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Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:32 29 September 2008& Lipton, 1997; Petersen, Smith, Ivnik, Kokmen,& Tangalos, 1994; Tounsi et al., 1999; Traykovet al., 2005). This pattern of performance in ADhas been interpreted as the consequence of encodingprocesses deficiency (Pasquier et al., 2001;Pillon et al., 1993), in accordance with resultsobtained with other memory tests (e.g., Greene,Baddeley, & Hodges, 1996).Nevertheless, considering implicit and explicitfeatures of retrieval may be important to investigatethe nature of memory decline in AD. Whereasexplicit recall refers to conscious and deliberaterecovery of past experiences, implicit recall is characterizedby spontaneous and nonconscious waysto access stored information (Graf & Schacter,1985). In particular, priming phenomena reflectthe impact of prior experience in the form of processingfacilitation without conscious rememberingof this experience. Among the various priming paradigms,perceptual priming consists in the repetitionof physically identical items and is modalityspecific (Carlesimo et al., 1999; Verfaellie, Keane,& Johnson, 2000). Numerous studies consistentlyfound a preservation of perceptual repetition primingin AD patients following short delays, particularlyin word identification tasks (Fleischman &Gabrieli, 1998; Fleischman et al., 1995, 2005;Keane, Gabrieli, Fennema, Growdon, & Corkin,1991; Keane, Gabrieli, Growdon, & Corkin, 1994;Koivisto, Portin, & Rinne, 1996; Russo &Spinnler, 1994).While numerous studies addressed short-termpriming in AD, whether such priming effectremains following long-lasting intervals has receivedless attention. A few studies using different paradigmscontributed to the suggestion that primingmagnitude in AD patients diminishes over time ata faster rate than in normal elderly adults. The tasksused included homophone spelling (Fennema-Notestine, Butters, Heindel, & Salmon, 1994), nonverbalstimuli discrimination (Heindel, Salmon,Fennema-Notestine, & Chan, 1998), picture naming(Mitchell & Schmitt, 2006), word fragmentcompletion (Heindel, Cahn, & Salmon, 1997), andlexical decision (Schnyer, Allen, Kaszniak, &Forster, 1999) procedures. The delay used also variedsubstantially across the studies. In the metaanalysison implicit memory in AD by Meiran andJelicic (1995), among the 17 studies using wordbasedperceptual priming, only 3 used a study–testdelay longer than 10 minutes. Thus, the authorsconsidered a delay of 10 minutes or more as a longtermdelay. This study–test delay proved to be usefulin evidencing differences between AD and controls,since AD patients’ performances in word-basedperceptual priming only differed from that ofLONG-TERM PRIMING IN ALZHEIMER’S DISEASE 829controls after a 10-minute delay. Nonetheless,Ostergaard (1994) used a noteworthy long-termpriming procedure in two word identificationtasks. Experimental conditions varied according tothe number of initial exposures with stimuli (onevs. multiple exposures) and according to the recalldelay. Whereas repetition priming in AD was compromisedafter a 10-minute delay in the conditioninvolving a single presentation of the target stimuli,a significant priming effect could be evidencedin the condition involving multiple presentations.Thus, repeated exposures with the material duringthe encoding phase appeared to strengthen memorytrace and facilitate incidental retrieval in ADpatients.Therefore, the status of long-term priming abilitiesin AD remains unclear. In this study, we comparedthe delayed recall performances of mild tomoderate AD patients and elderly controls accordingto different procedures of retrieval. We firstadministered the FCSR test involving three freeand cued recall trials, a recognition task, and adelayed recall. Finally, after an additional 30-minute delay, participants were submitted to acomputerized word identification task that consistedof identifying as quickly as possible a seriesof words comprising the words presented duringthe FCSR test and new words. A 30-minute delaywas used in order to decrease the likelihood ofexplicit contamination in normal controls (e.g.,Toth, Reingold, & Jacoby, 1994). The evidence ofsignificant priming performances in AD patientswould suggest the persistence of a memory traceafter a long-lasting delay.ParticipantsMETHODWe included 20 patients (ages ranged from 60 to84 years) meeting NINCDS-ADRDA (NationalInstitute of Neurological and Communicative Disordersand Stroke–Alzheimer’s Disease andRelated Disorders Association) criteria (McKahnet al., 1984) for probable AD. Characteristics ofthe participants are shown in Table 1. Patientswith a history of severe head injury (loss of consciousnessfor more than 48 hours), alcoholism,and depressive symptomatology were excluded.All the patients scored 20 or higher in the Mini-Mental State Examination (MMSE; Folstein,Folstein, & McHugh, 1975). We also included 20elderly controls (ages ranged from 60 to 84 years)matched with the AD group for age, sex, and levelof education. None of them manifested any sign of