Long-term maintenance of novel vocabulary in persons with chronic aphasia

Background: The study of novel word learning in aphasia can shed light on the functionality of patients' learning mechanisms and potentially help in treatment planning. Previous studies have indicated that persons with aphasia are able to learn some new vocabulary. However, these learning outcomes appear short-lived and evidence for the ability to use the newly learned words in the long term is lacking.

Aims: Participants with aphasia and matched controls underwent short training where they were taught to name novel objects with novel names. We studied the participants' word learning and particularly their long-term maintenance. We also examined whether the language and verbal short-term memory impairments of the participants with aphasia related to their ability to acquire and maintain phonological and semantic information on novel words.

Methods & Procedures: Two participants with nonfluent aphasia, LL and AR, and two matched controls took part in the experiment. They were taught to name 20 unfamiliar objects by repeating the names in the presence of the object picture. Half of the items carried a definition that was used to probe incidental semantic learning. There were four training sessions, a post-training test, and follow-up tests up to 6 months post-training. Learning measures included recognition of the trained objects, as well as spontaneous and cued recall in visual confrontation naming. Incidental semantic learning was measured by spontaneous recall of the definitions.

Outcomes & Results: Combining spontaneous and phonologically cued responses, LL acquired 70% and AR 55% of the novel words. With phonological cueing, LL named 50% of the items correctly up to 6 months post-training (vs 95–100% for the controls) and AR 25% up to 8 weeks post-training. AR's lexical-semantic processing, pseudoword repetition and verbal short-term capacity were inferior to those of LL. In line with this, AR learned fewer words and showed more decline in recognition memory for the trained items, and weaker recall of the semantic definitions.

Conclusions: Our results support previous findings that people with aphasia can learn to name novel items. More importantly, the results show for the first time that, with phonological cueing, an individual with aphasia can maintain some of this learning up to 6 months post-training. Moreover the results provide further evidence for the significance of the functional status of lexical-semantic processing on word learning success.     

Semantic knowledge in mild cognitive impairment and mild Alzheimer's disease

The aim of this study was to investigate memory in patients with mild cognitive impairment (MCI) and mild Alzheimer's disease (AD). Ten patients with MCI, 11 with AD and a group of age and education matched healthy control participants were assessed on a comprehensive battery of semantic memory tests, including traditional semantic memory measures and a non-verbal test of knowledge of object use. The MCI group was impaired on tests of category fluency and all three conditions of an object knowledge test (matching to recipient, function and action), plus a difficult object-naming test. The mild AD group showed additional impairments on traditional measures of semantic memory, including naming high frequency items, comprehension and semantic association. Together these findings suggest that semantic memory impairments occur early in the course of AD, more specifically in patients with "amnesic" MCI, and provide further evidence that impaired category fluency reflects semantic breakdown.     

Episodic and semantic memory in mild cognitive impairment

Little is known about episodic and semantic memory in the early predementia stage of Alzheimer's disease (AD), which is referred to as mild cognitive impairment (MCI). To explore person knowledge, item recognition and spatial associative memory, we designed the Face Place Test (FPT). A total of 75 subjects participated: 22 patients with early AD, 24 with MCI and 29 matched controls. As predicted, AD patients showed significant deficits in person naming, item recognition and recall of spatial location (placing). Surprisingly, subjects with MCI were also impaired on all components. There was no significant difference between AD and MCI except on the placing component. Analysis of the relationship between semantic (naming) and episodic (recognition and placing) components of the FPT revealed a significant association between the two episodic tasks, but not between episodic and semantic performance. Patients with MCI show deficits of episodic and semantic memory. The extent of impairment suggests dysfunction beyond the medial temporal lobe. The FPT might form the basis of a sensitive early indicator of AD.     

