[Albert Gombault (1844-1904). A pioneer of neuroscience].
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France↗
Biomedical subjects
B Lechevalier
Publications and source records attributed to B Lechevalier.
New questions on the hemispheric encoding/retrieval asymmetry (HERA) model assessed by divided visual-field tachistoscopy in normal subjects.
According to the hemispheric encoding/retrieval asymmetry (HERA) model, based on data obtained through functional neuroimaging, the left and right prefrontal cortices are preferentially, and, respectively, involved in long-term episodic memory encoding and retrieval. In this study, the HERA model was tested from a behavioral perspective using divided visual-field tachistoscopy. A recognition paradigm with both verbal and visuospatial materials was devised to differentiate memory-related effects (encoding vs. retrieval) from effects linked to the materials. The paradigm used lists of 12 and four items to assess long-term episodic memory and short-term memory, respectively. The aim of the latter condition was to test whether the HERA model is applicable in short-term memory. For long-term episodic memory, the data obtained validated the HERA model; the direction of the hemispheric asymmetry was found to depend on the type of materials used, whereas its magnitude was determined by the type of memory process. For verbal short-term memory, the HERA model seems to be confirmed. The pre-existing representations of the material could take into account the similarity of the hemispheric asymmetry pattern between short-term memory and long-term memory. In contrast, for visuospatial short-term memory, Baddeley's working memory model seems to better explain our results insofar as the asymmetries were essentially linked to the material in encoding but not in retrieval. This latter difference between short-term memory and long-term indicates that processes involved in LTM depend on episodic processes per se, hence, lending more support for the HERA model. Accordingly, these two memory systems seem to bring into play two different modes of hemisphere specialization.
Adult↗
Disorders in intentional gestural organization in Alzheimer's disease: combined or selective impairment of the conceptual and production systems?
This study examines disorders which affect the intentional gestural organization in Alzheimer's disease. An original and prospective protocol which assessed both the conceptual and production systems (with reference to the Roy and Square model 1985) was presented to 16 patients with Alzheimer's disease (mild to moderate dementia) and 40 healthy elderly subjects. Our study showed impairment of both systems in the Alzheimer's patients group. Two patients presented reverse performance profiles, which were characterized in one case by preservation of the conceptual system and impairment of the production system and in the other by the reverse dissociation. The findings demonstrated that disorders in the intentional gestural organization in Alzheimer's disease usually affect both the conceptual and production systems. The hypothesis concerning the existence of two functionally distinct systems underlying the organization of intentional body movement was corroborated (1) by a lack of significant correlation between the scores obtained in the assessment of the two systems and (2) by the demonstration of the double dissociation.
Aged↗
[Function imaging of the hippocampus in Korsakoff's syndrome].
A case of alcoholic Korsakoff syndrome is reported in a 47 year-old-man. Neuropsychological examination revealed an important both anterograd and retrograd amnesia but procedural and short-term memory were not affected nor was intellectual capacity. Cerebral IRM was normal. Pet scan demonstrated a previously unsuspected fact: the diminution of glucose metabolism in the two hippocampus and in the mamillary bodies.
Hippocampus↗
The neural substrates of memory systems impairment in Alzheimer's disease. A PET study of resting brain glucose utilization.
