Le développement de la mémoire de travail : perspectives dans le cadre du modèle de partage temporel des ressources

Working memory has a central role in cognitive development and its capacity is among the best predictors of high-level cognition and school achievement. Within the Time-Based Resource Sharing (TBRS) model, three main factors account for the development of working memory capacity. In this paper, we will review the main empirical evidence sustaining the impact of two of these factors on cognitive development. First, the amount of attention available for cognitive functioning might increase during childhood. Thus, for the same activities, older children would be able to process information faster than younger children. Within working memory span tasks, because the level of activation of memory traces decreases during the processing steps, any reduction of the duration of these steps directly diminishes the time during which the traces decay, and consequently increases the time available for reactivation or refreshing before the next processing step. These two effects jointly induce a stronger activation of the memory traces and a better recall of the to-be-maintained items. Second, because the main hypothesis of the TBRS model is that attention switches to refresh memory traces from processing to maintenance during the processing episodes, the efficiency of the refreshing mechanism should have a direct and strong impact on working memory functioning. An increase in the efficiency of this refreshing during childhood means that older children should take a greater advantage from the short pauses left free between each processing step. The level of activation of the memory traces would be then higher for older than for younger children, resulting in the classically observed increase in span. As a consequence, age-related changes in the efficiency of the refreshing could play a central role in working memory development.     

6-9岁儿童工作记忆的发展研究

以Baddeley工作记忆模型为基础考察儿童语音环路、视觉空间模板、中央执行的发展及其与复杂广度的关系。225名6-9岁被试完成9个任务,分别测量听力广度及工作记忆三个子系统的功能。发现工作记忆各个子成分的功能在6-9岁期间发展速度不同;中央执行与语音环路和视觉空间模板的联系随年龄增长加强;结构方程模型分析发现中央执行和语音环路功能对儿童听力广度都有显著的直接影响,表明言语复杂广度任务既涉及中央执行功能也涉及语音环路的存贮功能。     

Working memory retention systems: a state of activated long-term memory

High temporal resolution event-related brain potential and electroencephalographic coherence studies of the neural substrate of short-term storage in working memory indicate that the sustained coactivation of both prefrontal cortex and the posterior cortical systems that participate in the initial perception and comprehension of the retained information are involved in its storage. These studies further show that short-term storage mechanisms involve an increase in neural synchrony between prefrontal cortex and posterior cortex and the enhanced activation of long-term memory representations of material held in short-term memory. This activation begins during the encoding/comprehension phase and evidently is prolonged into the retention phase by attentional drive from prefrontal cortex control systems. A parsimonious interpretation of these findings is that the long-term memory systems associated with the posterior cortical processors provide the necessary representational basis for working memory, with the property of short-term memory decay being primarily due to the posterior system. In this view, there is no reason to posit specialized neural systems whose functions are limited to those of short-term storage buffers. Prefrontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Short-term memory capacity and phenomena such as displacement of information in short-term memory are determined by limitations on the number of pointers that can be sustained by the prefrontal control systems.     

Information processes in movement learning: capacity and structural interference effects

A series of experiments examined motor learning as an information processing activity occurring within a working short-term memory system and where response-produced feedback and knowledge of results (KR) are used to modify the action plan developed from previous attempts at the movement task. Use of interpolated activities in the KR delay interval allowed inferences to be made regarding the capacity and structural characteristics of these information processes. Results indicated no capacity limitations on the learning process but important structural effects were found. The results supported the idea that response-produced feedback is relatively unimportant as a feedback variable early in learning. Rather, the use of KR at a relatively high level of movement planning appears to be the important information processing activity underlying learning. Finally, the results supported the view that these information processes are related to cognitive problem solving activities.     

Information Processes in Movement Learning

A series of experiments examined motor learning as an information processing activity occurring within a working short-term memory system and where response-produced feedback and knowledge of results (KR) are used to modify the action plan developed from previous attempts at the movement task. Use of interpolated activities in the KR delay interval allowed inferences to be made regarding the capacity and structural characteristics of these information processes. Results indicated no capacity limitations on the learning process but important structural effects were found. The results supported the idea that response-produced feedback is relatively unimportant as a feedback variable early in learning. Rather, the use of KR at a relatively high level of movement planning appears to be the important information processing activity underlying learning. Finally, the results supported the view that these information processes are related to cognitive problem solving activities.     