Verbal learning and memory deficits in Mild Cognitive Impairment

Criteria for amnestic MCI rely on the use of delayed recall tasks to establish the presence of memory impairment. This study applied the California Verbal Learning Test to detail memory performance in MCI patients (n=70), as compared to control subjects (n=92) and AD patients (n=21). Learning across the 5 trials was different among the 3 groups. Learning strategy was also different, the MCI group showing less semantic clustering than the control group. However, both MCI patients and controls could benefit from semantic cueing. This study showed that beyond consolidation deficits, MCI patients have marked difficulties in acquisition and recall strategies.     

Connaissance des nouveaux mots de la langue française dans les troubles cognitifs légers de type amnésique et la maladie d’Alzheimer

Introduction

The first decline in cognitive performance in Alzheimer's disease can appear when assessing semantic memory and can be detected long before the typical symptoms of Alzheimer's disease (AD), appearing with Mild Cognitive Impairment (MCI).

Patients and method

We propose the French version of the New Words Interview (fNWI) using 22 words to investigate semantic knowledge. The fNWI uses 11 words, which entered the French dictionary between 1996 and 1997, and 11 other words, which entered between 2006 and 2007. Words were paired according to orthographic and semantic criteria. Each word was associated with three sub-tests: free evocation, discrimination of the best definition from three propositions, and recognition of the accurate word context (two sentences were proposed). Regarding evocation, we distinguished conceptual definition, life situation examples or examples by use. We tested 12 patients with AD, 12 patients with amnesic Mild Cognitive Impairment (aMCI) and 72 controls (12 were paired with patients for age and education level).

Results

MCI patients and AD patients exhibited lower performance than controls in the three sub-tests and for the words of both periods. From the early stage of MCI, the patients were more impaired in the fNWI than in the context recognition task, and they failed to provide conceptual definitions of new words. Therefore, MCI patients suffer from semantic impairments before obvious clinical signs of AD.

Conclusion

In patients with AD, performance worsened on all subtests, and more strongly in the definition discrimination task, which suggests the impairment of stored semantic knowledge. They provided fewer conceptual definitions and failed to use the strategy observed in MCI patients, who compensated for conceptual difficulties by providing examples.     

Verbal memory and verbal fluency in adolescents with schizophrenia spectrum disorders

Aim: Although impaired verbal memory and verbal fluency are frequently found in adults with schizophrenia, there has been a paucity of studies investigating adolescents with schizophrenia. Thus, the aim of the present study was to investigate the main subcomponents of verbal memory and verbal fluency in adolescents with schizophrenia spectrum disorders. Methods: Verbal learning and memory and verbal fluency was assessed in 21 adolescents with schizophrenia spectrum disorders (mean age, 15.4 years) compared with 28 healthy adolescents (mean age, 15.1 years). Results: The patient group performed significantly below healthy controls on measures of learning, delayed recall and on a frequency estimation task. No differences between the groups were found for measures of recognition, retention, implicit memory, or susceptibility to interference. Although they had impaired delayed recall the patients remembered most of what they actually learned. The patient group was impaired on phonological and semantic fluency, but there were no differences between the groups with respect to clustering or switching on the fluency tasks, when controlling for total output. There was no disproportionate impairment in semantic, as compared to phonological fluency, in the patient group. Conclusions: Adolescents with schizophrenia spectrum disorders exhibit impairments in verbal learning and verbal fluency, which might have an impact on the individual's everyday functioning.     

Semantic interference deficits and the detection of mild Alzheimer's disease and mild cognitive impairment without dementia.

Impairment in delayed recall has traditionally been considered a hallmark feature of Alzheimer's disease (AD). However, vulnerability to semantic interference may reflect early manifestations of the disorder. In this study, 26 mildly demented AD patients (mild AD), 53 patients with mild cognitive impairment without dementia (MCI), and 53 normal community-dwelling elders were first presented 10 common objects that were recalled over 3 learning trials. Subjects were then presented 10 new semantically related objects followed by recall for the original targets. After controlling for the degree of overall memory impairment, mild AD patients demonstrated greater proactive but equivalent retroactive interference relative to MCI patients. Normal elderly subjects exhibited the least amount of proactive and retroactive interference effects. Recall for targets susceptible to proactive interference correctly classified 81.3% of MCI patients and 81.3% of normal elderly subjects, outperforming measures of delayed recall and rate of forgetting. Adding recognition memory scores to the model enhanced both sensitivity (84.6%) and specificity (88.5%). A combination of proactive and retroactive interference measures yielded sensitivity of 84.6% and specificity of 96.2% in differentiating mild AD patients from normal older adults. Susceptibility to proactive semantic interference may be an early cognitive feature of MCI and AD patients presenting for clinical evaluation.     

