Updating positive and negative stimuli in working memory in depression.

Difficulties in the ability to update stimuli in working memory (WM) may underlie the problems with regulating emotions that lead to the development and perpetuation of mood disorders such as depression. To examine the ability to update affective material in WM, the authors had diagnosed depressed and never-disordered control participants perform an emotion 2-back task in which participants were presented with a series of happy, sad, and neutral faces and were asked to indicate whether the current face had the same (match-set) or different (break-set or no-set) emotional expression as that presented 2 faces earlier. Participants also performed a 0-back task with the same emotional stimuli to serve as a control for perceptual processing. After transforming reaction times to control for baseline group differences, depressed and nondepressed participants exhibited biases in updating emotional content that reflects the tendency to keep negative information and positive information, respectively, active in WM. Compared with controls, depressed participants were both slower to disengage from sad stimuli and faster to disengage from happy facial expressions. In contrast, nondepressed controls took longer to disengage from happy stimuli than from neutral or sad stimuli. These group differences in reaction times may reflect both protective and maladaptive biases in WM that underlie the ability to effectively regulate negative affect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working-memory capacity, proactive interference, and divided attention: Limits on long-term memory retrieval.

Two experiments examined how individual differences in working-memory capacity (WM) relate to proactive interference (PI) susceptibility. We tested high and low WM-span participants in a PI-buildup task under single-task or dual-task ("load") conditions. In Experiment 1, a finger-tapping task was imposed during encoding and retrieval of each list; in Experiment 2, tapping was required during encoding or retrieval. In both experiments, low spans showed greater PI than did high spans under no load, but groups showed equivalent PI under divided attention. Load increased PI only for high spans, suggesting they use attention at encoding and retrieval to combat PI. In Experiment 2, only low spans showed a dual-task cost on List 1 memory, before PI built up. Results indicate a role for attentional processing, perhaps inhibitory in nature, at encoding and retrieval, and are discussed with respect to theories of WM and prefrontal cortex function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and intelligence in children: What develops?

This study explored the contribution of the phonological and executive working memory (WM) systems to 205 (102 girls, 103 boys, 6 to 9 years old) elementary school children's fluid and crystallized intelligence. The results show that (a) a 3-factor structure (phonological short-term memory [STM], visual-spatial WM, and verbal WM) was comparable between age groups, (b) controlled attention and STM storage accounted for 67% of the age-related variance in WM, (c) effect sizes for direct paths from WM were substantially larger when predicting fluid intelligence than crystallized intelligence, and (d) the contribution of STM to intelligence was isolated to reading. The results suggest that the development of WM is distinct from STM, controlled attention plus storage accounted for age-related WM changes, and WM underlies age-related changes in both fluid and crystallized intelligence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working-memory capacity and the control of attention: The contributions of goal neglect, response competition, and task set to Stroop interference.

Individual differences in working-memory (WM) capacity predicted performance on the Stroop task in 5 experiments, indicating the importance of executive control and goal maintenance to selective attention. When the Stroop task encouraged goal neglect by including large numbers of congruent trials (RED presented in red), low WM individuals committed more errors than did high WM individuals on the rare incongruent trials (BLUE in red) that required maintaining access to the "ignore-the-word" goal for accurate responding. In contrast, in tasks with no or few congruent trials, or in high-congruency tasks that followed low-congruency tasks, WM predicted response-time interference. WM was related to latency, not accuracy, in contexts that reinforced the task goal and so minimized the difficulty of actively maintaining it. The data and a literature review suggest that Stroop interference is jointly determined by 2 mechanisms, goal maintenance and competition resolution, and that the dominance of each depends on WM capacity, as well as the task set induced by current and previous contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A controlled-attention view of working-memory capacity.