The aim of this study was to determine the neuronal basis for memory impairment in Alzheimer's disease by taking advantage of the clinical and metabolic heterogeneity of this pathology. To this end, 19 patients satisfying the NINCDSADRDA criteria for probably Alzheimer's disease of mild-to-moderate severity underwent a detailed examination of the five memory systems according to Tulving's model, together with a PET measurement of resting regional cerebral glucose utilization (CMRGlc). Compared with controls, the patients as a group showed the expected memory and metabolic profiles of impairment. Correlations (corrected for the effects of ageing) were calculated between memory scores and CMRGlc (normalized by the vermis CMRGlc) using two methods: (i) the classic regions-of-interest method, based on a priori hypotheses and individual coregistered structural MRI; and (ii) the statistical parametric mapping method which allows a systematic voxel-by-voxel analysis, in a more descriptive and exploratory way. Significant correlations were above chance levels and largely consistent between the two methods. They were almost exclusively positive (i.e. in the neurobiologically expected direction) and their distribution showed striking differences according to each memory system. Thus, verbal episodic memory impairment was related to changes in a large neuronal network including not only the limbic structures (mesial temporal cortex, thalamus and cingulate gyrus, with left side predominance) but also the parietotemporal and frontal association cortices of the right hemisphere, possibly on a compensatory basis. Regardless of modality, short-term memory tests were mainly correlated with bilateral activity in posterior association cortex, and also with activity in left prefrontal cortex for the visuospatial span, possibly indicating essentially uniform strategies for the performance of the different tasks. As predicted, semantic memory scores correlated with activity in temporoparietal and frontal association cortices of the left hemisphere, and also with activity in left cingulate cortex. Thus, for episodic, short-term and semantic memory, many findings fit classical neuropsychology, while most of the less expected ones were consistent with recent results from functional neuro-imaging in healthy subjects, notably with the hemispheric encoding/ retrieval asymmetry (HERA) model; only few findings suggested possible reorganization processes and/or recourse to unexpected cognitive strategy. Finally, only negative correlations were found for perceptual priming and procedural memory; although they could arise by chance, some of these unexpected findings give rise to interesting hypotheses about the cognitive relationships between the most and least affected memory systems. This study documents the validity and usefulness of our approach in unravelling the neural substrates of cognitive impairment in brain pathology without focal tissue loss such as that seen in neurodegenerative diseases.
Aged↗
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↗
Plasma superoxide dismutase and glutathione peroxidase activity in sporadic amyotrophic lateral sclerosis.
To determine the possible role of oxydative stress in the pathology of amyotrophic lateral sclerosis (SALS), we measured the plasma activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX), together with GPX and malone dialdehyde (MDA, a marker of lipoperoxydation) plasma concentrations in a sample of 21 SALS patients and 7 normal control (NC) subjects. MDA concentration and SOD activity were significantly higher, whereas GPX activity was significantly lower in SALS patients than in NC. Increased MDA concentration provides indirect confirmation of excess lipoperoxydation. Increased plasma SOD activity might reflect the involvement of extra-cellular SOD (SOD3), a hitherto unreported finding in SALS. Impaired GPX activity, which has already been found in red blood cells and brain tissue of SALS patients, might play a part in the pathogenesis of this disease.
Adult↗
Proliferating cell nuclear antigen (PCNA) in cerebral cavernomas: an immunocytochemical study of 42 cases.
BACKGROUND: The natural history and growth mechanisms of cerebral cavernous angiomas are unclear, which makes them difficult to manage. We attempted to evaluate the evolutive potential of cavernomas by studying the proliferative capacity of cells. METHODS: We studied 42 histologically verified cavernomas with monoclonal antibody to proliferating cell nuclear antigen (PCNA), an accessory protein of the cell cycle, the rate of which is increased in proliferative cells. The PCNA Labeling Index (PCNA LI) was calculated in each case, and the results were compared with histologic findings (lacy areas, thick walls, thrombi, hemosiderin) and clinical features (epilepsy, hematomas, pseudotumorous signs). RESULTS: Thirty-six of 42 cases (85.7%) revealed stained cells. PCNA LI ranged from 1 to 48% (mean: 23.39%). Statistical analyses showed a positive correlation between PCNA LI and the extent of lacy areas (p < 0.05). On the contrary, collagenous-walled and thrombotic areas rarely showed positively stained cells. We found no relationship between PCNA LI and clinical features. CONCLUSIONS: A proliferative capacity of endothelial cells does exist in some areas of cavernomas and may explain, besides thromboses and hemhorrages, the growth and even de novo appearance of these lesions. Occurrence of fragile blood cavities, thickening of others, and changes in blood flow may influence the evolution of lesions. Our results suggest that in cavernomas, some areas may undergo specific changes, which makes them more dynamic lesions than previously thought.
Adolescent↗
The structural components of music perception. A functional anatomical study.