Naming of objects, faces and buildings in mild cognitive impairment

Accruing evidence suggests that the cognitive deficits in very early Alzheimer's Disease (AD) are not confined to episodic memory, with a number of studies documenting semantic memory deficits, especially for knowledge of people. To investigate whether this difficulty in naming famous people extends to other proper names based information, three naming tasks – the Graded Naming Test (GNT), which uses objects and animals, the Graded Faces Test (GFT) and the newly designed Graded Buildings Test (GBT) – were administered to 69 participants (32 patients in the early prodromal stage of AD, so-called Mild Cognitive Impairment (MCI), and 37 normal control participants). Patients were found to be impaired on all three tests compared to controls, although naming of objects was significantly better than naming of faces and buildings. Discriminant analysis successfully predicted group membership for 100% controls and 78.1% of patients. The results suggest that even in cases that do not yet fulfil criteria for AD naming of famous people and buildings is impaired, and that both these semantic domains show greater vulnerability than general semantic knowledge. A semantic deficit together with the hallmark episodic deficit may be common in MCI, and that the use of graded tasks tapping semantic memory may be useful for the early identification of patients with MCI.     

Visual and visuospatial short-term memory in mild cognitive impairment and Alzheimer disease: role of attention

It has been proposed that visual recognition memory and certain attentional mechanisms are impaired early in Alzheimer disease (AD). Little is known about visuospatial recognition memory in AD. The crucial role of the hippocampus on spatial memory and its damage in AD suggest that visuospatial recognition memory may also be impaired early. The aim of the present study was to evaluate which modality, i.e. visual or visuospatial, is more implicated in the early memory impairment in AD. First, to determine onset of memory impairment, we compared the performances of patients with AD to those with amnestic mild cognitive impairment (MCI). Second, to determine the relative contribution of attentional impairment on the performance of MCI and AD patients, we tested the influence of a distractor in the interval between the memory image and recognition tests. Results showed that visuospatial short-term deficits appear earlier than visual short-term ones. In addition to mnemonic deficits, results showed attentional deficiency in both MCI and AD patients. Deficits of performances in visual modality seemed of attentional origin whereas those of visuospatial modality seemed of memory origin. The combination of attentional and mnemonic evaluation is likely to be a promising approach to finding predictive markers that distinguish MCI patients that convert to AD.     

Improved verbal learning in the semantic variant of primary progressive aphasia when using semantic cues

The semantic variant of primary progressive aphasia (PPA-S) is characterized by impairments in confrontation naming and single word comprehension. Although episodic memory may be relatively spared, there can be impairment in verbal learning tasks. We report a patient with PPA-S and impaired verbal learning who was tested to learn if when provided with semantic categories, her learning would improve. A 70-year-old right-handed woman with a 2-year history of progressive difficulties with word finding, naming, and memory was tested for language and memory deficits using the Hopkins Verbal Learning Test-Revised (HVLT-R). She was then retested with the HVLT-R after being provided with the three semantic categories to which these words belonged. Confrontation naming was impaired on the Boston Naming Test. Sentence repetition was normal. Comprehension testing with word picture matching and sentence comprehension was normal. On a test of semantic associations, Pyramids and Palm Trees, she was impaired. She was also impaired on tests of verbal learning (HVLT-R) (total: 13) but not recall. When a different version of the HVLT-R was given with the semantic categories of the words given beforehand, her scores improved (total: 26). This patient with PPA-S had an impairment of verbal learning, but not delayed recall. When given a semantic category cue beforehand, her verbal learning performance improved. This observation suggests that this patient did not spontaneously use semantic encoding. Using a semantic cueing strategy may help other patients with PPA-S improve their capacity for verbal learning.     

