Learning to adapt: Dynamics of readaptation to geometrical distortions.
The visual system can adapt to optical blur, whereby the adapted image is perceived as sharp. Here we show that adaptation reduces blur-induced biases in shape perception, with repeated adaptations (perceptual learning), leading to unbiased perception upon re-exposure to blur. Observers wore a cylindrical lens of +1.00 D on one eye, thus simulating monocular astigmatism. The other eye was either masked with a translucent blurred lens (monocular) or unmasked (dichoptic). Adaptation was tested in several repeated sessions with a proximity-grouping task, using horizontally or vertically arranged dot-arrays, without feedback, before, after, and throughout the adaptation period. A robust bias in global-orientation judgment was observed with the lens, in accordance with the blur axes. After the observer wore the lens for 2 h, there was no significant change in the bias, but after 4 h, the monocular condition, but not the dichoptic, resulted in reduced bias. The adaptation effect of the monocular 4-h adaptation was preserved, and even improved, when the lens was re-applied the next day, indicating learning. After-effects were observed under all experimental conditions except for the 4-h monocular condition, where learning took place. We suggest that, with long experience, adaptation is transferred to a long-term memory that can be instantly engaged when blur is re-applied, or disengaged when blur is removed, thus leaving no after-effects. The comparison between the monocular and dichoptic conditions indicates a binocular cortical site of plasticity.
Yehezkel
Oren
O
Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel Hashomer, Israel.
Sagi
Dov
D
Sterkin
Anna
A
Belkin
Michael
M
Polat
Uri
U
D000065:Accommodation, Ocular / Q000502:physiology*; D000221:Adaptation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D009473:Neuronal Plasticity; D012029:Refraction, Ocular / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology; D014793:Visual Cortex / Q000503:physiopathology; D055815:Young Adult