Brains on Brains Week 6: The Eye

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The blog “A Plastic Journey: Introspection of Brains Learning About Brains” delves into the qualia, feelings and thoughts brought forth in the authors’ brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course “NBE-E4210 – Structure and operation of the human brain.” The blog is written in the form of a fact-filled, loopy and introspective story. [Logo: Oxford University Press (2018).]

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Understanding vision was maybe the most important reason for me to start studying neuroscience. The eye, optics, light, iris, aperture, lens and gaze are all themes I’ve studied quite extensively in other disciplines like photography and visual journalism, but not with a focus on the brain. It’s a complicated process to make sense of the surrounding world by interpreting electromagnetic energy, light, and forming it into images that we can understand.

I’ve been disappointed over and over again by the inferiority of even the best digital cameras when compared against the human eye. It’s truly a magnificent machine, connected to something even more magnificent: our brains. Eye and camera are actually structurally quite similar. The cornea and lens of the eye have the same purpose as the lens groups have in a camera objective. The latter has to rely on cumbersome and slow mechanical movement of multiple lenses to change the focal distance, while the contraction and relaxation of the eye’s ciliary muscles can effectively change the refractive power of the lens.

Camera’s aperture blades are then used to control the amount of light entering the inner parts by changing the size of a hole, and basically the same happens in the pupillary reflex when the connections between brain stem and the muscles controlling the pupil change how much light the gets through. The light-sensitive diodes in camera’s sensor (or silver halide crystals in film) are used to convert the focused and adjusted light into either electric current or chemical reaction. In the eye photoreceptors (mostly rods and cones) convert (or tranduce) light into changes in membrane potential. This potential is further converted into chemical signal, and once again into membrane potential changes in postsynaptic horizontal and bipolar cells. This process where electrical is converted into chemical and back continues until the information reaches the ganglion cells.

But do we all see the world in the same way? I know many other animals don’t, and the vision of different species have evolved with different requirements for navigation, hunting and so on. But what about humans? Are colors somehow absolute, or are they just agreements we make to have a common idea of the world? Is everything we see an agreement? If the eye works like this it seems clear to me that our senses like vision can never provide the brain with any objective, neutral information about the world.

Posted by Free Willy

About Free Willy

The blog "A Plastic Journey: Introspection of Brains Learning About Brains" delves into the qualia, feelings and thoughts brought forth in the authors' brains upon learning about the human brain and its functions. The blog will follow loosely the structure of the course "NBE-E4210 - Structure and operation of the human brain." The blog is written in the form of a fact-filled, loopy and introspective story.
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