In 2 experiments the authors examined whether individual differences in working-memory (WM) capacity are related to attentional control. Experiment 1 tested high- and low-WM-span (high-span and low-span) participants in a prosaccade task, in which a visual cue appeared in the same location as a subsequent to-be-identified target letter, and in an antisaccade task, in which a target appeared opposite the cued location. Span groups identified targets equally well in the prosaccade task, reflecting equivalence in automatic orienting. However, low-span participants were slower and less accurate than high-span participants in the antisaccade task, reflecting differences in attentional control. Experiment 2 measured eye movements across a long antisaccade session. Low-span participants made slower and more erroneous saccades than did high-span participants. In both experiments, low-span participants performed poorly when task switching from antisaccade to prosaccade blocks. The findings support a controlled-attention view of WM capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional neuroimaging of working memory in schizophrenia: Task performance as a moderating variable.

Functional neuroimaging studies in schizophrenia have demonstrated abnormal activation of dorsolateral prefrontal cortex (DLPFC) during working memory (WM) performance. However, findings of increased and decreased activity have been reported. The authors used meta-analysis to investigate whether diverging results arise as a function of differential WM task performance between patients and control participants. Results indicate that the magnitude of the group difference in WM performance is a moderator of DLPFC activation differences, and concepts such as hypo- or hyperfrontality do not universally characterize WM findings in schizophrenia. Thus, the variability in the WM activation findings between participants with schizophrenia and control participants reflects the specific conditions under which WM functions are evaluated, not just the WM construct per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How are visuospatial working memory, executive functioning, and spatial abilities related? A latent-variable analysis.

This study examined the relationships among visuospatial working memory (WM) executive functioning, and spatial abilities. One hundred sixty-seven participants performed visuospatial short-term memory (STM) and WM span tasks, executive functioning tasks, and a set of paper-and-pencil tests of spatial abilities that load on 3 correlated but distinguishable factors (Spatial Visualization, Spatial Relations, and Perceptual Speed). Confirmatory factor analysis results indicated that, in the visuospatial domain, processing-and-storage WM tasks and storage-oriented STM tasks equally implicate executive functioning and are not clearly distinguishable. These results provide a contrast with existing evidence from the verbal domain and support the proposal that the visuospatial sketchpad may be closely tied to the central executive. Further, structural equation modeling results supported the prediction that, whereas they all implicate some degree of visuospatial storage, the 3 spatial ability factors differ in the degree of executive involvement (highest for Spatial Visualization and lowest for Perceptual Speed). Such results highlight the usefulness of a WM perspective in characterizing the nature of cognitive abilities and, more generally, human intelligence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory for visual features and conjunctions in schizophrenia.

The visual working memory (WM) storage capacity of patients with schizophrenia was investigated using a change detection paradigm. Participants were presented with 2, 3, 4, or 6 colored bars with testing of both single feature (color, orientation) and feature conjunction conditions. Patients performed significantly worse than controls at all set sizes but demonstrated normal feature binding. Unlike controls, patient WM capacity declined at set size 6 relative to set size 4. Impairments with subcapacity arrays suggest a deficit in task set maintenance: Greater impairment for supercapacity set sizes suggests a deficit in the ability to selectively encode information for WM storage. Thus, the WM impairment in schizophrenia appears to be a consequence of attentional deficits rather than a reduction in storage capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of working memory capacity in retrieval.

The verbal fluency task that requires generation of category exemplars and appears to be an example of what M. Moscovitch (1995) calls a strategic test of memory retrieval. Four experiments explored the role of individual differences in working memory (WM) capacity on verbal fluency under various secondary load conditions. High WM participants consistently recalled more exemplars. However, load conditions caused a decline in recall only for high WM participants. Low WM participants showed no effect of secondary workload on exemplar generation. WM group differences and load effects were observed even in the 1st min of retrieval, which suggests that differences were not due to differences in knowledge. A model of retrieval is supported that relies on cue-based-automatic activation, monitoring of output for errors, controlled suppression of previously recalled items, and controlled strategic search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Generality of Working Memory Capacity: A Latent-Variable Approach to Verbal and Visuospatial Memory Span and Reasoning.

