Biomedical subjects

Agnès Michon

Publications and source records attributed to Agnès Michon.

8 recordsLinked to original sources

PubMed2006

Decreased theta event-related synchronization during working memory activation is associated with progressive mild cognitive impairment.

BACKGROUND: Among the different quantitative electroencephalographic markers, theta activity is known to reflect neural resources involved in memory processes and directed attention. Previous studies suggested that synchronization likelihood analysis in theta-band frequency might be a sensitive method to identify early alterations of neuronal networks in mild cognitive impairment (MCI). METHODS: We report here a longitudinal study of 24 MCI patients with theta event-related synchronization (ERS) analysis during the n-back working memory task and neuropsychological follow-up after 1 year. Statistical analysis included analysis of variance and logistic regression to assess the relationship between cognitive decline and theta ERS. RESULTS: Upon follow-up, 13 MCI patients showed progressive MCI and 11 remained stable. In both groups, the phasic increase in theta amplitude after stimulus presentation did not depend on working memory load and electrode sites. Progressive MCI cases displayed significantly lower theta ERS power over all electrode sites compared to stable MCI cases. Theta ERS was significantly related to the cognitive outcome explaining 15.5% of its variability. In terms of MCI classification, the best combination of sensitivity and specificity was 0.87 and 0.60, respectively, with an area under the corresponding receiver operating characteristic curve reaching 76%. CONCLUSIONS: The present data indicate that a decrease in the early phasic theta ERS power during working memory activation may predict cognitive decline in MCI. This phenomenon is not related to working memory load but may reflect the presence of early deficits in directed attention-related neural circuits in MCI.

Aged↗

PubMed2006

Pain in severe dementia: self-assessment or observational scales?

OBJECTIVES: To assess the performance of self-assessment scales in severely demented hospitalized patients and to compare it with observational data. DESIGN: Prospective clinical study. SETTING: Geriatrics hospital and a geriatric psychiatry service. PARTICIPANTS: All patients who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for dementia, with a Mini-Mental State Examination score less than 11 and a Clinical Dementia Rating score of 3. MEASUREMENTS: Three self-assessment tools--the verbal, horizontal visual, and faces pain scales--were administered in randomized order. A nursing team independently completed an observational pain rating scale. Main outcomes were comprehension (ability to explain scale use and correctly indicate positions for no pain and extreme pain, on two separate occasions), inter- and intrarater reliability, and comparison of pain intensities measured by the different scales. RESULTS: Sixty-one percent of 129 severely demented patients (mean age 83.7, 69% women) demonstrated comprehension of at least one scale. Comprehension rates were significantly better for the verbal and the faces pain scales. For patients who demonstrated good comprehension, the inter- and intrarater reliability of the three self-assessment scales was high (intraclass correlation coefficient=0.88-0.98). Correlation between the three self-assessment scales was moderate to strong (Spearman correlation coefficient (r)=0.45-0.94; P<.001). Observational rating correlated at least moderately with self-assessment (r=0.25-0.63), although for patients reporting pain, the observational rating scale underestimated severity compared with all three self-assessment scales. CONCLUSION: Clinicians should not apply observational scales routinely in severely demented patients, because many are capable of reliably reporting their own pain.

Aged, 80 and over↗

PubMed2006

[Crisis intervention in dementia].

A crisis is an episode of acute disorganization with apparition of symptoms, leading the individual and his relatives to have recourse to the health system in emergency. It refers to a period of intra-psychic or interpersonal balance discontinuity. The management of the crisis, as it was proposed in psychiatric models since the seventies, aims not only to provide a psychological and immediate answer but also to use this crucial moment as an opportunity of change. Based on our experience in an acute care unit for demented patients, we discuss how the concept of crisis can be applied in psychiatric care of demented patients.

Adaptation, Psychological↗

PubMed2005

Early event-related potential changes during working memory activation predict rapid decline in mild cognitive impairment.

BACKGROUND: The conversion of mild cognitive impairment (MCI) to Alzheimer's disease is associated with substantial compromise of neocortical circuits subserving rapid cognitive functions such as working memory. Event-related potential (ERP) analysis is a powerful tool to identify early impairment of these circuits, yet research for an electrophysiological marker of cognitive deterioration in MCI is scarce. Using a "2-back" activation paradigm, we recently described an electrophysiological correlate of working memory activation (positive-negative working memory [PN(wm)] component) over parietal electrodes. METHODS: Ours was a longitudinal study of 24 MCI patients with ERP analysis at inclusion and neuropsychological follow-up after 1 year. We used ERP waveform subtraction analysis between the n-back and control tasks. Analysis of variance (ANOVA) was used to compare electroencephalograph latencies between progressive MCI (PMCI) and stable MCI (SMCI), and univariate regression was used to assess the relationship between neuropsychological measures at baseline and clinical outcome. RESULTS: Thirteen (54%) MCI patients showed PMCI, and 11 (46%) remained stable (SMCI). In SMCI, a PN(wm) component with significantly larger density compared to baseline was identified when subtracting the detection task for both the 1- and 2-back tasks. In contrast, in PMCI, the PN(wm) component was absent in both 1-back and 2-back conditions. Neuropsychological variables and n-back test performance at inclusion did not predict cognitive deterioration 1 year later. CONCLUSIONS: In conjunction with recent functional imaging data, the present results support the notion of an early dysfunction of neural generators within the parietal cortex in MCI. They also reveal that the absence of the PN(wm) component may provide an easily applicable qualitative predictive marker of rapid cognitive deterioration in MCI.

