Conversation so far:
What did Ai Weiwei release?
On 22 June 2011, the Chinese authorities released Ai Weiwei from jail after almost three months' detention on charges of tax evasion.
What did Ai Weiwei do after his release from jail?
After Ai Weiwei's release, his sister gave some details about his detention condition to the press, explaining that he was subjected to a kind of psychological torture.

Question: What kind of psychological torture was he subjected to?
Self-contained rewrite: What kind of psychological torture was Ai Weiwei subjected to?