Short-term monocular deprivation increases stereoacuity.
visual deprivation, stereoscopic vision, monocular deprivation
Cognition and Perception | Cognitive Neuroscience | Neurosciences | Optometry
Monocular deprivation early in life can impair vision permanently (Hubel and Wiesel, 1970), but deprivation during adulthood has been thought to be without effect. However, adults who were monocularly deprived for a few hours show a short-term gain increase in the formerly deprived eye relative to the undeprived eye (Lunghi et al., 2011; Zhou et al., 2013). This binocular imbalance should affect stereoacuity. We previously showed that stereoacuity improves after depriving each eye sequentially, presumably by increasing the gain in both eyes. Following that argument, we hypothesize that: (1) monocular deprivation should lower stereoacuity (as does an interocular mismatch in stimulus contrast), but (2) depriving both eyes simultaneously should improve performance because balance is preserved as gain increases. We measured stereoacuity with a two-line depth discrimination test immediately before and after deprivation. Deprivation consisted of covering one or both eyes with a translucent patch for 2.5h, in accordance with previous studies. The patched eye received only low frequency and low contrast inputs while the unpatched eye viewed the natural environment directly. Observers were stereo-normal adults. Binocular deprivation improved stereoacuity by 35%; but contrary to our predictions, monocular deprivation also improved stereoacuity by 27-55%. Alternating the eye being deprived in three cycles during the 2.5h period also improved stereoacuity by 40%. Stereoacuity gradually returned to pre-deprivation levels after deprivation. Improved performance was correlated with duration; prolonging monocular deprivation to 4.5h produced further improvement (67%), but 45min had no observable effect. Stereoacuity improved regardless of the type of deprivation (alternating, binocular or monocular). Therefore, our results suggest that monocular contrast gain control was not responsible for the effects induced by deprivation. Rather, sustained balanced binocular input appears to lower the gain of stereo mechanisms through an adaptation effect. Deprivation avoids the adapting binocular interactions, and allows transient recovery.
Ng, J. C. & Farell, B. (2016). Short-term monocular deprivation increases stereoacuity. Journal of Vision, 16(12):831-831. doi: 10.1167/16.12.831