The roles of the central executive and visuospatial storage in mental arithmetic: A comparison across strategies

Previous research has demonstrated that working memory plays an important role in arithmetic. Different arithmetical strategies rely on working memory to different extents—for example, verbal working memory has been found to be more important for procedural strategies, such as counting and decomposition, than for retrieval strategies. Surprisingly, given the close connection between spatial and mathematical skills, the role of visuospatial working memory has received less attention and is poorly understood. This study used a dual-task methodology to investigate the impact of a dynamic spatial n-back task (Experiment 1) and tasks loading the visuospatial sketchpad and central executive (Experiment 2) on adults' use of counting, decomposition, and direct retrieval strategies for addition. While Experiment 1 suggested that visuospatial working memory plays an important role in arithmetic, especially when counting, the results of Experiment 2 suggested this was primarily due to the domain-general executive demands of the n-back task. Taken together, these results suggest that maintaining visuospatial information in mind is required when adults solve addition arithmetic problems by any strategy but the role of domain-general executive resources is much greater than that of the visuospatial sketchpad.     

The Role of Memory in the Tower of London Task

The Tower of London (TOL) task is widely used as a neuropsychological test of planning. Relatively little is known of the cognitive components of the task, and in particular the role of memory in performance. The current studies on normal adults looked at the role of verbal and spatial working memory in the TOL. The effects of verbal and visuospatial dual-task manipulations on TOL performance were examined in an experiment with 36 participants. Both verbal and visuospatial executive secondary tasks caused poorer performance on the TOL; however, concurrent articulatory suppression enhanced performance. The results suggest that executive and spatial components are important in the task, and raise questions about the role of preplanning in the TOL.     

The role of memory in the Tower of London task

The Tower of London (TOL) task is widely used as a neuropsychological test of planning. Relatively little is known of the cognitive components of the task, and in particular the role of memory in performance. The current studies on normal adults looked at the role of verbal and spatial working memory in the TOL. The effects of verbal and visuospatial dual-task manipulations on TOL performance were examined in an experiment with 36 participants. Both verbal and visuospatial executive secondary tasks caused poorer performance on the TOL; however, concurrent articulatory suppression enhanced performance. The results suggest that executive and spatial components are important in the task, and raise questions about the role of preplanning in the TOL.     

Mental animation in the visuospatial sketchpad: Evidence from dual-task studies

We used the dual-task paradigm to provide evidence that inferring the motion of a component of a mechanical system (mental animation) is a spatial visualization process. In two experiments, participants were asked to solve mental animation problems while simultaneously retaining either a visuospatial working memory load (a configuration of dots in a grid) or a verbal memory load (a list of letters). Both experiments showed that mental animation interferes more with memory for a concurrent visuospatial load than with memory for a verbal load. Experiment 1 also showed that a visuospatial working memory load interferes more with mental animation than does a verbal memory load. Furthermore, Experiment 2 showed that mental animation interferes more with a visuospatial memory load than does a verbal reasoning task that takes approximately the same amount of time.     

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There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.     

Visuospatial and verbal memory in mental arithmetic

Working memory allows complex information to be remembered and manipulated over short periods of time. Correlations between working memory and mathematics achievement have been shown across the lifespan. However, only a few studies have examined the potentially distinct contributions of domain-specific visuospatial and verbal working memory resources in mental arithmetic computation. Here we aimed to fill this gap in a series of six experiments pairing addition and subtraction tasks with verbal and visuospatial working memory and interference tasks. In general, we found higher levels of interference between mental arithmetic and visuospatial working memory tasks than between mental arithmetic and verbal working memory tasks. Additionally, we found that interference that matched the working memory domain of the task (e.g., verbal task with verbal interference) lowered working memory performance more than mismatched interference (verbal task with visuospatial interference). Findings suggest that mental arithmetic relies on domain-specific working memory resources.     

