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Tuesday, April 2, 2013

The cerebral cortex


The molecular level of the organizational structure of the nervous system, corresponds to the cerebral cortex, which is organized in columns or modules of information exchange. These columns are perpendicular to the surface of the cortex, and have approximately 3 mm in length and between 0.5 and 1 mm wide and they are  recognized as forming separate anatomical entities that give rise to different quasi-independent functions, and even there is research indicating that perception and memory may be distributed through the nervous thanks to this system of organization. 

In this way, groups of cells forming vertical columns, which processed together information from the same source of stimulation, i.e. have the same receptive field have been described.

These columns were established by first time in the visual cortex, but the formal proposal of an organization in columns of the cerebral cortex, has been called the hypothesis in Colonnade and it was formulated by Mountcastle (cited in Arteaga and Pimienta, 2004). 

However more recent studies show the probability that other sensory areas consisting also in columns, even proposed that the frontal lobe, to the which is credited with the processing of the more abstract knowledge, has this kind of columnar organization.

This organization allows to the neocortex on the basis of a cortical hierarchy which permitted the development of generative models of perception that gave way to computational hierarchical models that allowed to make predictions about the anticipation (feedforward) and feedback of the neuronal conduction including segregation and topographic precision in both directions, whereupon it became clear that instead of a single upper and lower chambers via of the upper and lower areas There are bi-directional communication against the current in each compartment of the neocortex.

In this sense, it is speculated that these columns could be the fundamental unit of the organization in all evolution since the columns have similar sizes and shapes, not only within each species, but in all of them, giving the opportunity to be plastic, which represents the maximum evolutionary invention, since it allows the nervous system escape from the restrictions of its own genome and adapt to the pressures both environmental as a psychophysiological changes and experiences.

 This mechanism is activated by the matching entry from opposite poles of the neuron, which is exquisitely adapted to the final architecture to large-scale crust and is closely controlled by neuronal microcircuits.

All this adds a design which in addition to creative is controversial, that allows the sending of information contralateral (i.e. the right information is analysed in the left side) and recently has been said this  recognize and analyze the flow of energy that is possible thanks to the response of white matter and its relationship with the Corpus Callosum which extends the flow of information has different areas depending on the action on the environment that required.

This advantage is must in part to distribution patterns laminate making interaction with different receivers required to perform different functions. In this sense, both distribution laminar, as the relationship between areas and receptors, creates advantages for the acquisition of learning processes, but at the same time opens the door for various pathologies. 

References:

Arteaga, G. y Pimienta, H. (2004) Sobre la organización columnar de la corteza cerebral  Revista Colombiana de Psiquiatría. Suplemento No. 1, Vol. XXXIII.

Casper, S., Schleicher, A., Bacha-Trams, M., Palomero-Gallagher, N., Amunts, K., Zilles, K. (2012) Organization of the human inferior lobule based on receptor architectonics. Cerebral Cortex. Available at: http://cercor.oxfordjournals.org/content/23/3/615.full.pdf+html

Davis, SW., Kragel, JE., Madden, DJ., Cabeza, R. (2012) The architecture of the cross-hemispheric communication in the aging brain: linking behaviour to functional and structural connectivity. Cerebral Cortex. 22 (1) 232-242.

Larkum, M. (2013) A cellular mechanism for cortical associations: an organizing principle for the cerebral cortex. Trends in Neuroscience.

Pascual-Leone, A., Amedi, A., Fregni, F., Merabet, LB. (2005) The plastic human Brain cortex. Annual Review Neuroscience. 28. 377-401.

Woodrow, LS., and Dietmar, P. (2013) The functional benefits of critically in the Cortex. The Neuroscientist. 19 (1) 88-100.

                                                                                                   

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