Working Memory Demands Research Articles

Do children need reminders on the day–night task, or simply some way to prevent them from responding too quickly?

We previously reported better performance on the day–night task when a ditty was chanted between stimulus presentation and when children could respond (Diamond, Kirkham, & Amso, 2002). Here we investigated competing hypotheses about why the ditty helps. Does it help because it imposes a brief waiting time (the child waits while the ditty is chanted before responding)? Or, does the ditty help because of its content, providing information helpful to performing the task? One-third of the 72 children (age 4) were tested with the ditty previously used which reminds them: “Think about the answer; don’t tell me”. Another 24 children were tested with a ditty with no task-relevant content: “I hope you have a nice time; I like you”. One-third received the standard condition. Performance in both ditty conditions was comparable and better than in the standard condition. That indicates that a factor common to both ditties (that chanting them took time, allowing the prepotent response to subside and the more-considered answer to reach response threshold) likely accounts for their benefit. Whether a ditty reminded children what to do or not did not affect the results. The challenge of the day–night task for preschoolers is not its working memory demands but the need to inhibit a dominant response, making a different response instead.

Effect of working memory load on electrophysiological markers of visuospatial orienting in a spatial cueing task simulating a traffic situation.

Visuospatial attentional orienting has typically been studied in abstract tasks with low ecological validity. However, real-life tasks such as driving require allocation of working memory (WM) resources to several subtasks over and above orienting in a complex sensory environment. The aims of this study were twofold: firstly, to establish whether electrophysiological signatures of attentional orienting commonly observed under simplified task conditions generalize to a more naturalistic task situation with realistic-looking stimuli, and, secondly, to assess how these signatures are affected by increased WM load under such conditions. Sixteen healthy participants performed a dual task consisting of a spatial cueing paradigm and a concurrent verbal memory task that simulated aspects of an actual traffic situation. Behaviorally, we observed a load-induced detriment of sensitivity to targets. In the EEG, we replicated orienting-related alpha lateralization, the lateralized ERPs ADAN, EDAN, and LDAP, and the P1-N1 attention effect. When WM load was high (i.e., WM resources were reduced), lateralization of oscillatory activity in the lower alpha band was delayed. In the ERPs, we found that ADAN was also delayed, while EDAN was absent. Later ERP correlates were unaffected by load. Our results show that the findings in highly controlled artificial tasks can be generalized to spatial orienting in ecologically more valid tasks, and further suggest that the initiation of spatial orienting is delayed when WM demands of an unrelated secondary task are high.

Working Memory and Increased Activity Level (Hyperactivity) in ADHD: Experimental Evidence for a Functional Relation

Objective: Converging evidence indicates large magnitude deficits in the “working” component of working memory for children with ADHD. However, our understanding of the relation between these central executive deficits and ADHD behavioral symptoms remains limited due to problems with several commonly used working memory tests. Method: Children with ADHD (n = 25) completed a counterbalanced series of working memory tasks that differed only in memory set predictability. Results: Results indicated that central executive demands increased when memory set was unpredictable, as evidenced by moderate performance decreases (d = 0.22-0.56) and large changes in performance variability (d = 0.93-3.16) and response times (d = 1.74-4.16). Activity level remained relatively stable when memory set was unpredictable but decreased significantly over time when memory set was predictable. Conclusion: Results suggest that altering memory set predictability is a feasible method for increasing/maintaining central executive demands over time, and suggest a positive association between working memory demands and gross motor activity for children with ADHD.

Just-in-Time Supports in Augmentative and Alternative Communication

Individuals with developmental disabilities such as autism, physical disabilities, and intellectual disabilities frequently are candidates for augmentative and alternative communication (AAC) systems as well as visual supports. The purpose of this paper is to apply the business construct of just-in-time (JIT) to the field of AAC with particular reference to new possibilities for JIT support arising from the advent of the mobile technology revolution. In addition to a review of the history of JIT within AAC, a taxonomy of JIT supports is proposed. Potential benefits of JIT supports are postulated based on conceptual underpinnings related to working memory demands, situated cognition, and teachable moments. Implications of JIT supports are drawn for both the learner and the communication partners’ competencies. Finally, several directions for future research are posited.

