Gaën Plancher

Age effect on components of episodic memory and feature binding: A virtual reality study.

OBJECTIVE The aims were (1) to explore the effects of normal aging on the main aspects of episodic memory--what, where, and when,--and on feature binding in a virtual environment; (2) to explore the influence of the mode of learning, intentional versus incidental; and (3) to benchmark virtual environment findings collected with older adults against data recorded in classical neuropsychological tests. METHOD We tested a population of 82 young adults and 78 older adults without dementia (they participated in a short battery of neuropsychological tests). All the participants drove a car in an urban virtual environment composing of 9 turns and specific areas. Half of the participants were told to drive through the virtual town; the other half were asked to drive and to memorize the environment (itinerary, elements, etc.). All aspects of episodic memory were then assessed (what, where, when, and binding). RESULTS The older participants had less recollection of the spatiotemporal context of events than the younger with intentional encoding (p < .001), but similar recollection with incidental encoding (except for verbal spatial aspect). The younger participants showed better binding than older ones regardless of the type of encoding (p < .001). For the older participants the virtual test was sensitive to mnesic complaints as well as general cognitive changes (p < .05 to p < .01). CONCLUSION We view these results as an indication that virtual environments could provide helpful standard tools for assessing age effects on the main aspects of episodic memory.

The influence of action on episodic memory: A virtual reality study

A range of empirical findings suggest that active learning is important for memory. However, few studies have focused on the mechanisms underlying this enactment effect in episodic memory using complex environments. Research using virtual reality has yielded inconsistent results. We postulated that the effect of action depends on the degree of interaction with the environment and freedom in the planning of an itinerary. To test these hypotheses, we disentangled the interaction and planning components of action to investigate whether each enhances factual and spatial memory. Seventy-two participants (36 male and 36 female) explored a virtual town in one of three experimental conditions: (a) a passive condition where participants were immersed as passenger of the car (no interaction, no planning); (b) a planning-only condition (the subject chose the itinerary but did not drive the car); (c) an interaction-only condition (the subject drove the car but the itinerary was fixed). We found that itinerary choice and motor control both enhanced spatial memory, while factual memory was impaired by online motor control. The role of action in memory is discussed.

Forgetting at short term: When do event-based interference and temporal factors have an effect?

Memory tasks combining storage and distracting tasks performed at either encoding or retrieval have provided divergent results pointing towards accounts of forgetting in terms of either temporal decay or event-based interference respectively. The aim of this study was to shed light on the possible sources of such a divergence that could rely on methodological aspects or deeper differences in the memory traces elicited by the different paradigms used. Methodological issues were explored in a first series of experiments by introducing at retrieval computer-paced distracting tasks that involved articulatory suppression, attentional demand, or both. A second series of experiments that used a similar design was intended to induce differences in the nature of memory traces by increasing the time allowed for encoding the to-be-remembered items. Although the introduction of computer-paced distracting tasks allowed for a strict control of temporal parameters, the first series of experiments replicated the effects usually attributed to event-based interference. However, deeper encoding abolished these effects while time-related effects remained unchanged. These findings suggest that the interplay between temporal factors and event-based interference in forgetting at short term is more complex than expected and could depend on the nature of memory traces.

Forgetting from Working Memory: Does Novelty Encoding Matter?.

The sources of forgetting in working memory remain the matter of intense debate. According to the SOB model (serial order in a box; Farrell & Lewandowsky, 2002), forgetting in complex span tasks does not result from temporal decay but from interference produced by the encoding of distractors that are superimposed over memory items onto a composite memory. The main tenet of the model is that the encoding strength of a distractor is a function of its novelty, with novel distractors being encoded with a large encoding weight that interferes with other memories, whereas repeated distractors would result in negligible encoding weight and no further forgetting. In the present study, we tested the 2 main predictions issuing from this model. First, recall performance should be better in complex span tasks in which distractors are repeated than in tasks in which every distractor is novel. Second, increasing the number of novel distractors should lead to more interference and poorer recall. In 5 experiments in which we controlled for attentional demand and temporal factors, none of these predictions were verified, whereas a strong effect of the pace at which distracting tasks were performed testified that they involved forgetting. We conclude that, contrary to the SOB model, the novelty of distractors plays no role per se in forgetting. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Apport de la réalité virtuelle en neuropsychologie de la mémoire : étude dans le vieillissement

The principal interest of virtual reality is its potential to create experiments close to daily life with a perfect experimental control. In a first time, we review the studies illustrating the contribution of virtual reality for neuropsychology, mainly for memory study. In a second time, we present the results of an experiment in which the subjects were driving in a virtual town, that tested all the episodic memory components, i.e. the memories of what, where and when events happened. Young and elderly adults performed the virtual test, either with intentional or incidental encoding, and either in active (they drove a virtual car) or passive exploration of the town (they were passengers). The results showed that older subjects recalled the spatiotemporal context and the details of the events in a lower proportion than younger, as well in active as in passive condition. Subjects memory complaints were correlated with the virtual scores, but not with usual verbal episodic memory tests. Therefore, virtual tests seem to allow a better assessment of episodic memory than the usual ones, especially because of their spatiotemporal memory assessment, and appear to be a hopeful tool for a neuropsychology closer to patients daily life than the usual tests.

