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Biomedical subjects

E Salmon

Publications and source records attributed to E Salmon.

At least 55 records · Page 3Linked to original sources
PubMed1999

Fluorodopa uptake and glucose metabolism in early stages of corticobasal degeneration.

Fluorodopa (FDOPA) and fluorodeoxyglucose (FDG) PET was performed in six patients in early stages of corticobasal degeneration (CBD) and compared to Parkinson's disease (PD) patients with a similar degree of bradykinesia and rigidity and to healthy controls. Statistical parametric mapping analysis comparing CBD to controls showed metabolic decrease in premotor, primary motor, supplementary motor, primary sensory, prefrontal, and parietal associative cortices, and in caudate and thalamus contralateral to the side of clinical signs. Except for the prefrontal regions a similar metabolic pattern was observed when CBD was compared to PD. Putamen FDOPA uptake was decreased in both CBD and PD. Caudate FDOPA uptake in CBD patients was decreased contralateral to clinical signs when compared to controls, but was higher than in PD. In early stages of CBD, FDOPA and FDG PET patterns differed from those observed in PD. In CBD the asymmetry in FDOPA uptake was less pronounced than that of clinical signs or metabolic impairment.

Aged↗
PubMed1999

Executive dysfunction in Alzheimer's disease.

Executive functioning was examined in 20 patients with Alzheimer's disease (AD) and 20 normal elderly subjects. The results showed that AD patients present lower performance compared to control subjects in all executive tasks, confirming that some executive deficits may be present in the first stages of the disease. A factorial analysis suggested that these deficits can be related to two domains of the executive functions: the inhibition abilities and the capacity to co-ordinate simultaneously storage and processing of information. Moreover, the performance on these factors is correlated to different anterior and posterior cortical areas.

Aged↗
PubMed1999

Phonological loop and central executive functioning in Alzheimer's disease.

The phonological loop and central executive functioning were examined in patients with Alzheimer's disease (AD) and in normal elderly subjects. AD patients showed abnormal functioning of the phonological loop and decreased performance on tasks assessing the central executive. However, when AD patients were separated into two groups on the basis of their span level, both groups showed deficits of the central executive but only patients with the lower span level presented a dysfunction of the phonological loop as well as impaired performance in tasks of phonological discrimination, articulation rate and speed of processing. These results are interpreted in terms of progression of the disease, with high-span level patients being less severely demented and displaying deficits only in higher-level cognitive functions (such as manipulation of information stored in working memory) whereas patients with a low span level have impairments encompassing a series of more basic processes.

Aged↗
PubMed1999

Regional brain activity during tasks devoted to the central executive of working memory.

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed. A PET activation study was performed with four cognitive tasks, crossing conditions of temporary storage and manipulation of information. The manipulation of information induced an activation in the right (BA 10/46) and left (BA 9/6) middle frontal gyrus and in the left parietal area (BA7). The interaction between the storage and manipulation conditions did not reveal any significant changes in activation. These results are in agreement with the hypothesis that CE functions are distributed between anterior and posterior brain areas, but could also reflect a simultaneous involvement of controlled (frontal) and automatic (parietal) attentional systems. In the other hand, the absence of interaction between the storage and manipulation conditions demonstrates that the CE is not necessarily related to the presence of a memory load.

Adult↗
PubMed1999

Positive feedback interactions between microtubule and actin dynamics during cell motility.

The migration of tissue cells requires interplay between the microtubule and actin cytoskeletal systems. Recent reports suggest that interactions of microtubules with actin dynamics creates a polarization of microtubule assembly behavior in cells, such that microtubule growth occurs at the leading edge and microtubule shortening occurs at the cell body and rear. Microtubule growth and shortening may activate Rac1 and RhoA signaling, respectively, to control actin dynamics. Thus, an actin-dependent gradient in microtubule dynamic-instability parameters in cells may feed back through the activation of specific signalling pathways to perpetuate the polarized actin-assembly dynamics required for cell motility.

Actins↗
PubMed1999

Exploration of implicit artificial grammar learning in Parkinson's disease.

Parkinson's disease (PD) patients and matched control subjects were compared in an artificial grammar learning task, one of the main paradigms of implicit learning. The evaluation material was constructed in such a way that grammaticality judgements (classification task) made on the test strings could not be based on some superficial features of the learning strings: the grammatical and nongrammatical test strings did not differ according to different measures of chunk strength (based on the frequency with which their bigram and trigram components appear in the learning strings). Unknown to participants, two successive presentations of the set of test strings were allowed during the classification task. Results show that PD patients and controls performed at the same level during the first presentation of the test strings series, which suggests that the striatum is not (crucially) implicated in the ability to learn implicitly the complex conditional associations between elements present in a set of examples generated by a finite-state grammar. However, and contrary to control subjects, the classification performance of PD patients was at chance during the second presentation of the test strings. We argue that this latter result could be the consequence of the attentional deficit of PD patients.

