Yeah, my first guess is the movement of that faint inner line triggers the Parasol cells or some other movement detection cells in our retina (https://en.wikipe

Yeah, my first guess is the movement of that faint inner line triggers the Parasol cells or some other movement detection cells in our retina (https://en.wikipedia.org/wiki/Parasol_cell https://en.wikipedia.org/wiki/Parasol_cell). Possible underlying circuit: https://www.cell.com/neuron/pdf/S0896-627318%2930105-3.pdf https://www.cell.com/neuron/pdf/S0896-627318%2930105-3.pdf