Level-of-processing effects in word-completion priming: A neuropsychological study.

Recent reviews (A. S. Brown & D. B. Mitchell, see record 82:16176; B. Challis & D. R. Brodbeck, see record 79:30007) concluded that level-of-processing (LOP) manipulations affect priming in perceptual tasks, contrary to earlier suggestions that such tasks are insensitive to LOP. In 3 experiments with amnesic patients and control Ss, the authors examined the effect of LOP manipulations on priming in word-stem and word-fragment completion and on recognition memory. Amnesic patients exhibited reduced or near-zero LOP effects in word-completion priming compared with controls. LOP affected recognition memory for both amnesic patients and control Ss, confirming that the LOP manipulation affected explicit memory. When the effect of explicit retrieval on control performance was reduced by using a low-level encoding task, priming was the same for amnesic patients and controls. The authors suggest that LOP effects in word-completion priming tasks reflect the influence of explicit retrieval, which can be used usefully by control Ss but much less so by amnesic patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paired-associate learning and priming effects in amnesia: A neuropsychological study.

Conducted 4 experiments investigating the role of priming effects in paired-associate learning. Ss for all 4 experiments were 5 male and 3 female alcoholics (mean age 53.8 yrs; WAIS—R IQs 85–203) with Korsakoff syndrome. Control Ss were 26 male alcoholics (mean age 47.6 yrs). Exp I illustrated the distinction between the memory impairment of amnesic (Korsakoff) Ss and their intact priming ability. In Exp II, amnesic Ss showed good paired-associate learning for related word pairs but controls performed significantly better. Exp II also showed that the forgetting of related word pairs by amnesic Ss followed the same time course as the decay of word priming. Exp III showed that amnesic Ss were as good as controls at learning related word pairs when word-association tests were used. Exp IV showed that amnesic Ss exhibited normal priming when they were asked to free associate to words that were semantically related to previously presented words. Results indicate that both priming effects and paired-associate learning of related words depended on activation, a process that is preserved in amnesia. Activation is a transient phenomenon presumed to operate on and facilitate access to preexisting representations. (67 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact and long-lasting repetition priming in amnesia.

In 2 experiments, the ability of amnesic patients to exhibit long-lasting perceptual priming after a single exposure to pictures was evaluated. Ss named pictures as quickly as possible on a single occasion and later named the same pictures mixed with new pictures. In Exp 1, amnesic patients exhibited fully intact priming effects lasting at least 7 days. In Exp 2, the priming effect for both groups was shown to depend on both highly specific visual information and on less visual, more conceptual information. In contrast, recognition memory was severely impaired in the patients, as assessed by both accuracy and response time. The results provide the 1st report of a long-lasting priming effect in amnesic patients, based on a single encounter, which occurs as strongly in the patients as in normal Ss. Together with other recent findings, the results suggest that long-lasting priming and recognition memory depend on separate brain systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of intellectual deterioration on retention deficits in amnesic alcoholics.

The performance of matched groups of alcoholic Korsakoff's syndrome patients, amnesic alcoholics with intellectual deterioration, and nonamnesic alcoholic control patients was assessed on three experimental memory tests. On a task measuring rate of short-term forgetting, the Korsakoff's syndrome and demented groups were found to have equivalent forgetting rates and both showed significantly more rapid decay than the control group. The Korsakoff's syndrome and demented groups also performed similarly on a task designed to assess semantic encoding deficits by examining sensitivity to, and release from, proactive interference. In a third experiment, the findings of Graf, Squire, and Mandler (1984) were replicated, with both the amnesic and demented groups having normal semantic priming performance on word completion test. Again, no difference was found between the two amnesic groups on verbal free- and cued-recall tasks. These results suggest that the contribution of concurrent intellectual deterioration to the poor performance of alcoholic Korsakoff's syndrome patients on verbal retention tasks may not be as great as has been assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual thresholds and priming in amnesia.

The widely accepted idea that perceptual priming is intact in amnesia was challenged recently by the suggestion that perceptual identification (PID) thresholds are elevated in amnesia and that this impairment could mask a priming deficit by artificially inflating priming scores. The authors examined the PID thresholds of amnesic patients across a wide range of stimulus conditions and accuracy levels. Baseline thresholds and priming effects were fully intact for all amnesic patients except in a condition using small stimuli (1.1"?×?0.25" of visual angle). In that condition, only the patients with Korsakoff's syndrome were impaired. Accordingly, elevated perceptual thresholds are not a necessary consequence of amnesia, and normal priming in amnesia is not an artifact of threshold differences. The results support the conclusion that priming is independent of the brain structures important for declarative memory that are damaged in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the semantic networks in patients with dementia and amnesia.