工作记忆中“组块”概念的演化及理论模型

在Miller提出“神奇的数字7±2”之后,“块”被很多理论作为个体工作记忆加工过程中具有稳定结构并可用于衡量记忆容量的单位。但随着研究者对“组块”研究的深入,他们对组块的定义也在发生着改变。与此同时,不少研究发现个体的年龄阶段与其主要采用的组块层级相对应,但尚不清楚组块层级的转换是否存在固定的年龄区间,且对组块机制的解释仍存在分歧。因此本文针对组块定义的发展与演变、年龄阶段特征及其机制三方面展开综合讨论。未来的研究可以更多探讨长时记忆在工作记忆组块运行机制中的作用,完善不同年龄阶段个体的组块特征,以及怎样发挥复述策略和“少即是多”原则在组块过程中的优势等问题。     

How does the severity of a learning disability affect working memory performance?

Working memory performance was examined in children aged 11-12 years who had borderline, mild, and moderate learning disabilities. Comparisons with children of average abilities were used to determine whether those with more severe learning disabilities had greater impairments in working memory. Seven measures of working memory span were used to assess temporary phonological short-term storage (digit span, word span), temporary visuo-spatial short-term storage (pattern span, spatial span), and temporary short-term storage with additional processing, or central executive, demands (listening span. odd one out span, reverse digit span). Children with mild and moderate learning disabilities were impaired on all measures of working memory compared to children of average abilities. Children with borderline learning disabilities were just as good as children with average abilities on visuo-spatial and complex span tasks, but showed an impairment on phonological span tasks. Children with moderate learning disabilities were indistinguishable from children with mild learning disabilities on simple span tasks, but were significantly poorer than the mild group on the more demanding complex span tasks. For the group as a whole, working memory was strongly related to mental age.     

How does the severity of a learning disability affect working memory performance?

Working memory performance was examined in children aged 11-12 years who had borderline, mild, and moderate learning disabilities. Comparisons with children of average abilities were used to determine whether those with more severe learning disabilities had greater impairments in working memory. Seven measures of working memory span were used to assess temporary phonological short-term storage (digit span, word span), temporary visuo-spatial short-term storage (pattern span, spatial span), and temporary short-term storage with additional processing, or central executive, demands (listening span, odd one out span, reverse digit span). Children with mild and moderate learning disabilities were impaired on all measures of working memory compared to children of average abilities. Children with borderline learning disabilities were just as good as children with average abilities on visuo-spatial and complex span tasks, but showed an impairment on phonological span tasks. Children with moderate learning disabilities were indistinguishable from children with mild learning disabilities on simple span tasks, but were significantly poorer than the mild group on the more demanding complex span tasks. For the group as a whole, working memory was strongly related to mental age.     

Reduced short-term memory capacity in Alzheimer's disease: The role of phonological,lexical, and semantic processing

Individuals with Alzheimer's disease (AD) are often reported to have reduced verbal short-term memory capacity, typically attributed to their attention/executive deficits. However, these individuals also tend to show progressive impairment of semantic, lexical, and phonological processing which may underlie their low short-term memory capacity. The goals of this study were to assess the contribution of each level of representation (phonological, lexical, and semantic) to immediate serial recall performance in 18 individuals with AD, and to examine how these linguistic effects on short-term memory were modulated by their reduced capacity to manipulate information in short-term memory associated with executive dysfunction. Results showed that individuals with AD had difficulty recalling items that relied on phonological representations, which led to increased lexicality effects relative to the control group. This finding suggests that patients have a greater reliance on lexical/semantic information than controls, possibly to make up for deficits in retention and processing of phonological material. This lexical/semantic effect was not found to be significantly correlated with patients’ capacity to manipulate verbal material in short-term memory, indicating that language processing and executive deficits may independently contribute to reducing verbal short-term memory capacity in AD.     

Binding in short-term visual memory

The integration of complex information in working memory, and its effect on capacity, shape the limits of conscious cognition. The literature conflicts on whether short-term visual memory represents information as integrated objects. A change-detection paradigm using objects defined by color with location or shape was used to investigate binding in short-term visual memory. Results showed that features from the same dimension compete for capacity, whereas features from different dimensions can be stored in parallel. Binding between these features can occur, but focused attention is required to create and maintain the binding over time, and this integrated format is vulnerable to interference. In the proposed model, working memory capacity is limited both by the independent capacity of simple feature stores and by demands on attention networks that integrate this distributed information into complex but unified thought objects.     

