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. Author manuscript; available in PMC: 2011 Feb 22.
Published in final edited form as: Vision Res. 2009 Oct 1;50(4):424–432. doi: 10.1016/j.visres.2009.09.022

Figure 2.

Figure 2

Contrast polarity-specific motion stimuli. (A) A typical apparent motion stimulus, which comprises two brief flashes that occur in different spatial locations at different times, activates both ON- and OFF-cells in early motion processing. However, if the two spatially separate flashes are designed to have the same offset times, then motion cells specific to a single contrast polarity are selectively activated (Wehrhahn & Rapf, 1992). (B) An illustration of a multi-frame variable coherence RDM stimulus that targets OFF motion cells. Here four dots, whose luminance is lower than that of the background, are displayed in each frame with the signal direction being rightward (indicated by white arrow) at 50% coherence, and sample trajectories of the dots are shown for four frames. The number on the dot signifies the frame in which it appears. Temporal luminance profiles are shown at few signal dot locations to illustrate how our modification for RDM stimuli works. Signal dot lifetime is limited to two frames whenever possible to prevent confounding motion tails in response to high coherences.