Event-related brain potential examination of implicit memory processes: Masked and unmasked repetition priming.

The proposition that cortically based perceptual representation systems (PRSs) are responsible for some implicit priming phenomena was examined by using event-related potentials (ERPs) in repetition and masked word priming. Experiment 1 used an explicit recognition task, in which repeated words replicated previous ERP repetition priming effects, whereas masked repetition priming revealed a new ERP effect with a posterior topography. Experiment 2 demonstrated ERP and behavioral priming in a lexical decision task for repetition and masked repetition priming. Topographical mapping of ERP repetition priming effects involved both early and late effects over the right and left anterior regions, whereas masked priming produced only an early ERP effect posteriorly. These results suggest differences between early and late ERP priming effects in terms of explicit recollection. Moreover, a posterior PRS may not be involved in some longer term implicit repetition priming effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual implicit memory performance in Alzheimer's disease.

Alzheimer's disease (AD) patients often exhibit deficits on conceptual implicit memory tests such as category exemplar generation and word association. However, these tests rely on word production abilities, which are known to be disrupted by AD. The current study assessed conceptual implicit memory performance in AD patients and elderly control participants using a conceptual priming task that did not require word production (i.e., semantic decision). Memory performance was also examined using a category exemplar generation test (i.e., a conceptual priming task that required word production) and a recognition memory test. AD patients exhibited deficits on the semantic decision task, the category exemplar generation task, and the recognition memory task. The results indicate that the conceptual memory deficits observed in AD patients cannot be attributed completely to word production difficulties. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic priming and repetition priming from masked words: Evidence for a center-surround attentional mechanism in perceptual recognition.

Two lexical decision experiments compared semantic and repetition priming by masked words. Experiment 1 established prime–mask stimulus onset asynchronies (SOAs) with presence–absence detection judgments. Primes presented at detection-threshold SOAs produced equal facilitation for repeated and semantically related targets: 26 ms and 24 ms. Experiment 2 established SOAs with semantic judgments. Primes presented at 70% of the semantic-threshold SOA to mimic the exposure conditions of Experiment 1 produced slightly greater facilitation for repeated targets but a tendency toward inhibition for semantically related targets: 38 ms and –6 ms. These results confirm the D. Dagenbach et al (see record 1990-00392-001) report that strategies induced by threshold-setting tasks can influence masked priming. In addition, Experiment 2 suggests a mechanism for retrieving weakly activated semantic codes into consciousness that relies on the center-surround principle to enhance activation of sought-for codes and to inhibit related codes stored nearby in the semantic network. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact text-specific implicit memory in patients with Alzheimer's disease.

The ability of patients with Alzheimer's disease (AD) to acquire and retain text-specific knowledge was investigated in a rereading study. Ten AD patients (aged 59–84 yrs) and 10 normal control Ss read 2 passages 3 times, each as quickly as possible, and answered recognition memory questions after the 3rd reading of each passage. The AD patients had poor explicit memory as evidenced by impaired recognition memory for the passages. In contrast, normal decreases in the times required for successive readings of each passage for AD patients indicated intact implicit memory for the passages. The absence of facilitation across passages indicated that the rereading effect was text specific, suggesting that AD patients may retain the ability to form certain kinds of implicit new associations. Alternative accounts of the mechanism underlying text-specific priming, and of the nature of intact and impaired implicit memory in AD, are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Primed numbers: Exploring the modularity of numerical representations with masked and unmasked semantic priming.

In Experiment 1, participants classified a 1st number (prime) as smaller or larger than 5 and then performed the same task again on a 2nd number (target). In Experiment 2, participants classified a target number as smaller or larger than 5, while unknown to them a masked number was displayed for 66 ms prior to the target. Primes and targets appeared in Arabic notation, in verbal notation, or as random dot patterns. Two forms of priming were analyzed: quantity priming (a decrease in response times with the numerical distance between prime and target) and response priming (faster responses when the prime and target were on the same side of 5 than when they were not). Response priming transferred across notations, whereas quantity priming generally did not. Under conditions of speeded processing, the internal representation of numerical quantities seems to dissociate into multiple notation-specific subsystems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of priming in text rereading: intact implicit memory for new associations in older adults and in patients with Alzheimer's disease

