Decline in working memory updating through ageing: Intrusion error analyses

The present research examines the decline in working memory updating through age. Two experiments compared groups of participants in different age ranges (young‐old, 55–65 years, old, 66–75 years and old‐old, more than 75 years and, in Experiment 2 only, young, 20–30 years). Memory updating tasks were administered, which required participants to remember the smallest items in each list. To perform the task correctly, participants had to update information efficiently, reducing interference from items no longer relevant. Intrusion errors were computed and in the first experiment these were described as “intrusions of irrelevant items” (immediate exclusion) and “intrusions of once relevant items” (delayed exclusion). The oldest adults performed worse in memory updating and made a greater number of intrusion errors of once relevant information. In the second experiment results showed that increases in memory load (number of items that had to be remembered) and updating demand (number of potentially relevant items) impaired performance. The oldest adults had greater difficulty when the task demand was increased. Furthermore, they produced a higher number of intrusion errors, particularly when the updating demand was increased. It therefore appears that elderly people have specific difficulty in updating information in working memory by excluding irrelevant information.     

When working memory updating requires updating: Analysis of serial position in a running memory task

This study aimed to investigate updating in working memory (WM), analyzing the effects of task demand and memory resources on serial position curve (SPC), in a running memory task with slow pace presentation and a probed recognition procedure. These task conditions were supposed to produce an easier WM updating task, which may allow evidencing whether the task is performed through an active or a passive updating.     

Two dissociable updating processes in working memory

The authors show that the updating of working memory (WM) representations is carried out by the cooperative act of 2 dissociable reaction time (RT) components: a global updating process that provides stability by shielding WM contents against interference and a local process that provides flexibility. Participants kept track of 1-3 items (digits or Gibson figures). In each trial, the items either were similar to those in the previous trial or were different in any or all of the items. Experiments 1 and 2 established the existence of 2 independent RT components representing the 2 updating processes. Global updating cost was sensitive to total number of items in WM (set size), regardless of the number of items that actually were modified. Local updating cost was sensitive to the number of modified items, regardless of the set size. Experiment 3 showed that participants had to dismantle the representation formed by previous global updating in order to carry out new updating.     

Binding and content updating in working memory tasks

Working memory updating can involve processing of either a specific memory content or a binding. So far, research has focused mainly on single contents as objects of updating, via recall accuracy measures. Here, we have addressed more direct measurement of the updating process (i.e., response times), assessing individually the role of single contents, as well as bindings. To this end, we compared two updating tasks from separate research traditions: a RT‐based computer task and a classical accuracy‐based task. The former consisted of trials where measures of content and binding updating were obtained, allowing a dissociation between these two components. The latter measured recall accuracy and intrusion rate for lists of words under different conditions of maintenance/inhibition. These results enable a better understanding of the updating process for the dual components of binding and content updating, and their potential role in an accuracy‐based task. An overlap between the underlying components of updating tasks was demonstrated, specifically between binding updating RT and intrusion rate. Notably, binding updating appears to be a more sensitive measure in explaining results in the classical updating task.     

Content-context binding in verbal working memory updating: on-line and off-line effects

The role of content–context binding in working memory updating has received only marginal interest, despite its undoubted relevance for the updating process. In the classical updating paradigm, the main focus has been on the process of discarding information when new information is presented. Its efficacy has been determined by measurement of the accuracy of recalled, updated information. In the current study we measured the working memory updating process directly, employing a dynamic memory task composed of alternating sequences of learning, active maintenance and updating phases. Binding was manipulated by changing the type of updating (total or partial) and the strength of the perceptual connection between items. The on-line updating process and the off-line efficacy were separately analysed. Both on-line and off-line measures indicated that partial updating conditions, where the operation of updating content–context binding was required, were more demanding than both total updating conditions and memory and maintenance phases. Our results suggest that working memory updating can be identified not only as a process of substitution of information, but also as inhibition of no longer relevant information and, above all, as a binding updating.     

The neural correlates of updating information in verbal working memory

The aim of the present study was to re-examine cerebral areas subserving the updating function of the central executive with a running span task requiring subjects to watch strings of consonants of unknown length and then to recall serially a specific number of recent items. In order to dissociate more precisely the updating process from the storage function, a four-item instead of a six-item memory load was used, contrary to our previous study (Salmon et al., 1996). In addition, a serial recall procedure was preferred to a recognition procedure in order to suppress the use of visuospatial strategies. The most significant increase of rCBF occurred in the left frontopolar cortex (Brodmann's area 10), spreading to the left middle frontal (Brodmann's area 46). Results suggest that frontopolar activation underlies an updating process in working memory.     

