15. Vision & the Brain

There has been a considerable gap between posts. I finished Recollections of My Life a while ago, but have been unable to write about the final part. As the author advanced his narrative to the time of his writing, old age, I was moved by his grace and humility:

"I have aimed that my life should be, so far as possible, in accordance with the counsel of the philosopher, a living poem of intense action and of secret heroism on behalf of scientific culture. Poor is my work, but it has been as intense and original as my slender talents permitted"[595].

Thereupon, I was motivated yet again to try to one day illuminate this man's life and work. Cajal's narrative is weak and at times boring; he would admit as much. But he is not a literary man. Perhaps a different treatment of the material would yield a different result. Scientifically, there is a staining method called the Ehrlich method. In Chicago, a man jokingly said "How wonderful, we have been graced by the illustrious Dr. Ehrlich!" A funny coincidence.

I will be reading Cajal's final two non-scientific books: Charlas de café [Café Conversations] and El mundo visto a los 80 años [The World Seen from 80-Years-Old]. They must be ordered from Spain and I am broke, but traveling for a freelance job next week. Patience is a virtue.

Over the last couple of weeks, I have been using a great resource that my father found for me. In a set of DVDs called "Understanding the Brain," from the series "The Great Courses," Vanderbilt University professor and neuroscientist Dr. Jeanette Norden teaches neuroscience. I am a third of the way through the course and feel that I have already learned a great deal about the anatomy and physiology of the brain. The last two "lectures" have dealt with the vision system. I was struck by this axiom:

"Vision is a construct of the brain."

As it turns out, the eye provides very little information to the brain. Although it has about 100 million photoreceptors, only one million neurons transmit to a place called the lateral geniculate nucleus [LGN], which projects to the visual cortex at Brodmann's area 17. [Blah blah, but writing helps me cement the knowledge]. There, and at other higher-order places, the brain begins to form a percept that we experience as "sight." What's more, I was amazed to learn that we technically have a constant blind spot, a gap in the macula [neural sheet at the back of the eye] where the optic nerve exits. The brain merely fills in that blank. Therefore, vision is an entirely personal and subjective experience.

I have said that one of my main questions about Cajal concerns his vision. How did he look at tissue from the brain and see neurons, whereas the rest of the field saw a reticulum? Well, the neuron was always there. He merely [merely, ha!] had developed a brain that could construct the proper percept. How did he develop that brain? I have ideas, but I will save those. Remember, though, that "man can be the sculptor of his own brain." And:

"A persevering and deliberate effort is capable of moulding and organizing everything, from the muscle to the brain, making up the deficiencies of nature and even overcoming the mischances of character--the most difficult thing in life"[4].

Finally, Dr. Norden discussed our perception of color. She said that there are no blue cones in the fovea, our main visual part [we are "foveate" animals, with high visual acuity] at the center of the macula. When we look directly at something "blue," it is our brain that creates the color. Blue, therefore, is a state of mind. But of course, Picasso and the jazz men understood this . . .



Thanks! And special thanks to DW [and AH] for helping to guide me through an eclipse. Literally, it can be quite formative, as Cajal explains of 1860. Metaphorically/creatively, the same.