Mechanisms of spatial impairment in Alzheimer's disease subgroups: Differential breakdown of directed attention to global-local stimuli.

Global–local stimuli (e.g., a large 1 composed of small 2s) were presented to subgroups of patients with Alzheimer's disease (AD) and to normal controls in a directed-attention reaction time (RT) experiment. Pronounced dissociations in performance were found among the AD subgroups. Those patients who displayed greater impairment in verbal than in spatial skills on traditional clinical tests had particular difficulty processing local (detail) forms, whereas patients who had greater spatial than verbal impairment exhibited striking deficits in processing global (configural) forms. Results indicate that the AD patients were impaired primarily in inhibiting responses associated with their strong area when attending to forms in their weak area, although they did evince mild impairment in the perceptual processing of forms in their weak area as well. Thus, it appears that the AD patients' global–local processing deficits interacted with deficient inhibitory mechanisms to produce their patterns of deficits on the directed attention task. (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)     

Effects of generation on indirect measures of memory.

Subjects either read words (CHIMP) or generated words ("a small ape—C') during the study phase of three experiments. The effects of these encoding tasks on performance in two indirect, priming tests—word completion and word identification—were observed. The word completion test is a version of word stem completion in which subjects are shown the initial four letters of a five-letter word (e.g., CHIM_: CHIMP, CHIME) and are asked to add one letter to produce the first word that comes to mind. In word identification, subjects are shown a word briefly and are asked to identify it. Systematic comparisons of the two tests within single experiments showed that generation, either to semantic cues or to orthographic cues, had different effects on performance in the two tests: Word identification performance was lower for words generated rather than read, whereas word completion performance for words generated was indistinguishable from performance for words read. These results suggest that performance in different indirect tests depends on the processing of different types of information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual priming in perceptual identification for patients with Alzheimer's disease and a patient with right occipital lobectomy.

Two experiments examined explicit recognition memory and perceptual and conceptual contributions to implicit perceptual-identification repetition priming for patients with Alzheimer's disease (AD) and Patient M.S. with right-occipital lobectomy. Participants read words (perceptual encoding) and generated words (conceptual encoding) from a definition and letter cue (e.g., "a vehicle for moving the injured—a"). AD patients demonstrated impaired explicit and intact implicit memory for both perceptually and conceptually encoded words. M.S. demonstrated the opposite pattern: intact explicit and impaired implicit memory in both encoding conditions. The double dissociation between AD and M.S. on implicit and explicit memory tasks is discussed in terms of a putative visual memory mechanism in the right-occipital cortex that interacts with lexical mechanisms to yield perceptual-identification priming after perceptual and conceptual encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What does visual agnosia tell us about perceptual organization and its relationship to object perception?

The authors studied 2 patients, S.M. and R.N., to examine perceptual organization and its relationship to object recognition. Both patients had normal, low-level vision and performed simple grouping operations normally but were unable to apprehend a multielement stimulus as a whole. R.N. failed to derive global structure even under optimal stimulus conditions, was less sensitive to grouping by closure, and was more impaired in object recognition than S.M. These findings suggest that perceptual organization involves a multiplicity of processes, some of which are simpler and are instantiated in lower order areas of visual cortex (e.g., collinearity). Other processes are more complex and rely on higher order visual areas (e.g., closure and shape formation). The failure to exploit these latter configural processes adversely affects object recognition. (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)     

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)     

Level of processing affects priming in word fragment completion.

In 4 experiments, Ss studied words under learning conditions that promoted semantic or physical processing. An implicit word fragment completion test was administered (e.g., complete l ph t for elephant). When semantic and physical study conditions were manipulated between Ss (Exps 1 and 3) or within Ss in a blocked fashion (Exps 3 and 4), significant levels of processing (LOP) effects were obtained. When semantic and physical conditions were presented in a mixed list (Exps 2, 3, and 4), the LOP effect was smaller and not significant. A survey of the literature on LOP effects in implicit perceptual tests revealed that priming in these tests was consistently greater in the semantic than physical condition, with reports of statistically significant LOP effects. These findings contradict the widely held notion that LOP does not affect priming in implicit perceptual tests and have implications for contemporary accounts of performance in implicit and explicit measures of memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct comparison of two implicit memory tests: Word fragment and word stem completion.

In 3 experiments, the implicit memory tests of word fragment and word stem completion showed comparable effects over several variables: Study of words produced more priming than did study of pictures; no levels-of-processing effect occurred for words; more priming was obtained from pictures when Ss imaged the pictures' names than when they rated them for pleasantness; and forgetting rates were generally similar for the tests. A different pattern of results for the first 3 variables occurred under explicit test conditions with the same word fragments or word stems as cues. It is concluded that the 2 implicit tests are measuring a similar form of perceptual memory. Furthermore, it is argued that both tests are truly implicit because they meet the D. L. Schacter et al (1989) retrieval intentionality criterion: Levels of processing of words have a powerful effect on explicit versions of the tests but no effect on implicit versions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of proportion overlap and repeated testing on primed word fragment completion.