Aged↗

PubMed2003

Specific BACE1 genotypes provide additional risk for late-onset Alzheimer disease in APOE epsilon 4 carriers.

Alzheimer disease (AD) is characterized neuropathologically by neurofibrillary tangles and senile plaques. A key component of plaques is A beta, a polypeptide derived from A beta-precursor protein (APP) through proteolytic cleavage catalyzed by beta and gamma-secretase. We hypothesized that sequence variation in genes BACE1 (on chromosome 11q23.3) and BACE2 (on chromosome 21q22.3), which encode two closely related proteases that seem to act as the APP beta-secretase, may represent a genetic risk factor for AD. We analyzed the frequencies of single nucleotide polymorphisms (SNPs) in BACE1 and BACE2 genes in a community-based sample of 96 individuals with late-onset AD and 170 controls selected randomly among residents of the same community. The genotype data in both study groups did not demonstrate any association between AD and BACE1 or BACE2. After stratification for APOE status, however, an association between a BACE1 polymorphism located within codon V262 and AD in APOE epsilon 4 carriers was observed (P = 0.03). We conclude that sequence variation in the BACE1 or BACE 2 gene is not a significant risk factor for AD; however, a combination of a specific BACE1 allele and APOE epsilon 4 may increase the risk for Alzheimer disease over and above that attributed to APOE epsilon 4 alone.

Alzheimer Disease↗

PubMed2003

Metabolic correlates of behavioral and affective disturbances in frontal lobe pathologies.

OBJECTIVE: Although previous studies have shown that the human frontal cortex is involved in the experience of emotions as well as in social behavior, data regarding the exact anatomical substrates of behavioral and affective deficits in frontal lobe pathologies are still scarce. The aim of this study was to investigate the metabolic correlates of these deficits in a group of non-selected consecutive patients with frontal lobe lesions. PATIENTS AND METHODS: Clinicometabolic correlations between several emotional and social parameters and metabolic patterns in the frontal cortex and amygdala were investigated in 32 patients with frontal lobe pathologies. The behavioral disturbances were evaluated using the Lhermitte's informant questionnaire. Regional cerebral glucose metabolism was measured with [(18)F] fluorodeoxyglucose and high-resolution positron emission tomography. Statistical analysis was performed using both single variable correlation and multiple regression analyses. RESULTS: Both single variable and multivariate analyses demonstrate that decreased regional glucose metabolism in the right medial area 10 was associated with apathy. There were also significant negative relationships between metabolism in the right orbitofrontal cortex and stereotypy and indifference to rules. Impulsiveness, personality disturbances and loss of emotional control were associated with decreased metabolism in the left amygdala. CONCLUSIONS: In terms of clinicometabolic correlations, the present data support the implication of different functional anatomic systems in frontal lobe-related behavioral and affective disturbances. In particular, they imply that the classically described symptoms of impaired behavioral control may be related to right orbitofrontal cortex hypometabolism whereas impaired regulation of emotions may result from a functional damage of the left amygdala.

Adult↗

PubMed2003

[What is dementia? 1. The patient's perspective].

The dementia conveys representations in term of loss, loss of knowledge, loss of cognition, loss of autonomy, loss of awareness of the deficits, with for consequencies a loss of exchanges and social withdrawal. Because of the difficulty for the patient to communicate his (her) feelings, it is difficult to understand his (her) experience of living. The analysis of speech through interviews realized with Alzheimer'disease patients, shows that the person who feels to enter a shape of abnormality, suffers from the loss of control of his/her existence, change of the relationships with the circle of acquaintances, other people's opinion, and social stigmatisation.

Aged↗

PubMed2002

Neuropathological analysis of an adult case of the Cornelia de Lange syndrome.

Cornelia de Lange syndrome (CDLS) is a rare multisystemic malformative syndrome of uncertain etiology characterized by severe psychomotor and mental retardation. Here we report the neuropathological analysis of a 35-year-old patient who displayed the classical clinical symptomatology of CDLS. A congenital dysgenesis of the brain was evident including abnormal convolution patterns of the cerebral gyri, frontal lobe hypoplasia and focal lack of myelination in layers V and VI of the left temporal cortex. In addition, there were vascular scars in the CA2-3 region of the left hippocampus and in the right parietal cortex as well as a few neurofibrillary tangles in the CA fields of the hippocampus and in the entorhinal cortex. In contrast to previous reports, there were no midline cerebral dysgenesis and no ectopic neuron formations in the present case. Neuronal loss and gliosis were also absent in all cortical and subcortical areas. Our observations suggest that the main neurodevelopmental deficits in CDLS occur during the late phase of gestation. Conversely, early neurodegenerative changes are not characteristic of CDLS. In the light of previous studies in younger CDLS patients, the vascular and degenerative lesions observed in the present case may be secondary to his severe congenital heart abnormalities and self-injury behavior, respectively.

Adult↗