Illusory motion in Enigma: a psychophysical investigation.

Experiments to determine the optimum conditions for perceiving illusory motion in Engima-like patterns have also demonstrated that the illusory motion is not the result of unintended motion of the image on the retina due to microsaccades or accommodative changes in the lens of the eye but instead has a cortical origin. The perceived illusory activity is believed to be a consequence of neural signals emanating from high-contrast bars and edges in the image that emit randomly fluctuating signals, as expected from spiking cortical neurons. These fluctuations may induce illusory motion in the channels by a mechanism similar to that responsible for the Omega effect, in which sequences of random patterns of black dots presented in an annular channel produce the perception of illusory rotation of these dots within the annulus.