dr. lopera showed us in these cognitive test results. >> lopera: you can see, at 38-- >> stahl: even at 38, this man struggled-- as many older alzheimer's patients do-- to copy a complex drawing accurately. >> lopera: at 45. at 50. >> stahl: ah! oh! >> lopera: at 51. >> stahl: oh! dr. lopera was convinced that what he and madrigal were discovering was scientifically important, but even as they found more patients and more related families, he couldn't get anyone outside colombia to take notice. until 1993, when a harvard professor about alzheimer's in bogota, several hours away. >> ken kosik: there was a person in the audience, francisco lopera, who came up after the talk and said, "you know, there's-- i have a family here that w-- has-- early-onset alzheimer's." >> stahl: ken kosik, now at u.c. santa barbara, was that professor. a family. could've been four people. >> kosik: it could've been just four people. but he started to tell me how many it was. and as i listened to him, i me that i changed all my plans, went with him to medell?n. and-- we began a collaboration that goes on to this