Association Learning↗
PubMed1999

Methodological issues in a cost-of-dementia study in Belgium: the NAtional Dementia Economic Study (NADES).

The NAtional Dementia Economic Study (NADES) is an on-going prospective, one-year cohort study developed in Belgium to assess the socio-economic consequences of dementia in a group of patients and their caregivers (n = 400). Comparison is made with a group of subjects with cognitive impairment and no dementia (n = 100) and a group of subjects without any cognitive impairment (n = 100). Recruitment of subjects is based on screening of warning signs of dementia by general practitioners, followed by a Cambridge Mental Disorders of the Elderly Examination (CAMDEX) performed at home. This paper presents an overview of the study protocol and the rationale for basic design options, such as the choice of study population, screening strategy, and methods used for the case validation. It also presents preliminary results on the prevalence of dementia in general practice, the sensitivity and specificity of the warning signs as a screening test of dementia, and the validity of a computerised case ascertainment algorithm based on DSM-III-R criteria.

Aged↗
PubMed1999

Early thalamic and cortical hypometabolism in adult-onset dementia due to metachromatic leukodystrophy.

A case of early-onset adult dementia with family history of dementia is reported, characterised by neuropsychological deficits, suggesting frontal involvement, with mild non specific white matter abnormalities on CT scan. Familial Alzheimer's disease was suspected but the neuropathological diagnosis on brain biopsy was metachromatic leukodystrophy. 18FDG-PET revealed a very peculiar pattern of metabolic impairment in thalamic areas, in medial and frontopolar regions, and in occipital lobes. Neuropsychological follow-up showed relatively stable difficulties of long-term memory and signs of frontal lobe dysfunction, similar to those observed in subcortical dementias. MRI subsequently showed periventricular leukoencephalopathy. The brain metabolic pattern observed in that case of metachromatic leukodystrophy was quite different from that reported in other types of dementia.

Adult↗
PubMed1997

Functional anatomy of verbal and visuospatial span tasks in Alzheimer's disease.

The aim of the study was to emphasize cerebral regions which subserve the performance of short-term memory tasks in patients with Alzheimer's disease. We correlated scores obtained on span tasks with cerebral metabolism measured at rest with positron emission tomography. Scores obtained on the digit span task correlated with glucose metabolism in a brain area centered on the premotor cortex and extending to the adjacent motor and parietal gyri. There exists some evidence suggesting that this area may subserve the sequential organization of material stored in short-term memory. In a secondary analysis, we also observed significant interregional correlations between left-sided brain areas which are part of the neural network subserving verbal working memory processes in healthy controls. These data suggest that individual performance on verbal span tasks in AD patients may essentially depend on the preservation of their ordination processing capacity. The absence of correlation with prefrontal regions suggests that AD patients might not spontaneously engage central executive resources to reach their maximal span score. For simultaneous visuospatial span task, the performance of patients correlated with posterior brain regions, and not with prefrontal cortices.

Aged↗
PubMed1997

Anterior cingulate and motor network metabolic impairment in progressive supranuclear palsy.

Progressive supranuclear palsy is the prototype of subcortical dementia. Using positron emission tomography and statistical parametric mapping, we compared the glucose metabolic pattern obtained in this subcortical dementia to that observed in elderly healthy controls and in Alzheimer's disease, the prototype of cortical dementia. Progressive supranuclear palsy was characterized by a relative decrease of metabolism in anterior cingulate, adjacent supplementary motor area, precentral cortex, middle prefrontal cortex, midbrain tegmentum, globus pallidus, and ventrolateral and dorsomedial nuclei of thalamus. The data in progressive supranuclear palsy highlight predominant metabolic impairment in brain structures engaged in response selection, in attention for action, and in motor networks.

Aged↗
PubMed1997

Pathways of spindle assembly.

Recent studies have revealed that, in some systems, chromatin has the ability to stabilize microtubules and organize them into bipolar spindles independently of kinetochores and centrosomes. In addition, several molecules have been identified recently that are necessary for spindle assembly; these include proteins that regulate microtubule dynamics, proteins that organize microtubule minus ends into spindle poles, and members of the kinesin superfamily that reside on the chromosome arms.

Animals↗
PubMed1997

Positron emission tomography in parkinsonism.

Positron emission tomography provides researchers and clinicians with information on cerebral blood flow, metabolic pathways or neurotransmission systems, which may help to understand the physiopathology of movement disorders. Studies of the nigrostriatal dopaminergic pathway and data on cerebral glucose metabolism contribute to discriminate between parkinsonian syndromes. New techniques for image processing and statistical analysis, and brain activation studies better emphasize dysfunction of cortico-subcortical neuronal networks responsible for movement disorders, or functional modification after therapeutic action.

Basal Ganglia↗
PubMed1996

Postencephalitic stereotyped involuntary movements responsive to L-Dopa.

