The notion that artistic capability increases with dementia is both novel and largely unsupported by available literature. Recent research has suggested an emergence of artistic capabilities to be a by-product of involuntary behaviour seen with dementia, as opposed to a progression in original thinking (de Souza, et al., 2010). A far more complementary explanation comes from Hannemann (2006), who suggests that art offers an outlet for dementia patients to refine and sharpen their cognitive abilities. As dementia severely impedes linguistic skills, non-verbal therapeutic methods such as painting can permit dementia patients to express themselves in a way not possible verbally. Fractal analysis has been used to determine the authenticity of major works of art. Taylor et al., (1999) found that through a fractal analysis of Jackson Pollock’s paintings it was possible to distinguish authentic works from a large collection of fakes, demonstrating that when artists paint they instill within their work their own pattern of unique fractal behaviour. Can age-indexed variations in the fractal dimension of the works of artists anticipate specific cognitive deteriorations? More at NCBI.
If the above link is a bit too technical, try this handy summing up by Gizmodo (which I of course had to use).