Perceptual learning can be defined as a long lasting improvement in a perceptual skill following a systematic training, due to changes in brain plasticity at the level of sensory or perceptual areas. Its efficacy has been reported for a number of visual tasks, such as detection or discrimination of visual gratings (De Valois, 1977
Fiorentini & Berardi, 1980, 1981
Mayer, 1983), motion direction discrimination (Ball & Sekuler, 1982, 1987
Ball, Sekuler, & Machamer, 1983), orientation judgments (Fahle, 1997
Shiu & Pashler, 1992
Vogels & Orban, 1985), hyperacuity (Beard, Levi, & Reich, 1995
Bennett & Westheimer, 1991
Fahle, 1997
Fahle & Edelman, 1993
Kumar & Glaser, 1993
McKee & Westheimer, 1978
Saarinen & Levi, 1995), visual search tasks (Ahissar & Hochstein, 1996
Casco, Campana, & Gidiuli, 2001
Campana & Casco, 2003
Ellison & Walsh, 1998
Sireteanu & Rettenbach, 1995) or texture discrimination (Casco et al., 2004
Karni & Sagi, 1991, 1993). Perceptual learning is long-lasting and specific for basic stimulus features (orientation, retinal position, eye of presentation) suggesting a long-term modification at early stages of visual analysis, such as in the striate (Karni & Sagi, 1991
1993
Saarinen & Levi, 1995
Pourtois et al., 2008) and extrastriate (Ahissar & Hochstein, 1996) visual cortex. Not confined to a basic research paradigm, perceptual learning has recently found application outside the laboratory environment, being used for clinical treatment of a series of visually impairing conditions such as amblyopia (Levi & Polat, 1996
Levi, 2005
Levi & Li, 2009, Polat et al., 2004
Zhou et al., 2006), myopia (Tan & Fong, 2008) or presbyopia (Polat, 2009). Different authors adopted different paradigms and stimuli in order to improve malfunctioning visual abilities, such as Vernier Acuity (Levi, Polat & Hu, 1997), Gratings detection (Zhou et al., 2006), oculomotor training (Rosengarth et al., 2013) and lateral interactions (Polat et al., 2004). The common result of these studies is that a specific training produces not only improvements in trained functions, but also in other, untrained and higher-level visual functions, such as visual acuity, contrast sensitivity and reading speed (Levi et al, 1997a, 1997b
Polat et al., 2004
Polat, 2009
Tan & Fong, 2008). More recently (Maniglia et al. 2011), perceptual learning with the lateral interactions paradigm has been successfully used for improving peripheral vision in normal people (by improving contrast sensitivity and reducing crowding, the interference in target discrimination due to the presence of close elements), offering fascinating new perspectives in the rehabilitation of people who suffer of central vision loss, such as maculopathy patients, partially overcoming the structural differences between fovea and periphery that limit the vision outside the fovea. One of the strongest point, and a distinguishing feature of perceptual learning, is that it does not just improve the subject's performance, but produces changes in brain's connectivity and efficiency, resulting in long-lasting, enduring neural changes. By tailoring the paradigms on each subject's needs, perceptual learning could become the treatment of choice for the rehabilitation of visual functions, emerging as a simple procedure that doesn't need expensive equipment.