The effects of clinical motor variables and medication dosage on working memory in Parkinson’s disease

In this study, we investigate the interrelationship between clinical variables and working memory (WM) in Parkinson’s disease (PD). Specifically, the aim of the study was to investigate the relationship between disease duration, dopaminergic medication dosage, and motor disability (UPDRS score) with WM in individuals with PD. Accordingly, we recruited three groups of subjects: unmedicated PD patients, medicated PD patients, and healthy controls. All subjects were tested on three WM tasks: short-delay WM, long-delay WM, and the n-back task. Further, PD encompasses a spectrum that can be classified either into akinesia/rigidity or resting tremor as the predominant motor presentation of the disease. In addition to studying medication effects, we tested WM performance in tremor-dominant and akinesia-dominant patients. We further correlated WM performance with disease duration and medication dosage. We found no difference between medicated and unmedicated patients in the short-delay WM task, but medicated patients outperformed unmedicated patients in the long-delay WM and n-back tasks. Interestingly, we also found that akinesia-dominant patients were more impaired than tremor-dominant patients at various WM measures, which is in agreement with prior studies of the relationship between akinesia symptom and basal ganglia dysfunction. Moreover, the results show that disease duration inversely correlates with more demanding WM tasks (long-delay WM and n-back tasks), but medication dosage positively correlates with demanding WM performance. In sum, our results show that WM impairment in PD patients depend on cognitive domain (simple vs. demanding WM task), subtype of PD patients (tremor- vs. akinesia-dominant), as well as disease duration and medication dosage. Our results have implications for the interrelationship between motor and cognitive processes in PD, and for understanding the role of cognitive training in treating motor symptoms in PD.     

Working memory and attention in pediatric brain tumor patients treated with and without radiation therapy

Children are at risk for cognitive difficulties following the diagnosis and treatment of a brain tumor. Longitudinal studies have consistently demonstrated declines on measures of intellectual functioning, and recently it has been proposed that specific neurocognitive processes underlie these changes, including working memory, processing speed, and attention. However, a fine-grained examination of the affected neurocognitive processes is required to inform intervention efforts. Radiation therapy (RT) impacts white matter integrity, likely affecting those cognitive processes supported by distributed neural networks. This study examined working memory and attention in children during the early delayed stages of recovery following surgical resection and RT. The participants included 27 children diagnosed with pediatric brain tumor, treated with (n = 12) or without (n = 15) RT, who completed experimental and standardized measures of working memory and attention (n-back and digit span tasks). Children treated with radiation performed less well than those who did not receive radiation on the n-back measure, though performance at the 0-back level was considerably poorer than would be expected for both groups, perhaps suggesting difficulties with more basic processes such as vigilance. Along these lines, marginal differences were noted on digit span forward. The findings are discussed with respect to models of attention and working memory, and the interplay between the two.     

Behavioural and ERP Effects of Cognitive and Combined Cognitive and Physical Training on Working Memory and Executive Function in Healthy Older Adults

Cognitive and physical training have been shown to be effective in improving older adults’ cognition. However, it is not yet clear whether combined cognitive and physical training offers an advantage compared to cognitive training alone. Twenty-two older adults performed cognitive or combined cognitive and physical training in order to compare their effects on working memory event-related potentials (ERPs) and on working memory and executive function performance. Before and after eight weeks of training, performance in Plus Minus, Flanker, Updated Span, and Complex Span tasks was measured, and ERPs were registered during performance of an n-back task (0-back, 2-back, and 3-back). Post-training behavioural improvement was observed in Updated Span, Complex Span, and n-back tasks. During the n-back task, the N2/P3 complex was modulated by training, with a decrease in N2 amplitude and an increase in P3 amplitude in the posttraining session compared to the pretraining session. These changes in ERP components suggest that both types of training potentially reduce the need for attentional control to perform the tasks correctly and increase working memory capacity. Thus, based on our data, no conclusion can be reached on the direct advantage of combined training, either at behavioural or at neural level. However, the present study might suggest an indirect advantage of such a combined training, because the cognitive benefit was found to be highly similar in both types of training. Using combined cognitive and physical training may produce a potential improvement in general fitness and an increased appeal of training.     

