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Saturday, June 8, 2013

Study of the brain through images, cytoarchitecture and electrical activity

To continue our  journey around the annals of the history of the study of the brain, is worth mentioning that the neuroanatomy has undergone revolutionary changes in the last decades. That leap has been made possible thanks to the introduction of new imaging techniques such as: X-Ray computed tomography (CT, also called computed tomography CT), (PET) Positron Emission Tomography and Magnetic Resonance Imaging (MRI), thanks all these tools, it is possible to observe the structure and activity of the brain in unprecedented detail.

All those datas, specially volumetric and structural studies, CT and MRI are of crucial importance to understand brain differences and give answer to many questions, specially about neuro degenerative diseases (Allen, Bruss and Damasio, 2005). 

However, this neuro technological revolution did not begin from nothing or yesterday, all these amazing possibilities probably began  in 1783 with physician Luigi Galvani who was a passionate about anatomy,  and who had the idea of using electricity to move the leg of a dead frog. Does that sounds like Frankenstein?,  what was this idea of moving a leg of a dead frog?,  well, he began efforts to stimulate and visualize neural activity, and some explain this open a door to  analyze living brains now.

Many years later, in 1937, a neuroscientist Charles Sherrington could see points of light signals in neuronal activity, this surprised to a Spanish physiologist,  Jose Delgado, and  he used radio waves to study the brain of a bull in 1963.

But it was not until 1971 that voltage fluorescent studies begin to become popular, and during decade of  1980 with the fluorescent dye, it was possible to see how calcium concentration changes while it's synthesized in a cell, and this  opened doors for the study of the brain on a larger scale (Miesenbock, 2008).

I can't forget during  this tour, including another researcher that made important contributions to the study of the brain, so I must remember to Korbinian Broadman, who conducted research that allowed to distinguish 52 brain regions, thanks to his studies on cerebral cytoarchitecture made on histological samples that permitted find anatomical definitions of different brains, and his studies currently  are known as  areas of Broadman which are used to mapping the brain, since they have been associated with specific activities and brain functions  (Kandel, Schwartz & Jessel, 2000).

Among the researchers that devoted his time to understand the functions relate to anatomical  Broadmann's areas there is a name, Wilder Penfield, who was a Canadian neurosurgeon and during his surgeries he stimulated with an electric pulse small points on the surface of the brain at the same time he asked to patient if he or she  felt something (this was necessary to determine exactly which region he had to operate). 

He found out that when different regions of the brain are stimulated in this way, the patient could have different perceptions (Harrison, Ayling & Murphy, 2012). For example, when it was stimulated the occipital lobe, patient saw flashes of light, but if it was stimulated  the parietal area, persons could heard buzzing, or maybe noticed tingling in any part of the skin, or maybe if stimulation was done in another region the patient begin moving any part of the body. 

Based on these observations, Penfield made a neurocortex map,  since  he could find where each sensory modality was represented in a specific part of the cerebral cortex, and he figured out it was not only possible to relate  a cortical region for each sensory modality, but that each part of the body had assigned to a specific region in the cortex, but on the opposite side of the body; for example a patient responded to a  electrical  stimulation on the left motor cortex with a movement of right leg. 

Therefore all his research made  possible to recognize areas on the surface of the cerebral cortex and relate them to different processes, finding in each patient  areas  where it was possible to recognize a specific taste, a vivid childhood memory or the fragment of a long-forgotten melody (Sagan, 2003; Shreeve, 2005; Library of archives of Canada, 2009). 

One of the reported cases, is about a patient who during a brain surgery said, he could  listened with luxury of detail, a interpretation of a composition of orchestral when it stimulated an area specified in his brain with an electrode. Other patients experienced a specific emotion, a sense of familiarity or the full memory of an experience of childhood, all simultaneously, forgetting the fact they were in an operating room talking to the surgeon. 

Some patients explained these memories as small dreams, but did not appear in them the symbolism characteristic of  a reverie (Shepperd, 2004). In the specific case of electrical stimulation of the occipital lobe, which is related to the vision, a patient said to be seeing butterflies flying around, so real and palpable, that even lying on the operating table, stretched out the hand to catch them (Sagan, 2003). 

All this experiences gave a good idea how the brain is divided into areas and allowed to map and  understand much better those parcels of information processing.

 However, even though there have been isolated area and process specific, neuroscience still cannot understand how it is possible to carry out the processing of information and the storage and handling of data that day to allow us to understand the environment and adapt to it, and I think the main question of neuroscience is: how do electric and chemical impulses become subjective experiences?.


Allen, J.; Bruss, j. & Damasio, H. (2005) structure of the human brain. Research and science. 23 - January. 68-75.

Harrison TC., Ayling OGS, Murphy, TH. (2012) Cortical Disctinct circuit mechanisms for complex forelimb movement motor and map topography. Neuron. 72 (2) 397-409.

Kandel, E.; J.H Schwartz, Jessell, t. (2000) h Principles of Neural Science. New York: McGraw-Hill.

Library Archives of Canada (2009) Famous Canadian Physicians. (Available online):

Miesenbock, g. (2008) Lighting up the brain. Scientific American . Vol. 299. NUM. 4 34-43.

Sagan, C. (2003) the Dragons of Eden: speculations on the evolution of human intelligence. Barcelona. Criticism.

Shepherd, g. (2004) The synaptic organization of the brain. Oxford, University press.

Shreeve, j. (2005) Cornina complet brain: she is all... is here. National Geographic.  207  (3) 6-12.

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