The effects of acute resistance exercise on young and older males' working memory

ObjectivesThe aim of the current study was two-fold: to examine the effects of acute, moderate intensity resistance exercise (RE) on working memory in young and older males, respectively. DesignA two-study approach with a within-subjects design. MethodsStudy 1 recruited 20 young males aged 21–30 years. Participants underwent two experimental sessions, the exercise session and reading session, in a counterbalanced order. The RE protocol included two sets of 10 repetitions at 70% of 10-repetition maximum of eight muscle exercises. The Sternberg working memory paradigm with two probe types (in-set probes and out-of-set probes) was used as the cognitive task where reaction times (RT) and response accuracy were identified. Study 2 recruited 20 older male adults aged 65–72 years. The methods and experimental procedures were the same as Study 1. ResultsIn Study 1, young males demonstrated shorter RTs after the exercise treatment as compared with the reading treatment for both probe types. In Study 2, older males showed shorter RTs after the exercise treatment as compared with the reading treatment in the out-of-set probes only. ConclusionsWhile acute RE benefited working memory in both young and older males, rather than general facilitation, it was shown to have a disproportionately larger effect on older males for tasks involving higher working memory demands.

On the Cognitive Demands of Different Controller Dynamics

The cognitive workload of a steering task could reflect its demand on attentional as well as working memory resources under different conditions. These respective demands could be differentiated by evaluating components of the event-related potential (ERP) response to different types of stimulus probes, which are claimed to reflect the availability of either attention (i.e., novelty-P3) or working memory (i.e., target-P3) resources. Here, a within-subject analysis is employed to evaluate the robustness of ERP measurements in discriminating the cognitive demands of different steering conditions. We find that the amplitude of novelty-P3 ERPs to task-irrelevant environmental sounds is diminished when participants are required to perform a steering task. This indicates that steering places a demand on attentional resources. In addition, target-P3 ERPs to a secondary auditory detection task vary when the controller dynamics in the steering task are manipulated. This indicates that differences in controller dynamics vary in their working memory demands.

Deficits in comprehension of speech acts after TBI: The role of theory of mind and executive function

Theory of mind (ToM) is critical to effective communication following traumatic brain injury (TBI) however, whether impairments are specific to social cognition, or reflective of executive demands is unclear. This study examined whether ToM impairments are predicted by executive function difficulties using everyday conversation tasks. Twenty-five individuals with severe-TBI were compared to 25 healthy controls on low- and high-ToM tasks across four conditions: (1) low cognitive load, (2) high flexibility, (3) high working memory (WM) and (4) high inhibition. TBI individuals were impaired on high-ToM tasks in the WM condition. When the WM demands of the task were controlled, the impairments were no longer apparent. TBI individuals were not impaired on high-ToM tasks in the inhibition and flexibility conditions, suggesting these tasks may not have been sufficiently demanding of ToM abilities. The results suggest that ToM impairments in everyday communication may arise due to WM demands, in individuals with TBI.

Strategies for written additions in adults

Studies about strategies used by adults to solve multi-digit written additions are very scarce. However, as advocated here, the specificity and characteristics of written calculations are of undeniable interest. The originality of our approach lies in part in the presentation of two-digit addition problems on a graphics tablet, which allowed us to precisely follow and analyse individuals’ solving process. Not only classic solution times and accuracy measures were recorded but also initiation times and starting positions of the calculations. Our results show that adults largely prefer the fixed columnar strategy taught at school rather than more flexible mental strategies. Moreover, the columnar strategy is executed faster and as accurately as other strategies, which suggests that individuals’ choice is usually well adapted. This result contradicts past educational intuitions that the use of rigid algorithms might be detrimental to performance. We also demonstrate that a minority of adults can modulate their strategy choice as a function of the characteristics of the problems. Tie problems and additions without carry were indeed solved less frequently through the columnar strategy than non-tie problems and additions with a carry. We conclude that the working memory demand of the arithmetic operation influences strategy selection in written problem-solving.

