The research done by Ted De Yoe has shown that patients with our class of symptoms would perceive contrast to a higher degree than the avg. man.
But here is a paper showing evidence that viewing moving objects appear to increase in speed as the contrast between it and the surroundings increase: http://www.cns.nyu.edu/~mjh/papers_pdf/Spering_jov_5_455_05.pdf
This to me explains partly why trails are greater in high contrast circumstances because the speed of the object is perceived to move faster causing a more extended trail behind it.
