We have stated before that there is a similar biochemical basis responsible for all human sensory perception, thereby relating vision, audition, gestation, and olfaction. It is well known that there is a tripartite relationship underlying all human sensory perception involving (1) sensory receptor detection of incoming stimuli, (2) neural transmission of these stimuli, and (3) brain integration of this information.

We hypothesize that the first step of this process, sensory receptor detection, is based upon a biochemical mechanism that is similar to the mechanisms responsible for stimulus detection for all sensory processes.

We hypothesize that all sensory receptors depend upon stem cells for the development of their respective sensory receptor systems. This means that there are special and unique stem cells that are the basis for the complex receptor systems of vision, audition, gustation, and olfaction. Stem cells depend upon special growth factors that are both unique and similar in each sensory system. These growth factors stimulate each stem cell to generate the specialized sensory systems of their respective sense organs—the retina of the eye, the cochlear (organ of Corti) cells of the ear, the taste buds of the tongue and palate, and the olfactory epithelium of the nose.

Growth factors responsible for generation of these specialized organs are secreted in fluids that bathe each of these organs—the vitreous humor for the eye, the cochlear fluid for the ear, saliva for the tongue and palate, and nasal mucus for the nose. Each of these fluids contains many substances for maintenance of the multiple structures in these organs. Among these substances are growth factors that stimulate their respective stem cells and differentiate and generate the complex panoply of the sensory receptor complex in that specific sensory receptor system.

What makes these sensory systems similar is that many growth factors in each system are biochemically similar. For each system, enzymes such as carbonic anhydrase (CA) VI, adenylyl cyclase, cAMP, and cGMP are present in these bathing fluids and act in a similar manner on stem cells in each sensory system to initiate differentiation and maturation, which are both unique and similar to each system. Thus, these growth factors act in each sensory system to induce receptor maturation in each sensory system.

Pathology that inhibits secretion and synthesis of these growth factors inhibits differentiation and maturation of stem cells in each system and induces loss of sensory function: for vision—blindness, for audition—deafness, for gustation—hypogeusia, for olfaction—hyposmia. This growth factor pathology results in sensory receptor apoptosis, which renders the sensory receptor less capable of receiving incoming sensory information and thereby less capable of passing correct information about the stimulus to the brain. Recognition of the cause for this sensory loss can be detected by measurement of growth factor concentration in each biological fluid. Treatment of these losses can be corrected by increasing the concentration of these growth factors in each system.

Presentation of this concept will occur at Experimental Biology 2006, on April 3, and is in press in the FASEB J, 2006.