ZHANG Yudong’s research group of Institute of Optics and Electronics (IOE) collaborating with ZHOU Yifeng’s Lab of University of Science and Technology of China (USTC) proposed and verified a new visual perceptual learning method with the eye’s higher-order aberrations corrected by adaptive optics (AO) system. The experimental results indicated that this method will lead to more improvements on both contrast sensitivity and visual acuity than traditional perceptual learning method. This study was published in NATURE Scientific Reports on April 16th, 2012 (Zhou et al. The eye limits the brain’s learning potential. Scientific Reports. 364, 1-6 (2012); http://www.nature.com/srep/2012/120413/srep00364/full/srep00364.html). In addition, a Chinese patent (ZL200910262470.4) and two American patents (US Pat. 8,020,992 B2; US Pat. 8,020,991 B1) on this method were authorized to IOE and USTC. This finding was also reported by domestic media such as Guangming Daily and Wen wei po.

The pioneering work of Hubel and Wiesel established the concept of a critical period for visual development early in life in which sensory experience is essential to normal neural development. Although this is a fundamental concept in neurobiology it is also now recognized that some limited plasticity remains after this period well into adulthood. During recent decades, numerous studies have shown that a range of visual functions in normal adult subjects can be improved as a result of intensive training (termed perceptual learning). However, there is abundant evidence to indicate that this kind of learning-induced plasticity in adults while being possible is also very limited in extent. On the other hand, in the adult visual system, uncorrectable optical aberrations limit the quality of the retinal image, even when defocus is corrected by sphero-cylindrical lenses. These aberrations, termed higher order aberrations (HOAs), exist throughout the life span. ZHANG and collaborators wondered if HOAs set a fundamental limit to the benefits obtained from perceptual learning for the adult visual system.

ZHANG and collaborators measured the effects of perceptual learning on visual sensitivity with and without HOAs-correction, using a real-time closed-loop adaptive optics visual stimulator system. They found larger and more robust contrast sensitivity improvements when the HOAs were corrected than when they were left uncorrected. They showed that this is not due to the better optical quality per se or by the brain’s ability to utilize this information but a consequence of improved perceptual learning using images of higher optical quality. This also transferred to a significant improvement of visual acuity in the HOAs corrected perceptual learning group, compared with that of the HOAs-uncorrected group. These results confirm previous reports of brain plasticity well beyond the critical period and show that its benefits are even larger if the eye’s higher-order optical aberrations are corrected.

It is very important that these finding of enhanced visual plasticity in the adult, in both magnitude at the trained spatial frequency and extent of transfer to other spatial frequencies, is not only directly relevant to the development of new therapies applied in later life to redress brain dysfunction resulting from anomalous visual development earlier in life, but also shows that "supernormal" vision is achievable through the combination of recent advances in our understanding of optics and brain plasticity.