126 research outputs found
Neural changes associated with semantic processing in healthy aging despite intact behavioral performance
Semantic memory recruits an extensive neural network including the left inferior
prefrontal cortex (IPC) and the left temporoparietal region, which are involved in
semantic control processes, as well as the anterior temporal lobe region (ATL) which is
considered to be involved in processing semantic information at a central level. However,
little is known about the underlying neuronal integrity of the semantic network in normal
aging. Young and older healthy adults carried out a semantic judgment task while their
cortical activity was recorded using magnetoencephalography (MEG). Despite equivalent
behavioral performance, young adults activated the left IPC to a greater extent than older
adults, while the latter group recruited the temporoparietal region bilaterally and the left
ATL to a greater extent than younger adults. Results indicate that significant neuronal
changes occur in normal aging, mainly in regions underlying semantic control processes,
despite an apparent stability in performance at the behavioral level
Memory for public events in mild cognitive impairment and Alzheimer’s disease : the importance of rehearsal
Ribot’s law refers to the better preservation of remote memories compared with recent ones that presumably characterizes retrograde amnesia. Even if Ribot-type temporal gradient has been extensively studied in retrograde amnesia, particularly in Alzheimer’s disease (AD), this pattern has not been consistently found. One explanation for these results may be that rehearsal frequency rather than remoteness accounts for the better preservation of these memories. Thus, the aim of present study was to address this question by studying retrograde semantic memory in subjects with amnestic mild cognitive impairment (aMCI) (n = 20), mild AD (n = 20) and in healthy older controls (HC; n = 19). In order to evaluate the impact of repetition as well as the impact of remoteness, we used a test assessing memory for enduring and transient public events that occurred in the recent and remote past. Results show no clear temporal gradient across time periods (1960–1975; 1976–1990; 1991–2005; 2006–2011), but a better performance was observed in all three groups for enduring compared with transient events. Moreover, although deficits were globally found in both patients groups compared with HC, more specific analyses revealed that aMCI patients were only impaired on transient events while AD patients were impaired on both transient and enduring events. Exploratory analyses also revealed a tendency suggesting preservation of remote transient events in aMCI. These findings are discussed with regards to memory consolidation models
Vulnerability to semantic and phonological interference in normal aging and amnestic Mild Cognitive Impairment (aMCI)
Objective: To determine whether the increased vulnerability to semantic interference previously observed in amnestic mild cognitive impairment (aMCI) is specifically associated with semantic material or if it also affects other types of material, suggesting generalized executive and inhibitory impairment. Method: Seventy-two participants divided into two groups (33 aMCI, 39 normal control [NC]) matched for age and education were included. They completed a comprehensive neuropsychological examination, the French version of the Loewenstein Acevedo Scale for Semantic Interference and Learning (LASSI-L; semantic interference test), and a homologous experimental phonological test, the phonological interference and learning test. Independent sample t tests, mixed analysis of variance (ANOVA), and analysis of covariance (ANCOVA) on memory and interference scores were conducted to compare memory and interference in both conditions for both groups. Results: For memory scores, results revealed significant main effects of group (NC > aMCI) and condition (semantic > phonological) and significant interactions (poorer performance in the semantic condition for aMCI). aMCI committed more phonological false recognition errors, were disproportionately more vulnerable to retroactive semantic interference, and showed a higher percentage of intrusion errors associated with proactive semantic interference than NC. Conclusions: To our knowledge, this is the first study to compare vulnerability to interference in aMCI and normal aging with two similarly designed semantic and phonological word list learning tasks. Taken together, our results suggest that aMCI present with broad difficulties in source memory and inhibition, but that impaired deep semantic processing results in additional semantic intrusion errors during proactive interference and impacts their ability to show good recall after an interference list (greater semantic retroactive interference). Results are discussed according to the level-of-processing and activation/monitoring theories
L’apprentissage sans erreur : un principe efficace d’intervention dans la maladie d’Alzheimer et dans l’aphasie primaire progressive
L’intervention cognitive demeure une des perspectives de prise en charge les
plus utiles, dès la phase précoce, pour aider les patients atteints de trouble neurocognitif
