I doubt they really control their minds. I think those people have a pretty good idea what goes on outside, they are just stuck there. Any of them with half a brain would figure it out pretty quickly. It looks to me like their leader has a sad day comin'. He can't hold that out forever.
The government even filters and controls the internet as well there. Here is just a quick excerpt about North Korean media...
Radio and TV sets in North Korea are pre-tuned to government stations that pump out a steady stream of propaganda. The state has been dubbed the world's worst violator of press freedom by the media rights body Reporters Without Frontiers.
The totalitarian regime in North Korea keeps its people in a state of ignorance through tight control of the media
Reporters Without Borders, 2008
Meagre media for North Koreans
Press outlets and broadcasters - all of them under direct state control - serve up a menu of flattering reports about Kim Jong-il and his daily agenda. North Korea's economic hardships or famines are not reported.
However, after the historic Korean summit in Pyongyang in 2000, media outlets toned down their fierce denunciations of the Seoul government.
Ordinary North Koreans caught listening to foreign broadcasts risk harsh punishments, such as forced labour. The authorities attempt to jam foreign-based and dissident radio stations.
North Korea has a minimal presence on the internet. The web pages of North Korea's official news agency, KCNA, are hosted by the agency's bureau in Japan.