p016fig01.11 A sufficiently big mismatch between a bottom-up input pattern and a top-down expectation can activate the orienting system, which triggers a burst of nonspecific arousal that can reset the recognition category that read out the expectation.  In this way, unexpected events can reset short-term memory and initiate a search for a category that better represents the current situation.<BR>||  [category- top-down (TD) expectation; Bottom-up (BU) input pattern] -> Feature pattern -> BU-TD mismatch -> orienting system -> non-specific arousal -> category.