Something that has always interested me in writing is how differently a scene can be viewed or played out through the eyes of someone with a mental impairment. I've written as a mentally ill character on many occasions (manic depressives, schizophrenics etc.) but I'd like to try a totally different tactic. My primary idea is to write as a character who suffers from the chromosomal defect, Down's Syndrome. However I have no idea how to execute the idea. I have read such things as The Curious Incident of the Dog in the Night Time by Mark Haddon, in which the protagonist suffers from Asperger's syndrome, but the technique still seems fairly unbreakable to me. What I'd like to know is if anyone has done something like this in the past? And if so, how did they approach it?