Bérengère Guillery-Girard

Reduced specificity of autobiographical memory and aging: Do the executive and feature binding functions of working memory have a role?

Autobiographical memory (AM) is built up from various kinds of knowledge, from general to specific, via generative processes. Aging seems to particularly affect the episodic autobiographical information while preserving information that is more semantic. However, the mechanism of this deficit has not yet been thoroughly tested in relation to working memory. This study is designed to investigate, in a group of 100 subjects, the relationships between age, accessibility to different levels of AM specificity, and two main components of working memory: the central executive and the episodic buffer. We used a new task composed of four embedded verbal autobiographical fluencies (VAF) - from low to highest specificity levels - exploring lifetime periods, general events, specific events, and details, plus tasks exploring free recall of episodic AM and updating, shifting, inhibition, and feature binding in working memory. The results demonstrate that age-related difficulties increase with level of specificity of autobiographical knowledge, i.e., from semantic to episodic aspects. Moreover, regression analyses mainly show that increase in age-related deficit with level of specificity of AM is largely mediated by performance on executive functions (updating and inhibition) and to a lesser extent feature binding in working memory. The results confirm in episodic AM the executive/working memory aging hypothesis, and for the first time highlight the role of episodic buffer in associating the various different details of specific events that elicit the conscious recollection.

The relationship between working memory and episodic memory disorders in transient global amnesia.

In a previous study, we investigated the relationship between the disorders of both episodic memory and working memory in the acute phase of transient global amnesia (TGA). Since executive functions were spared, another dysfunction may be responsible for the binding and maintenance of multimodal informations and contribute to the encoding disorders observed in some patients [Quinette, P., Guillery, B., Desgranges, B., de la Sayette, V., Viader, F., & Eustache, F. (2003). Working memory and executive functions in transient global amnesia. Brain, 126, 1917-1934.]. The aim of this present study was to assess the functions of binding and maintenance of multimodal information during TGA and explore their involvement in episodic memory disorders. We therefore conducted a more thorough investigation of working memory in 16 new patients during the acute phase of TGA using two tasks designed to assess the binding process and both dimensions of the maintenance, namely the active storage and the memory load ability. We also investigated the nature of the episodic memory impairment in distinguishing between the performance of patients with preferential encoding deficits and those of patients with preferential storage disorders on the episodic memory task. This distinction was closely related to the severity of amnesia, i.e. an encoding disorder was observed rather in the early phase of TGA. The results showed that while the functions of binding and maintenance of multimodal information were intact in patients with storage disorders, they were impaired in the case of encoding deficits. These results are interpreted in the recent framework of episodic buffer proposed by Baddeley [Baddeley, A. D. (2000). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417-423] that represents an interface between working memory and episodic memory.

The time course of repetition effects for familiar faces and objects: An ERP study

Face and object priming has been extensively studied, but less is known about the repetition processes which are specific to each material and those which are common to both types of material. In order to track the time course of these repetition processes, EEG was recorded while 12 healthy young subjects performed a long-term perceptual repetition priming task using faces and object drawings. Item repetition induced early (N170) and late (P300 and 400-600 ms time-window) event-related potential (ERP) modulations. The N170 component was reduced in response to primed stimuli even with several hundred intervening items and this repetition effect was larger for objects than for faces. This early repetition effect may reflect the implicit retrieval of perceptual features. The late repetition effects showed enhanced positivity for primed items at centro-parietal, central and frontal sites. During this later time-window (400 and 600 ms at central and frontal sites), ERP repetition effects were more obvious at the left side for objects and at the right side for faces. ERP repetition effects were also larger for famous faces during this time-window. These later repetition effects may reflect deeper semantic processing and/or greater involvement of involuntary explicit retrieval processes for the famous faces. Taken together, these results suggest that among the implicit and explicit memory processes elicited by a perceptual priming task, some of them are modulated by the type of item which is repeated.

