It has been widely believed, based on a number of anatomical, physiological and psychophysical findings, that the human visual cortex initially analyzes spatial patterns independently of their movements, but Nishida's observations provide strong evidence against this basic hypothesis.
The new work utilized a visual illusion called multi-slit viewing, first reported in the 1970s. During this illusion, a pattern presented through stationary multiple slits becomes clearly visible when the pattern moves behind the slits. Two lines of evidence from the multi-slit viewing experiments support the conclusion that early motion processing indeed contributes to pattern perception. First, Nishida found that pattern perception is more impaired by a mask or adaptation stimulus moving in the same direction as the pattern than it is by one moving in the opposite direction. In the history of psychophysics, such direction selectivity of the masking and adaptation effects has been regarded as strong evidence of the involvement of motion-based mechanisms, and the new findings now demonstrate that this selectivity affects pattern perception. Second, the research shows that during multi-slit viewing, observers can see fine spatial components that are theoretically impossible to recover without the aid of motion information.
In contrast to general beliefs about how we perceive patterns, these findings indicate that the human brain uses the whole visual motion system to integrate spatial pattern information along the trajectory of motion. The work provides an answer to the question of why we can see clear patterns even when they are moving.
Shin'ya Nishida: "Motion-Based Analysis of Spatial Patterns by the Human Visual System"
Published in Current Biology, Volume 14, Number 10, May 25, 2004.
Journal
Current Biology