Improvement in acuity following motion adaptation: The role of information at different spatial frequencies

Prolonged exposure (adaptation) to blur, flicker or motion can transiently enhance visual acuity (VA). Such improvement could be linked to decreased contrast sensitivity (CS) for low spatial frequency (SF) image structure. Here, we determine if and why low SFs are required for such acuity improvement following adaptation. We measured CS using SF band-pass filtered optotypes with and without adaptation. We also measured CS for these stimuli in the presence of a SF low-pass fixed-contrast "pedestal". Adaptation to receding motion improves VA for conventional but not vanishing optotypes (which contain little low SF structure), indicating a crucial role for low SFs. Adaptation reduces CS at all SFs (particularly for the lowest SF). In unadapted observers - interestingly, however, CS for higher SF information is always enhanced/facilitated by a low SF pedestal. Therefore, any adaptation-driven suppression of low SFs must improve the discriminability (rather than detection) of high SFs to improve recognition. Using a simple filter-combination model, we show that recognition must be operating on information that has been combined across SFs.