How Do the Different Components of Episodic Memory Develop? Role of Executive Functions and Short-Term Feature-Binding Abilities

This study investigated the development of all 3 components of episodic memory (EM), as defined by Tulving, namely, core factual content, spatial context, and temporal context. To this end, a novel, ecologically valid test was administered to 109 participants aged 4-16 years. Results showed that each EM component develops at a different rate. Ability to memorize factual content emerges early, whereas context retrieval abilities continue to improve until adolescence, due to persistent encoding difficulties (isolated by comparing results on free recall and recognition tasks). Exploration of links with other cognitive functions revealed that short-term feature-binding abilities contribute to all EM components, and executive functions to temporal and spatial context, although ability to memorize temporal context is predicted mainly by age.

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.

How children suffering severe amnesic syndrome acquire new concepts

Recent studies revealed that children with developmental amnesia acquired new semantic information. However, they failed to investigate the growth of such knowledge during childhood, and they did not bring evidence concerning the putative role of residual episodic memory in semantic acquisition. This prospective study sought to clarify this issue by assessing both semantic and episodic memory in two amnesic children (RH and KF) with different neuropsychological profiles. We thus applied errorless semantic learning and vanishing cues methods, together with assessments of episodic memory using original recognition tasks within the same protocol. Results demonstrated learning and long-lasting maintenance of multicomponent concepts (comprising labels, categories and features) in both amnesic children. Importantly, episodic memory assessments revealed differential residual abilities in these children, which may account for their respective profiles of semantic acquisition. Thus, RH, who demonstrated residual episodic abilities, acquired normally. However, the learning of KF, who had a massive impairment of episodic memory, remained slower than her controls. In conclusion, even though an episodic impairment may slacken new semantic learning, our research provides new evidence for the de novo acquisition of semantic concepts in childhood amnesic syndrome and strengthens the idea that semantic learning can occur without any recruitment of episodic memory.

Semantic acquisition in childhood amnesic syndrome: a prospective study.

Amnesic patients can acquire new semantic knowledge despite a profound deficit of episodic memory. Although retrospective studies have been carried out on adults and children, prospective studies have been restricted to adults. The aim of the present work was to assess the acquisition of new semantic knowledge in amnesic children. The semantic protocol, composed of short, illustrated texts, was based on an original methodology which included an assessment of episodic memory on two occasions. Two amnesic children acquired new concepts despite major episodic disturbance, illustrated notably by a lack of recollection in episodic tasks. Our findings lend weight to the assumption that forming new semantic knowledge does not necessarily involve episodic memory, and provide methodological pointers for childrens neuropsychological rehabilitation.

Psychopathological factors, memory disorders and transient global amnesia

BACKGROUND Some studies have shown the presence of psychopathological disorders in transient global amnesia. AIMS To determine whether transient global amnesia is associated with psychopathological disorders and to assess the influence of these psychopathological disorders on memory impairments. METHOD Levels of anxiety and depression before and during transient global amnesia were rated. Memory performances were assessed by means of original episodic memory tasks and working memory tasks. These data were collected in 17 individuals observed during the very acute phase, 18 individuals examined in the peri-acute phase and 26 controls. RESULTS During the acute phase, participants with transient global amnesia displayed a higher level of anxiety and a more depressed mood than controls. An alteration of emotional state, as measured by the Adjective Mood Scale, was correlated with deficits in anterograde memory. CONCLUSIONS Transient global amnesia comprises sudden changes in peoples emotional state, which has a major impact on and interacts with episodic memory impairment.

Early age-related changes in episodic memory retrieval as revealed by event-related potentials

Familiarity is better preserved than recollection in ageing. The age at which changes first occur and the slope of the subsequent decline, however, remain unclear. In this study, we investigated changes in episodic memory, by using event-related potentials (ERPs) in young (m=24), middle-aged (m=58) and older (m=70) adults. Although behavioural performance did not change before the age of 65 years, changes in ERP correlates were already present in the middle-aged adults. The ERP correlates of recollection and monitoring processes were the first to be affected by ageing, with a linear decrease as age increased. Conversely, the ERP correlate of familiarity remained unchanged, at least up to the age of 65 years. These results suggest a differential time course for the age effects on episodic retrieval.

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

Several studies noted persistence of memory impairment following an episode of transient global amnesia (TGA) with standard tests.