There has not been a paper on human imaging studies on the illusory motion from the Rotating Snakes figure, but there are studies on at least three other kinds of illusory motions. A study by Zeki, Watson, and Frackowiak (
1993), using the positron emission tomography (PET), found activation in V5 (hMT) when the participant was observing an op-art image called Enigma. Second, there are fMRI studies on implied motion (Kourtzi & Kanwisher,
2000; Krekelberg, Vatakis, & Kourtzi,
2005). They found a significant difference in the BOLD signal in hMT+ between the observations of static images with and without figures that imply visual motion. The most important difference between these implied motion stimuli and the Rotating Snakes figure is that the latter evokes a unidirectional motion perception, which is as vivid as actual motion and also measurable psychophysically, e.g., by cancellation techniques (Hisakata & Murakami,
2008; Murakami et al.,
2006). Third, there are several fMRI studies discussing the correlations between hMT+ activities and the aftereffect of adaptation to visual motion (He, Cohen, & Hu,
1998; Huk, Ress, & Heeger,
2001; Tootell et al.,
1995). The adaptation to the first-order motion evokes illusory motion percept to static test stimulus (Mather, Ferstraten, & Anstis,
1998). The motion is consistent enough to be canceled by the physical motion in the opposite direction of motion perception, and this characteristic is quite alike to the motion percept from ‘Rotating Snakes’ figure. Therefore, it is quite likely that the neural mechanisms for physical motion are deeply involved in the ‘Rotating Snakes’ illusion and thus it is possible to elucidate the relevance of hMT+ activities as a neural basis of the illusory motion perception from a static image.