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Wednesday, March 6, 2013

Organisational structure of the nervous system: Large areas

If human brain is analyzed in a unsophisticated way, we can see the level of the molars structures, these are large areas referring to the hemispheric divisions and major structures. For example, a division that analyzes the brain from the halves, which is called them left hemisphere and the right hemisphere.

A finding that caused uproar in the neuroscience field was the discovering that if they study the two halves, they are not used for the same functions, this is each hemisphere governs motor skills (relating to the movement) and sensory (related to the senses) on the opposite side of the body, but is that one side of the brain is clearly dominant. This is known as hemispheric dominance and this domain determines if the individual will be right-handed or left-handed (Ayan, 2005).

The following image served a first mapping of functions, and although many have taken it as a rule, the brain does not work so coordinated and deterministic, is capable of making more flexible functions if required.

As you can see in the image, the brain functions are often divided on both sides, however, even though it has traditionally been attributed to the left hemisphere management of logical and intellectual, work related to people with large capacity for reasoning and the right hemisphere is known as the artistic and emotional side represented by artistic concerns, both are related from the other actually, occur as complementary since the art, for example, requires logical thinking and logical thinking has a touch of romanticism.

Another myth that has been maintained for a long time is that men are all left hemisphere, since they employ logic and cognitive skills, while women are all right hemisphere, as they are tender and retailers. This however, is only a sexist war, since both hemispheres work together.

This collaborative work is accomplished by the hemispheres are not isolated each other, a structure called the Corpus Callosum unites them. This structure is the larger interhemispheric commissure and connects across both hemispheres. The Corpus Callosum is composed of approximately 180-200 millions of axons that mostly come from the cells of the cerebral cortex and is capable of carrying 400 million pulses per second (Siffredi, Anderson, Leventer, Spencer-Smith, 2013; Steele, Bailey, Zatorre, and Penhune, 2013).

This growth takes place primarily during the pre natal period following a pattern of development from front to back and is the way that both hemispheres are intimately related and the reason why the impulses of a hemisphere and another make sense and relate them (Quintero Gallego, Manaut, Rodríguez, Pérez Santamaría, Gomez, 2003).

In addition, there is another structure forgotten most of the time, but it has gained strength in many researches by its role in the processing of the movement and some cognitive functions and is the cerebellum, which is considered a neuronal system responsible for regulating movements with very well defined actions on coordination, posture, tone and control of eye movements and fine movements, whose geometric organization was described by Ramón y Cajal in 1911 and that has also given rise to many assumptions and controversies during the past years, since the cerebellar cognitive functions have taken boom, as ever gathered more evidence of the involvement of this structure in the modulation of emotional control, sexuality and memory cognitive processes, as well as in the planning or the strategies of learning or language (Arriaga - Mendicoa, Otero - silicon and Crown - Vazquez, 1999;  Mediavilla, Molina and Puerto , 1996; Schlerf, Ivry and Diedrichsen, 2012).

One of those in charge of investigating this structure was Watson, who came to the conclusion that this structure could intervene in sensory processing (auditory, visual, tactile...), during the learning process. Previously, Marr, Albus, Eccles and other authors had developed his theories about the role of the learning of motor skills in cerebellar cortex, as well as emotion, motivation and reward processes (cited in Watson, 1978).

Well, from the end of 1960´s decade diverse neuroscientist  have developed different theories involving the cerebellum in motor skills learning and assume that this does not participate much in the acquisition of a sequence of movements, but in which they seem fluid and skilful, i.e., well learned.

In this sense, the main implication of the model proposed by Marr in the early 60s (cited in Mediavilla, Molina and Port, 1996) would be the cerebellum to learn to execute motor skills and that, when that happens, a simple or incomplete message of the cerebellum may cause the execution. To analyze the role of this structure, studies have been carried out with professional dancers, who depend on good cerebellar coordination to run his art.

Also has been implicated to the cerebellum in complex mental functions but not yet be determined with participation of processes and the way it does. In any case, the evidence supporting the consideration of the cerebellum as a learning machine, as defined it the classical theories, that define it as a structure that could be used for all kinds of neural, autonomic, motor or mental control (verbal and non-verbal) are increasing (Fatemi, Aldinger, Ashwood, Bauman, Blaha, Blatt, Chauhan, Chauhan, Dager, and Dickson, 2012).

A remarkable proof of involvement of the cerebellum in motor learning provided it the fact that, after this type of learning, synaptogenesis (emergence of new connections between neurons) occurs in the cerebellar cortex, which means that this structure is necessary and creates connections that work for the benefit of the process (Black, Isaacs, Anderson, Alcantara, and Greenough, 1990).


Arriaga –Mendicoa,  N., Otero – Silicio, E.  y Corona – Vázquez, T. (1999) Conceptos actuales sobre cerebelo y cognición. Rev. Neurol. 29- 1064-1075.

Ayan, S. (2005) Right brain may be wrong. Scientific American Mind. Vol. 16. Num. 2. 82-84.

Black, J.E., Isaacs, K.R., Anderson, B.J., Alcantara, A.A. y Greenough, W.T. (1990). Learning causes synaptogenesis, whereas motor activity causes angiogenesis, in cerebellar cortex of adult rats. Proc.Natl.Acad.Sci.USA. 87, 5568-5572.

Fatemi, H., Aldinger, KA., Ashwood, P., Bauman, ML., Blaha, D., Blatt, GJ., Chauhan, A., Chauhan V., Dager, SR., and Dickson, PE. (2012) Consensus paper: Pathological role of the cerebellum in Autism. The Cerebellum. 11 (3) 777-807.

Mediavilla, C.,  Molina, F.  y  Puerto, A. (1996) funciones no motoras del cerebelo. Psicothema. Vol. 8, nº 3, pp. 669-68.

Quintero Gallego, E., Manaut, E., Rodríguez, E., Pérez Santamaría, J., Gómez, C. (2003) Desarrollo diferencial del cuerpo calloso en relación con el hemisferio cerebral.  Revista española de neuropsicología. 5. 1. 49-64.

Schlerf, J., Ivry, RB., and Diedrichsen, J. (2012) Encoding of sensory prediction errors in the human cerebellum. The Journal of Neuroscience. 32 (14) 4913- 4922.

Siffredi, V., Anderson,, V., Leventer, RJ., Spencer-Smith,  MM. (2013) Neuropsychological profile of agenesis of the Corpus Callosum: A systematic Review. Developmental Neuropsychology.38 (1) 36-57.

Steele, CJ., Bailey, JA., Zatorre, RJ., and Penhune, VB. (2013) Early musical training and white-matter plasticity in the corpus callosum: Evidence for a sensitive period. The Journal of Neuroscience. 33 (3) 1282- 1290.

Watson, P.J. (1978) Nonmotor functions of the Cerebellum. Psychol. Bulletin, 85(5), 944-967.

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