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C Lalevée

Publications and source records attributed to C Lalevée.

8 recordsLinked to original sources
PubMed2003

[Familial idiopathic striato-pallido-dentate calcifications: clinical and brain imaging study in a family].

Familial idiopathic basal ganglia calcification (FIBGC) is a rare condition and its pathophysiology has not so far been elucidated. We report the results of a clinical study in two patients of a family affected with FIBGC. Brain imaging with 18-FDG-PET was performed in one. Psychiatric and cognitive troubles were the main clinical symptoms. Basal ganglia calcifications were associated with white matter lesions. The PET study performed in one patient revealed a striatal and a posterior cingulate hypometabolism. Posterior cingulate gyrus is involved in episodic memory processing, and could be involved in episodic memory deficit observed in this patient. These results suggest that a cortical dysfunction could be associated to the disease. The underlying mechanism, that could be a neuronal loss, a cortical deafferentation or an alteration of synaptic transmission, remains to be elucidated.

Adult↗
PubMed2001

Voxel-based mapping of brain hypometabolism in permanent amnesia with PET.

In this study, we used voxel-based mapping methods to compare the resting cerebral metabolic rate of glucose (CMRglc) measured with PET in five patients with permanent amnesia (three with chronic Wernicke-Korsakoff and two with postanoxia syndrome) to that of nine healthy age-matched subjects. We assessed (i) a group pattern of relative hypometabolism; and (ii) the consistency of this group pattern, if any, in individual subjects, according to etiology. The results from the group analysis documented that permanent amnesia is associated with hypometabolism in the thalamus, posterior cingulate cortex, and mesial prefrontal cortex (near the anterior cingulate gyrus), bilaterally, as well as in the left supramarginal and middle temporal gyri. The individual analysis showed that this group pattern was found in essentially each patient, regardless of the cause of amnesia. Thus, permanent amnesia is subtended by dysfunction in structures belonging to Papez/limbic circuits as well as in left-hemisphere areas typically concerned with verbal functions, probably through a mechanism of thalamo-cortical disconnection and possibly involved in retrograde amnesia. The use of a voxel-based method allowed us to map a common network of synaptic dysfunction in a neuropsychological syndrome regardless of etiology. Our results indicate that this should be a powerful method in functional neuropsychology.

Adult↗
PubMed2001

The nature of semantic memory deficits in Alzheimer's disease: new insights from hyperpriming effects.

While semantic memory deficits are a common landmark of Alzheimer's disease, the nature of these impairments remains to be clarified. Implicit tasks which assess semantic priming effects are often used to understand semantic deficits in Alzheimer's disease, but they have led to unclear conclusions because of methodological problems such as intervention of attentional mechanisms. To explore the effects of semantic priming in Alzheimer's disease and their relationship with semantic memory deficits, we used two tasks, one implicit and the other explicit. The implicit task was a lexical decision task to assess semantic priming, and in which pairs of words had coordinate (tiger-lion) or attribute relationships (zebra-stripe). The explicit task was a semantic knowledge task composed of namings and questions involving superordinate categories and attribute knowledge of concepts. The two tasks systematically assessed the integrity of the same concepts. This protocol was given to 53 Alzheimer's disease patients with mild to moderate dementia and to 20 controls. The Alzheimer's disease group as a whole obtained significantly greater priming effects (hyperpriming) than controls in the coordinate condition, and equivalent priming in the attribute condition. In the coordinate condition, a subgroup of 26 patients, with attribute knowledge deficits, had larger priming effects than both a subgroup without semantic deficits and the control group. These results show that in Alzheimer's disease the semantic priming effects vary according to the degree of attribute loss, and the presence of hyperpriming would reflect semantic memory deficits. This study unravels the fine-grained structure of semantic memory disturbances in Alzheimer's disease with mild to moderate dementia, affecting initially the attributes of concepts within a hierarchical network in which superordinate concepts remain preserved.

Aged↗
PubMed2001

[Contribution of positron emission tomography to functional neuroimaging in Alzheimer's disease].

