  The two striking components of retina, i.e., the light sensitive neural layer
in the eye, by which it responds to light are (the three types of) color
sensitive Cones and color insensitive Rods (which outnumber the cones 20:1).
The interaction between electromagnetic radiation and these photoreceptors
(causing transitions between cis- and trans- states of rhodopsin molecules in
the latter) offers a prime example of physical processes at the nano-bio
interface. After a brief review of the basic facts about vision, we propose a
quantum mechanical model (paralleling the Jaynes-Cummings model (JCM) of
interaction of light with matter) of early vision describing the interaction of
light with the two states of rhodopsin mentioned above. Here we model the early
essential steps in vision incorporating, separately, the two well-known
features of retinal transduction (converting light to neural signals): small
numbers of cones respond to bright light (large number of photons) and large
numbers of rods respond to faint light (small number of photons) with an
amplification scheme. An outline of the method of solution of these respective
models based on quantum density matrix is also indicated. This includes a brief
overview of the theory, based on JCM, of signal amplification required for the
perception of faint light. We envision this methodology, which brings a novel
quantum approach to modeling neural activity, to be a useful paradigm in
developing a better understanding of key visual processes than is possible with
currently available models that completely ignore quantum effects at the
relevant neural level.

Neurons and Cognition