Trait worry is associated with difficulties in working memory updating

The current study investigated the effects of trait worry, a subcomponent of trait anxiety, on the process of updating information in working memory (WM). A leading theory on anxiety and executive functions, attentional control theory (ACT), states that anxiety is not related to WM updating in emotionally neutral situations. Previous research, however, has focused almost exclusively on WM span tasks that primarily emphasised storage, rather than the updating of WM representations. Moreover, few studies have directly examined the effects of trait worry. In this study, 116 subjects performed a WM updating task that required the memorisation of short lists of words and the within-trial removal of some of these items from WM. Results indicated that levels of trait worry were not related to word-span performance, but were related to performance on trials that required subjects to effectively update WM. Moreover, these effects were observed only for trait worry, not for levels of anxious arousal or comorbid levels of dysphoria. These results support the hypothesis that trait worry is related to WM updating performance and thereby extend ACT in new directions.     

Aging and the intrusion superiority effect in visuo-spatial working memory

This study investigated the active component of visuo-spatial working memory (VSWM) in younger and older adults testing the hypotheses that elderly individuals have a poorer performance than younger ones and that errors in active VSWM tasks depend, at least partially, on difficulties in avoiding intrusions (i.e., avoiding already activated information). In two experiments, participants were presented with sequences of matrices on which three positions were pointed out sequentially: their task was to process all the positions but indicate only the final position of each sequence. Results showed a poorer performance in the elderly compared to the younger group and a higher number of intrusion (errors due to activated but irrelevant positions) rather than invention (errors consisting of pointing out a position never indicated by the experiementer) errors. The number of errors increased when a concurrent task was introduced (Experiment 1) and it was affected by different patterns of matrices (Experiment 2). In general, results show that elderly people have an impaired VSWM and produce a large number of errors due to inhibition failures. However, both the younger and the older adults' visuo-spatial working memory was affected by the presence of activated irrelevant information, the reduction of the available resources, and task constraints.     

Working memory at work: how the updating process alters the nature of working memory transfer

In three N-Back experiments, we investigated components of the process of working memory (WM) updating, more specifically access to items stored outside the focus of attention and transfer from the focus to the region of WM outside the focus. We used stimulus complexity as a marker. We found that when WM transfer occurred under full attention, it was slow and highly sensitive to stimulus complexity, much more so than WM access. When transfer occurred in conjunction with access, however, it was fast and no longer sensitive to stimulus complexity. Thus the updating context altered the nature of WM processing: The dual-task situation (transfer in conjunction with access) drove memory transfer into a more efficient mode, indifferent to stimulus complexity. In contrast, access times consistently increased with complexity, unaffected by the processing context. This study reinforces recent reports that retrieval is a (perhaps the) key component of working memory functioning.     

The focus of attention in working memory: evidence from a word updating task

Three experiments examined the cognitive costs of item switching within working memory with a novel word updating task, thereby extending previous research to the field of linguistic stimuli and linguistic-graphemic updating operations. In Experiments 1 and 2 costs for switching between working memory items were evident on the word level, and they increased with an increasing word set size (Experiment 2). In contrast, a surprisingly similar switch effect on the level of letters was not affected by word set size (Experiment 2). Experiment 3 showed that this effect is not simply based on the need for re-orienting visual spatial attention. To account for the overall picture of results, a recursive model of attentional foci is proposed. Moreover, individual working memory span appears to be associated with the accuracy of item switching, but not with its speed.     

The focus of attention in working memory: Evidence from a word updating task

Three experiments examined the cognitive costs of item switching within working memory with a novel word updating task, thereby extending previous research to the field of linguistic stimuli and linguistic-graphemic updating operations. In Experiments 1 and 2 costs for switching between working memory items were evident on the word level, and they increased with an increasing word set size (Experiment 2). In contrast, a surprisingly similar switch effect on the level of letters was not affected by word set size (Experiment 2). Experiment 3 showed that this effect is not simply based on the need for re-orienting visual spatial attention. To account for the overall picture of results, a recursive model of attentional foci is proposed. Moreover, individual working memory span appears to be associated with the accuracy of item switching, but not with its speed.     

Modifying memory for a museum tour in older adults: Reactivation-related updating that enhances and distorts memory is reduced in ageing

Memory reactivation, the activation of a latent memory trace when we are reminded of a past experience, strengthens memory but can also contribute to distortions if new information present during reactivation is integrated with existing memory. In a previous study in young adults we found that the quality of memory reactivation, manipulated using the principle of encoding specificity and indexed by recollection ratings, modulated subsequent true and false memories for events experienced during a museum tour. Here in this study, we examined age-related changes in the quality of memory reactivation on subsequent memory. Memories of museum stops in young and older adults were reactivated and then immediately followed by the presentation of a novel lure photo from an alternate tour version (i.e., reactivation plus new information). There was an increase in subsequent true memories for reactivated targets and for subsequent false memories for lures that followed reactivated targets, when compared to baseline target and lure photos. However, the influence of reactivation on subsequent memories was reduced in older adults. These data reveal that ageing alters reactivation-related updating processes that allow memories to be strengthened and updated with new information, consequently reducing memory distortions in older adults compared to young adults.     