The contributions of text meaning, new between-word associations, and single-word repetition to priming in text rereading in younger and older adults, and in patients with Alzheimer's disease. (AD), were assessed in Experiment 1. Explicit recognition memory for text was also assessed. Equivalent single-word and between-word priming was observed for all groups, even though patients with AD showed impaired explicit memory for individual words in the text. The contribution of generalized reading task skill to priming in meaningless text rereading in younger adults was assessed in Experiment 2. Generalized reading task skill was also found to contribute to priming. These results reveal 3 mechanisms of priming: new between-word associations for meaningful and meaningless text, individual word repetition for meaningless text, and general task or skill factors for meaningless text. All priming mechanisms appear to be intact in older adults and in patients with AD.     

Repetition priming in normal aging and Alzheimer's disease: A review of findings and theories.

On repetition priming tasks, memory is measured indirectly as a change in performance due to recent experience. It is often functionally and neurally dissociated from performance on explicit memory tasks, which directly measure conscious recall or recognition of recent events. Repetition priming has therefore been extensively studied in normal aging and Alzheimer's disease, which feature mild to severe changes in explicit memory. Initial studies indicated that repetition priming was immune to the effects of aging and greatly reduced in Alzheimer's disease (AD). As more studies have been performed, however, these initial conclusions appear less clear than before and, in the case of AD, actually misleading. The purpose of this article is to provide a comprehensive review of this rapidly expanding literature, articulate the issues that are critical to interpreting the empirical results, and discuss what new conclusions are suggested by the overall pattern of findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast effects in priming paradigms: Implications for theory and research on implicit attitudes.

Contrast effects have been studied in dozens of experimental paradigms, including the measurement of attitudes in the social psychological literature. However, nearly all of this work has been conducted using explicit reports. In the present research the authors employed a variety of different types of priming tasks in order to gain insight into the nature of contrast effects and the role that automatic processes might play in their emergence. They report 6 experiments. In Experiments 1 and 2 the replicability and robustness of automatized contrast effects across 2 types of implicit tasks are established. Experiments 3–6 were conducted in order to further understand the nature of these effects and whether they are best understood in terms of spreading activation vs. response-based models of priming. In the course of accounting for their findings, the authors propose and validate a response-mapping framework, which provides insight into some longstanding ambiguities in the priming literature. Implications for theories of contrast and models of evaluative priming are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of aging and Alzheimer's disease on conceptual implicit and explicit memory.

The effects of aging and Alzheimer's disease (AD) on conceptual explicit and implicit memory were examined. Three groups of participants patients with AD; age-matched, older control participants; and younger control participants made deep (semantic) or shallow (nonsemantic) judgments about low-dominant category exemplars. Explicit memory was measured by category cued recall and implicit memory was measured by priming on a category-exemplar generation task. Younger participants had enhanced cued recall and priming following deep, relative to shallow, encoding; this indicated that both memory measures were conceptually driven. Aging reduced explicit, but not implicit, test performance, and it did not reduce conceptually driven processes for either test. In contrast, AD reduced explicit and implicit test performance, and it impaired conceptually driven memory processes for both tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for multiple mechanisms of conceptual priming on implicit memory tests.

The authors examined effects of encoding manipulations on 4 conceptual implicit memory tasks: word-cued association, category-cued association, category verification, and abstract concrete classification. Study-phase conceptual elaboration enhanced priming for word-cued association with weakly associated words (Experiment 3), and for category-cued association with high- and low-dominance exemplars (Experiments 4 and 5), but did not enhance priming for word-cued association with strongly associated words (Experiments 1 and 2), for category verification with high- and low-dominance exemplars (Experiment 5), or for abstract/concrete classification (Experiment 7). Forms of priming that were unaffected by conceptual elaboration were not mediated by perceptual processes because they were unaffected by study-test modality changes (Experiments 6 and 8). The dissociative effects of conceptual elaboration on conceptual-implicit tasks suggest that at least 2 dissociable mechanisms mediate conceptual priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can “pure” implicit memory be isolated? A test of a single-system model of recognition and repetition priming.

