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M Sarazin

Publications and source records attributed to M Sarazin.

11 recordsLinked to original sources
PubMed2002

Reversible leukoencephalopathy in cerebral amyloid angiopathy presenting as subacute dementia.

This report concerns a 71-year-old woman who had rapid progressive dementia along with myocloni and increased blood pressure. Cranial computed tomography and magnetic resonance imaging scans showed bilateral widespread white matter changes with mass effect. A brain biopsy revealed an amyloid angiopathy in leptomeningeal as well as cerebral cortex arteries. After 2 months of antihypertensive treatment, a dramatic improvement of cognitive functions and a spectacular regression of leukoencephalopathy were observed. We suggest that hypertensive encephalopathy may worsen or reveal cerebral amyloid angiopathy.

Aged↗
PubMed2002

[Mild Cognitive Impairment or pre-demential Alzheimer's disease?].

The concept of Mild Cognitive Impairment (MCI) is proposed to define a state of cognition where the deficiency is greater than expected for a subject's age and socio-cultural background, but not sufficiently severe to satisfy the criteria of nosographic classifications of dementia. The concept of MCI cannot provide an etiological diagnosis but can be useful for recognizing and following patients with mild impairment. It raises the question of early diagnosis of Alzheimer's disease. The risk of progression to dementia is greater in patients with MCI, particularly those whose memory is the only domain involved - "amnesic MCI". Patients with amnesic MCI can be distinguished from those with MCI with multiple domains slightly impaired or non-amnesic MCI where only one domain (language, visual-spatial.) other than memory is involved. Depending on the type of deficiency, amnesic MCI may progress to different types of disease states. At the early stage of pure memory impairment, a distinction should be made between Alzheimer-related memory disorders and those related to another neurological conditions or the brain aging process. The question is whether the diagnosis of Alzheimer's disease can be made at this stage. Biological markers and brain imaging provide useful information, but these diagnostic tools remain imprecise and have not been validated for routine use. The process of diagnosis must therefore focus on an analysis of the cognitive impairment. The predementia phase of Alzheimer's disease is characterized by a progressive "hippocampal" decline in memory, sometimes associated with impaired execution. A careful analysis of the cognitive impairment helps identify "hippocampal amnesia syndrome" suggestive of the diagnosis of Alzheimer's disease.

Aged↗
PubMed2001

[Procedural learning and Parkinson disease: implication of striato-frontal loops].

OBJECTIVE: To investigate procedural learning in non demented patients with idiopathic Parkinson's disease (PD). BACKGROUND: Experimental evidence implicate the basal ganglia in procedural learning. Selective impairment has more recently been described in patients with frontal lesions. METHODS: The performance of 20 demented patients and 15 matched normal controls was studied in the serial reaction time task (SRTT). Performance on procedural task was further compared with that of 9 normal controls and with patients' performance on tests assessing explicit memory, executive functions and global efficiency. RESULTS: The group of patients with PD showed impaired procedural learning. The difference of response time between the repeated and the non-repeated blocks was smaller in PD when compared to controls. Subsequent analyses separated PD patients into two subgroups according to their performance on SRTT, measured by the rebound effect. PD patients whose learning was normal differed from PD patients whose learning was impaired on performance in tests sensitive to frontal lobe dysfunction. CONCLUSION: These results confirm the implication of the striatum in procedural learning and suggest that performance on cognitive procedural learning depends on the striato-frontal circuits.

Aged↗
PubMed2000

Isoplanatism in a multiconjugate adaptive optics system.

Turbulence correction in a large field of view by use of an adaptive optics imaging system with several deformable mirrors (DM's) conjugated to various heights is considered. The residual phase variance is computed for an optimized linear algorithm in which a correction of each turbulent layer is achieved by applying a combination of suitably smoothed and scaled input phase screens to all DM's. Finite turbulence outer scale and finite spatial resolution of the DM's are taken into account. A general expression for the isoplanatic angle thetaM of a system with M mirrors is derived in the limiting case of infinitely large apertures and Kolmogorov turbulence. Like Fried's isoplanatic angle theta0,thetaM is a function only of the turbulence vertical profile, is scalable with wavelength, and is independent of the telescope diameter. Use of angle thetaM permits the gain in the field of view due to the increased number of DM's to be quantified and their optimal conjugate heights to be found. Calculations with real turbulence profiles show that with three DM's a gain of 7-10x is possible, giving the typical and best isoplanatic field-of-view radii of 16 and 30 arcseconds, respectively, at lambda = 0.5 microm. It is shown that in the actual systems the isoplanatic field will be somewhat larger than thetaM owing to the combined effects of finite aperture diameter, finite outer scale, and optimized wave-front spatial filtering. However, this additional gain is not dramatic; it is less than 1.5x for large-aperture telescopes.

Journal Article↗
PubMed2000

Influence on bone metabolism of dietary trace elements, protein, fat, carbohydrates, and vitamins.

Osteoporosis is a multifactorial disease driven primarily by the genetic factors that control bone metabolism. Among environmental factors, diet may play a key role, affording a target for low-cost intervention. Calcium and vitamin D are well known to affect bone metabolism. Other nutrients may influence bone mass changes; for instance, a number of trace elements and vitamins other than vitamin D are essential to many of the steps of bone metabolism. A wide variety of foods provide these nutrients, and in industrialized countries deficiencies are more often due to idiosyncratic eating habits than to cultural influences. Both culture and vogue influence the amount of carbohydrate, fat, and protein in the typical diet. In children, the current trend is to reduce protein and to increase carbohydrate and fat. Data from epidemiological and animal studies suggest that this may adversely affect bone mass and the fracture risk.