The semantic networks of 13 patients with Alzheimer's disease (AD), 13 patients with Huntington's disease (HD), 8 amnesic (AM) patients, and 26 controls were generated by multidimensional scaling and Pathfinder analyses of their responses on a triadic comparison task. The semantic networks of HD and AM patients were essentially normal, whereas the networks of AD patients were deviant in a number of ways. The AD patients' networks were dominated by a different dimension, had fewer common links, and consisted of associations of atypical strength. These results suggest that structural alteration of semantic networks is characteristic of Alzheimer's disease and is not evident in all forms of dementia and amnesic conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive impairment following frontal lobe damage and its relevance to human amnesia.

Whether frontal lobe pathology can account for some of the cognitive impairment oberved in amnesic patients with Korsakoff's syndrome was investigated. Various cognitive and memory tests were given to patients with circumscribed frontal lobe lesions, patients with Korsakoff's syndrome, non-Korsakoff amnesic patients, and control Ss. Patients with frontal lobe lesions were not amnesic. Nevertheless, they exhibited 2 deficits that were also exhibited by patients with Korsakoff's syndrome but not by other amnesic patients: (a) impairment on the Wisconsin Card Sorting Test and (b) impairment on the Initiation and Perseveration subscale of the Dementia Rating Scale. Thus, frontal lobe pathology can explain some of the cognitive deficits observed in patients with Korsakoff's syndrome. (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)     

Semantic homophone priming in patients with dementia of the Alzheimer's type.

To examine the role of semantic processes in the verbal priming deficits of patients with dementia of the Alzheimer type (DAT), 15 DAT patients, 8 amnesic patients, and 12 controls were administered a homophone spelling bias task. Ss' spellings were biased against their previously preferred homophone spellings by presenting the homophones aurally in a semantically related context. The results showed that DAT patients were not significantly different from controls or amnesic patients on the immediate priming measure. However, both patient groups' semantic priming effects decayed more rapidly and their recognition performance was significantly impaired in relation to those for control Ss. These results suggest that DAT patients can perform normally on some semantic priming tasks if the task demands are within the capacity of the patients' remaining intact semantic structure and if the delay between presentations is brief. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired priming of new associations in amnesia.

We assessed priming of new associations in amnesic patients and healthy control subjects in a paradigm developed by P. Graf and D. L. Schacter (see record 1986-12203-001). Subjects were presented unrelated word pairs embedded in sentences (e.g., A BELL was hanging over the baby's CRADLE) and were asked to rate how well the sentences related the two words. Subjects were then given a word completion test. They were shown three-letter word stems and were asked to complete the stem with the first word that came to mind. In the same context condition, each word stem was presented together with the word that had appeared in the same sentence during study (e.g., BELL-CRA ). In the different context condition, each stem was presented together with a new word that had never been presented (e.g., APPLE-CRA ). Control subjects completed more words in the same context condition than in the different context condition. In contrast, amnesic patients did not complete any more words in the same context condition than in the different context condition. Indeed, across two experiments none of the amnesic patients exhibited consistent priming of new associations. Thus, although amnesic patients do exhibit entirely normal priming of preexisting memory representations, they do not appear to exhibit priming of new associations in this paradigm. (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)     

Implicit/explicit memory dissociation in Alzheimer's disease: The consequence of inappropriate processing?

Dual-process theories of recognition posit that perceptual fluency contributes to both familiarity-based explicit recognition and perceptual priming. However, the priming-without-recognition dissociation, as observed through the intact mere exposure effect and impaired recognition in patients with Alzheimer's disease (AD), might indicate that familiarity and perceptual priming are functionally distinct. This study investigated whether the AD patients' processing strategies at testing may explain this priming-without-recognition dissociation. First, we replicated the priming-without-recognition effect in 16 patients who exhibited intact exposure effects despite null recognition. Second, we showed that, under identical conditions, inducing a holistic processing strategy during recognition testing increased AD patients' recognition--performance was similar for AD patients and healthy control participants. Furthermore, prompting analytic processing during both priming and recognition tasks decreased AD patients' performance in both tasks. These findings suggest that the extent to which AD patients use perceptual fluency in priming and recognition tasks is contingent on their processing approach. The choice of processing strategy may depend on how difficult patients perceive the task to be. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Role of Color in the Implicit Memory Performance of Healthy Older Adults and Individuals With Alzheimer's Disease.

