Event-related potentials and the recognition memory exclusion task.

Subjects heard words that were presented in either a male or a female voice, and were required to perform one of two encoding tasks according to the gender of the voice. At test studied words were presented visually, along with a set of words new to the experiment. Subjects were required to respond on one key to words belonging to one of the two classes of studied word (targets), and to respond on a different key both to words belonging to the other study class (non-targets), and to words new to the experiment. In comparison to the event-related potentials (ERPs) elicited by new words, the ERPs elicited by correctly detected targets exhibited two temporally and topographically distinct positive going effects: one of these was phasic, showed a parietal maximum, and was larger over the left than the right hemisphere. The second effect was more sustained in time, frontally distributed, and was larger over the right hemisphere. The ERPs elicited by correctly classified non-targets contained the parietal effect only. These findings confirm that retrieval of contextual information in tests of recognition memory (recollection) is associated with two distinct ERP modulations. While one of these may be closely tied to process necessary for recollection, the other may reflect less obligatory processes which operate on the products of successful retrieval.