Susceptibility of spatial and verbal working memory to demands of the central executive

We used a dual-task paradigm to examine the degree to which domain-specific spatial and verbal subsystems depend on the domain-general central executive. Forty participants were asked to retain spatial or verbal information while performing a concurrent secondary task related to simple arithmetic. The secondary tasks consisted of three cognitive processes: single-digit addition, a digit-carrying operation, and digit reading. The single-digit addition and carry operation include central executive functioning, while digit reading relies solely on the phonological loop. The single-digit addition caused a performance decrement on the spatial working memory task, while the digit reading impaired performance on the verbal working memory task. The carry operation interfered with recall accuracy on both working memory tasks. The spatial working memory task was significantly correlated with the verbal working memory task only when the secondary task was more demanding on the central executive. Our results suggest that spatial working memory rather than verbal working memory is susceptible to failure of central executive functioning and that the central executive plays an important role in regulating the cognitive demands of different domains.     

Posttraumatic stress disorder is associated with limited executive resources in a working memory task

Patients with posttraumatic stress disorder (PTSD) can show declines in working memory. A dual-task design was used to determine whether these impairments are linked to executive control limitations. Participants performed a Sternberg memory task with either one or four letters. In the dual-task condition, the maintenance period was filled with an arrow flanker task. PTSD patients were less accurate on the working memory task than were controls, especially in the dual-task condition. In the single-task condition, both groups showed similar patterns of brain potentials from 300 to 500 ms when discriminating old and new probes. However, when taxed with an additional task, the event-related potentials (ERPs) of the PTSD group no longer differentiated old and new probes. In contrast, interference resolution processes in both the single- and dual-task conditions of the flanker task were intact. The lack of differentiation in the ERPs reflects impaired working memory performance under more difficult, dual-task conditions. Exacerbated difficulty in performing a working memory task with concurrent task demands suggests a specific limitation in executive control resources in PTSD.     

Exploring the visuo-spatial scratch pad

A series of four studies examines the relationship between the visuo-spatial scratch pad, the central executive and the articulatory loop. For this purpose a visuo-spatial memory task that does not have a large verbal component was developed. In Experiment 1 this task was used to demonstrate that the scratch pad, although functionally independent of the articulatory loop, is subject to interference from a tracking task. Experiment 2 examined the locus of interference of the tracking task with spatial memory. It was shown that interference is confined to the encoding phase; post presentation tracking does not disrupt visuo-spatial representation. Experiment 3 demonstrated that the tracking task employed requires some central executive resources. The final experiment examined the effect of a near-span consonant memory load on the spatial memory task. Disruption only occurred when the verbal load preceded, or was concurrent with, the spatial task. The results suggest that central executive resources are probably required to operate the scratch pad in most circumstances. However, minimal central capacity is required for maintenance rehersal.     

High-performers use the phonological loop less to process mental arithmetic during working memory tasks

This study investigated the effects of three working memory components—the central executive, phonological loop, and visuospatial sketchpad—on performance differences in complex mental arithmetic between individuals. Using the dual-task method, we examined how performance during two-digit addition was affected by load on the central executive (random tapping condition), phonological loop (articulatory suppression condition), and visuospatial sketchpad (spatial tapping condition) compared to that under no load (control condition) in high- and low-performers of complex mental arithmetic in Experiment 1. Low-performers showed an increase in errors under the random tapping and articulatory suppression conditions, whereas high-performers showed an increase of errors only under the random tapping condition. In Experiment 2, we conducted similar experiments on only the high-performers but used a shorter presentation time of each number. We found the same pattern for performing complex mental arithmetic as seen in Experiment 1. These results indicate that high-performers might reduce their dependence on the phonological loop, because the central executive enables them to choose a strategy in which they use less working memory capacity.     