Reconciling Two Computational Models of Working Memory in Aging

It is well known that working memory performance changes with age. Two recent computational models of working memory, TBRS* and SOB-CS, developed from young adults WM performances are opposed regarding the postulated causes of forgetting, namely time-based decay and interference for TBRS* and SOB-CS, respectively. In the present study, these models are applied on a set of complex span data produced by young and older adults. As expected, these models are unable to account for the older adult data. An investigation on the effect of the main parameters of these models showed that the poorer performance of older adults does not come from a weaker encoding of item but rather from difficulties during the free time that immediately follows each distractor, as well as from a higher level of confusion between items. These results are discussed with respect to the current theories of working memory and aging.

Virtual reality as a tool for assessing episodic memory

The principal attraction of virtual reality is its potential to create experiments close to daily life with perfect experimental control. We performed an experiment in a virtual town in order to develop a better episodic memory assessment. We tested all components of episodic memory. Young and elderly adults participated in the virtual test: they were either in an active exploration or in a passive exploration of the town. The results showed that older persons recalled the spatiotemporal context and the details of the events in a lower proportion compared to younger ones regardless of the active or passive condition. But no difference was found between active and passive exploration in measures of episodic memory. Finally, correlations mainly appeared between memory complaint and virtual scores, but not with a classical verbal episodic memory test. The virtual test seems to allow a better assessment of episodic memory compared to classical studies, especially because of its components of spatiotemporal memory assessment. In conclusion, virtual reality appears to offer the possibility of developing neuropsychological tools closer to the daily life of patients.

Under Which Conditions Can Older Participants Maintain Information In Working Memory

ABSTRACT Background/Study Context: Age-related deficits in working memory (WM) are commonly described in the literature. However, age-related deficits in WM maintenance mechanisms have received less attention. Based on recent models of WM, the present study aims at determining the conditions under which older adults are able to maintain information. More precisely, we wondered whether the cognitive load effect, taken as evidence for active maintenance in WM, is observed in normal aging and whether it interacts with the level of interference of a concurrent task. Methods: Young (mean age = 21.62; SD = 2.51) and healthy older (mean age = 71.92; SD = 5.18) participants performed a complex WM task. They had to remember five images while reading three words presented after each image. We compared trials in which every word was new (inducing high interference) with trials where words were repeated (inducing low interference). The pace at which the reading task was performed was either fast or slow, resulting in a high or a low cognitive load. Results: As suggested in the literature, young participants presented better performance at slow pace compared with fast pace but were not influenced by interference. Older participants also performed better at slow pace but only when interference was low. Interestingly, the older population showed negative correlations between slow-pace trials and switching abilities. Finally, although computational simulations with time-based resource sharing* (TBRS*) provide a good fit for young adult performance, several parameters had to be adjusted to fit the older participants’ performance, including duration of trace refreshing. Conclusion: Our findings suggest that a decrease in WM performance with aging can be explained by a difficulty in taking advantage of WM maintenance opportunities, especially in conditions of high interference. The computational investigations are consistent with this interpretation given that the parameters to be adjusted involve maintenance in WM. Finally, the computational approach seems a relevant way to address causes of forgetting in aging.

Influence of suggestion in the DRM paradigm: what state of consciousness is associated with false memory?

We assessed the effect of suggestion on the Deese-Roediger-McDermott paradigm and associated it with the Remember-Know-Guess paradigm. Undergraduate students were given either lists of semantically related words or texts containing these words. After the recall task, if participants did not produce the critical lure, the experimenter suggested that the word had been present, using either a question (moderate suggestion) or an assertion (strong suggestion); these conditions were compared to a condition without suggestion. Afterwards, participants took a recognition test. The results showed that strong suggestions lead to more false recognitions than other conditions and the state of consciousness associated with false recognitions tends to be a feeling of knowing rather than remembering, regardless of the verbal version (list or text). Therefore moderate suggestions did not lead to more false recognitions compare to no suggestion. We discuss the impact of suggestion on consciousness associated with false memories.

What is the time course of working memory attentional refreshing

One way of maintaining information in working memory is through attentional refreshing, a process that was recently shown to be independent from verbal rehearsal. In the classical working memory complex span task, the usual assumption is that memoranda are refreshed in a cumulative fashion, starting from the first item, going in a forward order until the latest one, and cycling until there is no time to continue the process. However, there is no evidence that refreshing operates in that way. The present study proposes a computational modelling study, which constitutes a powerful method to investigate alternative hypotheses. Different refreshing schedules are investigated within computational implementation of the time-based resource sharing model. Their ability to fit three sets of behavioral data and to reproduce the major time-based resource sharing predictions were evaluated using standard model selection criteria. Besides an already published schedule in which the attentional focus is expanded, it appeared that one schedule, the least-activated-first, outperforms the classical cumulative one. The memory trace refreshed at a given time is the one that is the least activated in working memory at that time. These findings characterized the time course of attentional refreshing in working memory and specified the contribution of refreshing to primacy and recency effects. Moreover, in the light of various fields of cognitive psychology, we propose that such refreshing schedules can operate without a homunculus within a general framework including cognitive control and strategic considerations.