In 1954, at the age of 5 years, our patient had an encephalitic syndrome associated with a prolonged lethargic state. After this episode, he developed a severe parkinsonian syndrome that, after a few years, was associated with axial dystonia and stereotyped abnormal movements of the upper limbs. This complex and progressive extrapyramidal syndrome had many similarities to the encephalitis lethargica as described by von Economo. Results of cerebral computed tomography and magnetic resonance imaging were normal. Fluorodopa positron emission tomography showed a significant bilateral reduction of tracer accumulation in both putamen, similar to that observed in patients with idiopathic Parkinson's disease. However, in this patient, treatment with L-Dopa suppressed all akinetic, dystonic and dyskinetic symptoms. The effectiveness of L-Dopa was abolished by administration of a D2 antagonist and was fully reproduced by a D2 agonist. In conclusion, this patient presented a complex postencephalitic, extrapyramidal syndrome, with akinetic symptoms and involuntary movements. These symptoms appeared to be related to a limited lesion of the dopaminergic neurons of the zona compacta of the substantia nigra.

Adult↗
PubMed1996

Regional brain activity during working memory tasks.

The first aim of our PET study was to replicate previous findings concerning the brain areas activated by a verbal working memory task. The second aim was to specify the neural basis of the central executive, using a task of working memory updating. Our data confirm that the lower left supramarginal gyrus and premotor area are the key regions subserving short-term verbal memory processes. They also suggest that the updating memory task is related to middorsolateral prefrontal activation, most probably responsible for the updating function of the central executive. An unexpected, predominantly right activation occurred in the inferior parietal region during the verbal memory updating task, which we related to a visuospatial strategy used to maintain the information in short-term memory. A third purpose was to explore the brain regions activated by a nonverbal, visual memory task, and our results confirm the importance of the superior occipital gyrus in the visual short-term memory.

Adult↗
PubMed1996

Combined study of cerebral glucose metabolism and [11C]methionine accumulation in probable Alzheimer's disease using positron emission tomography.

There is a characteristic decrease in glucose metabolism in associative frontal and temporo-parietal cortices of patients suffering from Alzheimer's disease (AD). The decrease in metabolism might result from local neuronal loss or from a decrease of synaptic activity. We measured in vivo [11C]methionine accumulation into proteins with positron emission tomography (PET) to assess cortical tissue loss in AD. Both global regional activity and compartmental analysis were used to express [11C]methionine accumulation into brain tissue. Glucose metabolism was measures with [18F]fluorodeoxyglucose and autoradiographic method. Combined studies were performed in 10 patients with probable AD, compared to age-matched healthy volunteers. There was a significant 45% decrease of temporo-parietal glucose metabolism in patients with AD, and frontal metabolism was lowered in most patients. Temporo-parietal metabolism correlated to dementia severity. [11C]methionine incorporation into temporo-parietal and frontal cortices was not significantly decreased in AD. There was no correlation with clinical symptoms. Data suggest that regional tissue loss, assessed by the decrease of [11C]methionine accumulation, is not sufficient to explain cortical glucose hypometabolism, which reflects, rather, reduced synaptic connectivity.

Aged↗
PubMed1996

Frontal lobe dementia presenting as personality disorder.

The early differential diagnosis of frontal lobe dementia is particularly difficult because changes of personality or behaviour overwhelm intellectual and cognitive impairments. We report the case of a patient presenting with paranoid personality disorder who refused to collaborate in neuropsychological testing. Initial functional imaging showed frontal hypometabolism that served as an early marker of frontal lobe dysfunction.

Brain↗
PubMed1996

[Parkinsonian syndrome and post-encephalitic stereotyped involuntary movements responsive to L-dopa].

In 1954, when he was five years old, a patient suffered from encephalitis with a prolonged lethargic state. Following this episode, he presented a severe parkinsonian syndrome which was associated, after a few years, with an axial dystonia and stereotyped involuntary movements of the upper limbs. These abnormal movements were particular by their coordinated appearance, their rhythmicity and their relative slowness. Treatment with L-dopa suppressed all akinetic, dystonic and dyskinetic symptoms. At age of 40 years, all the akinetic, dystonic and dyskinetic symptoms reappeared after drug withdrawal. Cerebral computed tomography, magnetic resonance imaging and fluorodeoxyglucose positron emission tomography were normal. Fluorodopa positron emission tomography revealed a significant bilateral reduction of tracer accumulation in the posterior part of both putamen, similar to that observed in patients with idiopathic Parkinson's disease. In this patient, pharmacological tests revealed that effectiveness of L-dopa was abolished by administration of a D2 antagonist, and was fully reproduced by a D2 agonist. Clinical signs, pharmacological data and past-medical history strongly suggested a limited lesion of the zona compacta of substantia nigra induced by viral agression. This complex and progressive extrapyramidal syndrome had strong similarities with the lethargic encephalitis of Von Economo and its late symptoms. Other diseases associating akinesia and dyskinesia or dystonic phenomena, like dopa-sensitive dystonia and juvenile Parkinson's disease, are very unlikely. Thus, the persistance of sporadic forms of Von Economo's encephalitis could be discussed.

Adult↗