1. The challenge
Neuroscience has established that sensations, including those by which the physical world is knowable, are innate. The implication that the sensation of color is innate and evoked by the brain, rather than received from the eyes or being an aspect of the electromagnetic spectrum, is counterintuitive. More jarring still is that the same applies to the sensation of light. Commonsense rebels against the notion that the sensation of light is innate and as such private, or phenomenal.
Even Newton, who conceded that experienced color is brought about by the “sensorium” and contending that achromatic white light is a combination of colors, could not bring himself to make explicit the conclusion that the sensation of light, like that of color, is “sensorium”- dependent. This reluctance or inability to make explicit the implication that since the sensations of color are innate and phenomenal, so are the sensations of brightness and lightness.
This is the very reason that identifying the molecular and cellular determinants of the sensation of light (i.e. applying the notion of neural correlates of consciousness to the sensation of light) will have a shocking impact on the knowledge enterprise.
2. The three phases of the undertaking
2.1. First, it is necessary to prove the sensation of light is innate. The direct electrical stimulation of the visual cortex of persons that are not cortically blind elicits sensations of light (phosphenes). This has been demonstrated in normally seeing persons and in persons who lost their vision. It remains to be demonstrated that the same is true in the case of born blind children.
Such a procedure is both possible and necessary in order to provide such children with cortical visual prosthetics. Such prosthetics have been developed (Dobelle 2000) and confirming that the electrical stimulation of the visual cortex does elicit the sensations of light in persons who lost their vision. Recently I urged some organizations to test such cortical visual prostheses on children born blind. I believe that by 2020 such tests would confirm that these cortical visual prostheses elicit sensations of light in the born blind.
2.2. Next, it is necessary to identify the locus-specific cells of interest. It is known that a lesion in the color area in the visual cortex can leave a person completely colorblind but leave intact the sensation of light and dark as well as visual sensation of motion direction. Current literature does not yet identify the brain locus that evokes the sensation of light
The following conceptual framework resolves this issue, making it accessible to empirical verification: any cells or circuits that create an illusion of a given sensation are those that evoke that sensation under normal circumstances.
Specifically, it is necessary to identify in the visual cortex locus-specific cells that are selectively activated if, and only if, the subject experiences a sensation of light through external or direct electrical stimulation. Anna Wang Roe, et al (2005) identified cells in the thin stripes of visual area V2 that are directly involved in producing a brightness illusion. Hence, visual area V2 is one of the areas of the visual cortex containing cells and circuits that evoke a sensation of light.
2.3. A cell type’s proteome is a determinant of intrinsic function. The morphology of a neuron, as in any cell type of a given organism, is determined primarily by its continually-expressed proteins. Thus, here exists a unique proteome characteristic of cells that evoke the sensation of light. Present day single-cell sequencing techniques make it possible to identify the unique proteome of the cells of interest.
I believe that meeting the challenge of any of the three phases would justify a Nobel Prize. Meeting all three phases would bring to an end the era that began with Locke and Hume, based on the denial of innate sensations emotions and cognitions, and mark the advent of a new era regarding the nature of consciousness.