Event-related functional imaging and episodic memory

Electrical and haemodynamic measures of neural activity can be time-locked to an event-of-interest, such as the presentation of a stimulus or a behavioural response, Both of these measures can be employed in studies where the aim is to elucidate the relationship between neural activity and cognitive processes. This review highlights a number of considerations that arise when these techniques are employed in pursuit of this goal, with a particular emphasis on functional imaging studies of retrieval from episodic memory. The review includes: a discussion of some limitations that each technique imposes at the stage of experimental design, consideration of the relative strengths and weaknesses of each technique, a commentary on assumptions that are common to both, and a brief review of the ways in which these techniques can be extended in order to index two distinct classes of cognitive operations that have correspondingly distinct neural signatures. (C) 2001 Elsevier Science Ltd. All rights reserved.