If we could consciously see single photons, we would experience too much visual “noise” in very low light, and so this filter is a necessary adaptation, not a weakness.
From what I understand, the rhodopsin protein will sometimes become spontaneously activated without having to absorb light. Since a single activation is enough to trigger the next cell to fire, this makes the system so sensitive that it is noisy when it is dark. So it makes sense that rather than considering every triggering event as a positive signal, some later step in the signal processing chain would require a certain number photoreceptor cells to activate before it lets the signal pass through into our consciousness.
I have not looked further into the processing chain, so I don’t know at what level this threshold is applied. It could be that multiple neurons need to activate to provide enough of an impulse to activate the optic nerve - or it could be that the signal from a single event does propagate all the way to the visual cortex, and the visual cortex filters these low signals. I suspect that this is well known, but I shouldn’t allow myself to spend time on this today. I will try to find out when I do have time, as this is a very interesting topic!
Thanks! I appreciate you reading it :)
The first paragraph points out the following:
From what I understand, the rhodopsin protein will sometimes become spontaneously activated without having to absorb light. Since a single activation is enough to trigger the next cell to fire, this makes the system so sensitive that it is noisy when it is dark. So it makes sense that rather than considering every triggering event as a positive signal, some later step in the signal processing chain would require a certain number photoreceptor cells to activate before it lets the signal pass through into our consciousness.
I have not looked further into the processing chain, so I don’t know at what level this threshold is applied. It could be that multiple neurons need to activate to provide enough of an impulse to activate the optic nerve - or it could be that the signal from a single event does propagate all the way to the visual cortex, and the visual cortex filters these low signals. I suspect that this is well known, but I shouldn’t allow myself to spend time on this today. I will try to find out when I do have time, as this is a very interesting topic!