Retinal neurons - images and relationships part 1

Ok, here is the in-depth examination of the functions of different classes of retinal neurons.All these neuronal types can be developed from retinal stem cells

Photoreceptors: Rods and cones

Cones - come in red, blue and green-sensing varieties (in humans at least, but I digress!). Cones are responsible for all of your high-def colour vision. They are found most densely in the central retina. The combinations of different levels of red, green and blue cone activation are translated by the brain into all the different colours that we see.

Rods - These cells are more sensitive than cones and respond to much lower quantities of light. They are responsible for your vision at low light levels - the reason that your vision is in shades of grey at night is that rods are doing all the work. They do not distinguish between colours, only levels of brightness.

Rods and cones pass their signals onto nearbybipolar cells and horizontal cells via synapses. Bipolar cells can receive input from many photoreceptors (found at the edges of the retina, this setup provides high sensitivity) or one photoreceptor can output to many bipolar cells (found more centrally, this gives greater acuity of vision). A neuron can have many synaptic inputs and outputs.

Horizontal cells are involved in visual processing. They sharpen outlines in the image that hits your retinas, emphasising lines and boundaries. (explanation via link below) Maybe some kind of grid pattern would be appropriate? Basically, this kind of processing is like pressing the "sharpen image" button on photoshop. Quick and universal, sharpens edges.

Bipolar cells are basically sites of integration. They take the signals from photoreceptor and horizontal cells, add them together and send a signal of variable strength on to amacrine cells and ganglion cells.

A good, more in-depth explanation of retinal neuron connections

More in part 2!