This work explores the cerebral structures involved in the appreciation of music. We studied six young healthy subjects (right handed, French, without musical talent), using a high resolution PET device (CTI 953B) and 15O-labelled water. In three tasks, we studied the effects of selective attention to pitch, timbre and rhythm; a final task studied semantic familiarity with tunes (considered as divided attention for pitch and rhythm). These four tasks were performed on the same material (a tape consisting of 30 randomly arranged sequences of notes). We selected a paradigm, without a reference task, to compare the activations produced by attention to different parameters of the same stimulus. We expected that the activations recorded during each task would differ according to the differences in cognitive operations. We found activations preferentially in the left hemisphere for familiarity, pitch tasks and rhythm, and in the right hemisphere for the timbre task. The familiarity task activated the left inferior frontal gyrus, Brodmann area (BA) 47, and superior temporal gyrus (in its anterior part, BA 22). These activations presumably represent lexico-semantic access to melodic representations. In the pitch task, activations were observed in the left cuneus/precuneus (BA 18/19). These results were unexpected and we interpret them as reflecting a visual mental imagery strategy employed to carry out this task. The rhythm task activated left inferior Broca's area (BA 44/6), with extention into the neighbouring insula, suggesting a role for this cerebral region in the processing of sequential sounds.
Adult↗
Familial cavernous malformations in a large French kindred: mapping of the gene to the CCM1 locus on chromosome 7q.
OBJECTIVES: To characterise clinically a large French family affected with cerebral cavernomas and to check for linkage of this condition to chromosome 7. METHODS: A family, originating from Normandy and in which five members had undergone surgery for cavernomas, was extended. All members older than 18 were studied clinically and by neuroimaging. Genetic linkage analysis was conducted using 11 polymorphic microsatellite markers located between D7S502 and D7S479. RESULTS: The family included three generations. Among the 25 members investigated, 11 had an abnormal cerebral MRI, eight of them being symptomatic, and 12 were asymptomatic with a normal MRI. The status of the two remaining members could not be established on the basis of clinical and MRI data. The family reported shares some striking features with other previously linked families--namely, a high clinical penetrance and the presence of multiple lesions within most of the affected members. A lod score of 4.04 was obtained with marker D7S657 with no recombinant. Significant lod scores were also obtained with D7S524 (Zmax=3.32 at 0=0.00) and D7S630 (Zmax=3.44 at 0=0.00). These results establish linkage of the condition found in this family to chromosome 7. Haplotype analysis strongly suggests that the gene is telomeric to D7S802 and centromeric to D7S479. CONCLUSIONS: These data confirm linkage of cerebral cavernous malformations to chromosome 7 in a non-Hispanic family.
Adolescent↗
[Multiple and unilateral paralysis of the cranial nerves revealing 2 cerebellar infarctions].
A 86 year old man suffered multiple palsies of the right V, VI, VII, VIII, IX and X cranial nerves preceded for several weeks by transient diplopia, facial palsy and vertigo. The CT scan and MRI showed two infarcts sitting in the territories of the right postero-inferior cerebellar artery and the right antero-inferior cerebellar artery. A cerebellar syndrome developed several days later. Although cranial nerves palsies are very commun following infarcts of the cerebellar arteries, their occurrence without other neurological deficit, especially cerebellar syndrome, seems to be rare.
Aged↗
[Clinical and cognitive study of apraxia in cortico-basal atrophy. A selective disorder of the production system].
The aim of this study was to characterize the different processes underlying apraxic disorders in cortico-basal degeneration. Three patients were submitted to a prospective paradigm elaborated in the theoretical framework proposed by Roy and Square (1985). This cognitive model postulates a two-steps system in the control mechanisms in limb praxis: the conceptual system and the production system. Our results, strictly similar for the three patients, showed a sparing of the conceptual system and an impairment of the production system with a dramatic lack in the control of the temporal and spatial aspects of the gestures. These results suggest a dysfunction of the premotor cortex including the supplementary motor area.
Aged↗
Agraphia in Alzheimer's disease: an independent lexical impairment.
This study was conducted to delineate the pattern of the writing impairments in 12 patients with Alzheimer type dementia. The patients performed writing tasks involving regular and irregular words and nonwords given by dictation as well as a decision test composed of printed words and pictures requiring phonologic, lexical, and semantic processing. Writing from dictation demonstrated a predominant, but nonisolated, lexical deficit. In order to better evaluate this lexical disorder, the correlation between the dictation writing scores and the decision task scores was analyzed. No significant correlation was found among scores for irregular words, phonologically plausible errors, and scores of the lexical or semantic decision tasks, but there was a significant correlation among scores for the nonwords, nonphonological spelling errors, and scores of the phonologic decision task using printed words. These results would suggest that the "lexical" deficit in agraphia, i.e., difficulty in retrieval or loss of the spelling representations of words, is independent of the lexical or semantic capacities involved in other modalities.
