Crazy optical illusion 6
This totally freaking crazy optical illusion has been making the rounds online over the last little while It’s very simple: stare at the red dot in the full photo below for 30 seconds and then quickly shift your gaze away to any plain, flat surface. (It helps a bit if you then blink a lot.)
So how do these opponent cell neurons express the different colours? By changing the rate at which they fire. Each one has a base rate — if the neurons fire more or less often than that, you see the corresponding colour. So, for instance, if you look at a red firetruck, the red-green neuron begins to fire at a different rate, and you see red. If you look at a green plant, it fires at a different rate, and you see green. (Whether red or green corresponds to a faster or slower rate depends on the particular neuron and its location in your visual system.)
That brings us back to the optical illusion.
When you look at a negative image like this one, your opponent cell neurons adjust their firing rate just like they usually do. In this case, since the image of the woman is composed of shades of blue, the yellow-blue neurons fire at a faster or slower rate, and you see blue. But it takes energy to change the firing rate — and these neurons are lazy little bastards. When you stare at an image for a while, they run out of energy and go back to their base rate. So now, essentially, they’ve re-calibrated; the blue woman has become the new normal. When you suddenly look away, the neurons react to the sudden lack of blueness. They change their firing rate again and you see the woman in yellow.
This is the same reason that when you stare at something red for a while and then look away, you see green. And vice versa.
It’s crazy how the brain works.