Neural Underpinnings of Working Memory in Adult Survivors of Childhood Brain Tumors.

Adult survivors of childhood brain tumors are at risk for cognitive performance deficits that require the core cognitive skill of working memory. Our goal was to examine the neural mechanisms underlying working memory performance in survivors. We studied the working memory of adult survivors of pediatric posterior fossa brain tumors using a letter n-back paradigm with varying cognitive workload (0-, 1-, 2-, and 3-back) and functional magnetic resonance imaging as well as neuropsychological measures. Survivors of childhood brain tumors evidenced lower working memory performance than demographically matched healthy controls. Whole-brain analyses revealed significantly greater blood-oxygen level dependent (BOLD) activation in the left superior / middle frontal gyri and left parietal lobe during working memory (2-back versus 0-back contrast) in survivors. Left frontal BOLD response negatively correlated with 2- and 3-back working memory performance, Auditory Consonant Trigrams (ACT), and Digit Span Backwards. In contrast, parietal lobe BOLD response negatively correlated with 0-back (vigilance task) and ACT. The results revealed that adult survivors of childhood posterior fossa brain tumors recruited additional cognitive control resources in the prefrontal lobe during increased working memory demands. This increased prefrontal activation is associated with lower working memory performance and is consistent with the allocation of latent resources theory.

Hyperactivity in boys with attention-deficit/hyperactivity disorder (ADHD): The role of executive and non-executive functions

Motor activity of boys (age 8–12 years) with (n=19) and without (n=18) ADHD was objectively measured with actigraphy across experimental conditions that varied with regard to demands on executive functions. Activity exhibited during two n-back (1-back, 2-back) working memory tasks was compared to activity during a choice-reaction time (CRT) task that placed relatively fewer demands on executive processes and during a simple reaction time (SRT) task that required mostly automatic processing with minimal executive demands. Results indicated that children in the ADHD group exhibited greater activity compared to children in the non-ADHD group. Further, both groups exhibited the greatest activity during conditions with high working memory demands, followed by the reaction time and control task conditions, respectively. The findings indicate that large-magnitude increases in motor activity are predominantly associated with increased demands on working memory, though demands on non-executive processes are sufficient to elicit small to moderate increases in motor activity as well.

Cerebellar fMRI Activation Increases with Increasing Working Memory Demands.

The aim of the present study was to explore cerebellar contributions to the central executive in n-back working memory tasks using 7-T functional magnetic imaging (fMRI). We hypothesized that cerebellar activation increased with increasing working memory demands. Activations of the cerebellar cortex and dentate nuclei were compared between 0-back (serving as a motor control task), 1-back, and 2-back working memory tasks for both verbal and abstract modalities. A block design was used. Data of 27 participants (mean age 26.6 ± 3.8years, female/male 12:15) were included in group statistical analysis. We observed that cerebellar cortical activations increased with higher central executive demands in n-back tasks independent of task modality. As confirmed by subtraction analyses, additional bilateral activations following higher executive demands were found primarily in four distinct cerebellar areas: (i) the border region of lobule VI and crus I, (ii) inferior parts of the lateral cerebellum (lobules crus II, VIIb, VIII, IX), (iii) posterior parts of the paravermal cerebellar cortex (lobules VI, crus I, crus II), and (iv) the inferior vermis (lobules VI, VIIb, VIII, IX). Dentate activations were observed for both verbal and abstract modalities. Task-related increases were less robust and detected for the verbal n-back tasks only. These results provide further evidence that the cerebellum participates in an amodal bilateral neuronal network representing the central executive during working memory n-back tasks.