[Correction Notice: An erratum for this article was reported in Vol 65(1) of Canadian Journal of Experimental Psychology/Revue canadienne de psychologie expérimentale (see record 2011-05804-006). In the article there was an error in Equation B2 in Appendix B.] Implicit memory is widely regarded as an unconscious form of memory. However, evidence for what is arguably a defining characteristic of implicit memory—that its contents are not accessible to awareness—has remained elusive. Such a finding of “pure” implicit memory would constitute evidence against a single-system model of recognition and priming that predicts that priming will not occur in the (true) absence of recognition. In three experiments, using a rapid serial visual presentation procedure at encoding, we tested this prediction by attempting to replicate some previous studies that claimed to obtain pure implicit memory. We found no evidence of priming in the absence of recognition; instead, priming and recognition were associated across experiments: when priming was absent, recognition was also absent (Experiments 1 and 2), and when priming was reliably greater than chance, recognition was similarly greater than chance (Experiment 3). The results are consistent with the prediction of a single-system model, which was fit to the data from all the experiments. The results are also consistent with the notion that the memory driving priming is accessible to awareness. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Limitations of the distinctions between conceptual and perceptual implicit memory: A study of Alzheimer's disease.

Previous studies suggested that perceptual implicit memory is spared in Alzheimer's disease (AD) but conceptual implicit memory is not. This dissociation is often invoked to support views of implicit memory that distinguish between perceptual and conceptual processing or systems. This study investigated an alternate hypothesis: that methodological differences between perceptual and conceptual implicit tests could account for differences in performance. Fourteen AD participants, 16 elderly controls, and 16 younger controls participated in structurally parallel conceptual and perceptual tests of implicit memory that required production of studied items. Results showed normal perceptual and conceptual priming when participants with AD generated items at study but impaired priming in both tests when they merely repeated items. These results are inconsistent with both systems and processing views of implicit memory and suggest that similarity of study and test procedures is more important than the inferred theoretical construct. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistent repetition priming in picture naming and its dissociation from recognition memory.

The current experiments investigated the longevity of repetition priming and dissociations between different memory measures. Picture-naming latencies revealed robust repetition priming in four separate studies: Previously named pictures were named faster than new pictures. The magnitude of this naming facilitation was stable across 1 to 6 weeks. The apparent temporal invulnerability of repetition priming was in marked contrast to the decline in episodic recognition memory across 6 weeks, suggesting a dissociation between implicit and explicit memory. Additional evidence of this dissociation was observed within each session: Naming facilitation for repeated pictures occurred regardless of whether those particular pictures were consciously recognized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Episodic effects on picture identification: Implications for theories of concept learning and theories of memory.

The effects of differences in study processing on free recall of picture names and on generalization in picture identification were investigated. Experience with degraded pictures produced poorer subsequent free recall of picture names than did naming intact pictures. For the test of picture identification, pictures that were identical to a studied picture, pictures that shared a name with a studied picture (same name), and new test pictures were presented, and the amount of clarification required to identify a picture was measured. Experience with degraded pictures produced better subsequent identification of identical test pictures but poorer later identification of same-name test pictures than did naming intact pictures. The importance of these episodic effects for theories of concept learning and theories of memory is discussed. It is argued that distinctions between memory systems (e.g., episodic-semantic) must be couched in terms of a theory of concept learning and that the data are inconsistent with a simple distinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociative effect of massed repetition on implicit and explicit measures of memory.

Ss saw or heard words presented once, or repeated 4 or 16 times in massed fashion, and then received an implicit or explicit memory test. Massed repetition did not increase priming on word fragment completion beyond that obtained from a single presentation but did enhance performance on various explicit tests (free recall, recognition, question cued recall, and word fragment cued recall) and an implicit general knowledge test. Modality of presentation affected implicit and explicit word fragment cued tests but did not affect performance on any of the other tests. Levels of processing affected performance on implicit and explicit question cued tests. These results are consistent with a transfer appropriate processing account of dissociations among memory measures and imply that massed repetition promotes conceptual processing but does not entail a repetition of perceptual-based processes responsible for priming on word fragment completion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition memory and familiarity judgments in severe amnesia: No evidence for a contribution of repetition priming.

