Biomedical subjects

V de la Sayette

Publications and source records attributed to V de la Sayette.

At least 19 recordsLinked to original sources

PubMed2006

Long-term memory following transient global amnesia: an investigation of episodic and semantic memory.

BACKGROUND: Several studies noted persistence of memory impairment following an episode of transient global amnesia (TGA) with standard tests. AIM: To specify long-term memory impairments in a group of patients selected with stringent criteria. METHODS: Both retrograde and anterograde memory were investigated in 32 patients 13-67 months after a TGA episode with original tasks encompassing retrograde semantic memory (academic, public and personal knowledge), retrograde episodic memory (autobiographical events) and anterograde episodic memory. RESULTS: Patients had preserved academic and public knowledge. Pathological scores were obtained in personal verbal fluency for the two most recent periods, and patients produced less autobiographical events than controls. However, when they were provided time to detail, memories were as episodic as in controls regardless of their remoteness. Anterograde episodic tasks revealed a mild but significant impairment of the capacity of re-living the condition of encoding, i.e. the moment at which words were presented. CONCLUSIONS: Patients who have suffered from an episode of TGA manifest deficits of memory focused on the retrieval of both recent semantic information and episodic memories and especially the capacity of re-living. These deficits may not result from a deterioration of memory per se but rather from difficulties in accessing memories.

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PubMed2005

Using voxel-based morphometry to map the structural changes associated with rapid conversion in MCI: a longitudinal MRI study.

Capturing the dynamics of gray matter (GM) atrophy in relation to the conversion from mild cognitive impairment (MCI) to clinically probable Alzheimer's disease (AD) would be of considerable interest. In this prospective study we have used a novel longitudinal voxel-based method to map the progression of GM loss in MCI patients over time and compared converters to non-converters. Eighteen amnestic MCI patients were followed-up for a predefined fixed period of 18 months and conversion was judged according to NINCDS-ADRDA criteria for probable AD. Each patient underwent a high-resolution T1-weighted volume MRI scan both at entry in the study and 18 months later. We used an optimal VBM protocol to compare baseline imaging data of converters to those of non-converters. Moreover, to map GM loss from baseline to follow-up assessment, we used a modified voxel-based morphometry (VBM) procedure specially designed for longitudinal studies. At the end of the follow-up period, seven patients had converted to probable AD. Areas of lower baseline GM value in converters mainly included the hippocampus, parahippocampal cortex, and lingual and fusiform gyri. Regions of significant GM loss over the 18-month follow-up period common to both converters and non-converters included the temporal neocortex, parahippocampal cortex, orbitofrontal and inferior parietal areas, and the left thalamus. However, there was significantly greater GM loss in converters relative to non-converters in the hippocampal area, inferior and middle temporal gyrus, posterior cingulate, and precuneus. This accelerated atrophy may result from both neurofibrillary tangles accumulation and parallel pathological processes such as functional alteration in the posterior cingulate. The ability to longitudinally assess GM changes in MCI offers new perspectives to better understand the pathological processes underlying AD and to monitor the effects of treatment on brain structure.

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PubMed2004

[At the boundary between normal aging and Alzheimer disease].

Accurately predicting the development of probable Alzheimer's disease (AD) early in the course of the disease would have major implications. Hence, the pre-dementia stage of AD has become a major topic of current research. Amnestic 'mild cognitive impairment' (MCI) has recently emerged as the most convenient avenue to address this Issue, since most of MCI patients will progress to AD, at a rate of 10% to 15% per Year, suggesting that MCI represents the clinical manifestation of incipient AD (Petersen et al., 2001). However, all MCI patients would probably not convert to AD, at least in the near future, so that the Issue of prospective longitudinal studies is to detect specific indices of rapid conversion. In this paper, we focus on longitudinal studies using either neuropsychology, or morphological or functional neuroimaging to find predictive markers allowing to distinguish those MCI patients that rapidly convert to AD from those that do not develop the disease during the follow-up period. Whereas functional neuroimaging, and more specifically FDG-PET, seems particularly accurate to predict AD, the combination of multiple approaches is likely to be a promising avenue.