Executive dysfunction in patients with spinocerebellar ataxia type 3

The aim of this study was to assess the cognitive functions of patients with spinocerebellar ataxia type 3(SCA3). We examined 15 patients with genetically confirmed SCA3 and 15 healthy control subjects matched for age, years of education, and intellectual ability. We administered verbal memory (word recall and word recognition) and executive function tasks (word fluency test, forward and backward digit and visual span tests, Kana Pick-out Test, Trail Making Test, and conflicting instructions and a Go/NoGo task from the Frontal Assessment Battery). We found that patients with SCA3 had significantly lower scores than the healthy control subjects on the word recall, semantic, and letter fluency, and backward digit span tests, while word recognition was well preserved. The other executive function tests showed preserved functions in the SCA3 group, indicating that visual working memory, and attention and inhibition control were not affected. The patients with SCA3 showed impaired word recall and intact word recognition, and accordingly, episodic memory encoding and storage processes in short-term memory were preserved. In category and letter-fluency tests, impairment was attributable to word-retrieval from semantic memory. Impaired verbal working memory may be involved in the retrieval of verbal information from phonological storage by means of continuous subvocal rehearsal, rather than a deficit in initial phonological encoding. Essential executive dysfunction in patients with SCA3 may be due to damage in the cerebellar cortex–ventral dentate nucleus–thalamus–prefrontal cortex circuits, which are involved in strategic retrieval of verbal information from different modes of memory storage.     

Visual object recognition in early Alzheimer's disease: deficits in semantic processing

OBJECTIVES: The purpose of the present study was to divide visual object recognition into different stages and to reveal which of these stages are impaired in early Alzheimer's disease (AD). METHODS: Performance in object detection, familiarity detection, semantic name and word categorization, and identification with naming were studied by using two-choice reaction-time tasks. Ten patients with newly diagnosed AD and 14 healthy subjects were studied. RESULTS: Patients with early AD had impairments in several stages of the object recognition process. After controlling for the basic visuomotor slowness, they were as fast and as accurate as the controls in object detection, but had difficulties in all stages that required semantic processing. CONCLUSIONS: Semantic memory impairments contribute to the deficits in visual object recognition in early AD. Thus, the semantic memory deficit may be manifested in several ways in the difficulties that AD patients experience in everyday life.     

Impaired semantic knowledge underlies the reduced verbal short-term storage capacity in Alzheimer's disease

A decrease in verbal short-term memory (STM) capacity is consistently observed in patients with Alzheimer's disease (AD). Although this impairment has been mainly attributed to attentional deficits during encoding and maintenance, the progressive deterioration of semantic knowledge in early stages of AD may also be an important determinant of poor STM performance. The aim of this study was to examine the influence of semantic knowledge on verbal short-term memory storage capacity in normal aging and in AD by exploring the impact of word imageability on STM performance. Sixteen patients suffering from mild AD, 16 healthy elderly subjects and 16 young subjects performed an immediate serial recall task using word lists containing high or low imageability words. All participant groups recalled more high imageability words than low imageability words, but the effect of word imageability on verbal STM was greater in AD patients than in both the young and the elderly control groups. More precisely, AD patients showed a marked decrease in STM performance when presented with lists of low imageability words, whereas recall of high imageability words was relatively well preserved. Furthermore, AD patients displayed an abnormal proportion of phonological errors in the low imageability condition. Overall, these results indicate that the support of semantic knowledge on STM performance was impaired for lists of low imageability words in AD patients. More generally, these findings suggest that the deterioration of semantic knowledge is partly responsible for the poor verbal short-term storage capacity observed in AD.     

Learning and maintaining new vocabulary in persons with aphasia: Two controlled case studies

Background: Novel word learning of persons with aphasia is little studied, even though a better understanding of learning processes would inform development of effective treatment strategies. Recent evidence suggests some remaining verbal learning capacity in persons with aphasia. Long-term maintenance of newly learned active vocabulary has not been reported previously in persons with aphasia.