The effects of optimism and pessimism on updating emotional information in working memory

In the present study we elucidate the emotional and executive control interactions that might underlie optimism and pessimism. Participants completed a self-report measure of optimism/pessimism and performed an emotion faces categorisation task and an emotion n-back task in which they indicated whether each of a series of faces had the same or a different emotional expression (happy, sad, neutral) as the face presented two trials before. Trials were structured to measure latency to update emotional content in working memory (WM). More pessimistic individuals formed connections among positive stimuli, and broke connections among positive and sad stimuli, in WM more slowly than did less pessimistic individuals; levels of optimism/pessimism did not affect the rate with which individuals formed and broke connections among neutral representations in WM. It appears, therefore, that levels of pessimism are related to specific affective cognitive mechanisms in WM that may be involved in emotion regulation.     

Executive functions and achievements in school: Shifting, updating, inhibition, and working memory

Links have recently been established between measures of educational attainment and both verbal and visuo-spatial aspects of working memory. Relationships have also been identified between specific executive functions—shifting, updating, and inhibition—and scholastic achievement. In the present study, scholastic attainment, shifting, updating, inhibition, and verbal and visuo-spatial working memory were assessed in 11- and 12-year-old children. Exploratory factor analysis identified two executive factors: one associated with updating functions and one associated with inhibition. Updating abilities were closely linked with performance on both verbal and visuo-spatial working memory span tasks. Working memory was closely linked with attainment in English and mathematics, and inhibition was associated with achievement in English, mathematics, and science. Domain-specific associations existed between verbal working memory and attainment in English, and between visuo-spatial working memory and attainment in English, mathematics and science. Implications of the findings for the theoretical analysis of executive functioning, working memory and children's learning are discussed.     

Executive functions and achievements in school: Shifting,updating, inhibition,and working memory

Links have recently been established between measures of educational attainment and both verbal and visuo-spatial aspects of working memory. Relationships have also been identified between specific executive functions—shifting, updating, and inhibition—and scholastic achievement. In the present study, scholastic attainment, shifting, updating, inhibition, and verbal and visuo-spatial working memory were assessed in 11- and 12-year-old children. Exploratory factor analysis identified two executive factors: one associated with updating functions and one associated with inhibition. Updating abilities were closely linked with performance on both verbal and visuo-spatial working memory span tasks. Working memory was closely linked with attainment in English and mathematics, and inhibition was associated with achievement in English, mathematics, and science. Domain-specific associations existed between verbal working memory and attainment in English, and between visuo-spatial working memory and attainment in English, mathematics and science. Implications of the findings for the theoretical analysis of executive functioning, working memory and children's learning are discussed.     

All updateable objects in working memory are updated whenever any of them are modified: evidence from the memory updating paradigm

In a series of experiments, participants were required to keep track of 1 or 2 working memory (WM) objects, having to update their values in 80% of the trials. Updating cost, defined as the difference between update and non-update trials, was larger when 2 objects were involved compared with when there was only 1 object was involved. This finding was interpreted as evidence that the updating process encompasses both objects in WM, even though only 1 of them is actually updated. This feature of WM updating is limited to objects defined as "updateable," throughout the trial sequence. The results are explained by the need to reprogram the phonological loop when updating or the need for desynchronization followed by resynchronization of WM contents.     

Age differences in verbal and visuo-spatial working memory updating: evidence from analysis of serial position curves

Memory updating is the ability to select and update relevant information and suppress no-longer-relevant data. The few studies in this area, targeting mainly the verbal domain, have investigated and confirmed an age-related decline in working memory updating ability (De Beni & Palladino, 2004; Van der Linden, Bredart, & Beerten, 1994). The present research examines the ability of younger and older adults to update information in verbal and visuo-spatial running memory tasks. Results showed that the participants' performance was higher in the verbal than in the visuo-spatial task. Nonetheless, independently of the task domain, an age-related decline in updating performance was found. Moreover, analysis of serial positions suggested that, in the updating procedure, the participants were not attempting to actively maintain items, preferring to adopt a low-effort, "recency-based" strategy. The use of this type of strategy is more evident in older participants, as shown in both the accuracy performance and the proportion of intrusion errors.     

Similarity-based interference in a working memory numerical updating task: age-related differences between younger and older adults

Similarity among representations held simultaneously in working memory (WM) is a factor which increases interference and hinders performance. The aim of the current study was to investigate age-related differences between younger and older adults in a working memory numerical updating task, in which the similarity between information held in WM was manipulated. Results showed a higher susceptibility of older adults to similarity-based interference when accuracy, and not response times, was considered. It was concluded that older adults' WM difficulties appear to be due to the availability of stored information, which, in turn, might be related to the ability to generate distinctive representations and to the process of binding such representations to their context when similar information has to be processed in WM.