Savant

Kim Peek, the savant who was the inspiration for the main character in the movie Rain Man

Savant syndrome () is a rare condition in which someone with significant mental disabilities demonstrates certain abilities far in excess of average. The skills that savants excel at are generally related to memory. This may include rapid calculation, artistic ability, map making, or musical ability. Usually, only one exceptional skill is present.

Those with the condition generally have a neurodevelopmental disorder such as autism spectrum disorder or have a brain injury. About half of cases are associated with autism, and these individuals may be known as "autistic savants".

From Wikipedia