Aging↗

PubMed2004

The dynamic time course of memory recovery in transient global amnesia.

AIMS: To investigate the dynamic time course of transient global amnesia (TGA)--that is, the process of recovery and the interindividual variability--by testing four patients during the day of TGA itself (on three occasions) and at follow up (on two occasions). METHODS: A specially designed protocol focusing on semantic (both conceptual and autobiographical knowledge) and episodic (both anterograde and retrograde components) memory. RESULTS: Every patient showed marked impairment of both anterograde and retrograde episodic memory during the acute phase, with a relative preservation of personal and conceptual semantic knowledge. During the following phase, the authors observed similarities and differences among the patients' patterns of recovery. In general, retrograde amnesia recovered before the anterograde amnesia and anterograde episodic memory was recovered gradually in every case. In contrast, shrinkage of retrograde amnesia was more heterogeneous. In two of the patients, this shrinkage followed a chronological gradient and the most remote events were recovered first. In the two other patients, it depended more on the strength of the trace, and there was no temporal gradient. For the latter, an executive deficit could account for difficulties in accessing both conceptual knowledge and autobiographical memories. CONCLUSIONS: This profile of recovery suggests a "neocortical to medial temporal" process in every case, and the possibility of an additional frontal dysfunction in some cases. Hence, the acute phase seems to be characterised by a common episodic impairment. This variability between subjects appears in the recovery phase with two different patterns of impairment.

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PubMed2003

Mild cognitive impairment: Can FDG-PET predict who is to rapidly convert to Alzheimer's disease?

Patients with mild cognitive impairment (MCI) were assessed, and a metabolic profile associated with conversion to AD at 18-month follow-up was sought. As compared with nonconverters (n = 10), converters (n = 7) had lower fluorodeoxyglucose uptake in the right temporoparietal cortex (p = 0.02, corrected for cluster size), without individual overlap. Awaiting replication in an independent sample, these findings suggest that among patients with MCI, fluorodeoxyglucose PET may accurately identify rapid converters.

Alzheimer Disease↗

PubMed2002

Transient global amnesia: concomitant episodic memory and positron emission tomography assessment in two additional patients.

Transient global amnesia (TGA) is characterized by a profound but transient deficit of episodic memory. The study of cerebral blood flow and oxygen metabolism with positron emission tomography (PET) provides relevant pathophysiologic data, but only three patients have been reported so far and in only one was concomitant neuropsychological testing performed. We report here the concomitant neuropsychological and PET assessment of two additional patients. Episodic disturbance was characterized by a storage disturbance for one case and an incapacity to learn episodic associations in the other, illustrating cognitive heterogeneity despite similar neurological presentation. PET findings disclosed mild but significant changes in the amygdala (right or left) and left posterior hippocampus, which could account for both the storage disturbance and the inability to associate episodic components. The PET findings also argued in favor of a vascular disturbance accompanying TGA.

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PubMed2001

Semantic acquisition without memories: evidence from transient global amnesia.

Transient global amnesia (TGA), characterised by a profound anterograde amnesia, is a model of interest to study the acquisition of novel meanings independent of episodic functioning. Three patients were tested during a TGA attack, two in the early recovery phase and the third during the acute phase of TGA, with a semantic priming task involving a restructuring process of conceptual knowledge. During TGA, all patients demonstrated priming effects. Results obtained the day after the episode with the same task showed that these effects persisted at least one day. Episodic memory seems not to be critical for the formation of novel connections among unrelated semantic representations, in accordance with Tulving's model of memory, i.e. episodic memory is not necessary for the acquisition of semantic information.

Acute Disease↗

PubMed2001

Entorhinal cortex disruption causes memory deficit in early Alzheimer's disease as shown by PET.

Voxel-based mapping of the correlations between cognitive scores and resting-state brain glucose utilization measured by PET has recently emerged as a novel way to reveal in living patients with Alzheimer's disease (AD) the neural systems whose disruption underlies particular neuropsychological, especially mnemonic, deficits. We have now applied this approach using a novel cognitive paradigm designed to selectively assess verbal episodic memory, and show that in early AD disruption of the left entorhinal cortex underlies this memory deficit, consistent with post mortem data showing that this brain area is affected earliest and most severely by tau pathology in AD.

