The frequency-doubling illusion is an apparent doubling of spatial frequency when a sinusoidal grating is modulated rapidly in temporal counterphase. Recently, it has been proposed that the illusion arises from a spatially nonlinear ganglion cell class. The presence of this illusion therefore indicates abnormalities in the retina such as glaucoma.
A more recent study's results argue against the hypothesis that spatially nonlinear retinal ganglion cells are the physiological substrate of the frequency-doubling illusion. A cortical loss of temporal phase discrimination may be the principal cause of the illusion, whereas spatial phase information (i.e., grating position) is retained.
Sensitivity to the spatial-frequency-doubling illusion was also positively correlated with reading lag and coherent motion. The results provide good support for a magno deficit in dyslexia that has its origins at a retinal level with impairment in—at least partially—M(y)-cell activity.