习得性空间联结的迁移依赖于语义工作记忆

采用练习迁移范式与双任务范式相结合的设计来探讨练习所习得的空间联结在工作记忆中如何表征。被试先进行不一致空间的刺激—反应映射练习任务, 五分钟后, 随机迁移到单任务(Simon任务)或者双任务(Simon任务+语义工作记忆负荷任务或空间工作记忆负荷任务)。结果发现：不一致的练习能使单任务出现反转的Simon效应, 但语义工作记忆负荷会使反转的Simon效应消失, 而空间工作记忆负荷却对反转的Simon效应没有影响。实验结果表明练习产生的空间联结依赖于语义工作记忆。     

The influence of working memory load on the Simon effect

The contribution of spatial and verbal working memory (WM) to the processing of stimulus location in the Simon task was examined in two experiments. Subjects performed the Simon task in single- and dual-task conditions. In the dual-task conditions, individuals first encoded the locations of four boxes/pseudocharacters or the identity of seven characters in memory, then responded to the color of a Simon stimulus, and finally received a test for the WM set. The Simon effect was insensitive to spatial WM load and was abolished by verbal WM load. These data reveal a role of verbal WM in the processing of spatial location in the Simon task. In addition, the data are inconsistent with dual-route models of the Simon effect and may support response discrimination accounts of the mechanisms underlying the processing of spatial location in the Simon task.     

Is judgment of random time intervals biased and capacity-limited?

 Recently, random generation of time intervals has been proposed as a procedure to impair executive processing in a dual-task paradigm without substantial interference with phonological and visuo-spatial working memory resources. A fundamental assumption of this procedure is that humans are able to distinguish time sequences on their degree of randomness. The present study tests this assumption. To this end, non-biased, repetition-biased, alternation-biased sequences and repetitive rhythms were judged under conditions of higher or lower executive load. In Exp. 1, load depended on the presentation speed, while in Exp. 2, a dual-task condition was used with either a concurrent number-copying task or an arithmetic task. It was found that the participants could distinguish repetitive rhythms from more or less random sequences, and that both accuracy of this judgment and latency were affected by the concurrent load. The findings are taken as a first indication that random time judgment is capacity-limited. Received: 9 September 1999 / Accepted: 1 October 1999     

Visuospatial working memory influences the interaction between space and time

How do representations of space inform our perception of time? In language, spatial vocabulary is frequently used to describe temporal concepts, and spatial information biases temporal perception even in non-verbal tasks. In contrast, temporal information typically exerts little, if any, influence on the perception of spatial extent. Here, we used spatial and temporal reproduction tasks, both with and without verbal and spatial dual tasks, to investigate the mechanism underlying the asymmetric relation between space and time. Specifically, we tested whether the asymmetric interference between spatial and temporal stimulus attributes arises from interference in verbal or visuospatial working memory. We found that loading visuospatial working memory, but not verbal working memory, eliminated the asymmetric pattern of interference. This suggests that the interference between spatial and temporal representations arises due to processing constraints in visuospatial working memory. These findings are discussed in terms of the load theory of attention and the relative automaticity with which spatial and temporal information is processed.     

Executive Resources and Item-Context Binding: Exploring the Influence of Concurrent Inhibition,Updating, and Shifting Tasks on Context Memory

Previous research has demonstrated that context memory performance decreases as a result of cognitive load. However, the role of specific executive resources availability has not been specified yet. In a dual-task experiment, participants performed three kinds of concurrent task engaging: inhibition, updating, or shifting operations. In comparison with a no-load single-task condition, a significant decrease in item and context memory was observed, regardless of the kind of executive task. When executive load conditions were compared with non-specific cognitive load conditions, a significant interference effect was observed in the case of the inhibition task. The inhibition process appears to be an aspect of executive control, which relies on the same resource as item-context binding does, especially when binding refers to associations retrieved from long-term memory.     

Estimating the executive demands of a one-back choice reaction time task by means of the selective interference paradigm

The present study proposes a new executive task, the one-back choice reaction time (RT) task, and implements the selective interference paradigm to estimate the executive demands of the processing components involved in this task. Based on the similarities between a one-back choice RT task and the n-back updating task, it was hypothesized that one-back delaying of a choice reaction involves executive control. In three experiments, framed within Baddeley's (1986) working-memory model, a one-back choice RT task, a choice RT task, articulatory suppression, and matrix tapping were performed concurrently with primary tasks involving verbal, visuospatial, and executive processing. The results demonstrate that one-back delaying of a choice reaction interferes with tasks requiring executive control, while the potential interference at the level of the verbal or visuospatial working memory slave systems remains minimal.     