Aged↗

PubMed2001

Voxel-based mapping of brain hypometabolism in permanent amnesia with PET.

In this study, we used voxel-based mapping methods to compare the resting cerebral metabolic rate of glucose (CMRglc) measured with PET in five patients with permanent amnesia (three with chronic Wernicke-Korsakoff and two with postanoxia syndrome) to that of nine healthy age-matched subjects. We assessed (i) a group pattern of relative hypometabolism; and (ii) the consistency of this group pattern, if any, in individual subjects, according to etiology. The results from the group analysis documented that permanent amnesia is associated with hypometabolism in the thalamus, posterior cingulate cortex, and mesial prefrontal cortex (near the anterior cingulate gyrus), bilaterally, as well as in the left supramarginal and middle temporal gyri. The individual analysis showed that this group pattern was found in essentially each patient, regardless of the cause of amnesia. Thus, permanent amnesia is subtended by dysfunction in structures belonging to Papez/limbic circuits as well as in left-hemisphere areas typically concerned with verbal functions, probably through a mechanism of thalamo-cortical disconnection and possibly involved in retrograde amnesia. The use of a voxel-based method allowed us to map a common network of synaptic dysfunction in a neuropsychological syndrome regardless of etiology. Our results indicate that this should be a powerful method in functional neuropsychology.

Adult↗

PubMed2001

In vivo mapping of gray matter loss with voxel-based morphometry in mild Alzheimer's disease.

Up till now, the study of regional gray matter atrophy in Alzheimer's disease (AD) has been assessed with regions of interest, but this method is time-consuming, observer dependent, and poorly reproducible (especially in terms of cortical regions boundaries) and in addition is not suited to provide a comprehensive assessment of the brain. In this study, we have mapped gray matter density by means of voxel-based morphometry on T1-weighted MRI volume sets in 19 patients with mild AD and 16 healthy subjects of similar age and gender ratio and report highly significant clusters of gray matter loss with almost symmetrical distribution, affecting mainly and in decreasing order of significance the medial temporal structures, the posterior cingulate gyrus and adjacent precuneus, and the temporoparietal association and perisylvian neocortex, with only little atrophy in the frontal lobe. The findings are discussed in light of previous studies of gray matter atrophy in AD based either on postmortem or neuroimaging data and in relation to PET studies of resting glucose consumption. The limitations of the method are also discussed in some detail, especially with respect to the segmentation and spatial normalization procedures as they apply to pathological brains. Some potential applications of voxel-based morphometry in the study of AD are also mentioned.

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PubMed2001

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↗

PubMed2001

The nature of semantic memory deficits in Alzheimer's disease: new insights from hyperpriming effects.

While semantic memory deficits are a common landmark of Alzheimer's disease, the nature of these impairments remains to be clarified. Implicit tasks which assess semantic priming effects are often used to understand semantic deficits in Alzheimer's disease, but they have led to unclear conclusions because of methodological problems such as intervention of attentional mechanisms. To explore the effects of semantic priming in Alzheimer's disease and their relationship with semantic memory deficits, we used two tasks, one implicit and the other explicit. The implicit task was a lexical decision task to assess semantic priming, and in which pairs of words had coordinate (tiger-lion) or attribute relationships (zebra-stripe). The explicit task was a semantic knowledge task composed of namings and questions involving superordinate categories and attribute knowledge of concepts. The two tasks systematically assessed the integrity of the same concepts. This protocol was given to 53 Alzheimer's disease patients with mild to moderate dementia and to 20 controls. The Alzheimer's disease group as a whole obtained significantly greater priming effects (hyperpriming) than controls in the coordinate condition, and equivalent priming in the attribute condition. In the coordinate condition, a subgroup of 26 patients, with attribute knowledge deficits, had larger priming effects than both a subgroup without semantic deficits and the control group. These results show that in Alzheimer's disease the semantic priming effects vary according to the degree of attribute loss, and the presence of hyperpriming would reflect semantic memory deficits. This study unravels the fine-grained structure of semantic memory disturbances in Alzheimer's disease with mild to moderate dementia, affecting initially the attributes of concepts within a hierarchical network in which superordinate concepts remain preserved.

