Sensory maps and brain development the midbrain auditory nucleus had receptive fields independent of nature and intensity of the sound. Roger Sperry proposed a chemical gradient model for eye rotation and for neuronal wiring diagram. Retinal neurons and target cells had identification tags in the form of chemical gradients so that the projection of neurons would be orderly. For a topographic map of the visual world, the map first forms during neural development via molecular signals, such as chemospecific matching between molecular gradients. The molecular basis of sensory maps and brain development is a field that is being actively explored. The most recent work has
OPN1LW LWS cone cells into horizontal cells, bipolar cells, amacrine cells, and finally ganglion cells before continuing to the brain via the optic nerve. Ganglion cells compile the signal from the LWS cones with all other cone signals that occurred in response to the light that was seen, and pass the overall signal into the optic nerve. The cones themselves do not process colour, it is the brain that decides what colour is being seen by the signal combination it receives from the ganglion cells. Before humans evolved to be a trichromatic species, our vision was dichromatic and consisted of only