can affect on the brain structure, which opens up the possibility a complete new field on areas as architectural designs which could modify the way they build  homes, offices and schools in order to allow more enriched environments that seek better cognitive functioning.

But what about brains who suffers an injury?, current research indicates that plasticity exists, during the pre and post natal, recognizing the existence of critical periods to make this happens, however, once the synaptic connections are established and they break or deteriorate, the pattern of cortical reorganization  the functional recovery of different capabilities is not the same, while the basic mechanisms of plasticity are shared by all the cortex.

However, there are peculiarities in the patterns of recovery depending on the type of injury, mainly finding the following modalities: linguistic and sensory motor, neuropsychological injuries

Regarding the recovery of a motor injury, it is known that  structures of the cerebral cortex is constantly changing in response to training, or behavioral and motor acquisitions. It is thus that the construction of functional maps of motor areas that have been made possible thanks to the use of three neuroimaging techniques: Transcranial magnetic stimulation: which is one way not-invasive stimulation of the cerebral cortex, it’s one of the latest tools that have built-in neuroscience, both for purposes of study and research; functional magnetic resonance imaging: which are a type of magnetic resonance imaging in which the response is measured hemodynamics (blood flow) related to the neural activity in the brain or spinal cord; also we can find the Positron Emission Tomography: which is a technique used on nuclear medicine that produces a three-dimensional image of the body's functional processes,  these techniques that have made possible the understanding of the way in which the motor cortex adapts and changes in response to injury and therapeutic intervention.

Studies conducted in people with central hemiplegia, show that functional recovery through rehabilitation, produces mechanisms of plasticity that differ depending on the timing of the injury.

When the injury requires a longer recovery time and therefore more long-term treatment, permanent changes in the cerebral cortex are generated. In most of the cases new motor routes are created starting  at the motor cortex in the healthy hemisphere and are directed in a ipsilateral manner (contrary), in a way that takes place the functional recovery of the affected side. While in other less numerous group of patients, new axons from the motor cortex not damaged are wrongly projected bilaterally, producing a less functional recovery with intense movements in mirror, this is an example of wrong adaptive plasticity where the patient moves the left hand, at the same time that moves right hand (Diaz-Arribas, Pardo-Hervas, Tabares-washing, Rios-lago and Maestu, 2006) . 

Talking about linguistic recovery, neurobiological studies provide data corresponding to language and its configuration in a certain moment of neurodevelopmental, have allowed increasingly better understand the role of language and their behavior after injury.

In this sense it is known that children around 4 years old have very well located the representation of language in the left hemisphere, in the majority of cases, virtually unchanged in the adult. However, these studies have found evidence that brain cortex involved in linguistic functions is also sensitive to the experience, so the centers related to the language processes  are not stable over time, and expand or contract depending on the experience, since new words are learned or  we stop employ others throughout our life.

Apparently, this area is initially broader throughout the perisylvian areas, which are focusing as it reaches the competence in the language, on the basis of increased complexity and level of specialization, in such a way that the peripheral areas which originally related to the language retains this ability as a secondary capability latent, capable of supplementing or completing the linguistic function in case of injury of the primary area (Hernandez-Muela, Mules, and Mattos, 2004).

However, it is worth mentioning that lesions of the left hemisphere are associated with greater involvement of the normal activity of the right hemisphere and an atypical asymmetry in activations of the perisylvian during linguistic activities area, to a greater extent when the injury takes place in early stages, that when it happens at later stages in life (Gage, 2007).

In this way, as a result of brain plasticity that happens after injury occurred in early stages, diverse studies have been found an increase in the prefrontal, frontoparietal and lower bottom regions activation, for expressive language, and inferior temporal, temporary front and temporary regions for the receptive language. Probably, because these structures are related with the area responsible for functions associated to the language in early stages, that with the maturing and growing complexity of the neural connections, so these are free depending on the type of tasks, but retain this ability, latent form to resume its function in case of later injury (Gollin, 1981; Maciques, 2004; Tubino, 2004; Ginarte, 2007).

In this sense, an early lesion that took place before the first year of life, leads to an extensive reorganization both of the right and left hemisphere, this is known as adaptive plasticity, as occurs in the motor cortex, but there is evidence of plasticity in the regions responsible for the language after a neurological damage, may be different in the case of the motor domain (Diaz-Arribas, Pardo-Hervas, Tabares-Lavado, Rios-Lago and Maestú, 2006).

