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Biomedical subjects

Yves Samson

Publications and source records attributed to Yves Samson.

6 recordsLinked to original sources
PubMed2002

Temporal pole hypometabolism may be linked to a reduction of grey matter in temporal lobe epilepsy.

In order to gain further insight into the pathophysiology of temporal pole hypometabolism, we decided to perform a voxel-based automated analysis of structural MRI in epileptic patients with or without temporal pole hypometabolism. After fully automated segmentation of cerebral grey matter from structural T1-weighted MRI scans, we applied the automated technique of statistical parametric mapping (SPM) to the analysis of grey matter of nine control subjects, and 18 patients with right medial temporal lobe epilepsy with (n = 13) or without (n = 5) significant temporal pole hypometabolism. Group comparisons between subject controls and epileptic patients with temporal pole hypometabolism showed a reduction of grey matter located into the superior part of the right temporal pole, the right hippocampus and the left parahippocampal gyrus. Epileptic patients without temporal pole hypometabolism did not exhibit temporal pole grey matter abnormalities. These findings suggest that a reduction of temporal pole neocortical grey matter might contribute to temporal pole hypometabolism in temporal lobe epilepsy.

Adult↗
PubMed2002

Dopaminergic function and dopamine transporter binding assessed with positron emission tomography in Parkinson disease.

BACKGROUND: Measuring progression of Parkinson disease (PD) using positron emission tomography may help demonstrate the efficacy of neuroprotective treatments. To date, (18)F-dopa has been the gold standard to measure presynaptic dopaminergic function in PD, but this tracer might overestimate the rate of neuronal death in PD because its uptake also depends on dopamine turnover rather than exclusively on the density of dopaminergic terminals in the striatum. The latter might be assessed using newly developed ligands of the membrane dopamine transporter. OBJECTIVE: To compare the striatal uptakes of (18)F-dopa and (76)Br-FE-CBT, a dopamine transporter ligand, in patients with PD. PATIENTS AND METHODS: The striatal uptakes of (76)Br-FE-CBT and (18)F-dopa were compared using positron emission tomography in 10 patients with early PD and 8 with advanced PD. Correlation of uptakes with motor performance was investigated. RESULTS: The reduction in (76)Br-FE-CBT binding to 43% of control values was more severe than the reduction in (18)F-dopa uptake (63% of control values) in the putamen of patients with early PD. No significant difference was found between either tracer's uptake in the putamen of patients with advanced PD. Motor performance was highly correlated to (18)F-dopa uptake, whereas correlation to (76)Br-FE-CBT binding was weak. CONCLUSIONS: Uptake of (18)F-dopa may be up-regulated in early PD, suggesting a compensatory increase of dopamine synthesis in surviving dopaminergic terminals. Positron emission tomography dopamine transporter ligands and (18)F-dopa give complementary information on the presynaptic status of the nigrostriatal dopaminergic system and might be associated to investigate the efficacy of neuroprotective treatments in PD.

Aged↗
PubMed2002

Insular cortex involvement in mesiotemporal lobe epilepsy: a positron emission tomography study.

Somesthetic and emotional symptoms that are common in patients with mesial temporal lobe epilepsy are usually related to hippocampo-amygdalar complex involvement. Recent stereo-electroencephalographic studies have shown a relationship between such symptoms and epileptic insular discharges. To further investigate this problem, we carried out a positron emission tomography study using fluorodeoxyglucose (18F-FDG) and flumazenil (11C-FMZ) in mesial temporal lobe epilepsy patients. The aim of our study was to assess the existence of a cortical insular involvement in order to examine its clinical correlates and the relationship between the postoperative outcome and the insular involvement. Fluorodeoxyglucose and flumazenil-positron emission tomography studies were carried out in 18 patients with mesial temporal lobe epilepsy patients. A statistical parametric mapping (SPM96) was performed to analyze the data in comparison to 18 healthy volunteers. For each set of fluorodeoxyglucose and flumazenil images a group and an individual analysis were performed. In addition, a region of interest analysis was performed to validate the results. Focusing on the metabolic abnormalities, we also investigated the role of insular cortex in the symptoms experienced by the patients and the prognostic value of insular metabolic abnormalities. Highly significant hypometabolism and BZR binding decreases were detected in the insular cortex. Results were similar using the region of interest approach. Insular involvement (mainly ipsilateral to the seizure focus) was present in 60% of the patients. Emotional symptoms correlated with hypometabolism in the anterior part of the ipsilateral insular cortex, whereas somesthetic symptoms correlated with hypometabolism in the posterior part. No relationship between postoperative outcome and ipsilateral insular hypometabolism was found. Unilateral mesial temporal lobe epilepsy is associated with insular hypometabolism and benzodiazepine receptor loss. Our results also suggest that the anterior part of the insular cortex is involved in the emotional symptoms and the posterior insular cortex is involved in the somesthetic symptoms. Hypometabolism located in the insula did not influence postoperative outcome after anterior lobectomy.

Adolescent↗
PubMed2002

The neuroanatomical substrate of sound duration discrimination.

We investigated the neuroanatomical substrate of sound duration discrimination, using the same experimental design as in a previous study on sound intensity discrimination [J. Neurosci. 18 (16) (1998) 6388]. Seven normal subjects were trained to detect deviant sounds presented with a slightly longer duration than a 300 ms long standard harmonic sound, using a Go/No Go paradigm. Individual psychometric curves were assessed using a three-step psychoacoustic procedure. Subjects were then scanned while passively listening to the standard sound, and while discriminating changes in sound duration at four different performance levels (d'=1.5, 2.5, 3.5 and 4.5). Analysis of regional cerebral blood flow (rCBF) data outlined activation, during the discrimination conditions, of a right hemispheric fronto-parietal network very similar to the one previously observed for intensity discrimination, as well as additional activation in the right prefrontal cortex (Brodmann Area (BA) 10), bilateral basal ganglia and cerebellar hemispheres. These findings suggest that discrimination of sound duration, as for discrimination of sound intensity, involves two cerebral networks: a supramodal right fronto-parietal cortical network responsible for allocation of sensory attentional resources, and a network of regions such as the basal ganglia, cerebellum, and right prefrontal cortex, more specifically involved in the temporal aspects of the discrimination task.

Acoustic Stimulation↗
PubMed2002

[An anatomofunctional brain database].

This study proposes a closer look at the neuropsychological method defined as the study of the neural bases of the behavioural and cognitive functions using an organisation-representation model for current data and knowledge of the brain, and the application of an anatomofunctional database. A Centre of Cognitive Anatomy (CAC) was set up for the collection and processing of neuronatomical, neuropsychological, and psycho-behavioural data for patients presenting sequels of focal brain damage. Such a system would allow concurrent treatment of anatomical and functional data. We would expect the results from such a model to produce stable 'anatomofunctional laws' that would be independent of all inter-individual variations in the functioning of the brain and could be checked against the entire database of information. A direct application would be the improvement of cognitive and/or behavioural rehabilitation of patients with brain damage.

Brain↗