Cognitive, Affective, & Behavioral Neuroscience 2002, 2 (2), 162-173 Neural correlates of the formation and realization of delayed intentions ROBERT WEST and KEISHA ROSS-MUNROE University of Notre Dame, Notre Dame, Indiana Prospective memory (PM) can be thought of as the ability to successfully form and later realize inten- tions that must be delayed over some period of time. In this study, event-relatedbrain potentials were used to explore the neural activity associated with the formation and realization of an intention. Greater negativityover the frontal-polar region was associatedwith intention formation trialsin which the intention was later realized. On PM cue trials, an N300 was associated with the detection of a cue. For PM cue trials, a late positive complex was observed that might have reflectedthe retrievalof an in- tention from memory, and a frontal slow wave was observed that might have reflected the activity of a neural system that supported disengagement from the ongoing activity when the cue was detected. Prospective memory (PM) can be thoughtof as the abil- tach the message, should I check my sent mail folder, or ity to form and laterrealize intentionsthat must be delayed can I expect a return message from my colleague, who is over some period of time (Einstein & McDaniel, 1990; somewhat perplexedupon receivinga message with no at- Meacham & Leiman, 1982). Prospective remembering is a tachment (monitoring)? complex activitythat can be conceptualizedas includingat Laboratory-based studies of PM generally try to simu- least five phases: intention formation,adelay period last- late the various phases of prospectiveremembering by hav- ing minutes, hours, or days, during which it is not possible ing individualsform one or more simple intentions at the to realize the intention,a performanceintervalduringwhich outset of a task(s) (e.g., press the “C” key any time an an- it is appropriate to realize the intention, realization of the imal name—the PM cue—is encountered over the course intentionduring the performance interval, and monitoring of the task you are aboutto perform). The subjectsare then the success or failure of an intended action (Ellis, 1996). engaged in some task, designated the ongoing activity As an example of these different phases, suppose that I sit (Ellis & Kvavilashvili, 2000), which serves to instantiate down at my computer with the intention of sending a col- the delay period. This task could involve processing words league the results of a recently completedexperiment as an within the context of a short-term recall task (Einstein & e-mail attachment (intention formation). I load my e-mail McDaniel, 1990) or a semantic judgment task (West & program, open a new message, and then type a brief over- Craik, 1999). The performance interval would reflect in- view of the results of some preliminary analyses and de- stances in which an animal name is presented, and real- scribe the structure of the data set (delay period). During ization of the intention would reflect pressing the appro- this time, I am probablynot continuallyrehearsing the de- priate key when an animal is present. When a PM cue is sire to attach the file, although the intention is likely to be present, the individual is expected to make a prospective maintainedabovesome baselinelevelof activation(Goschke response but could just as easily make a response that is & Kuhl, 1993; Marsh, Hicks, & Bink, 1998). When the appropriate to the ongoingactivity, resulting in a failure to message is completed (performance interval), I click the realize the intention. Monitoring of successful or failed attachmentbutton,locate the appropriate file, and include prospectiveresponses has not been extensivelystudied, al- it with the message (realization). I then send the message though some evidence has indicated that individuals are off into cyber-space, content with the knowledge that I sensitive to missed PM cues (West & Craik, 1999). have completed my task. Or have I? Did I remember to at- The duration of the delaybetween the formation of an in- tentionand the performance interval varies widely in both laboratory and real-world settings, ranging from seconds or minutes to hours or even days. For instance, in the exam- The research described in this paper was supported by grants from the ple of attaching a message to an e-mail, the delay period American Foundationfor Aging Research and the Faculty Research Pro- gram, University of Notre Dame, awarded to the first author. K. Ross- might be as brief as a couple of minutes; in contrast, if in Munroe was supported by the CANDAX McNair Summer Research the morning I plan to return a paper to a student in an af- Program for Minority Students. Portions of the data were reported at ternoon class, the