title: Flicker adaptation or superimposition raises the apparent spatial frequency of coarse test gratings.
abstract: Independent channels respond to both the spatial and temporal characteristics of visual stimuli. Gratings <3 cycles per degree (cpd) are sensed by transient channels that prefer intermittent stimulation, while gratings >3 cpd are sensed by sustained channels that prefer steady stimulation. From this we predict that adaptation to a spatially uniform flickering field will selectively adapt the transient channels and raise the apparent spatial frequency of coarse sinusoidal gratings. Observers adapted to a spatially uniform field whose upper or lower half was steady and whose other half was flickering. They then adjusted the spatial frequency of a stationary test (matching) grating on the previously unmodulated half field until it matched the apparent spatial frequency of a grating falling on the previously flickering half field. The adapting field flickered at 8 Hz and the spatial frequency of the gratings was varied in octave steps from 0.25 to 16 cpd. As predicted, adapting to flicker raised the apparent spatial frequency of the test gratings. The aftereffect reached a peak of 11% between 0.5 and 1 cpd and disappeared above 4 cpd. We also observed that superimposed 10 Hz luminance flicker raised the apparent spatial frequency of 0.5 cpd test gratings. The effect was not seen with slower flicker or finer test gratings. Altogether, our study suggests that apparent spatial frequency is determined by the balance between transient and sustained channels and that an imbalance between the channels caused by flicker can alter spatial frequency perception.
authors: Japan Society for the Promotion of Science, Dept of Psychology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0109, United States. Electronic address: sakaneko@ucsd.edu.
authors: Sae
authors: S
authors: Kaneko
authors: Department of Ophthalmology and Visual Sciences, University of British Columbia, 4480 Oak St., Vancouver, BC V6H 3V4, Canada. Electronic address: giaschi@mail.ubc.ca.
authors: Deborah
authors: D
authors: Giaschi
authors: Dept of Psychology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0109, United States. Electronic address: sanstis@ucsd.edu.
authors: Stuart
authors: S
authors: Anstis
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D000360:Afterimage / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D009903:Optical Illusions / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D014796:Visual Perception / Q000502:physiology*
keywords: Adaptation; Aftereffect; Flicker; Grating; Spatial frequency; Temporal frequency