Dr. David Berson

It's vibrating, it's oscillating.

Well, in a sense, photons are certainly moving through space.

We think about photons as particles, and that's one way of thinking about light.

But we can also think of it as a wave, like a radio wave.

Either way is acceptable.

And the radio waves have frequencies, like the frequencies on your radio dial.

And certain frequencies in the electromagnetic spectrum can be detected by neurons in the retina.

Those are the things we see.

But there are still different wavelengths within the light that can be seen by the eye.

And those different wavelengths are unpacked in a sense or decoded by the nervous system to lead to our experience of color.

Essentially, different wavelengths give us the sensation of different colors.

through the auspices of different neurons that are tuned to different wavelengths of light.

Right.

Right.

So if you imagine that in the first layer of the retina where this transformation occurs from electromagnetic radiation into neural signals, that you have different kinds of sensitive cells.

that are expressing, they're making different molecules within themselves for this express purpose of absorbing photons, which is the first step in the process of seeing.

Now it turns out that altogether there are about five proteins like this that we need to think about in the typical retina.

But for seeing color, really it's three of them.

So there are three different proteins, each absorbs light with a different preferred frequency.

And then the nervous system keeps track of those signals, compares and contrasts them to extract some understanding of the wavelength composition of light.