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2 MILLET ET AL.Downloaded By: [Millet, Xavier] At: 10:57 4 November 2009relevance of such distinction in AD and have reported thatAD patients exhibited normal priming in identificationtasks and diminished priming performances in productiontasks (Fleischman et al., 2001; Gabrieli et al., 1999).Among the variety of tasks used to investigate implicitmemory in normal aging and AD, word-stem completionpriming (Warrington & Weiskrantz, 1974) is incontestablythe most frequently used. In this task,participants are given a three-letter beginning word-stemand are asked to evoke the first word that comes to mind.A priming effect is reflected by a higher probability tocomplete the word stems with the previously studiedwords than with new (unstudied) words. According tothe perceptual–conceptual distinction, word-stemcompletion that is perceptually driven should be consideredas a perceptual priming task (Roediger et al., 1989)and thus should not be affected in AD. On the contrary,the identification–production distinction would predictimpaired word-stem completion priming in AD since thetask requires production processes involving the competitionbetween multiple alternative responses (Fleischmanet al., 2001; Gabrieli et al., 1999). Regarding the availableresults, the number of studies reporting reducedword-stem completion priming and the number ofstudies reporting no impairment appear approximatelyequivalent. In attempts to clarify such discrepancy, twometa-analyses assessed the integrity of word-stemcompletion priming in AD (Meiran & Jelicic, 1995;Russo & Spinnler, 1994). Both concluded that wordstempriming is affected in AD. However, followingthese meta-analyses, numerous studies provided inconsistentresults (Arroyo-Anllo, Ingrand, Neau, Aireault,& Gil, 2004; Beauregard, Chertkow, Gold, & Bergman,2001; Cacho Gutierrez, Garcia Garcia, & FernandezCalvo, 2000; Camus et al., 2003; Carlesimo et al., 1999;Deweer et al., 1994; Downes et al., 1996; Fleischmanet al., 1997; Koivisto, Portin, Seinela, & Rinne, 1998;Kuzis et al., 1999; Park et al., 1998; Pasquier, Grymonprez,Lebert, & Van der Linden, 2001).Methodological variations have been proposed toexplain the discrepancy of word-stem completionpriming results in AD (Fleischman & Gabrieli, 1998). Inparticular, variability in encoding conditions could be agood candidate. Indeed, while word-stem completionstudies in AD generally share equivalent implicit testphaseprocedures, the instructions delivered at encodingwere considerably different. The participants could berequested to respond whether the word contains a particularletter (Gabrieli et al., 1994, 1999), to pronouncethe letter corresponding to a numerical position (Scott,Wright, Rai, Extern-Smith, & Gardiner, 1991), or tocount the number of vowels (Carlesimo et al., 1999) orsyllables (Kuzis et al., 1999) within the target word.Encoding phase instructions could also lead participantsto read words aloud (Dick, Kean, & Sands, 1989;Downes et al., 1996; Fleischman et al., 1997; Gabrieli et al.,1999; Huberman, Moscovitch, & Freedman, 1994;Keane et al., 1991; Koivisto et al., 1998; LaVoie &Faulkner, 2008) or silently (Beauregard et al., 2001) or torate on a scale whether they liked or disliked a word orwhether the words are pleasant or unpleasant (Bäckman,Almkvist, Nyberg, & Andersson, 2000; Bondi &Kaszniak, 1991; Carlesimo et al., 1998, 1999; Fleischmanet al., 1999; Pasquier et al., 2001; Randolph, 1991;Shimamura, Salmon, Squire, & Butters, 1987). Otherconditions putting emphasis on the meaning of the wordrequired participants to generate words from a givendefinition (Fleischman et al., 1999; Fleischman et al.,1997) or from a related word (Scott et al., 1991), or tocomplete a sentence with single word endings (Grosse,Wilson, & Fox, 1990). Moreover, participants could alsobe requested to provide correct definition of words(Burke, Knight, & Partridge, 1994; Carlesimo et al.,1999; McGeorge, Taylor, Della Sala, & Shanks, 2002;Partridge, Knight, & Feehan, 1990; Russo & Spinnler,1994) or answer “yes or no” to questions relying onsemantic knowledge on a particular word (Beauregardet al., 2001; Gabrieli et al., 1994, 1999).As may be seen, the instructions given to participantsat the encoding phase are particularly heterogeneous. Itcan be hypothesized that the nature of processes thatoperate during encoding influences the magnitude oflater implicit retrieval in AD patients. The effect ofencoding manipulation on implicit memory tasks hasbeen widely debated with numerous studies concludingthat little or no effect of level of processing could bereported in completion priming tasks (e.g., Challis,Velichkovsky, & Craik, 1996; Graf, Mandler, & Haden,1982; Roediger, Weldon, Stadler, & Riegler, 1992).Some studies in AD reported similar results (Beauregardet al., 2001; Burke et al., 1994; Fleischman et al., 1999;Fleischman et al., 1997; Russo & Spinnler, 1994; Scott et al.,1991). On the other hand, a significant effect of conceptualself-generation processes has been repeatedlyreported on word-fragment (Gardiner, 1988; Schwartz,1989) and word-stem (Bassili, Smith, & MacLeod, 1989;Carlesimo, 1994; Carlesimo et al., 1999) completiontasks. Thus, word-stem completion priming could alsobe regarded as a conceptual priming task. Moreover,when meta-analyses on implicit memory tasks includingword-stem completion priming consider encodingmanipulation, a constant advantage of deep over shallowprocessing is reported (Brown & Mitchell, 1994;Challis & Brodbeck, 1992). In AD, some studies evidencingnormal word-stem completion priming performancesfollowing semantic generation supported the conclusionthat an elaborate conceptual encoding condition may benecessary for AD patients to facilitate word-stem completionpriming (Grosse et al., 1990; Partridge et al.,1990). Moreover, Maki and Knopman (1996) evidencedthat AD patients exhibited intact generation primingonly in the situation involving elaborative conceptualgeneration of items whatever the perceptual or conceptualnature of the retrieval procedure. The authors concludedfor the necessity of reinstating at retrieval thespecific operation initially required at encoding phase toimprove priming performances in AD, consistently withthe latest model by Roediger, Gallo, and Geraci (2002)providing a more procedural approach of memory.Thus, it can be hypothesized that considering the natureof encoding condition could contribute to clarify wordstemcompletion priming performances in AD.