Have a look at the following static pictures:There are more of them here.On the same website this PDF describes findings.However I could not find any explanation why this phenomenon happening. Is it caused by eye structure itself? Can phenomenon be explained, for example, by combination of uneven density of visual receptors from center to peripherals of the eye together with saccadic eye movement and slight delays in visual nerve signal propagation?Or it is creation of visual cortex due to some processes in image interpretation?I will appreciate any references to the research papers.  
Why do I see those static pictures as they are moving
perception;vision