When combined with cognitive investigations, functional neuroimaging methods such as positron emission tomography allow to depict the neural substrates that underlie the neuropsychological alterations in Alzheimer's disease. Capitalising on the variance in both cognitive performances and resting cerebral metabolic rate of glucose (CMRGlc) in Alzheimer's disease, it is possible to correlate these two quantitative variables on a pixel-by-pixel basis and to generate maps showing the significant correlations in stereotaxic space. Some examples using this approach in the domain of memory disorders are presented in this brief review. We notably show that the localisation of the significant correlations differs from one memory system to another, as evaluated by clinical memory tasks. This approach also unravels the compensatory mechanisms that take place with evolution of the disease. Over and above its interest in clinical neuropsychology, this method constitutes a new source of inferences complementary to the classic activation paradigm in normal subjects, as the latter identifies the cerebral structures that are involved with, but not necessarily indispensable for, the normal execution of the task. This approach highlights the interest of combining functional neuroimaging and neuropsychology to better understand the neural substrates of cognitive deficits in both patients with memory disorders and elderly normal subjects.

Alzheimer Disease↗
PubMed1999

Episodic memory in transient global amnesia: encoding, storage, or retrieval deficit?

OBJECTIVES: To assess episodic memory (especially anterograde amnesia) during the acute phase of transient global amnesia to differentiate an encoding, a storage, or a retrieval deficit. METHODS: In three patients, whose amnestic episode fulfilled all current criteria for transient global amnesia, a neuropsychological protocol was administered which included a word learning task derived from the Grober and Buschke's procedure. RESULTS: In one patient, the results suggested an encoding deficit, and in two others, a storage deficit. CONCLUSIONS: The encoding/storage impairment concerning anterograde amnesia documented in our patients stands in clear contrast with the impairment in retrieval which must underly the retrograde amnesia that also characterises transient global amnesia. This dissociation in turn favours the idea of a functional independence among the cognitive mechanisms that subserve episodic memory.

Aged↗
PubMed1998

Preservation of cognitive procedural memory in a case of Korsakoff's syndrome: methodological and theoretical insights.

Using the Tower of Hanoï puzzle, Butters, et al. in 1985 illustrated the difficulties in learning the procedure and questioned the suitability of this task for assessment of the cognitive procedural memory in Korsakoff's syndrome. Our objective, in the light of these criticisms, was to show preservation of cognitive procedure capacities with the Tower of Hanoï for a man (P.F.) who was suffering from alcoholic Korsakoff's syndrome. For this procedural task, some aids helped to compensate in part for the difficulties with declarative memory and with working memory. In this condition, P.F. was able to learn the cognitive procedure. This study suggests that cognitive procedure memory may be preserved in some patients suffering from Korsakoff's syndrome and that this may be shown when a suitable task is used. The result makes it possible to discuss the interaction between declarative and procedural knowledge in the solving of the Tower of Hanoï.

Alcohol Amnestic Disorder↗
PubMed1998

[Clinical evaluation of memory].

An assessment of memory is relevant in many clinical contexts, but its objectives differ from one situation to another. An initial investigation should make it possible to define these objectives and to formulate hypotheses following the interview with the patient and/or his family and with the help of the overall anamnestic data. The tests proposed would aim at answering the questions according to the particular case of the patient: the supposed disorders, a suggested diagnosis, but also demographic data such as age and educational level. Consequently there is no across-the-board examination of memory and this assessment must be situated in a specific theoretical context. Memory is no longer considered as a single but as a compound function made up of different, relatively independent systems. The examination not only seeks to show the deficits which have a certain significance according to the clinical context, but also aims at bringing out preserved abilities which may contribute to the establishing of the diagnosis and on which rehabilitation and cognitive management may be based. In this article we present several methods of memory assessment with reference to the ideas of Tulving and Schacter, who propose five different memory systems: episodic memory, working memory, semantic memory, perceptive representation system and procedural memory. These assessments are made using standardized tools (tests, questionnaires) and experimental paradigms which have recently emerged in clinical neuropsychology (study of priming effects, of acquisition of skills). One of the present issues is the problem of reconciling the use of standard tools with that of the more sophisticated paradigms drawn up in the light of the most recent theoretical models. Another objective is to relate the findings of these tests to the difficulties the patients have in their everyday lives and so to achieve an ecological understanding of memory disorders.

Humans↗