Commentary: “Poverty impedes cognitive function” and “The poor's poor mental power”

Commentary: “Poverty impedes cognitive function” and “The poor's poor mental power”

Response control networks are selectively modulated by attention to rare events and memory load regardless of the need for inhibition

Recent evidence has sparked debate about the neural bases of response selection and inhibition. In the current study, we employed two reactive inhibition tasks, the Go/Nogo (GnG) and Simon tasks, to examine questions central to these debates. First, we investigated whether a fronto-cortical-striatal system was sensitive to the need for inhibition per se or the presentation of infrequent stimuli, by manipulating the proportion of trials that do not require inhibition (Go/Compatible trials) relative to trials that require inhibition (Nogo/Incompatible trials). A cortico-subcortical network composed of insula, putamen, and thalamus showed greater activation on salient and infrequent events, regardless of the need for inhibition. Thus, consistent with recent findings, key parts of the fronto-cortical-striatal system are engaged by salient events and do not appear to play a selective role in response inhibition. Second, we examined how the fronto-cortical-striatal system is modulated by working memory demands by varying the number of stimulus-response (SR) mappings. Right inferior parietal lobule showed decreasing activation as the number of SR mappings increased, suggesting that a form of associative memory – rather than working memory – might underlie performance in these tasks. A broad motor planning and control network showed similar trends that were also modulated by the number of motor responses required in each task. Finally, bilateral lingual gyri were more robustly engaged in the Simon task, consistent with the role of this area in shifts of visuo-spatial attention. The current study sheds light on how the fronto-cortical-striatal network is selectively engaged in reactive control tasks and how control is modulated by manipulations of attention and memory load.

Behavioral Laterality and Aging: The Free-Recall Dichotic-Listening Right-Ear Advantage Increases With Age

The effect of aging on brain asymmetry was studied under consideration of possible confounding effects of known age-related decline in higher cognitive functioning. In a sample of 3,680 participants aged 20–79 years, laterality was assessed with a verbal, free-recall dichotic-listening paradigm with one stimulus pair presentation per trial, minimizing working-memory and cognitive-control demands during task performance. Laterality, reflected as right-ear preference for dichotic stimuli, was found to be increased in older age (above 60 years). This effect was due to a reduced report of left-ear stimuli, while the report of right-ear stimuli stayed on comparable levels across all ages.

What's the Problem? Familiarity Working Memory, and Transfer in a Problem-Solving Task.

The contributions of familiarity and working memory to transfer were examined in the Tower of Hanoi task. Participants completed 3 different versions of the task: a standard 3-disk version, a clothing exchange task that included familiar semantic content, and a tea ceremony task that included unfamiliar semantic content. The constraints on moves were equivalent across tasks, and each could be solved with the same sequence of movements. Working memory demands were manipulated by the provision of a (static or dynamic) visual representation of the problem. Performance was equivalent for the standard Tower of Hanoi and clothing exchange tasks but worse for the tea ceremony task, and it decreased with increasing working memory demands. Furthermore, the standard Tower of Hanoi task and clothing exchange tasks independently, additively, and equivalently transferred to subsequent tasks, whereas the tea ceremony task did not. The results suggest that both familiarity and working memory demands determine overall level of performance, whereas familiarity influences transfer.

Examining the influence of working memory on updating mental models.

The ability to accurately build and update mental representations of our environment depends on our ability to integrate information over a variety of time scales and detect changes in the regularity of events. As such, the cognitive mechanisms that support model building and updating are likely to interact with those involved in working memory (WM). To examine this, we performed three experiments that manipulated WM demands concurrently with the need to attend to regularities in other stimulus properties (i.e., location and shape). That is, participants completed a prediction task while simultaneously performing an n-back WM task with either no load or a moderate load. The distribution of target locations (Experiment 1) or shapes (Experiments 2 and 3) included some level of probabilistic regularity, which, unbeknown to participants, changed abruptly within each block. Moderate WM load hampered the ability to benefit from target regularities and to adapt to changes in those regularities (i.e., the prediction task). This was most pronounced when both prediction and WM requirements shared the same target feature. Our results show that representational updating depends on free WM resources in a domain-specific fashion.

Social working memory and its distinctive link to social cognitive ability: an fMRI study.

Engaging social working memory (SWM) during effortful social cognition has been associated with neural activation in two neurocognitive systems: the medial frontoparietal system and the lateral frontoparietal system. However, the respective roles played by these systems in SWM remain unknown. Results from this study demonstrate that only the medial frontoparietal system supports the social cognitive demands managed in SWM. In contrast, the lateral frontoparietal system supports the non-social cognitive demands that are needed for task performance, but that are independent of the social cognitive computations. Moreover, parametric increases in the medial frontoparietal system, but not the lateral frontoparietal system, in response to SWM load predicted performance on a challenging measure of perspective-taking. Thus, the medial frontoparietal system may uniquely support social cognitive processes in working memory and the working memory demands afforded by effortful social cognition, such as the need to track another person's perspective in mind.