Extended the idea of a proportion overlap (PPO) effect in perceptual identification to a word fragment completion (WFC) test of implicit memory. 80 university students studied a list of words (e.g., cheetah) and received an implicit WFC test (e.g., complete -h--t-h). On the test, the ratio of studied to nonstudied items (PPO) was 0, 25, 50, 75, or 100%. Ss were administered the identical test twice. PPO did not affect priming in WFC, on either the 1st or 2nd test. Also, the completion of studied and nonstudied fragments increased over repeated tests, but priming (the studied–nonstudied rate) remained unchanged. The PPO of items between study and test does not affect performance on primed WFC. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directed forgetting of trauma cues in adult survivors of childhood sexual abuse with and without posttraumatic stress disorder

The authors used a directed-forgetting task to investigate whether psychiatrically impaired adult survivors of childhood sexual abuse exhibit an avoidant encoding style and impaired memory for trauma cues. The authors tested women with abuse histories, either with or without posttraumatic stress disorder (PTSD), and women with neither abuse histories nor PTSD. The women saw intermixed trauma words (e.g., molested), positive words (e.g., confident), and categorized neutral words (e.g., mailbox) on a computer screen and were instructed either to remember or to forget each word. Relative to the other groups, the PTSD group did not exhibit recall deficits for trauma-related to-be-remembered words, nor did they recall fewer trauma-related to-be-forgotten words than other words. Instead, they exhibited recall deficits for positive and neutral words they were supposed to remember. These data are inconsistent with the hypothesis that impaired survivors exhibit avoidant encoding and impaired memory for traumatic information.     

Word and tone working memory deficits in schizophrenia

BACKGROUND: Verbal memory deficits have been reported in many studies of patients with schizophrenia. We evaluated the specificity of these deficits by comparing patients and control subjects on several verbal and nonverbal auditory memory tests. METHODS: Performance of stable, medicated outpatients with DSM-III-R diagnoses of schizophrenia (N = 38) was compared with that of healthy subjects (N = 39) on a word list immediate recall task, tone delayed discrimination tasks, and word and tone serial position tasks. Before memory testing, patients were divided into 2 groups based on their ability to perform normally on a screening test requiring pitch discrimination and sustained attention. RESULTS: The nonverbal tests were more difficult for control subjects than the verbal tests. Despite this, patients who performed normally on the screening test of perception and attention performed normally on both nonverbal tests but had highly significant deficits on both verbal tests (P<.001 and P = .02). Patients who performed poorly on the screening test had highly significant performance deficits on all the memory tests. CONCLUSIONS: One subgroup of patients with schizophrenia has a selective deficit in verbal memory despite normal motivation, attention, and general perceptual function. Another group has deficits in multiple aspects of cognitive function suggestive of failure in early stages of information processing.     

Ribosomal RNA: a key to phylogeny

Subjects studied a list of words (e.g., cheetah) and received an implicit word fragment completion test (complete -h-t-h). On the test, the ratio of studied to nonstudied items (proportion overlap) was 0, 25, 50, 75, or 100%. Subjects were administered the identical test twice. Proportion overlap did not affect priming in word fragment completion, on either the first or second test. Also, the completion of studied and nonstudied fragments increased over repeated tests, but priming (the studied-nonstudied rate) remained unchanged. The proportion overlap of items between study and test does not affect performance on primed word fragment completion.     

Comparison of reading and spelling in patients with probable Alzheimer's disease.

Patients with probable Alzheimer's disease (AD) are reported to show mild, but reliable, difficulties reading aloud and spelling to dictation exception words, which have unusual or unpredictable correspondence between their spelling and pronunciation (e.g., touch). To understand the cognitive dysfunction responsible for these impairments, 21 patients and 27 age- and education-matched controls completed specially designed tests of single-word oral reading and spelling to dictation. AD patients performed slightly below controls on all tasks and showed mildly exaggerated regularity effects (i.e., the difference in response accuracy between words with regular spellings minus exception words) in reading and spelling. Qualitative analyses, however, did not demonstrate response patterns consistent with impairment in central lexical orthographic processing. The authors conclude that the mild alexia and agraphia in AD reflect semantic deficits and nonlinguistic impairments rather than a specific disturbance in lexical orthographic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Divided attention and memory: Evidence of substantial interference effects at retrieval and encoding.

