EVENT-RELATED POTENTIALS AS INDIRECT MEASURES OF RECOGNITION MEMORY

Event-related potentials (ERPs) were recorded during an auditory word- recognition task to determine whether they can be used as indirect mea sures of recognition memory, defined as the ability to differentiate l earned from unlearned material when no overt recognition response from the subject is required. A modified version of the two-choice reactio n time task developed by Alien, Iacono and Danielson (Alien et al., 19 92) was used. In three recognition tasks, administered on two consecut ive days, subjects were instructed to indicate recognition of recently learned words. These words were presented along with unlearned words and along with previously learned words which both required a non-reco gnition response. Recently learned target words as well as previously learned nontarget words elicited a centro-parietal positivity around 5 00-1000 ms post-stimulus. The size and onset of this late positivity ( P300) were affected by the requirement of an overt recognition respons e. The results suggest that ERPs are sensitive to differences between learned and unlearned words, to some extent independently of the behav ioral response. ERPs may therefore be used as indirect measures of rec ognition memory. In addition, because the present results held for sti muli presented in the auditory modality and because recognition indice s were still observed after a one-day interval between learning and te sting, this procedure might prove useful in various applications when the integrity of memory is in question.