<unk>  is defined as uncontrollable repetition of a particular response, such as a word, phrase, or gesture, despite the absence or cessation of a stimulus, usually caused by brain injury or other organic disorder.
If an issue has been fully breached and discussed to a point of resolution it is not uncommon for something to trigger the re-investigation of the matter.  This can happen at any time during a conversation.  This is particularly true with those who have had traumatic brain injuries.
Those with Asperger's syndrome also display a form of<unk>  in that they focus on one or a number of narrow interests. A person with Asperger's might go to a department store repeatedly to look at air conditioners.
Several researchers have tried to connect<unk>  with a lack of inhibition; however, this connection could not be found, or was small.
Perseveration
Disgust
Impaction
Derealization
Aversion to happiness
Depersonalization
Delusion
Withdrawal