However, the plastic changes are not limited only to the motor cortex or the language, but it also occurs in sensory systems. In this regard, an example is the case of hearing, which requires connection with environmental sounds as stimuli and whose processing is important for verbal communication, so it is a decisive step for the acquisition of language. This sensory modality is known that there is an auditory critical period for language acquisition. So was demonstrated in studies conducted in deaf children after application of cochlear implants (Hernandez-muela, mules and Mattos, 2004).

  In this regard, in terms of language difficulties secondary to the existence of a sensory deficit by hearing loss, it is necessary to consider two situations: the first one, is when hearing loss takes place prior to the acquisition of language, in the very early stages, while a second situation occurs when the loss hearing occurs subsequent to the acquisition of the language.

     In the first case, the plasticity will be through a migration of the function, while in the second case, the potentiation will be to more long term and will require the support of cochlear implant (Coplan, 1985; Hernandez-Muela, Mules and Mattos, 2004).

The other sensory aspect to consider is the visual capacity, even tought plasticity of visual fields is not well known, it’s possible to talk about at least two situations, on the one hand, when the visual cortex is damaged by a traumatic injury, and when, despite the strength of the occipital cortex, or if by peripheral reasons, it is not possible to develop the vision.

With respect to the first situation, some descriptive studies show the transfer of function from the visual cortex to adjacent areas on the occipital cortex, such as posterior regions of the parietal and temporal lobes, similar to the hearing process, which is called plasticity by migration (Castroviejo, 1996; Deacon, 2000; Ginarte, 2007).

Talking about the second situation, which presents peripheral blindness, caused by tumors in the optic chiasm for example, may be determinants of blindness at very early stages, it has shown the existence of the so-called mode cross plasticity i.e. Permanent reorganization that allows in principle do not own capabilities to a certain area, which appears to increase or facilitate compensatory alternative perceptions of deficit sensory. These changes involve mechanisms neuroplasticos in which areas that processed certain information, accept, process, and respond to other types of information from different sensory modality (Hernandez-Muela, Mules, and Mattos, 2004;Ginarte, 2007).

This way is usually explained the process of plasticity of occipital cortex from blind children ocurred at early stages, which facilitates and at the same time is result of the learning to read Braille, which creating occipital cortex networks ranging from motor areas that allow the movement of the fingers on the paper, and the areas that usually is used for viewing the letters in compensation by the absence of vision. This widening of the cortical representation of the index finger may be due to two mechanisms: the first, by unmasking of silent connections (increase of synaptic efficacy), in the same area injured or deficient and adjacent, and the second, structural plasticity, while other studies have shown the expansion, in the cortex somatosensory representation of the finger index, fundamental Braille readingwith what it says is that people can "see" through their fingers, as they achieve recognition of shapes and even colors at the touch of a surface (Poch, 2001).

References:

Díaz-Arribas, M., Pardo-Hervás, P., Tabares-Lavado, M., Ríos-Lago, M. y Maestú, F. (2006) Plasticidad del sistema nervioso central y estrategias de tratamiento para la reprogramación sensoriomotora: comparación de dos casos de accidente cerebrovascular isquémico en el territorio de la arteria cerebral media. Rev Neurol. 42 (3): 153-158

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

Gage, F. (2007) Brain, repairs yourself. In Floyd E, Bloom (2007) The best of the brain from Scientific American: mind, matter, and tomorrow’s brain. Washington DC. Dana Press.

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.

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

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

Shreeve, J. (2005) Cornina’s brain: all she is… is here. National Geographic. Vol. 207. num. 3.  6-12.

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

Stem cells in adults and embryos

I will continue this time with the topic of neuro-plasticity and I can mention that there are two lines of research which are currently the most studied: on the one hand, it is the idea that postnatal human brain has adultstem cells apparently remain during the adulthood and that they can help rising new neurons, this line of work has opened a door in the field of regenerative medicine because until recently, was believed to be the brain ability to restore its function through neural regeneration was null. 

In this sense some researchers isolated brain live stem cells from human corpses up to five days after the body died. This was possible  keeping frozen the bodies and it was observed that cells obtained from these bodies gave rise to new neurons and glial cells in vitro, so currently, it is believed that the presence of brain stem cells can at least in part, explain the great plasticity and functional improvement seen in patients after cerebral damage, even extensive injury. However, it is not known yet, the specific role and regenerative capacity in response to different congenital and acquired diseases of the central nervous system (Belkind-Gerson and Suárez-Rodriguez, 2004; Aguilar, 2005). 

