The contrast sensitivity function (CSF) is routinely assessed in clinical evaluation of vision and is the primary limiting factor in how well one sees. CSF improvements are typically brought about by correction of the optics of the eye with eyeglasses, contact lenses or surgery. We found that the very act of action video game playing also enhanced contrast sensitivity, providing a complementary route to eyesight improvement.Contrast sensitivity, the ability to detect small increments in shades of gray on a uniform background, is one of the main limiting factors in a wide variety of visual tasks 1 . Unfortunately, it is one of the aspects of vision that is most easily compromised. This problem affects thousands of people worldwide, including those with professional activities requiring excellent eyesight, aging populations 2 and individuals who are clinically evaluated for vision problems such as amblyopia 3 . Although deterioration of the optical quality of the eye can decrease contrast sensitivity 3 , optical changes alone cannot account for the diverse array of situations in which the CSF is compromised. Instead, neural factors also appear to be at work. It may therefore be possible to develop interventions that enhance the CSF through neural plasticity. Such an intervention would be of great clinical benefit as a complement to the standard clinical approaches, which are mainly directed at enhancing the optical quality of the eye.Sizeable performance improvements, brought about through brain plasticity, have been documented in various aspects of vision after training 4 . Yet identification of a training regimen that can improve the CSF, or contrast detection, has remained elusive. Traininginduced improvements have been reported for contrast discrimination 5 but not for contrast detection 6,7 . In addition, the documented improvements are typically restricted to the trained stimulus, limiting their practical and theoretical value. The CSF per se has proven difficult to improve. There are some indications that radiologists may exhibit enhanced contrast sensitivity 8 , but the causal effect of experience remains to be established. Studies that directly address training-induced changes in contrast detection show improvements only when using experimental conditions that are known to produce poor performance, such as testing away from fixation or using diagonal orientations 9,10 . Yet, to be clinically relevant, CSF improvements need to be documented in foveal vision and with cardinal orientations, where human performance is at its best. To the best of our knowledge, CSF improvements Expert action video game players (VGPs) were compared to gender-and age-matched nonaction game players (NVGPs) in a CSF procedure 11 ( Fig. 1a and Supplementary Note 1 online). Because we were interested in the effect of gaming on everyday eyesight, participants were tested binocularly with their current eye prescription. We were interested in whether vision, which should not be far from optimal under such conditions in young ad...

We examined contrast sensitivity and suprathreshold apparent contrast with natural images. The spatial-frequency components within single octaves of the images were removed (notch filtered), their phases were randomized, or the polarity of the images was inverted. Of Michelson contrast, root-mean-square (RMS) contrast, and band-limited contrast, RMS contrast was the best index of detectability. Negative images had lower apparent contrast than their positives. Contrast detection thresholds showed spatial-frequency-dependent elevation following both notch filtering and phase randomization. The peak of the spatial-frequency tuning function was approximately 0.5-2 cycles per degree (c/deg). Suprathreshold contrast matching functions also showed spatial-frequency-dependent contrast loss for both notch-filtered and phase-randomized images. The peak of the spatial-frequency tuning function was approximately 1-3 c/deg. There was no detectable difference between the effects of phase randomization and notch filtering on contrast sensitivity. We argue that these observations are consistent with changes in the activity within spatial-frequency channels caused by the higher-order phase structure of natural images that is responsible for the presence of edges and specularities.

We conclude that the gap junctions observed between mammalian cones, including those in the human fovea, represent genuine electrical coupling. Because the space constant of the resulting neural blur is less than that of the optical blur, the signal-to-noise ratio can be markedly improved before the nonlinear stages with little compromise to visual acuity.

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Impaired optic flow perception may contribute to the visuospatial disorientation of Alzheimer's disease (AD). We find that 36% of AD patients have elevated perceptual thresholds for left/right outward radial optic flow discrimination. This impairment is related to independent visual motion processing deficits affecting the perception of left/right motion-defined boundaries and in/out radial motion. Elevated optic flow thresholds in AD are correlated with greater difficulty in the Road Map test of visuospatial function (r = -0.5) and in on-the-road driving tests (r = -0.83). When local motion cues are removed from optic flow, subjects must rely on the global pattern of motion. This reveals global pattern perceptual deficits that affect most AD patients (85%) and some normal elderly subjects (21%). This deficit might combine with impaired local motion processing to undermine the alternative perceptual strategies for visuospatial orientation. The greater prevalence of global pattern deficits suggests that it might precede local motion processing impairments, possibly relating to the sequence of early hippocampal and later posterior cortical damage that is typical of AD.