Aged↗
Memory disorders in Alzheimer's disease and the organization of human memory.
The Squire and Zola-Morgan parallel organization model of the memory and the Tulving hierarchical model were developed mainly through the study of amnesic patients. The predictions of these two models are different, the first being more open to double dissociations and less restrictive than the second. Alzheimer's Disease is characterized by a differential impairment of the memory systems and by an interindividual variability which may take the form of dissociations between preserved and disturbed abilities in some patients. The objective of this study was to use the memory dysfunctions of patients with AD to test the validity of the two models. Analysis of the group data provided an average profile of memory disturbance consistent both with much of the data given in AD literature and with the two models. Using a multiple single-case strategy, we demonstrated several simple dissociations which are for the greater part compatible with the two models. Two of the dissociations underline the limits of the Tulving model, which otherwise accounts for a lot of results. The study supports the relevance of AD for the understanding of the cognitive architecture of the human memory.
Aged↗
Hereditary neuropathy with liability to pressure palsies with a partial deletion of the region often duplicated in Charcot-Marie-Tooth disease, type 1A.
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Adult↗
[Akinetic mutism with right hemiplegia caused by infarction in the territory of the left anterior cerebral artery].
A 65 years old woman with chronic high blood pressure and diabetes mellitus presented with a mutism akinetic of sudden onset and a right total hemiplegia with a Babinski sign secondary to a left anterior cerebral artery infarction. She had had six months earlier a transient gait disturbance. At that time, the CT scan showed lacunar infarcts of the head of both caudate nuclei. Neuropathological examination revealed that the left infarction of the anterior cerebral artery involved the superior frontal gyrus, the supplementary motor area, the cingulate gyrus and the corpus callosum. There were also multiple lacunes of the head of both caudate nuclei, anterior limb of the internal capsules, white matter, basal ganglia and thalami. The mutism akinetic was thought to be the result of a bilateral disruption of a functional loop including on each side, the supplementary motor area, the cingulate gyrus, the subcallosal tract and the head of the caudate nucleus. On the right side, the lesion of the caudate nucleus could have interrupted this loop normally involved in the induction of voluntary movements and in the communication with the external surroundings.
Aged↗
[Celiac disease in adults revealed by sensory-motor neuropathy].
Central or peripheral nervous system complications are occasionally observed in adult patients with celiac disease. Several mechanisms have been proposed including vitamin deficiency, vascular inflammation and a direct effect of gluten intolerance. Typical nerve fiber damage due to demyelinization has been suggested. We observed a 65-year old woman with a right peroneal nerve palsy superimposed on a diffuse peripheral neuropathy who was found to have folic acid deficiency which in turn led to the diagnosis of adult celiac disease. Electrophysiological and histological studies demonstrated a predominantly demyelinating peripheral neuropathy which responded first to parenteral folic acid supplementation and second to a gluten-free diet. The mechanisms of peripheral nerve damage in adult celiac disease are briefly discussed and the possible role of folic acid deficiency is emphasized.
Aged↗
[Diagnosis of vascular dementia].
Vascular dementia is most often the result of multiple lesions affecting deep brain structures and the white matter. Diagnosis sometimes appears much simpler than it really is. Indeed, it is difficult to evaluate the impairment of higher brain functions and even to affirm dementia. Although the definition of dementia is simple theoretically, in clinical practice it is sometimes particularly difficult to assess when neurological impairments cause a socio-professional handicap. Two pitfalls should be avoided. First, a patient with signs of mental deficiency and a vascular lesion of brain vessels so easily identified by CT scan or MRI does not necessarily have vascular dementia. Secondly and inversely, dementia could be missed in a patient with a physical handicap whose defective mental functions go unnoticed both by his family and physician. Unlike Alzheimer's disease where neuropsychological problems predominate because these patients retain good physical autonomy for a long time, patients with vascular dementia are not explored routinely for neuropsychological disorders which may be hidden by more obvious neurological symptoms. Such disorders, especially gait disorders, are however the key to diagnosis. Mixed dementia is a third pitfall. This concept is based on histological findings and should not be used as a "catch-all" category. During the patient's lifetime diagnosis is probably impossible; current clinical scales do not take it into consideration.
Dementia, Vascular↗