p214fig05.25 The sequence of events whereby a novel input pattern can activate a category which, in turn, reads out its learned top-down expectation to be matched against the input pattern.  Error correction thus requires the use of a Match Detector that has properties of the Processing Negativity ERP.<BR>||  How is an error corrected.  During bottom-up learning, top-down learning must also occur so that the pattern that is read out top-down can be compared with the pattern that is activated by bottom-up inputs. Match detector: Processing Negativity ERP. 1. top-down, 2. conditionable, 3. specific, 4. match