majeur à compenser leurs déficits cognitifs et maintenir leur indépendance fonctionnelle
dans la vie quotidienne. L’apprentissage sans erreur représente un ensemble de principes
et de techniques visant à éliminer ou réduire au maximum les erreurs commises dans un
contexte d’apprentissage ou de réapprentissage. Dans cet article, nous examinons l’efficacité de ce principe d’apprentissage dans le contexte de la démence de type Alzheimer
et de l’aphasie primaire progressive. Sur la base des données actuelles, l’apprentissage
sans erreur se révèle être efficace pour (ré)apprendre de nouvelles informations ou habiletés procédurales. Dans certains cas, les gains de l’apprentissage sans erreur perdurent
à long terme et ce principe d’apprentissage pourrait permettre d’augmenter la motivation
et de réduire la frustration liée à l’échec et aux déficits. Il existe néanmoins des divergences dans les résultats entre les études qui pourraient refléter des différences dans
les paramètres des interventions. En conclusion, ces interventions devraient cibler des
apprentissages qui ont une utilité pour les patients et qui leur permettent de préserver leur
indépendance plus longtemps et ainsi améliorer leur qualité de vie.Alzheimer’s disease (AD) and primary progressive aphasia (PPA) are age-related
neurodegenerative diseases characterized by a slowly progressive cognitive decline that
significantly impacts functional autonomy. Cognitive interventions remain one of the most
useful management perspectives to help patients compensate for their cognitive and functional deficits in everyday life. Errorless learning represents a set of principles and methods
aimed at eliminating or minimizing errors in a learning context, which was initially applied
to patients with an amnesic syndrome. In this article, we examine the effectiveness of this
learning principle in the context of AD and PPA. Based on current data from the literature,
errorless learning appears to be useful in (re)learning new information or procedural skills
in AD and APP, such as relearning names or certain independent activities of daily living. In
addition, the benefits of errorless learning are maintained at follow-up. There are, however,
discrepancies in the results between studies which could reflect differences in the learning
methods employed and in the parameters of the interventions. In conclusion, such interventions should primarily target learning that is useful for patients and that allows them to
preserve their autonomy longer and improve their quality of life
The impact of time and repeated exposure on famous person knowledge in amnestic Mild cognitive impairment and Alzheimer’s disease
Objective: Famous people knowledge has been shown to be impaired early in Alzheimer’s disease (AD) and amnestic mild cognitive impairment (aMCI). However, the question of whether recently acquired knowledge is more impaired than remotely acquired knowledge remains a matter of debate. The aim of this study was to investigate the patterns of semantic memory impairment in aMCI and AD by investigating two factors that may influence the retrieval of such knowledge, namely remoteness and frequency of repetition of information over time. Method: Three groups (19 controls, 20 aMCI and 20 AD patients) were compared on a test assessing general and specific biographical knowledge about famous people, where the period of acquired fame (remote vs recent) and the type of fame (enduring vs transient) were controlled for. Results: Global performance of aMCI and AD patients was significantly poorer than that of controls. However, different patterns of recall were observed as a function of time and type of fame. A temporal gradient was found in both patient groups for enduring names but not for transient ones, whereby knowledge about remote enduring famous persons was better recalled. Patients were more impaired at questions assessing specific biographical knowledge (unique to an individual) than more general knowledge. Conclusions: Tests of famous people knowledge offer a unique opportunity to investigate semantic deficits in aMCI and AD, because they make it possible to estimate the time at which memories were acquired, as well as the type of fame. Results are discussed in light of memory consolidation models.
Keywords
Single and Multiple Domain Amnestic MCI: two sides of the same coin?
Background. Amnestic Mild Cognitive Impairment (aMCI) is considered a transition
stage between normal aging and Alzheimer's disease (AD). Two main clinical subtypes
of aMCI have been identified: 1) aMCI single domain (aMCI-SD), with isolated episodic
memory impairments, and 2) aMCI multiple domain (aMCI-MD), with episodic memory
impairments and deficits in one or more other cognitive domains.
Aims.To map the pattern of gray matter (GM) atrophy associated with aMCI-SD, aMCIMD
and mild AD.
Methods. A group of aMCI-SD, aMCI-MD characterized by executive function disorders,
mild AD patients and cognitively unimpaired age-matched subjects underwent a
comprehensive neuropsychological assessment and a high-definition MR brain scan.
Voxel-based morphometry (VBM) analysis was used to characterize the GM tissue loss
in each patient group, and the common pattern of GM atrophy in aMCI-SD and aMCIMD.
