What evolutionary advantage affords most of the nerves on the left hemisphere of the body to be attached to the right hemisphere, and vice versa? For example, the right visual field is processed in the left hemisphere, and vice versa. Why should this be so? I can see no reason for this. Originally I considered that this would somehow allow for some redundancy in case of injury, since having to cross the network from one side to the other forces the nervous system to mesh, but I don't really know the reason.
Maybe for survival? If one side of the brain mix with the other side to make something (one), ok. But if ( ALL) of something is in one place, more likely to die.
When the time comes to meet your maker, ask him (or her). Personally I would guess that some cave creature got its head twisted around 180 degrees in a fight and front became back and back became front and it eventually became our ancestor.
I am thinking that it had to evolve from one of our ancestors, long before the apes. The question is, what advantage did it offer that creature, if any? The flat worm is the first animal to have a brain and bilateral symmetry: http://en.wikipedia.org/wiki/Timeline_of_human_evolution I wonder if they have the left/right crossconnect as well?
lol to kinda sidestep the original direction of this thread, I am a right brained trader. In iq tests, I score high in abstract reasoning and need to visualize and 'feel' information for it to register at a higher level. My background is in music and is accomplished and extensive. I mention this because music deals with layers of extreme (and moderate) dynamics coupled with vast timing changes. As a percussionist of almost 30 years, an educator and developer of champions, and, as a hired gun for a professional symphony orchestra, I literally see myself as a human clock/timer who feels my way through trading.
"Experiments show that most children rank highly creative (right brain) before entering school. Because our educational systems place a higher value on left brain skills such as mathematics, logic and language than it does on drawing or using our imagination, only ten percent of these same children will rank highly creative by age 7. By the time we are adults, high creativity remains in only 2 percent of the population." LEFT BRAIN FUNCTIONS uses logic detail oriented facts rule words and language present and past math and science can comprehend knowing acknowledges order/pattern perception knows object name reality based forms strategies practical safe RIGHT BRAIN FUNCTIONS uses feeling "big picture" oriented imagination rules symbols and images present and future philosophy & religion can "get it" (i.e. meaning) believes appreciates spatial perception knows object function fantasy based presents possibilities impetuous risk taking ------------------------------------------- "The main theme to emerge... is that there appear to be two modes of thinking, verbal and nonverbal, represented rather separately in left and right hemispheres respectively and that our education system, as well as science in general, tends to neglect the nonverbal form of intellect. What it comes down to is that modern society discriminates against the right hemisphere." -Roger Sperry (1973) -------------------------------------------- KEY The left side of our body is "wired" to the right side of our brain, and vice versa. For whatever reason nature did this cross-over, it applies even to our eyes, which process a majority of their sensory data on opposite sides of the brain. We can thank Nobel Prize Winner (1981) Roger Sperry for this next contribution. Sperry conducted what are sometimes called the "split-brain" experiments. Here's how it went: A patient suffering from uncontrolled seizures had an area of his brain removed by surgery in an attempt to control his illness. This area just happened to be the corpus collosum, which was suspected of having developed lesions (short circuits). Following his surgery, Sperry's patient seemed completely normal -- almost. A series of tests were conducted where each "half" of the patient was isolated from the other. Different visual and tactile information could then be presented to the patient's left or right side, without the other side knowing. The results were astounding. With their communications link severed, each side of the patient's brain was functioning independently. Although this did not prevent his ability to walk, talk and eat, some unexpected findings were encountered in some of the higher brain functions when each side was examined independently of the other. The right hand and eye could name an object, such as a pencil, but the patient could not explain what it was used for. When shown to the left hand and eye, the patient could explain and demonstrate its use, but could not name it. Further studies showed that various functions of thought are physically separated and localized to a specific area on either the left or right side of the human brain. This functional map is consistent for an estimated 70 to 95 percent of us.
The War of the Brains The two brains not only see the world in vastly different ways but, in our current society, the left side just "doesn't get" what the right side is all about. It tends to dismiss anything significant coming into consciousness from its "flaky" cranial twin. Sometimes two sides can actually disagree, resulting in our perception of emotional turmoil from the expressive protests of right brain. Our conscious mind can only focus on data from one brain at a time. We can switch from one side to the other very quickly (with our corpus collosum intact) but that's not always the most efficient way to act and eventually ultimate authority to enter consciousness is delegated to one brain or the other. In our modern world, this battle is almost always won by the left brain. It appears that most people will never reach their maximum potential because of compromises that have been made between these two governing bodies. Sometimes skills which the right brain can perform better are routinely handled, with less skill, by the left brain. Ideally, both brains work together in people with optimum mental ability. This coordinating ability may be the key to superior intellectual abilities. In most people, however, the left brain takes control, choosing logic, reasoning and details over imagination, holistic thinking and artistic talent. Methods have been devised to "shut off" the left brain, allowing the right side to have its say. Creative writing courses often use this method to combat "writer's block." The logical left side is easily bored by lack of input and tends to "doze off" during such activities as meditation (repeating a mantra or word over and over) or in sensory deprivation environments. The right brain is then able to "sneak" into our consciousness, filling our minds with emotional and visual vignettes and freely associated images. All too quickly, though, the left brain will assert itself and dispense with these irrational images, asserting its Spock-like logical dominance and the right brain will have to be content to find expression in dreams. http://www.viewzone.com/bicam.html
isn't the crossover a result of vision, images are inverted as they travel through the lenses of our eyes and as well need to be transposed laterally, hence left eye right brain it would be interesting to learn what if any differences their are for those who have never had any eyesight, whether hemispheric difference is as great for them
You may be interested in the following post, both the quoted text and the response to myself: http://www.elitetrader.com/vb/showthread.php?s=&postid=2032896&highlight=music#post2032896