Bone Density↗
PubMed1998

Clinicometabolic dissociation of cognitive functions and social behavior in frontal lobe lesions.

OBJECTIVE/BACKGROUND: Case studies suggest a dissociation between cognitive functions that have been impaired after damage to the dorsolateral prefrontal cortex and social skills disturbed when the ventromedial prefrontal areas are affected. Because this dissociation had not been confirmed in a clinical setting, clinicometabolic correlations were sought in 13 patients with various lesions of the prefrontal cortex. DESIGN/METHODS: The clinical assessment included extensive testing of executive functions and evaluation of behavioral abnormalities based on an informant questionnaire. Regional cerebral glucose metabolism (rCMRGlu) was measured with [l8F] fluorodeoxyglucose ([18F] FDG) and 31-slide high-resolution PET. RESULTS: Executive-function test performance was significantly correlated with rCMRGlu in the dorsolateral prefrontal cortex (Brodmann's areas 8, 9, 45, 46, and 47) and anterior cingulate cortex (Brodmann's areas 24 and 32). Behavioral scores were significantly correlated with rCMRGlu in the frontopolar (Brodmann's area 10) and orbitofrontal cortex (Brodmann's areas 11, 12, 13, and 14). CONCLUSION: These results show that impaired executive functions and serial skill deficits are associated with distinct metabolic patterns in patients with frontal lobe pathology. In agreement with activation studies in normal subjects, our data suggest the existence of a modular organization of the frontal cortex in humans, as previously reported in nonhuman primates.

Adult↗
PubMed1996

Memory for spatial location is affected in Parkinson's disease.

Are the striato-frontal neuronal circuits implicated in learning of item-specific spatial coordinates? To answer this question, we compared the performance of 20 patients with Parkinson's disease to that of 14 controls matched for age, global cognitive efficiency and mood, on a visuo-spatial learning task with little involvement of motor and constructive functions, allowing control of encoding and comparison of free recall, cued recall and recognition. Compared to controls, patients showed a severe memory impairment for visuo-spatial location of pictures, contrasting with relative preservation of verbal memory, and mild difficulties in perceptive visuo-spatial and executive functions. These results implicate striato-frontal neuronal circuits in memory for spatial location.

Aged↗
PubMed1995

Primary central nervous system lymphoma: treatment with chemotherapy and radiotherapy.

Between 1989 and 1993, 22 HIV negative patients with primary central nervous system lymphoma (PCNLS) were treated with three different regimens. In group A, 13 patients received preradiotherapy systemic and intrathecal methotrexate (MTX), radiotherapy (RT) and three courses of post-RT chemotherapy (CT) with thiotepa and procarbazine. In group B, 4 patients received a similar CT only after RT and without intrathecal MTX in 3/4 cases. In group C, 5 elderly patients received CT alone. In group A, 9/13 patients achieved response after pre-RT CT and 12/13 were in complete response (CR) after RT. After a median follow-up of 27 months, 8/13 (62%) patients are alive but 4 have leucoencephalopathy and cognitive dysfunction. In group B, all 4 patients were in CR after RT but the 3 patients who did not receive intrathecal MTX died within 10 months with meningeal recurrence. In group C, 4/5 patients had a response to CT. 2 patients died of recurrent tumour at 5 and 10 months, and 2 are living in CR 11+ and 21+ months after diagnosis, 1 after salvage CT. Combined treatment with RT and CT is useful in PCNSL but adequate treatment of the meninges is required. CT alone is sometimes of value in elderly patients in whom RT is not indicated.

Adult↗
PubMed1995

Dynamical recurrent neural networks--towards environmental time series prediction.

Dynamical Recurrent Neural Networks (DRNN) (Aussem 1995a) are a class of fully recurrent networks obtained by modeling synapses as autoregressive filters. By virtue of their internal dynamic, these networks approximate the underlying law governing the time series by a system of nonlinear difference equations of internal variables. They therefore provide history-sensitive forecasts without having to be explicitly fed with external memory. The model is trained by a local and recursive error propagation algorithm called temporal-recurrent-backpropagation. The efficiency of the procedure benefits from the exponential decay of the gradient terms backpropagated through the adjoint network. We assess the predictive ability of the DRNN model with meterological and astronomical time series recorded around the candidate observation sites for the future VLT telescope. The hope is that reliable environmental forecasts provided with the model will allow the modern telescopes to be preset, a few hours in advance, in the most suited instrumental mode. In this perspective, the model is first appraised on precipitation measurements with traditional nonlinear AR and ARMA techniques using feedforward networks. Then we tackle a complex problem, namely the prediction of astronomical seeing, known to be a very erratic time series. A fuzzy coding approach is used to reduce the complexity of the underlying laws governing the seeing. Then, a fuzzy correspondence analysis is carried out to explore the internal relationships in the data. Based on a carefully selected set of meteorological variables at the same time-point, a nonlinear multiple regression, termed nowcasting (Murtagh et al. 1993, 1995), is carried out on the fuzzily coded seeing records. The DRNN is shown to outperform the fuzzy k-nearest neighbors method.

Environmental Monitoring↗
PubMed1984

[Not Available].

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France↗