Neural efficiency in working memory tasks: The impact of task demand

Studies of human intelligence provide strong evidence for the neural efficiency hypothesis, which suggests more efficient brain functioning (i.e., less or more focused activation) in more intelligent individuals. Recent studies have specified the scope of the neural efficiency hypothesis by suggesting that the relationship between brain activation and intelligence only holds true for problems of moderate difficulty and can be altered through training and is only found in frontal brain regions. We investigated the moderating roles of task difficulty and training on the neural efficiency phenomenon in the context of working memory (WM) training.In two studies of 54 participants (study 1) and 29 participants (study 2), cortical activation was assessed by means of electroencephalography (EEG), or more precisely by means of event-related desynchronization (ERD) in the upper alpha band. ERD was assessed during the performance of WM tasks in a pre-test – training – post-test design, comparing groups of lower and higher intelligence.We found supportive evidence for the neural efficiency hypothesis only in moderately difficult WM tasks in frontal brain regions, even in the absence of performance differences. There was no effect of intelligence on the simple or highly demanding, adaptive WM tasks. In the latter task, however, an intelligence-related difference emerged at the behavioral level, but training did not modulate the relationship between intelligence and brain activation.These results corroborate the moderating role of task difficulty in the neural efficiency hypothesis in the context of WM demands and suggest that training does not impact the neural efficiency phenomenon in the context of WM demands.

Syntactic comprehension and working memory in children with specific language impairment, autism or Down syndrome

This study examined syntactic assignment for predicates and reflexives as well as working memory effects in the sentence comprehension of children with Specific Language Impairment (SLI), Down syndrome (DS), high functioning Autism (HFA) and Typical Language Development (TLD). Fifty-seven children (35 boys and 22 girls) performed a computerised picture-selection sentence comprehension task. Predicate attachment and reflexive antecedent assignment (with working memory manipulations) were investigated. The results showed that SLI, HFA and DS children exhibited poorer overall performance than TLD children. Children with SLI exhibited similar performance to the DS and HFA children only when working memory demands were higher. We conclude that children with SLI, HFA and DS differ from children with TLD in their comprehension of predicate and reflexive structures where the knowledge of syntactic assignment is required. Working memory manipulation had different effects on syntactic comprehension depending on language disorder. Intelligence was not an explanatory factor for the differences observed in performance.

Dysfunctional Activation and Brain Network Profiles in Youth with Obsessive-Compulsive Disorder: A Focus on the Dorsal Anterior Cingulate during Working Memory.

Brain network dysfunction is emerging as a central biomarker of interest in psychiatry, in large part, because psychiatric conditions are increasingly seen as disconnection syndromes. Understanding dysfunctional brain network profiles in task-active states provides important information on network engagement in an experimental context. This in turn may be predictive of many of the cognitive and behavioral deficits associated with complex behavioral phenotypes. Here we investigated brain network profiles in youth with obsessive-compulsive disorder (OCD), contrasting them with a group of age-comparable controls. Network interactions were assessed during simple working memory: in particular, we focused on the modulation by the dorsal anterior cingulate cortex (dACC) of cortical, striatal, and thalamic regions. The focus on the dACC was motivated by its hypothesized role in the pathophysiology of OCD. However, its task-active network signatures have not been investigated before. Network interactions were modeled using psychophysiological interaction, a simple directional model of seed to target brain interactions. Our results indicate that OCD is characterized by significantly increased dACC modulation of cortical, striatal, and thalamic targets during working memory, and that this aberrant increase in OCD patients is maintained regardless of working memory demand. The results constitute compelling evidence of dysfunctional brain network interactions in OCD and suggest that these interactions may be related to a combination of network inefficiencies and dACC hyper-activity that has been associated with the phenotype.