Although the Alzheimer's disease (AD) patients in this study were severely impaired in recognition performance, their naming performance demonstrated normal priming across transformations in object color. This is evidence for preserved implicit shape-based memory performance in AD patients. For colored-object decision, healthy older adult control participants but not AD patients showed priming for new associations between previously encountered object shapes and colors. The author argues, on the basis of this colored object decision performance, that the deficits present in AD do not allow shape and color to be integrated to form a novel unitized representation that can be used to benefit cognitive performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological dissociations between priming and recognition: A single-system connectionist account.

A key claim of current theoretical analyses of the memory impairments associated with amnesia is that certain distinct forms of learning and memory are spared. A compelling example is that amnesic patients and controls are indistinguishable in repetition priming but amnesic patients are impaired at recognizing the study items. The authors show that this pattern of results is predicted by a single-system connectionist model of learning in which amnesia is simulated by a reduced learning rate. They also demonstrate that the model can reproduce the converse pattern in which priming but not recognition is impaired if the input is assumed to be additionally degraded in a priming test. The authors conclude that dissociations between priming and recognition do not require functionally or neurally distinct memory systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Artificial grammar learning depends on implicit acquisition of both abstract and exemplar-specific information.

The contributions of exemplar-specific and abstract knowledge to artificial grammar learning were examined in amnesic patients and controls. In Experiment 1, grammatical rule adherence and chunk strength exerted separate effects on grammaticality judgments. Amnesic patients exhibited intact classification performance, demonstrating the same pattern of results as controls. In Experiment 2, amnesic patients exhibited impaired declarative memory for chunks. In Experiment 3, both amnesic patients and controls exhibited transfer when tested with a letter set different than the one used for training, although performance was better when the same letter sets were used at training and test. The results suggest that individuals learn both abstract information about training items and exemplar-specific information about chunk strength and that both types of learning occur independently of declarative memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is striatal dopaminergic receptor imbalance responsible for levodopa-induced dyskinesia?

Amnesic patients often exhibit spared priming effects on implicit memory tests despite poor explicit memory. In previous research, we found normal auditory priming in amnesic patients on a task in which the magnitude of priming in control subjects was independent of whether speaker's voice was same or different at study and test, and found impaired voice-specific priming on a task in which priming in control subjects is higher when speaker's voice is the same at study and test than when it is different. The present experiments provide further evidence of spared auditory priming in amnesia, demonstrate that normal priming effects are not an artifact of low levels of baseline performance, and provide suggestive evidence that amnesic patients can exhibit voice-specific priming when experimental conditions do not require them to interactively bind together word and voice information.     

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)     

Effects of spacing and repetition on amnesic patients' performance during perceptual identification, stem completin, and category exemplar production.

The effects of repetition and spacing of repetitions on amnesic patients' implicit task performance was studied. Amnesic patients and control participants performed a perceptual identification task, a word-stem completion task, and a category exemplar production task after the presentation of target words repeated within a list. Repetition proved to have no effect on perceptual identification or on word-stem completion, but it did play a role in category exemplar production. As expected, the amnesic patients demonstrated normal performance on the perceptual identification and word-stem completion tasks. However, on category exemplar production, the amnesic patients' performance was significantly below that of the control participants, and the 2 groups differentially responded to repetition. The normal control participants' spontaneous ability to analyze semantic features of words led to unconscious priming of the category and its links to the exemplars after only one presentation of a word. Amnesic patients. on the other hand, seemed to rely more on the fluency produced by multiple presentations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An event-related potential examination of masked and unmasked repetition priming in Alzheimer's disease: Implications for theories of implicit memory.

Fifteen patients diagnosed with Alzheimer's disease (AD) and 26 matched older controls engaged in a lexical-decision task with a list of words and nonwords while event-related brain potentials (ERPs) were recorded. Two repetition conditions were embedded in the list: words repeated at relatively long lags or words repeated shortly after a brief masked presentation. Although older controls displayed behavioral and ERP repetition priming for words repeated at long lags, consistent with previous studies, AD patients displayed neither. In contrast, both controls and AD patients displayed an ERP repetition priming effect for words repeated shortly after a brief masked presentation. ERP priming effects for masked and unmasked repetition differed in older controls, and additionally, the ERP masked priming effect differed between controls and AD patients. Results are discussed in the context of studies that have examined memory performance in brain-damaged populations using an impaired-intact dichotomy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)