The frequency-doubling illusion is an apparent doubling of
spatial frequency when a
sinusoidal
A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in m ...
grating is modulated rapidly in temporal counterphase. Recently, it has been proposed that the illusion arises from a spatially nonlinear
ganglion
A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympatheti ...
cell class. The
contrast threshold
Contrast is the contradiction in luminance or colour that makes an object (or its representation in an image or display) distinguishable. In visual perception of the real world, contrast is determined by the difference in the colour and brightn ...
values needed for perceiving this physiological effect are used in frequency doubling technology perimetry for the detection of even early phases of
glaucoma.
A more recent study's results argue against the hypothesis that spatially
nonlinear
In mathematics and science, a nonlinear system is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathematicians, and many other ...
retinal ganglion cells are the physiological substrate of the frequency-doubling illusion. A cortical pathway 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
Dyslexia, also known until the 1960s as word blindness, is a disorder characterized by reading below the expected level for one's age. Different people are affected to different degrees. Problems may include difficulties in spelling words, r ...
that has its origins at a retinal level with impairment in—at least partially—M(y)-cell activity.
References
{{Reflist
Eye
Illusions