Through the Neural Magnifying Glass: Visual Acuity and Motion-Aftereffect

• Published in: i-Perception (London) Vol. 5; no. 5; p. 479
• Main Authors: Boyle, S.C, Jenkins, R, Lages, M
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.08.2014; SAGE Publishing
• ISSN: 2041-6695; 2041-6695
• DOI: 10.1068/ii48

A Sloan- or Snellen-type visual acuity chart is commonly used for routine eye examination. This test serves as a benchmark for visual acuity where observers read out letters of decreasing size at a recommended viewing distance. The smallest readable letter size is typically used as a measure of visual acuity. For example, vision of 20/20 and 10/10 describe the ability to resolve letters that subtend 5 minutes of arc at a viewing distance of 20 (6m) and 10 feet (3m), respectively. Here we show that adaptation to a rotating spiral and the ensuing motion aftereffect (MAE) significantly alters visual acuity in normal observers. In one group 44 observers adapted to contracting motion and in a second group 30 observers adapted to expanding motion. The results clearly demonstrate that the expanding MAE facilitated subsequent letter recognition whereas the contracting MAE impaired letter recognition. We conclude that illusory expansion enlarges the apparent size of letters thereby increasing perceptual fields and number of feature detectors. Illusory contraction on the other hand reduces the apparent size of the letters thereby decreasing perceptual fields and number of feature detectors. It is an astonishing characteristic of the visual system that motion adaptation can improve visual acuity – a measure that is typically related to the optics of the eye rather than feature recognition and cognitive inference