The effect of bilingualism on lexical learning and memory across two language modalities: some evidence for a domain-specific,but not general,advantage

ABSTRACT

The present study was conducted to replicate bilingual advantages in short-term memory for language-like material and word learning in young adults and extend this research to the sign domain, ultimately with the goal of investigating the domain specificity of bilingual advantages in cognition. Data from 112 monolingual hearing non-signers and 78 bilingual hearing non-signers were analysed for this study. Participants completed a battery of tasks assessing sign and word learning, short-term memory, working memory capacity, intelligence, and a language and demographic questionnaire. Overall, the results of this study suggested a bilingual advantage in memory for speech-like material – no other advantage (or disadvantage) was found. Results are discussed within the context of recent large-scale experimental and meta-analytic studies that have failed to find bilingual advantages in domain-general abilities such as attention control and working memory capacity in young adults.     

Reduced short-term memory capacity in Alzheimer's disease: the role of phonological, lexical, and semantic processing

Individuals with Alzheimer's disease (AD) are often reported to have reduced verbal short-term memory capacity, typically attributed to their attention/executive deficits. However, these individuals also tend to show progressive impairment of semantic, lexical, and phonological processing which may underlie their low short-term memory capacity. The goals of this study were to assess the contribution of each level of representation (phonological, lexical, and semantic) to immediate serial recall performance in 18 individuals with AD, and to examine how these linguistic effects on short-term memory were modulated by their reduced capacity to manipulate information in short-term memory associated with executive dysfunction. Results showed that individuals with AD had difficulty recalling items that relied on phonological representations, which led to increased lexicality effects relative to the control group. This finding suggests that patients have a greater reliance on lexical/semantic information than controls, possibly to make up for deficits in retention and processing of phonological material. This lexical/semantic effect was not found to be significantly correlated with patients' capacity to manipulate verbal material in short-term memory, indicating that language processing and executive deficits may independently contribute to reducing verbal short-term memory capacity in AD.     

Role of Working Memory in Typically Developing Children’s Complex Sentence Comprehension

The influence of three mechanisms of working memory (phonological short-term memory (PSTM capacity), attentional resource control/allocation, and processing speed) on children's complex (and simple) sentence comprehension was investigated. Fifty two children (6-12 years) completed a nonword repetition task (indexing PSTM), concurrent verbal processing-storage task (indexing resource control/allocation), auditory-visual reaction time (RT) task (indexing processing speed), and a sentence comprehension task that included complex and simple sentences. Correlation and regression analyses were run to determine the association between the memory variables and sentence comprehension accuracy. Results revealed: (1) none of the memory variables correlated with simple sentence comprehension, (2) resource control/allocation and processing speed correlated significantly with complex sentence comprehension, even after covarying for age, and (3) attentional functioning and processing speed predicted complex sentence comprehension (after accounting for age). Results were interpreted to suggest that working memory is significantly involved in school age children's comprehension of familiar complex sentence structures.     

Short-term memory and sentence processing: Evidence from neuropsychology

Traditional models of memory assume that short-term memory, as measured by memory span, plays an important role in linguistic processing and the learning ofverbal information. Contradicting this view are findings from a brain-damaged patient, E.A., who, despite a verbal memory span of about two items, demonstrated normal sentence comprehension in a variety oftasks. She was, however, impaired whenever verbatim phonological information had to be maintained or learned. These results and those from other patients with reduced span suggest that the phonological storage capacity that is critical to memory span plays only a limited role in language processing, specifically in the maintenance and learning of phonological forms. Implications for models of short-term memory are discussed. It is argued that short-termmemory should be seen as deriving from the processing and retentive capacities of language processing modules, with span tasks drawing on only a subset of these modules.     

Models provide specificity: Testing a proposed mechanism of visual working memory capacity development

Numerous studies have established that visual working memory has a limited capacity that increases during childhood. However, debate continues over the source of capacity limits and its developmental increase. Simmering (2008) adapted a computational model of spatial cognitive development, the Dynamic Field Theory, to explain not only the source of capacity limitations but also the developmental mechanism. Capacity is limited by the balance between excitation and inhibition that maintains multiple neural representations simultaneously in the model. Development occurs according to the Spatial Precision Hypothesis, which proposes that excitatory and inhibitory connections strengthen throughout early childhood. These changes in connectivity result in increasing precision and stability of neural representations over development. Here we test this developmental mechanism by probing children's memory in a single-item change detection task. Results confirmed the model's predictions, providing further support for this account of visual working memory capacity development.     