A latent-variable study examined whether verbal and visuospatial working memory (WM) capacity measures reflect a primarily domain-general construct by testing 236 participants in 3 span tests each of verbal WM. visuospatial WM, verbal short-term memory (STM), and visuospatial STM. as well as in tests of verbal and spatial reasoning and general fluid intelligence (Gf). Confirmatory' factor analyses and structural equation models indicated that the WM tasks largely reflected a domain-general factor, whereas STM tasks, based on the same stimuli as the WM tasks, were much more domain specific. The WM construct was a strong predictor of Gf and a weaker predictor of domain-specific reasoning, and the reverse was true for the STM construct. The findings support a domain-general view of WM capacity, in which executive-attention processes drive the broad predictive utility of WM span measures, and domain-specific storage and rehearsal processes relate more strongly to domain-specific aspects of complex cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familiarity enhances visual working memory for faces.

Although it is intuitive that familiarity with complex visual objects should aid their preservation in visual working memory (WM), empirical evidence for this is lacking. This study used a conventional change-detection procedure to assess visual WM for unfamiliar and famous faces in healthy adults. Across experiments, faces were upright or inverted and a low- or high-load concurrent verbal WM task was administered to suppress contribution from verbal WM. Even with a high verbal memory load, visual WM performance was significantly better and capacity estimated as significantly greater for famous versus unfamiliar faces. Face inversion abolished this effect. Thus, neither strategic, explicit support from verbal WM nor low-level feature processing easily accounts for the observed benefit of high familiarity for visual WM. These results demonstrate that storage of items in visual WM can be enhanced if robust visual representations of them already exist in long-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in working memory within a nomological network of cognitive and perceptual speed abilities.

It has become fashionable to equate constructs of working memory (WM) and general intelligence (g). Few investigations have provided direct evidence that WM and g measures yield similar ordering of individuals. Correlational investigations have yielded mixed results. The authors assess the construct space for WM and g and demonstrate that WM shares substantial variance with perceptual speed (PS) constructs. Thirty-six ability tests representing verbal, numerical, spatial, and PS abilities; the Raven Advanced Progressive Matrices; and 7 WM tests were administered to 135 adults. A nomological representation for WM is provided through a series of cognitive and PS ability models. Construct overlap between PS and WM is further investigated with attention to complexity, processing differences, and practice effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Focusing the spotlight: Individual differences in visual attention control.

A time-course analysis of visual attention focusing (attentional constraint) was conducted in groups of participants with high and low working memory spans, a dimension the authors have argued reflects the ability to control attention. In 4 experiments, participants performed the Eriksen flanker paradigm under increasing levels of speed stress. Conditional accuracy functions were derived to measure the time course of attentional constraint. The data showed that accuracy rates rose toward asymptote at different rates, with participants with high working memory spans reaching peak performance before participants with low working memory spans. The authors interpret these data in terms of a rate of attention constraint model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impulsive decision making and working memory.

Decision making that favors short-term over long-term consequences of action, defined as impulsive or temporally myopic, may be related to individual differences in the executive functions of working memory (WM). In the first 2 experiments, participants made delay discounting (DD) judgments under different WM load conditions. In a 3rd experiment, participants high or low on standardized measures of impulsiveness and dysexecutive function were asked to make DD judgments. A final experiment examined WM load effects on DD when monetary rewards were real rather than hypothetical. The results showed that higher WM load led to greater discounting of delayed monetary rewards. Further, a strong direct relation was found between measures of impulsiveness, dysexecutive function, and discounting of delayed rewards. Thus, limits on WM function, either intrinsic or extrinsic, are predictive of a more impulsive decision-making style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in working memory and complex cognition.