By this reason, this line of research has focused on studying the fact that under certain conditions, stem cells can be differentiated towards cell type required to regenerate the damaged tissue signals acquired directly on the site of the lesion, since once there is a neural injury, damaged neurons come in contact with the myelin sheath which has released other injured neurons, and since myelin contains several inhibitors, that prevent neurons that have not died to restore their connections, it is not possible even to understand the mechanisms in which it is possible to restore functions (Belkind-Gerson, Suarez-Rodriguez, 2004).

This capacity has generated other kinds of studies searching answers of cell regeneration, which direct their efforts towards the calls stem cells.

 These are embryonic cells, i.e. their destination still has not been decided and will be transformed through a process of differentiation and proliferation in different types of cells. These are very different from any other in the body which can be used to regenerate tissue-specific. The neural stem cells are those which is capable of self-renewal and that can generate other kinds of cells different from them through an asymmetric cell division process, so you are defined by their multipotency. These cells are found in bone marrow and they have been used successfully to generate heart tissue (León Carrión, 2003, Hernandez-Muela, Mules, Mattos, 2004; Shreeve, 2005).

Foto
ian tunkin

Certainly this breaks with the dogma that neurons do not grow spontaneously in every part of the adult brains, however, research pioneers began in the decade of the 90s, when researchers in the field of Neurobiology found that mature brains of some mammals were able to generate new neurons.

Of course, biologists believed that this was only possible in young brains, but Elizabeth Gould of the Rockefeller University, showed that new cells grew in adult brains, in particular, it has been found in the hippocampus (part of the limbic system, responsible for learning and memory processes) hundreds of new cells grow every day.

 Since then, many more researchers have shown the cells destined to become neurons travel from the ventricle of the olfactory bulb, especially in a pair of structures responsible for receiving information that olfactory cells in the nose.

Although no one is sure why the olfactory bulb requires so many new neurons.  It can be speculated that this being a necessary structure for learning new information, it is essential to add neurons to create connections between existing neurons and new, thus increasing the brain power to process and store the new information (León Carreón, 2003, Avaria, 2005, Shors, 2009). 

      

While there are other investigations focus on neurogenesis (growth, spontaneous or induced neurons)and the discovery of new neurons out of the hippocampus and the olfactory bulb, these not have systematized their findings, and one of the reasons is that the methods used to prove the existence of neurogenesis is difficult, although recently they have come to detect neural growth in the bone marrow of adults.

Even when neurogenesis depends on the genetic component, the various contributions to this theme in works with other species such as mice have become so clear that different laboratories have tried to make progress with humans. In fact researchers United States and Sweden, showed that this was possible also in humans, though not with as much clarity as in other species (Shors, 2009; Gage, 2007; Avaria, 2005; Leon Carrion, 2003).

In animal studies, it was found that in only a couple of weeks, most of these newly born neurons, died, unless the animal was challenged to learn something. This new learning, which required much effort, especially kept alive those cells. But works have found that neurons are not necessary for all types of learning, because even though they can play a role in the resolution of problems, based on past experience, they are not generated at specific times, since its production is linked mostly with a large number of environmental factors.

 For example it has been observed that alcohol use delays the generation of new cells, while the rate of neurogenesis can be increased by the exercise. This was demonstrated in research with mice, which spent a great time running on a wheel and increased twice the neuronal production compared with mice with a sedentary lifestyle (Shors, 2009).

      

However, even though this discovery takes a turn to the neurobiological research, unanswered questions remain, which do not allow all the application of these findings to identify the effects of learning on the survival of new neurons, for example: what neurotransmitters and receptors, proteins are involved?, and how do they operate these mechanisms?; Why do these new neurons helps learning to integrate neural networks? or Do they only promotes the survival of those that are already connected?; do these neurons contribute to knowledge?.

The goal is that these studies will help to understand degeneration neuronal, but mainly people health, mainly to avoid diseases such as Alzheimer's and Parkinson's, as well as understand the neural processes related to the developmental disorders. 

References: 

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

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

Belkind-Gerson, J.  y  Suárez-Rodríguez, R.  (2004) Regeneración cerebral. Realidades, posibilidades y esperanzas. An Med Asoc Med Hosp ABC. 49 (4): 201-207.