The amnesic patient E.P. has demonstrated normal levels of repetition priming and at-chance recognition performance (S. B. Hamann & L. R. Squire, 1997), suggesting that the sense of familiarity used to make a recognition memory judgment is not based on the same mechanism responsible for repetition priming. However, the recognition tests previously used may have discouraged the use of familiarity and encouraged reliance on episodic memory. This issue was addressed in 5 experiments with E.P., 3 other amnesic patients with hippocampal damage, and 8 healthy controls. In Experiments 1–3, which were designed to discourage the use of episodic memory, the amnesic patients were impaired and E.P. performed at chance. In Experiments 4 and 5A, a stem-completion priming task was combined with a recognition memory task on each trial. E.P.'s priming was intact, yet his recognition memory performance was at chance. This suggests that although recognition memory judgments may be made on the basis of familiarity, repetition priming is not the source of this feeling of familiarity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of repetition priming on recognition memory: Testing a perceptual fluency-disfluency model.

Five experiments explored the effects of immediate repetition priming on episodic recognition (the "Jacoby-Whitehouse effect") as measured with forced-choice testing. These experiments confirmed key predictions of a model adapted from D. E. Huber and R. C. O'Reilly's (2003) dynamic neural network of perception. In this model, short prime durations pre-activate primed items, enhancing perceptual fluency and familiarity, whereas long prime durations result in habituation, causing perceptual disfluency and less familiarity. Short duration primes produced a recognition preference for primed words (Experiments 1, 2, and 5), whereas long duration primes produced a preference against primed words (Experiments 3, 4, and 5). Experiment 2 found prime duration effects even when participants accurately identified short duration primes. A cued-recall task included in Experiments 3, 4, and 5 found priming effects only for recognition trials that were followed by cued-recall failure. These results suggest that priming can enhance as well as lower familiarity, without affecting recollection. Experiment 4 provided a manipulation check on this procedure through a delay manipulation that preferentially affected recognition followed by cued-recall success. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lexical semantic and associative priming in Alzheimer's disease.

Semantic memory impairment was investigated in patients with probable Alzheimer's disease (AD) using a threshold oral word reading task to assess priming of different lexical relationships. Healthy elderly controls showed significant priming for associatively related nouns (tempest-teapot) and also for nouns semantically related either because both designate basic-level exemplars of a common superordinate category (cousin-nephew) or because the target names the superordinate category of the prime (daughter-relative). AD patients, in contrast, showed preserved priming of lexical associates but impaired priming of certain semantic relationships. They showed no priming between words designating coordinate exemplars within a category, despite preserved priming of the superordinate category label. Findings are consistent with the view that at least part of the semantic deficit in AD is due to disruption of semantic knowledge that affects relationships among basic-level concepts, more than the relationships between these concepts and their corresponding superordinate category of membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information processing for masked and unmasked stimuli in schizophrenia and old age.

Compared 36 hospitalized schizophrenics, depressives, and normal elderly Ss (mean ages 24.7, 31.8, and 67.5 yrs) on tasks involving the identification of briefly exposed masked and unmasked stimuli. The critical stimulus duration (CSD), defined as the minimum exposure required to consistently identify a target stimulus without a mask, was obtained for each S. The target stimulus was followed by a pattern mask. Masking functions were estimated at 3 levels of exposure duration, including the S's CSD. At each exposure duration the mask followed at 4 interstimulus intervals. The elderly required longer durations for criterion identification of unmasked stimuli than the other Ss. For masked stimuli, however, the elderly did not differ from depressed inpatients, and both of these groups exceeded the schizophrenics when the test stimulus was exposed at Ss' CSD. Results indicate that when the initial availability of input information is controlled, schizophrenics show a mask-induced deficit relative to depressed inpatients, but the elderly do not. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)