Biomedical subjects

B Guillery

Publications and source records attributed to B Guillery.

6 recordsLinked to original sources

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.

Aged↗

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↗

PubMed2000

Functional neuroanatomy of amnesia: positron emission tomography studies.

In this article, we review the principles of, and provide examples for, the new approach of functional neuropsychology in the field of amnesia. In the permanent amnesic syndrome, positron emission tomography (PET) can provide statistical maps of the brain regions with significantly impaired resting metabolism in comparison with control subjects. These regions include not only Papez's circuit but also the left supramarginal gyrus, which may explain in part the retrograde amnesia present in most cases of amnesic syndrome. This approach is also of great interest in transient global amnesia (TGA) because the defect of episodic memory is highly selective and occurs without permanent damage. The few available PET studies in TGA suggest the dysfunction of a distributed network including the hippocampal region and the prefrontal cortex, with a different pattern individually. Further studies will be necessary to better understand the relationships between the precise cognitive deficits in TGA and the pattern of brain hypometabolism. In Alzheimer's disease (AD), the study of the correlations between memory test scores and metabolic values across a sample of subjects provides a map of those brain structures whose synaptic pathology dysfunction underlies the particular neuropsychological alteration. The distribution of the sites of correlations shows striking differences according to each memory system. This approach should open the way for the unravelling of the neurobiological substrates of both cognitive impairment and compensatory mechanisms in neurodegenerative diseases. Over and above their applications in neurological research, such studies in brain-diseased subjects are particularly useful for establishing cognitive and neurobiological models of human memory, because they allow the highlighting of the neural networks that are essential for memory function. From a cognitive neuroscience perspective, the functional neuropsychology of amnesia is, therefore, complementary to the classic activation paradigm in normal subjects, which identifies the cerebral structures that are involved with, but not necessarily indispensable for, the execution of the task.

Alzheimer Disease↗

PubMed2000

[The assessment of long-term memory and semantic knowledge].

Following a previous review about the different components of memory (Eustache et al., Revue Neurologique, 1998), this paper is devoted to the evaluation of both autobiographical and semantic memory. An original method to analyse autobiographical memory is proposed. The different tasks used for the analysis of semantic memory are detailed with a particular emphasis given to the category -specific semantic impairments.

Humans↗

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↗

PubMedDate not supplied

[The assessment of episodic memory: theory and practice].

Episodic memory refers to a system which stores personally experienced events located in time and in space. It is characterized by autonoetic consciousness allowing a subject to be aware of his/her own identity throughout subjective time and to perceive the present as both a continuation of his/her past and as a prelude to his/her future. Current studies of episodic memory should take into account all these features. However, most episodic memory tests are restricted to memory performance and do not really measure episodic memory. In this article, after defining the terms of context and states of awareness, we describe two original tasks designed specially to investigate episodic memory: the 'Quoi-Où-Quand' (What-Where-When) and the 'TEMPau'. The first task allows the study of anterograde amnesia whereas the second consists of an assessment of retrograde amnesia. These two tasks include both scores of memory performance and measures of states of awareness using a procedure derived from the Remember/Know paradigm.

Amnesia, Retrograde↗