Interesting you should mention idio-savants, Ebbie. I just watched a fascinating documentary on the CBC tonight about a young savant from London. He is extremely gifted both mathematically and linguisticly.

He has been diagnosed as autistic, but with a difference. Unlike most with autism, he not only functions very well on a social level, he can communicate how he is processing numbers in his brain. (basically they take on shapes and colour and appear as pieces of a jigsaw puzzle) During the documentary he learned to speak extremely functional and subtley nuanced Icelandic in 7 days.

The scientists who were working with him, suggested that what was going on in his brain was similar to what BaldEagle2 has outlined.