Friday, January 4, 2013

Evolution in Action: Humans and Visualization

Humans are incredibly complex organisms. Some observe the complexity and conclude that such an entity could not possibly have been arrived at by the essentially random process of mutation coupled with natural selection. Others study the complexity and conclude that such a structure could have only been arrived at by random mutation and natural selection. No competent engineer would have designed such a complex mess.

V. S. Ramachandran devotes a chapter in his book The Tell-Tale Brain to visualization. His interest in how humans interpret visual data is driven by the relative availability of data on relevant brain function and by the hope that understanding this function will provide enlightenment concerning the less-well-understood brain functions. Our interest derives from the insight provided relevant to evolution and complexity.

Ramachandran tells us that we must first disabuse ourselves of the notion that the image projected on the sensors in our eyes is viewed and studied by the brain directly.

"....the brain creates symbolic descriptions. It does not recreate the original image, but represents the various features and aspects of the image in totally new its own alphabet of nerve impulses. These symbolic encodings are created partly in out retina itself but mostly in your brain. Once there, they are parceled and transformed and combined in the extensive network of visual brain areas that eventually let you recognize objects. Of course, the vast majority of this processing goes on behind the scenes without entering your conscious awareness, which is why it feels effortless and obvious...."

There are actually two pathways by which visual material is processed and presented as actionable information.

"The so-called old pathway starts in the retinas, relays through an ancient midbrain structure called the superior colliculus, and then projects—via the pulvinar—to the parietal lobes....The old pathway enables us to orient toward objects and track them with our eyes and heads."

"The new pathway, which is highly developed in humans and in primates generally, allows sophisticated analysis and recognition of complex visual scenes and objects."

Within the new pathway there is a shunt that short-circuits some of the higher order functions in order to gain speed in response.

"....bypasses high-level object perception—and the whole rich penumbra of associations....and shunts quickly to the amygdala, the gateway to the emotional core of the brain, the limbic system. This shortcut probably evolved to promote fast reaction to high-value situations, whether innate or learned."

The human visualization scheme has many functions to perform. How complex is this structure? Ramachandran tells us that there are at least thirty areas of the brain that participate. He includes this wiring chart that has been developed via the study of monkeys. Humans are presumably more complex.

Note that there is a great amount of feedback that is provided at each stage of processing.

"What these back projections are doing is anybody’s guess, but my hunch is that at each stage in processing, whenever the brain achieves a partial solution to a perceptual ‘problem’—such as determining an object’s identity, location, or movement—this partial solution is immediately fed back to earlier stages. repeated cycles of such an iterative process help eliminate dead ends and false solutions when you look at ‘noisy’ visual images....In other words, these back projections allow you to play a sort of ‘twenty questions’ game with the image, enabling you to rapidly home in on the correct answer. It’s as if each of us is hallucinating all the time and what we call perception involves merely selecting the one hallucination that best matches the current input."

It is a rather small leap to the conclusion that the old pathway is a primitive form of awareness that was maintained and carried along while more complex functions evolved. Ramachandran tells an interesting story about a patient who suffered brain damage that eliminated the function of the new pathway. The patient was blind in his right visual field as we would define blindness. However, the eyes and old pathway still functioned. Nevertheless, when requested to, the patient was able to place his finger on a spot of light that was projected on his right. He did this without any conscious awareness of the light or how he was able to do this. This phenomenon was labeled "blindsight." How suggestive is this of the type of response to a stimulus that one might expect from a worm or some other low-level creature.

Lower-order animals have simpler visualization systems.

"Carnivores and herbivores probably have fewer than a dozen visual areas and no color vision. The same holds for our own ancestors, tiny nocturnal insectivores scurrying up tree branches..."

The ability to develop complex systems of vision is apparently not that difficult in nature.

"....the ability to see is so useful that eyes have evolved many separate times in the history of life. The eyes of the octopus are eerily similar to our own, despite the fact that our last common ancestor was a blind aquatic slug- or snail-like creature that lived well over half a billion years ago."

The data presented by scientists is consistent with the picture of evolution as a process of adding structures to an existing framework. There is no opportunity to go back and reengineer the underlying structures for efficiency. This leads to exotic solutions to simple problems, and to redundancies and features that no longer have a discernible function.

 The ability to grasp the power of evolution becomes clearer when we consider that the vast times involved allow for millions and millions of generations to occur.

One of the aspects of our evolved brains that Ramachandran dwells on in his book is that our brains abhor uncertainty. It is easy to explain this as a survival mechanism. In time of danger, quick decisions and actions are required. Those who equivocate tend to get eaten by larger animals. A side effect of this attribute is the difficulty involved in changing an established behavior pattern or belief by mere rational logic. Such a change involves emotional distress, and emotion usually trumps reason. Our political process is characterized by this fact.

While my studies continue to provide proof of evolution and wonder at the beauty and power of the process, they also lead me to be more tolerant of those who, coming from a different direction, have trouble recognizing reality.

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