The genesis of Outsider Art could well be traced to an imagined prehistoric cave wall, to the work of your favorite eccentric visionary (think William Blake), or to the mythic artist-genius dreamed up by Romantic philosophers and poets. Outsider Artists began to emerge as a force to be reckoned with during the early 1920's, with the publication of two pioneering studies of art made on asylum inmates, conducted by European psychiatrists in search of universal truths about human creativity.
German Expressionists soon fell in love with the schizophrenic artists presented in these books--especially Adolf Wölfli, Karl Brendel and August Naterrer--and adopted them as creative muses by appropriating their imagery. In Paris, the Surrealists looked to the same books for inspiration, and also to Spiritualist Mediums such as Augustin Lesage and Helene Smith who were famous local practitioners of automatic drawing.
It wasn't until after World War II that Outsider Art was truly recognized as more than simply source material for the modernist avant-garde. The French artist Jean Dubuffet took the Surrealist obsession with Outsiders to a new level by daring to collect and exhibit their work. Not only did he champion the artwork of schizophrenics and local mediums, but he also celebrated art made by eccentric isolates and self-taught laborers. Dubuffet recognized in the work of these divergent groups one unifying trait: a raw quality untouched by academic rules or current trends.
In 1947, Dubuffet staged a ground-breaking, manifesto-driven exhibition in Paris, aptly naming his category art brut (Raw Art). Dubuffet's Collection de l'Art Brut grew in the subsequent decades, and eventually found a home in Lausanne, Switzerland, in 1976. This unique collection might well have remained in isolation, if not for the publication of a 1972 study of art brut entitled Outsider Art written by the British scholar Roger Cardinal. Cardinal's book, and his 1979 London exhibition Outsiders, launched Outsider Art as a powerful global force that continues to challenge and redefine the limits of what we call art.
Here's a nice link, http://www.outsiderartfair.com/outsider_art