delay period could extend over several meetings of the Psychonomic Society (2000) and the Cognitive Neuro- hours. There is empiricalevidenceindicatingthat the length science Society (2001). Correspondence concerning this article should be addressed to R. West, Department of Psychology,University of Notre of the delay has relatively little effect on the efficiency of Dame, 118 Haggar Hall, Notre Dame, IN 46556 (e-mail: west.19@nd. prospectivememory for intervalsof 15 or 30 min (Einstein, edu). Holland, McDaniel, & Guynn, 1992). In contrast, other Copyright 2002 Psychonomic Society, Inc. 162 ERPS AND PROSPECTIVE MEMORY 163 evidence has indicated that imposing even a brief delay semantically related by pressing one of two keys. For PM between the presentation of a PM cue and the opportunity cue trials, the word pair was presented in uppercase letters, to realize the intention can disrupt the efficiency of and the individualswere instructed that when this change prospective remembering (Einstein, McDaniel, Manzi, was recognized, a third key should be pressed, reflecting Cochran, & Baker, 2000; West & Craik, 2001). In the realizationof the intention.Finally,for PM lure trials, one present study, we used a PM task in which the delay period of the words was presented in uppercase letters, and one was relatively short, approximately 10–20 sec. If it is the of the words was presented in lowercase letters. On these case that there are differences in the neural mechanisms trials, the individualswere instructedthat this changeshould underlying the formation and realization of intentions be ignored and that a semantic judgment should be made. over short and long delays, the results of the present study In West et al. (2001), we reasoned that if noticing were should be considered to be most representative of those relativelyautomatic and sensitive to data-driveninfluences, mechanisms supporting prospective remembering over such as the change in letter case, it would be reflected by relatively brief delays. modulationsof the ERPs that differentiated PM cue trials McDaniel and Einstein (1992) have proposed that the and PM lure trials from ongoing activity trials. We also realization of an intentionduring the performance interval reasoned that search would be associated with modula- arises through the interaction of multiple component tions of the ERPs that differentiated PM cue trials from processes. These include a prospective component that PM lure trials and ongoingactivitytrials, becausea prospec- supports the recognition of a PM cue and a retrospective tive response would be required only on PM cue trials. In component that supports recovery of the intended action two experiments, detection of the PM cue was associated from memory. The results of recent behavioral studies with a phasic negativity (N300) that was broadly distrib- have demonstrated that these two aspects of PM can be uted over the occipital-parietalregionof the scalp, peaked dissociated. In one study, the prospective component was around 300 msec after stimulus onset, and differentiated influenced more strongly by a change in the perceptual PM cue and PM lure trials from ongoing activitytrials. In characteristics of the PM cue from formation of the in- contrast, realization of the intentionwas associated with a tentionto presentationof the cue than by the degree of se- more sustained parietal-positivity–right-frontal-negativity mantic relatedness between the PM cue and the intention (late positivecomplex, or LPC). The amplitudeof the LPC (Cohen, West, & Craik, 2001). In contrast, the retrospec- was greater for PM cue trials than for PM lure or seman- tive component was influenced more strongly by the de- tic judgment trials (West et al., 2001). gree of semantic relatedness between the PM cue and the We also observed that the amplitude of the N300 was intentionthan by a change in the perceptualcharacteristics modulatedby the intentionto make a prospectiveresponse. of the PM cue from formation of the intention to presen- This finding seemed somewhat inconsistentwith the idea tation of the cue. These findings led to the proposal that that noticing is a data-driven process (Einstein & Mc- the prospectivecomponentmay be most sensitive to data- Daniel, 1996) and led to the suggestion that the detection driven influences and that the retrospective component of a PM cue may be achievedthrough the attentionalmod- may be most sensitive to conceptually driven influences ulation of those neural systems that support processing of (Cohen et al., 2001; Einstein & McDaniel, 1996). the defining features of the PM cue (West et al., 2001).This This proposal is consistent with the noticing 1 search proposal was based on extensive evidence indicating that model of PM (Einstein