Results. The results revealed that aMCI-SD and aMCI-MD are characterized by a
common pattern of GM atrophy within the medial temporal cortex, predisposing to AD
and correlating with the severity of verbal memory symptoms. Moreover, the pattern of
GM atrophy observed in aMCI-SD, aMCI-MD and mild AD revealed that, from an
anatomical point of view, these three clinical syndromes could represent three severity
points along the continuum between normal aging and AD
Differential involvement of the anterior temporal lobes in famous people semantics
The ability to recognize a famous person occurs through semantic memory. Previous
neuroimaging studies have shown that the anterior temporal lobes (ATLs) are involved
in the recognition of famous people. However, it is still a matter of debate whether
the semantic processing of names or pictures of famous people has an impact on
the activation of ATLs. The aim of this study was to explore the pattern of activation
associated with a semantic processing of famous people based on face and written name
stimuli. Fifteen healthy young individuals participated in our fMRI study, in which they
were asked to perform a semantic categorization judgment task, based on profession, of
visually presented pictures, and names of famous people. Neuroimaging findings showed
a common pattern of activation for faces and names mainly involving the inferior frontal
regions, the posterior temporal lobe, the visual cortex, and the ATLs. We found that
the comparison names vs. pictures lead to significant activation in the anterior superior
temporal gyrus. On the other hand, faces vs. names seemed associated with increased
activation in the medial ATL. Moreover, our results demonstrated that the functional
connectivity network anchored to the medial ATL, compared to the anterior STG, is more
connected to the bilateral occipital lobe and fusiform gyrus that are regions implicated in
the visual system and visual processing of faces. This study provides critical evidence of
the differential involvement of ATL regions in semantics of famous people
Comprehension of concrete and abstract words in patients with selective anterior temporal lobe resection and in patients with selective amygdalo-hippocampectomy
The role of the anterior temporal lobe (ATL) in semantic memory is now firmly established.
There is still controversy, however, regarding the specific role of this region in processing
various types of concepts. There have been reports of patients suffering from semantic
dementia (SD), a neurodegenerative condition in which the ATL are damaged bilaterally, who
present with greater semantic impairment for concrete concepts than for abstract concepts, an
effect known as reversal of the concreteness effect. This effect has previously been interpreted
as reflecting degraded visual-perceptual features of objects due to damage to the inferior
temporal lobes such as is observed in SD. Temporal lobe atrophy in SD, however, is bilateral
even if it usually predominates to the left ATL, and it has been found to extend beyond the
ATL, throughout the temporal lobes including medial and posterior temporal lobe regions.
The question therefore remains whether greater impairment for concrete concepts results from
damage to the ATL or from damage to the visual association cortex, and if unilateral damage
can produce such a deficit.
The aim of the present study was to investigate the processing of concrete and abstract
words in rare patients who underwent a selective ATL surgical resection, and to compare their
performance with that of patients with selective medial temporal lobe damage sparing the
ATL region. Seven patients with a selective unilateral anterior temporal resection (ATL), 15
patients with a selective unilateral amygdalo-hippocampectomy (SeAH), and 15 healthy ageand education-matched controls underwent detailed neuropsychological assessment and
carried out a semantic similarity judgement task evaluating their comprehension of concrete
and abstract words. Results showed that both ATL and SeAH groups were significantly
impaired on the semantic task relative to the control group. Within the patient groups,
however, comprehension of concrete words was significantly more impaired than that of
abstract words in the ATL group, while comprehension of abstract and concrete words was equally affected in the SeAH group. Results of this study suggest that the ATL region may
play a critical role in processing concrete concepts, and that the reversal of the concreteness
effect observed in ATL patients may result from damage to a categorical organization
underlying the representation of concrete concepts
An examination of semantic impairment in amnestic MCI and AD : What can we learn from verbal fluency?
Introduction
The Verbal Fluency Test (VF) is commonly used in neuropsychology. Some studies have demonstrated a marked impairment of semantic VF compared to phonemic VF in Alzheimer’s disease (AD). Since amnestic Mild Cognitive Impairment (aMCI) is associated with increased risk of conversion to incident AD, it is relevant to examine whether a similar impairment is observed in this population. The objective of the present empirical study is to compare VF performance of aMCI patients to those of AD and elderly controls matched one-to-one for age and education.
Method
Ninety-six participants divided into three equal groups (N = 32: AD, aMCI and Controls) were included in this study. Participants in each group were, on average, 76 years of age and had 13 years of education. A repeated measures ANOVA with the Group (AD, aMCI, NC) as between-subject factor and the Fluency condition (“P” and “animals”) as within-subject factor was performed. T-tests and simple ANOVAs were also conducted to examine the interaction.
Results
There was a significant interaction between the groups and the verbal fluency condition. In AD, significantly fewer words were produced in both conditions. In contrast, participants with aMCI demonstrated a pattern similar to controls in the phonemic condition, but generated significantly fewer words in the semantic condition.
Conclusion
These results indicate a semantic memory impairment in aMCI revealed by a simple, commonly-used neuropsychological test. Future studies are needed to investigate if semantic fluency deficits can help predict future conversion to AD
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