A SPATIOTEMPORAL ANALYSIS OF RECOGNITION-RELATED EVENT-RELATED BRAIN POTENTIALS

Words correctly recognized as previously studied (i.e. old) elicit gre ater amounts of positive event-related brain potential (ERP) activity over posterior scalp between 400 and 800 ms than do previously unstudi ed (i.e. new) words. While investigators have reported that this old/n ew effect consists of more than one subcomponent, the spatio-temporal parameters of these possible subcomponents, as well as any other patte rns of brain activity associated with recognition, remain incompletely specified. Thus, ERPs were recorded from 32 scalp sites while 13 subj ects performed four repetitions of a study-test recognition paradigm. The subjects' task was to decide whether each word was old or new and press the appropriate button as quickly as possible. The timing and to pography of the ERPs elicited by old and new words was assessed with t opographic profile comparisons on the areas with a variety of temporal windows, and visualized with potential and CSD maps. The results reve aled that seven patterns of ERP activity, dissociable on the basis of their topography, timing and response to experimental variables, were elicited between 300 and 2000 ms. Three of these appeared as subcompon ents of the old/new effect (maximal over left medial frontal, left par ietal-occipital and right central-frontal scalp), another was related to decision confidence and/or memory trace strength (maximal over left central scalp) and three others appeared to be related to more genera l aspects of recognition (maximal over the frontal poles, midline fron tal scalp and right frontal scalp). Taken together, the seven distinct patterns of neural generator activity described here support the hypo thesis that retrieval of information from episodic memory depends on a collection of different processes that occur in a temporally and spat ially distributed neural circuit. (C) 1998 Elsevier Science B.V.