The relations among assessments of working memory (WM) and a range of complex cognitive abilities were examined. In 2 experiments participants completed 2 WM tasks designed to assess verbal and nonverbal WM, as well as assessments of verbal intelligence, nonverbal intelligence, and academic achievement. Verbal WM had no relationship with nonverbal intelligence, whereas nonverbal WM had no relationship with verbal intelligence and academic achievement. A reanalysis of P. C. Kyllonen & R. E. Christal (see PA, Vol 78:32248; Experiment 1) is reported in which multiple indicators of WM were used to identify verbal and nonverbal WM factors; both of these WM factors were heavily saturated with a second-order factor, g (61% and 69%, respectively). Convergent and discriminant validation of the multidimensionality of WM was found in the patterns of correlations among the first-order Working Memory, General Knowledge, and Speed factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working Memory Impairments in Schizophrenia: A Meta-Analysis.

Working memory (WM) deficit is a cardinal cognitive symptom of schizophrenia, but the differences among the tasks and measures used to assess WM make it difficult to compare across studies. The authors conducted a meta-analytic review to address 3 major questions: (a) Do patients with schizophrenia show WM deficits across diverse methodology; (b) Is WM deficit supramodal; and (c) Does the WM deficit worsen with longer delays? The results indicate that significant WM deficit was present in schizophrenia patients in all modalities examined. Increasing delay beyond 1 s did not influence the performance difference between schizophrenia patients and healthy control participants in WM. These results suggest that WM deficit in schizophrenia is modality independent and that encoding and/or early part of maintenance may be problematic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural mechanisms of interference control underlie the relationship between fluid intelligence and working memory span.

Fluid intelligence (gF) and working memory (WM) span predict success in demanding cognitive situations. Recent studies show that much of the variance in gF and WM span is shared, suggesting common neural mechanisms. This study provides a direct investigation of the degree to which shared variance in gF and WM span can be explained by neural mechanisms of interference control. The authors measured performance and functional magnetic resonance imaging activity in 102 participants during the n-back WM task, focusing on the selective activation effects associated with high-interference lure trials. Brain activity on these trials was correlated with gF, WM span, and task performance in core brain regions linked to WM and executive control, including bilateral dorsolateral prefrontal cortex (middle frontal gyrus; BA9) and parietal cortex (inferior parietal cortex; BA 40/7). Interference-related performance and interference-related activity accounted for a significant proportion of the shared variance in gF and WM span. Path analyses indicate that interference control activity may affect gF through a common set of processes that also influence WM span. These results suggest that individual differences in interference-control mechanisms are important for understanding the relationship between gF and WM span. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Working Memory Consolidation Is Abnormally Slow in Schizophrenia.

This study reports evidence that patients with schizophrenia demonstrate a slowing of working memory (WM) consolidation, which is the process of transforming transient perceptual representations into durable WM representations. Sixteen schizophrenia patients and 16 healthy control participants performed a task measuring the visual WM consolidation rate in a change-detection paradigm. A target display containing 3 colored squares was followed by a variable delay of 17-483 ms, a pattern mask, and then a test stimulus. This pattern mask does not interfere with perception but disrupts WM consolidation. Control participants reached no-mask performance by 250 ms, indicating completed WM consolidation, whereas patients failed to reach no-mask performance by 483 ms. Slowed consolidation may play an important and largely unrecognized role in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the Origins of the Task Mixing Cost in the Cuing Task-Switching Paradigm.

Poorer performance in conditions involving task repetition within blocks of mixed tasks relative to task repetition within blocks of single task is called mixing cost (MC). In 2 experiments exploring 2 hypotheses regarding the origins of MC, participants either switched between cued shape and color tasks, or they performed them as single tasks. Experiment 1 supported the hypothesis that mixed-tasks trials require the resolution of task ambiguity by showing that MC existed only with ambiguous stimuli that afforded both tasks and not with unambiguous stimuli affording only 1 task. Experiment 2 failed to support the hypothesis that holding multiple task sets in working memory (WM) generates MC by showing that systematic manipulation of the number of stimulus-response rules in WM did not affect MC. The results emphasize the role of competition management between task sets during task control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)