Selective attention is a primary determinant of the relationship between working memory and general learning ability in outbred mice

A single factor (i.e., general intelligence) can account for much of an individuals' performance across a wide variety of cognitive tests. However, despite this factor's robustness, the underlying process is still a matter of debate. To address this question, we developed a novel battery of learning tasks to assess the general learning abilities (GLAs) of mice. Using this battery, we previously reported a strong relationship between GLA and a task designed to tax working memory capacity (i.e., resistance to competing demands). Here we further explored this relationship by investigating which aspects of working memory (storage or processing) best predict GLAs in mice. We found that a component of working memory, selective attention, correlated with GLA comparably to working memory capacity. However, this relationship was not found for two other components of working memory, short-term memory capacity and duration. These results provide further evidence that variations in aspects of working memory and executive functions covary with general cognitive abilities.     

Adult age differences in working memory

Active and passive measures of short-term memory over a large segment of the adult life span were compared. Two hundred twenty-eight volunteers, aged 30 to 99 years, performed the digit span forward and backward task, the Peterson-Peterson task, and a new working memory task in which active manipulation of information is emphasized. Age differences were slight for passive tasks. For the working memory task, significant declines were found between the ages of 60 to 69 and 70+ years. It is suggested that the age differences may be due to a decrease in the flexibility with which processing changes are made.     

Peer Relationships and Emotional Well-Being of Children with Sickle Cell Disease: A Controlled Replication

This study investigated the effects of stimulus presentation modality on working memory performance in elementary school-age children ages 7–13. The experimental paradigm implemented a multitrial learning task incorporating three presentation modalities: Auditory, Visual, and simultaneous Auditory plus Visual. The first experiment compared the learning and memory performance of older and younger elementary school children. The second experiment compared verbal learning and memory performance in elementary school children with major depressive disorder (MDD) to the performance of nondepressed children. All participants benefited from the pictorial presentation of information during learning and recall of information as compared to the auditory presentation alone. Both age and socioeconomic status affected working memory performance in typically developing children. Children with depression demonstrated a more passive learning style during the auditory list acquisition. The present study supports the pictorial superiority hypothesis in verbal learning tasks and the theory that working memory matures during elementary school years. Furthermore, current results indicate that complex working memory measures are not entirely independent of previous experience.     

Neurocognitive Contributions to Motor Skill Learning: The Role of Working Memory

ABSTRACT

Researchers have begun to delineate the precise nature and neural correlates of the cognitive processes that contribute to motor skill learning. The authors review recent work from their laboratory designed to further understand the neurocognitive mechanisms of skill acquisition. The authors have demonstrated an important role for spatial working memory in 2 different types of motor skill learning, sensorimotor adaptation and motor sequence learning. They have shown that individual differences in spatial working memory capacity predict the rate of motor learning for sensorimotor adaptation and motor sequence learning, and have also reported neural overlap between a spatial working memory task and the early, but not late, stages of adaptation, particularly in the right dorsolateral prefrontal cortex and bilateral inferior parietal lobules. The authors propose that spatial working memory is relied on for processing motor error information to update motor control for subsequent actions. Further, they suggest that working memory is relied on during learning new action sequences for chunking individual action elements together.     

Reasons for the growth of traditional memory span across age

Three studies, covering together the age range from 3 to 16 years, show the relationships between age, short-term memory span, and language abilities. The growth of the traditional memory span in childhood is systematically related to a concomitant growth of language abilities as tested with CELF-3 Screening, two tests of word knowledge, a test of reception of grammar (TROG-2), and the British Picture Vocabulary Test (BPVS). Linear regression and ANCOVA analyses show that the growth of memory span is fully explained by the growth of language abilities in the three studies that covered different subsamples of children. In a confirmatory factor analysis a two-factor model fits the data well and shows that a “crystallised” language factor is strongly related to age, whereas a “fluid” short-term memory factor is unrelated to age. The two-factor model gives support to Baddeley's multicomponent model of working memory, and the current data suggest that the capacity of the phonological store is fully developed in children younger than 4 years old. The authors hold that chunking capacity, highly dependent on language abilities, is a major source of memory span growth with age. Rather than an increase in the number of chunks, or episodes retained in short-term memory (=chunk span), it is argued that childhood memory span development reflects an increase in the size of each chunk (=chunking capacity).