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PubMed2000

[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↗

PubMed1999

Cervical cord and dorsal medullary infarction presenting with retro-orbital pain.

A 36-year-old woman experienced an excruciating right retro-orbital paroxysmal headache after a stroke of the anterior two-thirds of the right hemicord at the C1 level (anterior spinal artery territory) and the dorsal medulla (posterior spinal artery territory). A right vertebral artery dissection was demonstrated. This unusual infarct mimicked a cluster headache attack or paroxysmal hemicrania.

Adult↗

PubMed1999

Episodic memory in transient global amnesia: encoding, storage, or retrieval deficit?

OBJECTIVES: To assess episodic memory (especially anterograde amnesia) during the acute phase of transient global amnesia to differentiate an encoding, a storage, or a retrieval deficit. METHODS: In three patients, whose amnestic episode fulfilled all current criteria for transient global amnesia, a neuropsychological protocol was administered which included a word learning task derived from the Grober and Buschke's procedure. RESULTS: In one patient, the results suggested an encoding deficit, and in two others, a storage deficit. CONCLUSIONS: The encoding/storage impairment concerning anterograde amnesia documented in our patients stands in clear contrast with the impairment in retrieval which must underly the retrograde amnesia that also characterises transient global amnesia. This dissociation in turn favours the idea of a functional independence among the cognitive mechanisms that subserve episodic memory.

Aged↗

PubMed1999

Cluster headache-like attack as an opening symptom of a unilateral infarction of the cervical cord: persistent anaesthesia and dysaesthesia to cold stimuli.

A 54 year old man experienced excruciating left retro-orbital pain with lacrimation and redness of the eye representative of a cluster headache attack. This was followed by left hemiparesis with plegia of the lower limb and left Horner's syndrome. Five days later the hemiparesis recovered while the patient developed hypoanaesthesia to cold stimuli that evoked painful burning dysaesthesia on the right side below the C4 level. MRI disclosed a discrete infarct in the left lateral aspect of the cord at C2 level concomitant to a left vertebral artery thrombosis. This limited infarct and the clinical symptoms suggest a hypoperfusion in the peripheral arterial system of the left hemicord, supplied both by the anterior and posterior spinal arteries. Cluster headache-like attack and persistent dysaesthesia to cold stimuli are discussed respectively in view of the central sympathetic involvement and partial spinothalamic system dysfunction.

Anesthesia↗

PubMed1998

Paraneoplastic cerebellar syndrome and optic neuritis with anti-CV2 antibodies: clinical response to excision of the primary tumor.

OBJECTIVE: To describe a patient with a paraneoplastic cerebellar syndrome and optic neuritis with circulating anti-CV2 antibodies and clinical improvement after excision of a small cell lung carcinoma. DESIGN: Report of a case. SETTING: A 62-year-old man simultaneously developed a severe cerebellar syndrome and a bilateral optic neuritis predominantly in the left eye (visual acuity, 20/25 in the right eye; < 20/400 in the left eye; and bilateral swelling of the optic discs). MAIN OUTCOME AND RESULTS: Anti-CV2 antibodies, recently described as associated with paraneoplastic neurological syndrome, were detected in the patient's serum sample. These antibodies were demonstrated to react with the cytoplasm of a subpopulation of oligodendrocytes in the white matter of rat brain in the cerebellum, brainstem, spinal cord, and optic chiasm. The patient was found to have a small cell lung carcinoma, which was removed. After excision of the tumor, the cerebellar syndrome improved dramatically and the papilledema disappeared despite aftereffects of the optic neuritis. CONCLUSIONS: These findings were consistent with the diagnosis of a paraneoplastic neurological syndrome, although both optic neuritis and remission of the cerebellar syndrome are uncommon patterns of paraneoplastic syndromes. CV2 antigen expression by the oligodendrocytes of the cerebellum, brainstem, spinal cord, and optic chiasm correlated with the clinical syndrome observed in our patient. However, the precise pathophysiological role of anti-CV2 antibodies is still unknown.

Autoantibodies↗

PubMed1998

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.

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