The general principle garnered from analysis of sensory input to the nervous system is that the system actually constructs human reality. It is apparent, through many different characteristics of the nervous system, that sensory input is subject to a great deal of interpretation and maniputaltion to produce what is ultimately experienced as reality. A primary example which illustrates the capability of the nervous system to construct reality is the lateral inhibition network of the eye. Upon exploration of this system of neurons, one finds that the brain is actually infering information about reality and placing it in our reality. The nervous system does not receive the sensory input that corresponds directly to the output that is reality.
There are a plethora of other examples which indicate that the nervous system is making up information, many of which neurobiologists are probably not aware. The implications of the fact that the brain constructs much of human reality are wide-reaching and powerful. They essentially indicate that the reality that exists as the universe is much more complex then the human can percieve. However, through the selection of evolution, humanity has only retained the necessary sensory characteristics to allow the species to survive as best as possible. The physiology of the human body has evolved so that in a universe which contains many different types of potential sensory information, humanity must only make use of some to sort out the complexities of true reality. For example, if we were able to detect all possible waves of the electromagnetic spectrum, it would be impossible for us to distinguish what should exist as reality. However, there are other species which have the ability to detect other wavelengths, defining reality for them.
In terms of behavior, the concept that the brain actually processes sensory information through interpretation and manipulation and outputs a reality dinstinctly different from that which is inputed may help in explaining some of the aspects of behavior that have been deemed difficult to explain. Should neurobiologists have the ability to determine the workings of the brain in terms of how it presents inputs as outputs, there will not only be a better understanding of the universe as a whole and the nervous system, but also the uniqueness that is human behavior.
A pretty ambitious task for neurobiology, but I actually agree with you in principle. Clearly though different organisms have different "realities", as you say, so one can't exactly say that humans have those that are "necessary", at least not uniquely necessary. Can you be more specific about why we have the limited set of inputs we have? And perhaps about how this all explains "some of the aspects of behavior that have been deemed difficult to explain"? PG PG