Contributed talks II: Differential effects of chromatic and luminance flicker on detection of large versus small visual stimuli

Previous studies have shown that detectability of large spots (≥ 1°) can be reduced following exposure to temporal contrast modulation. We examined detection thresholds of small, diffraction-limited flashes following flicker presented in various spatiochromatic configurations with an adaptive optics scanning light ophthalmoscope. Circular, 543 nm increments of varying diameter (1, 3, or 23 arcmin) were presented to the fovea for on a 1.4° background following presentation of isoluminant (i.e., red/green) or isochromatic (i.e., orange/black) checkerboards flickering at 3.75 Hz. Stimulus onset asynchrony (SOA; relative to flicker offset) varied between 33 and 500 ms, and detection thresholds were obtained at each SOA using an adaptive staircase procedure. Compared to control measurements, sensitivity to the 23 arcmin stimulus was reduced following both chromatic and luminance flicker. The magnitude of flicker-induced sensitivity loss decreased as SOA increased, reaching a plateau at ~250 ms at a level ~0.3 log units below control sensitivity. These results suggest that larger spots engage mechanisms susceptible to both short-term and sustained desensitization processes. In comparison, the detectability of the 1 and 3 arcmin stimuli was largely unaffected by exposure to flicker of either type, implying small spots engage a more complex confluence of pathways in processing. Further investigation is necessary to untangle the pathway(s) mediating detection of small spots.