In 5 divided attention (DA) experiments, students (24 in each experiment) performed visual distracting tasks (e.g., recognition of words, word and digit monitoring) while either simultaneously encoding an auditory word list or engaging in oral free recall of the target word list. DA during retrieval, using either of the word-based distracting tasks, produced relatively larger interference effects than the digit-monitoring task. DA during encoding produced uniformly large interference effects, regardless of the type of distracting task. Results suggest that when attention is divided at retrieval, interference is created only when the memory and concurrent task compete for access to word-specific representational systems; no such specificity is necessary to create interference at encoding. During encoding, memory and concurrent tasks compete primarily for general resources, whereas during retrieval, they compete primarily for representational systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in implicit and explicit memory: Time course and encoding effects.

Young and older adults were tested at three delays on word-stem completion or cued recall following semantic or structural word judgments. Identical three-letter stems were present at retrieval for both implicit (completion) and explicit (cued recall) tasks; only the intention to recall list words differed. The young adults outperformed the older adults on both implicit and explicit task at all test delays. Under some conditions, the older but not the young adults performed more poorly on cued recall than on stem completion, suggesting a possible failure to use implicitly available information to support explicit remembering. These results suggest that some forms of implicit memory decline with normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual and conceptual memory processes in global amnesia.

To determine whether global amnesia reflects a selective deficit in conceptual processing, amnesic and control Ss performed 4 memory tasks that varied processing and retrieval requirements. A study-phase modality (auditory/visual) manipulation validated the nature of processing (perceptual and conceptual) engaged by each task. Amnesic patients were impaired on perceptual and conceptual explicit memory tasks (word-fragment and word-associate cued recall) and were intact on perceptual and conceptual implicit memory tasks (word-fragment completion and word association). These results are consistent with the view that limbic-diencephalic structures damaged in amnesia mediate, in part, processes typically engaged during explicit retrieval. The results are inconsistent, however, with the characterization of that deficit as being one of conceptual processing per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment in category fluency in ischemic vascular dementia.

The underlying mechanisms for impaired output on letter (F, A, and S) and category (e.g., animal) word list generation (WLG) tasks in subcortical ischemic vascular dementia (IVD) were investigated. Normal control (NC) and Alzheimer's disease (AD) participants were also studied. IVD and NC participants performed better on category than letter WLG tasks, whereas the opposite was observed among AD participants. IVD participants produced fewer responses than AD participants on letter WLG tasks, but there was no difference between AD and IVD participants on the "animal" WLG task. AD participants scored lower than IVD and NC participants on animal WLG indexes measuring semantic knowledge. There were few differences between IVD and NC participants. The reduced output on the animal WLG task for IVD participants is consistent with search-retrieval deficits. The reduced output of AD participants may be caused by degraded semantic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic activation of phonological information in reading: evidence from the semantic relatedness decision task

A semantic relatedness decision task was used to investigate whether phonological recording occurs automatically and whether it mediates lexical access in visual word recognition and reading. In this task, subjects read a pair of words and decided whether they were related or unrelated in meaning. In Experiment 1, unrelated word-homophone pairs (e.g., LION-BARE) and their visual controls (e.g., LION-BEAN) as well as related word pairs (e.g., FISH-NET) were presented. Homophone pairs were more likely to be judged as related or more slowly rejected as unrelated than their control pairs, suggesting phonological access of word meanings. In Experiment 2, word-pseudohomophone pairs (e.g., TABLE-CHARE) and their visual controls (e.g., TABLE-CHARK) as well as related and unrelated word pairs were presented. Pseudohomophone pairs were more likely to be judged as related or more slowly rejected as unrelated than their control pairs, again suggesting automatic phonological recording in reading.     

Component processes of conceptual priming and associative cued recall: The roles of preexisting representation and depth of processing.

The authors investigated depth-of-processing effects on conceptual priming by comparing incidental (implicit) and intentional (explicit) tests of word association. In Experiment 1, depth of processing at study influenced priming of weak and medium associates but not of strong associates. In Experiment 2, depth of processing influenced priming of weak associates but not of compound phrases (e.g., coathanger), whose preexperimental association strength matched that of weak associates. In Experiment 3, the same pattern persisted when study was auditory and test was visual, ensuring that priming was conceptual and not perceptual. In all experiments, in matched intentional tests, depth-of-processing effects occurred for all association strengths and for both phrases and associates, suggesting that the incidental tests were uncontaminated by voluntary retrieval, because they showed depth-of-processing effects only for some materials and not others, within the same participants and tests. Because depth-of-processing effects on involuntary free-association priming depend on the presence versus absence of a cohesive preexperimental representation, the memory-systems and conceptual/perceptual processing approaches to memory-test dissociations require modification to account for component processes of conceptual priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)