Aims: To explore learning and long-term maintenance of novel words in persons with aphasia.

Methods & Procedures: Two English-speaking males with chronic anomic aphasia and two age-matched controls were taught novel names of 20 unfamiliar objects. Half of the words were taught with semantic information (definition) and half without. Participants were instructed to learn the names. The experiment included four training sessions, one post-training test and four follow-up tests administered 1 week, 4 weeks, 8 weeks, and 6 months post-training. We tested explicit learning of the new names through visual confrontation naming. In addition, incidental learning of semantic information was probed over the follow-up period.

Outcomes & Results: The two participants with aphasia learned 6–8 of the 20 novel names during the training. However, this new vocabulary dissipated during the 6-month follow-up. As expected, the controls showed better performance both in acquisition and in maintenance of the new vocabulary over the follow-up period. As regards the accuracy of semantic information, the aphasic participant with semantic impairment demonstrated worse incidental learning of semantic information than controls and the participant with intact lexical semantics.

Conclusions: Some new vocabulary can be acquired even in chronic aphasia but the ability to spontaneously retrieve the newly learned words gradually dissipates over the weeks following learning. Our results also indicate an interaction between the level of lexical-semantic processing skills and incidental learning of new lexical-semantic knowledge in aphasia.     

Neural correlates of naming newly learned objects in MCI

Our objective was to study the neural correlates of naming of newly learned unfamiliar objects in subjects with mild cognitive impairment (MCI) and in age-matched controls, by using positron emission tomography (PET). Prior to the PET scanning, each subject underwent a 4-day long training period in which 40 names of rare unfamiliar objects were taught. The stimuli consisted of five categories: unfamiliar objects for which both the name and the definition (=semantic support) were given during training, unfamiliar objects with only the name given, unfamiliar objects with no information given, familiar objects and visual noise patterns. The unfamiliar objects mainly represented ancient domestic tools unknown to modern-day people. When naming newly learned objects trained without semantic support, the MCI group showed increased activation in the anterior cingulate when compared with the controls. Our results suggest that the naming of newly learned objects posed additional executive and attentional demands on the patients.     

Yes/No Versus Forced-Choice Recognition Memory in Mild Cognitive Impairment and Alzheimer's Disease: Patterns of Impairment and Associations with Dementia Severity

Memory tests are sensitive to early identification of Alzheimer's disease (AD) but less useful as the disease advances. However, assessing particular types of recognition memory may better characterize dementia severity in later stages of AD. We sought to examine patterns of recognition memory deficits in individuals with AD and mild cognitive impairment (MCI). Memory performance and global cognition data were collected from participants with AD (n?=?37), MCI (n?=?37), and cognitively intact older adults (normal controls, NC; n?=?35). One-way analyses of variance (ANOVAs) examined differences between groups on yes/no and forced-choice recognition measures. Individuals with amnestic MCI performed worse than NC and nonamnestic MCI participants on yes/no recognition, but were comparable on forced-choice recognition. AD patients were more impaired across yes/no and forced-choice recognition tasks. Individuals with mild AD (≥120 Dementia Rating Scale, DRS) performed better than those with moderate-to-severe AD (<120 DRS) on forced-choice recognition, but were equally impaired on yes/no recognition. There were differences in the relationships between learning, recall, and recognition performance across groups. Although yes/no recognition testing may be sensitive to MCI, forced-choice procedures may provide utility in assessing severity of anterograde amnesia in later stages of AD. Implications for assessment of insufficient effort and malingering are also discussed.     