Gage, F. (2007) Brain, repairs yourself. In Floyd E, Bloom (2007) The best of the brain from Scientific American: mind, matter, and tomorrow’s brain. Washington DC. Dana Press.

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

León Carrión, J. (2003) Células madre, genética y neuropsicología. Revista Española de Neuropsicología. 5 (1) 1-13. 

Shors, T. (2009) Saving new brain cells. Scientific American. Vol. 300. num. 3. 41-48.

Our brain is not programmed to reading or writing

The title is certainly somehow confused, but here I'll explain you how I came up to this.

I am advisor of a very intelligent woman who is studying musical cognition and her work proposes a relationship between the processes of reading and writing music and natural language. We have written a couple of articles which we hope to publish soon, but while we were working with her thesis I made comments, and about a paragraph I wrote her the following note: remember that our brain is not evolutionarily programmed for reading and writing.  

She knows me very well and of course she has read my writings both scientific as my blog, so I never could imagine that a simple comment would take us to a fascinating explanation which I would like to share with all of you.

"Our brain processes learning, including the process of reading and writing, tell me how come is not evolutionarily programmed to do this?"

The evolutionary process has led the species to acquire different skills, which have taken thousands of years to become part of the system, and therefore conquer a brain structure which command it. 

Vision is for example, a victory that has taken much more time to development than the language. Each evolutionary triumph is a process of adaptation, which involves different prototypes that never seems to arrive at the final product, since nature makes adjustments depending on the environment, and although sometimes we take for granted that we are born with our fabulous capabilities  to understand the world but not all of them have a genetic complement.

That is the case of the reading and writing acquisition, it's not something  even ontogeny arises from the moment of birth, because children require at least between 4 and 6 years to start the acquisition process, and many more years to consolidate it.

When we think in terms of history of human evolution, we can see how language is a process that requires  hearing the differences of every letter of the alphabet, and language recognition, and that involved the development of hearing, and probably the first acoustic traits were environmental, which allowed beginning to distinguish different sounds such as rain, singing of birds or wild animal sounds, and through many years and effort, led to the conquest of the language, which is, is a trophy of homo sapiens, as some claim.

The development of the vision began as is estimated around 600 million years ago in vertebrates, maybe after hearing. If we think of the cosmic calendar that Carl Sagan gave us to find life on Earth, we will be able to see that language arose more or less in November and literacy, which involves integration of signs at eye level and its relationship with the sounds of the alphabet, (see the sound of language) I think arises around the last minute of December...

Babies can listen through the medium within the womb, although hearing in an air environment is different from the aquatic environment, even though a few days old baby is able to recognize sounds, although it does not distinguish them, and gradually begins the process to make differences with the sounds of the language, to begin an amazing preparation to modulate it, repeat it and finally begin to talk and conversations If this is culturally stimulated. 

The same should happen with the reading and writing process, since we can find find people who know how to speak, but cannot read and write. This step requires environmental stimulation and the reason is simple, the emergence of the reading - writing, it was not an ability shared by all people, only a few had access to learning and developing skill, the bulk of the population had no access to the alphabet, books or writing.

With the arrival of Gutenberg's printing press, many more people could have access to the books, provided they could pay them... so it took many years before literacy became a learning with open access among the population, but if we think  that this happened at the last moment of December 31st in the Cosmic Calendar, then is easier to understand why our  brain does not have sufficient practice to develop it without help.

What my student and I are exploring, is the way that our brain is using are sharing the musical and natural language (We think music was first, and we have shared for many thousands of years, so no one teaches us how to move hips when we heard drums), and this same brain structures are shared by literacy, to conform this new  cognitive skill.

For this reason that when a child has difficulties in the acquisition or consolidation school learning process, we recommend to thinkabout baby steps, finally the human specie has need thousands of years to learn and we never stop.

References:

Lamb, T., Collin, SP., Pugh, Jr., e. (2007) Evolution of the vertebrate eye: opsin photoreceptors, retine and eye cup. Nature reviews Neuroscience, 8, 960-976.

Masterson, B., Heffner, H., and Ravissa, r. (2005) The evolution of human hearing. The Journal of the Acoustical Society of America. 45, 966.