Re-examining the contribution of visuospatial working memory to inhibition of return

Castel and colleagues (Percept Psychophys 65(6):970–981, 2003) proposed that visuospatial working memory is needed to retain and update the irrelevant but attended location in an inhibition of return (IOR) procedure. In a series of three experiments, we re-examined this hypothesis by loading visuospatial working memory and manipulating the timing of encoding. When the visuospatial memory items were presented right after the cue, as in Castel et al. (Percept Psychophys 65(6):970–981, 2003), we replicated the lack of IOR in the dual-task condition (Experiment 1). However, when we presented the visuospatial memory items before the spatial cue, to control for retroactive interference in encoding, we found robust IOR effects (Experiment 2); the effect remained strong even when participants were prevented from using verbal labels to rehearse the memory material (Experiment 3). We conclude that IOR does not seem to depend on retaining the position of the irrelevant cue in visuospatial working memory.     

Interference with spatial working memory: An eye movement is more than a shift of attention

In the present experiments, we examined whether shifts of attention selectively interfere with the maintenance of both verbal and spatial information in working memory and whether the interference produced by eye movements is due to the attention shifts that accompany them. In Experiment 1, subjects performed either a spatial or a verbal working memory task, along with a secondary task requiring fixation or a secondary task requiring shifts of attention. The results indicated that attention shifts interfered with spatial, butnot with verbal, working memory, suggesting that the interference is specific to processes within the visuospatial sketchpad. In Experiment 2, subjects performed a primary spatial working memory task, along with a secondary task requiring fixation, an eye movement, or an attention shift executed in the absence of an eye movement. The results indicated that both eye movements and attention shifts interfered with spatial working memory. Eye movements interfered to a much greater extent than shifts of attention, however, suggesting that eye movements may contribute a unique source of interference, over and above the interference produced by the attention shifts that accompany them.     

Visuospatial working memory and mental representation of spatial descriptions

The purpose of the present research is to investigate whether different components of working memory (WM) are involved in processing spatial and nonspatial texts. The interference effects of two concurrent tasks on comprehension and recall of two kinds of text were investigated in two experiments. Each participant listened to a spatial and a nonspatial text, with one of two concurrent tasks: articulatory suppression or spatial tapping. The dependent variables in Experiment 1 were accuracy of recall and verification of information inferred from the texts. In Experiment 2 response times in the verification task were also considered. Results support the hypothesis that verbal and spatial components of working memory are differentially involved in the comprehension and memory of spatial and nonspatial texts, with a selective interference effect of the spatial concurrent task on the spatial text and an interference effect of the verbal concurrent task on both the spatial and nonspatial texts. These effects emerged for recall, sentence verification, and response times. Our findings confirm previous results showing that the verbal component of working memory is involved in the process of text comprehension and memory. In addition, they show that visuospatial working memory is involved, in so far as the text conveys visuospatial information.     

Executive processes in visual and spatial working memory tasks

Three experiments are reported, which have investigated the nature of the cognitive mechanisms that underlie performance on specific visuo-spatial working memory tasks, with the emphasis on exploring the extent of central executive involvement. Experiments 1 and 2 employed oral random digit generation as an executive task within a dual-task paradigm. The results of both experiments indicated that visuo-spatial tasks that involve sequential processing of information show more interference with random digit generation than do visuo-spatial tasks that involve simultaneous processing. The third experiment substituted oral random digit generation for executive tasks that did not involve memory for serial order (vigilance tasks adapted from Vandierendonck, De Vooght, & Van der Goten, 1998b). The results indicated significant interference between the vigilance tasks and the sequential visuo-spatial task, but not with the simultaneous visuo-spatial task. Overall the results of the three experiments are interpreted as indicating that serial sequential visuo-spatial tasks involve executive resources to a significantly greater extent than do simultaneous visuo-spatial tasks, and that this can have implications for studies that attempt to make use of such tasks to fractionate separable visual and spatial components within working memory.