The nature of lexico-semantic processing deficits in mild cognitive impairment

Lexico-semantic impairments in Alzheimer disease (AD) have been attributed to abnormalities in both intentional and automatic access to semantic memory. However, the order in which these impairments appear during the course of the disease is unclear. We sought to answer this question by documenting lexico-semantic impairments in 61 subjects with mild cognitive impairment (MCI), a pre-AD stage, and by comparing them to those of 39 AD and 60 normal elderly (NE) subjects. All subjects were tested with intentional access tasks (picture naming and semantic probes), automatic access tasks (lexical decision and priming), and executive function tasks (Stroop and Stroop-Picture naming). Results indicated that the MCI group was only impaired on tasks of intentional access relative to the AD group who was impaired on both types of tasks. Because most MCI subjects eventually develop AD, these results suggest that intentional access to semantic memory is impaired before automatic access. Further, impairments on the Stroop-Picture naming task but not on the Stroop task, suggest that lexico-semantic impairments in the MCI group may be related to inhibition deficits during semantic search. Findings are discussed in light of executive dysfunctions within the framework of semantic memory theories.     

Lexicality effects in word and nonword recall of semantic dementia and progressive nonfluent aphasia

Background: Verbal working memory is an essential component of many language functions, including sentence comprehension and word learning. As such, working memory has emerged as a domain of intense research interest both in aphasiology and in the broader field of cognitive neuroscience. The integrity of verbal working memory encoding relies on a fluid interaction between semantic and phonological processes. That is, we encode verbal detail using many cues related to both the sound and meaning of words. Lesion models can provide an effective means of parsing the contributions of phonological or semantic impairment to recall performance.

Methods & Procedures: We employed the lesion model approach here by contrasting the nature of lexicality errors incurred during recall of word and nonword sequences by three individuals with progressive nonfluent aphasia (a phonological dominant impairment) compared to that of two individuals with semantic dementia (a semantic dominant impairment). We focused on psycholinguistic attributes of correctly recalled stimuli relative to those that elicited a lexicality error (i.e., nonword → word OR word → nonword).

Outcomes & Results: Patients with semantic dementia showed greater sensitivity to phonological attributes (e.g., phoneme length, wordlikeness) of the target items relative to semantic attributes (e.g., familiarity). Patients with PNFA showed the opposite pattern, marked by sensitivity to word frequency, age of acquisition, familiarity, and imageability.

Conclusions: We interpret these results in favour of a processing strategy such that in the context of a focal phonological impairment patients revert to an over-reliance on preserved semantic processing abilities. In contrast, a focal semantic impairment forces both reliance on and hypersensitivity to phonological attributes of target words. We relate this interpretation to previous hypotheses about the nature of verbal short-term memory in progressive aphasia.     

The impairment of verbal semantic memory: a single case study.

We report our investigations of a single patient in whom there was a selective impairment of semantic memory. She had a marked deficit of individual word comprehension although other language and linguistic skills were relatively preserved. Here we document that her failures in word comprehension were stable over a long time period. She made "phonological" errors in defining meanings, which we argue are analogous to "visual" errors in reading. On verbal learning tasks her performance was shown to be relatively preserved, a finding which provides evidence of the dissociation of verbal semantic memory and episodic (event) memory.     

Cognitive and memory deficits in untreated Parkinson's disease and amyotrophic lateral sclerosis patients: A comparative study

Summary We investigated the profile of cognitive and memory deficits of 22 Parkinson's disease (PD), 24 amyotrophic lateral sclerosis (ALS) patients and 26 age-matched controls. The patients were at the early phase of the disease and untreated. The ALS patients exhibited deficits in simple visuoperceptual functions and in complex visuoperceptual reasoning (Digit Symbol and Block Design tests), whereas the PD patients showed deficits only in simple visuoperceptual functions. Moreover, both ALS and PD patients had impairment in tasks requiring set shifting from one reaction to another that may suggest frontal lobe dysfunction. The ALS and PD patients also showed impairment in the task of learning a word list with effort-demanding organization of the material to be remembered. However, preserved delayed recall of logical passages suggests that memory, per se, is not impaired in ALS or in PD. The patterns of errors in a test of recognition of learned words imply, at least partially, different underlying deficits in the two diseases. An inability to inhibit irrelevant information may contribute to memory impairment in ALS patients, whereas the memory deficit in PD may derive from lowered motivation or initiating behaviour.