Wright, S. (1931) Evolution in Mendelian populations. Genetics. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1201091/pdf/97.pdf

Brain programming

There is nothing more fascinating to me than hearing my husband and his colleagues  when they talk about programming problems. The programming language allows any device capable of responding to such code, to do so fabulous things that make us buying them, looking at them or playing for hours and hours with them, virtually we become addicted to them.

A simple task, as accepting a click on a button or the touch on a tab, involves long chains of operations that allow  to the device to have contact with the user, to do this, developers build more sophisticated sequential chains, linked in logical commands that tell the system what to do, when to do it and what information to show if the user hasn't done something correctly. That is what advertisers call intelligent devices.

Those talks delights me because I can imagine the amount of logical sequences that our brain made from the first moment when it’s build only  by  two cells to the last second when that it is disconnected. Apparently simple tasks, as open your eyes every morning, would involve thousands of lines of code, because they require to tell to the system what muscles are used, patterns of opening, the recognition if eyes are closed, because if they are open obviously cannot have a task that involves opening them, and I know that this sounds so stupid, but motor diseases allow us to recognize that this sequence should be recognized. That task has been attributed to the cerebellum together with the Corpus Callosum, but the script must be written.

As we have two eyes, they must be opened in coordination, and once opened, they will recognize the light, shapes, and sent signals to begin making daily decisions.

If you have observed the decision-making, Bayesian systems and schemes, please add to all this programming language and then you can imagine the thousands of connections that makes the brain every second. Even if this is the  only process, we can say Henry Markram is going to spend years and years building a brain and I hope he can succeed before he died; but the real challenge is not to build sequences, the problem is that these sequences should be adapted to respond to the environment, so are open constantly evolving systems.

Those who only read about studies published in press and little neuroscientific, easily fall into the idea that there is a structure for each action. Ramón y Cajal studied almost every area of the brain, and even in those years, he found that the brain adapts to the needs. Maybe I am an enthusiast of neuro plasticity and in some decades from now, we will find that it is a mistake, but we learn in science and re learn all the time. As well as my friend Irina Pechonkina has  taught me, the true task is not learning, but unlearn to this adaptation. 

The programming tasks that involve making conscious the scripts needed to run a task, in cognition, this is called Metacognition, I explain it in a simple way: this is the ability to tell each small task and sequence to execute an action.

The brain must be set not only the relationship between neurons, but between molecules, genes, and bacterias, it must respond to an environment that does not change only by the climate, but by the type of toys that we use, the words we hear, culture and other circumstances surrounding a system that generates lines infinite sequences that allow us to do tasks that seem simple.

Current studies show that there is the DNA of the DNA, which leads me to remember those years that I worked hard to understand Wittgenstein theories, who spoke about a  language of the language, which called meta language, and when I could understand the concept, someone with an evil tone threw one book on my  table in which Wittgenstein explained the meta-meta language.

Do not think that I have lost the idea that gives rise to this writing, if we return the task of open your eyes in the morning, think that sometimes the eyes open slowly, because recognizing the amount of light in the room, know that it is time to get up, but and if there is a noise that produces a s tate of alert, your eyes will be opened and will seek the source of noise, sometimes open by carefully because we are lying down with the face on the pillow... that sometimes forgets to remove contact lenses, which sucks the moisture from the eye and open them is difficult than usual.

The idea is not to imagine all possible conditions, I am there are N minus 1, but if we think that the scripts are not always clear, as the original order was written, there are many circumstances which must be considered.

Sometimes, colleagues of my husband tell him that he wants to reinvent the wheel, but,in his quest for efficiency he can search  breaking programming commands and get away with it. I wonder if that would be making learning?, and if so, because we must tell everyone how and that he must learn, instead of allowing people to  suit their actions to the environment, because in the end, not always may apply learned sequences.

In this sense, children with neurodevelopmental disorders, teach us that recognize sequences that carry out for tasks and because they carry them out incorrectly, sometimes because they do not recognize the task, or part of the sequence is wrong, and ultimately learn that the goal is the objective, and not the repetition of the error.

I know that it is foolish to say that the brain functions like a computer, but so far, technology has taught devices in a better way, than  many schools have achieved with learners. I don't blame teachers, even curriculum designers by not leaving the box and innovate. In theory you learn from mistakes, but it seems that education, not yet recognized the mistake, so the system continues  sending  signals that something has gone wrong, but let's not forget that children have the right to learn, in their own way, because there is an evolutionary program created for this purpose.