Improved matrix reasoning is limited to training on tasks with a visuospatial component

Recent studies (e.g.,  and ) have provided evidence that scores on tests of fluid intelligence can be improved by having participants complete a four week training program using the dual n-back task. The dual n-back task is a working memory task that presents auditory and visual stimuli simultaneously. The primary goal of our study was to determine whether a visuospatial component is required in the training program for participants to experience gains in tests of fluid intelligence. We had participants complete variations of the dual n-back task or a short-term memory task as training. Participants were assessed with four tests of fluid intelligence and four cognitive tests. We were successful in corroborating Jaeggi et al.'s results, however, improvements in scores were observed on only two out of four tests of fluid intelligence for participants who completed the dual n-back task, the visual n-back task, or a short-term memory task training program. Our results raise the issue of whether the tests measure the construct of fluid intelligence exclusively, or whether they may be sensitive to other factors. The findings are discussed in terms of implications for conceptualizing and assessing fluid intelligence.     

Individual differences in media multitasking and performance on the <Emphasis Type="Italic">n</Emphasis>-back

A number of studies have recently examined the link between individual differences in media multitasking (using the MMI) and performance on working memory paradigms. However, these studies have yielded mixed results. Here we examine the relation between media multitasking and one particular working memory paradigm—the n-back (2- and 3-back)—improving upon previous research by (a) treating media multitasking as a continuous variable and adopting a correlational approach as well as (b) using a large sample of participants. First, we found that higher scores on the MMI were associated with a greater proportion of omitted trials on both the 2-back and 3-back, indicating that heavier media multitaskers were more disengaged during the n-back. In line with such a claim, heavier media multitaskers were also more likely to confess to responding randomly during various portions of the experiment, and to report media multitasking during the experiment itself. Importantly, when controlling for the relation between MMI scores and omissions, higher scores on the MMI were associated with an increase in false alarms, but not with a change in hits. These findings refine the extant literature on media multitasking and working memory performance (specifically, performance on the n-back), and suggest that media multitasking may be related to the propensity to disengage from ongoing tasks.     

Working memory training improves visual short-term memory capacity

Since antiquity, philosophers, theologians, and scientists have been interested in human memory. However, researchers today are still working to understand the capabilities, boundaries, and architecture. While the storage capabilities of long-term memory are seemingly unlimited (Bahrick, J Exp Psychol 113:1–2, 1984), working memory, or the ability to maintain and manipulate information held in memory, seems to have stringent capacity limits (e.g., Cowan, Behav Brain Sci 24:87–185, 2001). Individual differences, however, do exist and these differences can often predict performance on a wide variety of tasks (cf. Engle What is working-memory capacity? 297–314, 2001). Recently, researchers have promoted the enticing possibility that simple behavioral training can expand the limits of working memory which indeed may also lead to improvements on other cognitive processes as well (cf. Morrison and Chein, Psychol Bull Rev 18:46–60 2011). However, initial investigations across a wide variety of cognitive functions have produced mixed results regarding the transferability of training-related improvements. Across two experiments, the present research focuses on the benefit of working memory training on visual short-term memory capacity—a cognitive process that has received little attention in the training literature. Data reveal training-related improvement of global measures of visual short-term memory as well as of measures of the independent sub-processes that contribute to capacity (Awh et al., Psychol Sci 18(7):622–628, 2007). These results suggest that the ability to inhibit irrelevant information within and between trials is enhanced via n-back training allowing for selective improvement on untrained tasks. Additionally, we highlight a potential limitation of the standard adaptive training procedure and propose a modified design to ensure variability in the training environment.     

Individual differences in musical training and executive functions: A latent variable approach

Learning and performing music draw on a host of cognitive abilities, and previous research has postulated that musicians might have advantages in related cognitive processes. One such aspect of cognition that may be related to musical training is executive functions (EFs), a set of top-down processes that regulate behavior and cognition according to task demands. Previous studies investigating the link between musical training and EFs have yielded mixed results and are difficult to compare. In part, this is because most studies have looked at only one specific cognitive process, and even studies looking at the same process have used different experimental tasks. Furthermore, most correlational studies have used different “musician” and “non-musician” categorizations for their comparisons, so generalizing the findings is difficult. The present study provides a more comprehensive assessment of how individual differences in musical training relate to latent measures of three separable aspects of EFs. We administered a well-validated EF battery containing multiple tasks tapping the EF components of inhibition, shifting, and working memory updating (Friedman et al. in Journal of Experimental Psychology: General, 137, 201–225, 2008), as well as a comprehensive, continuous measure of musical training and sophistication (Müllensiefen et al., in PLoS ONE, 9, e89642, 2014). Musical training correlated with some individual EF tasks involving inhibition and working memory updating, but not with individual tasks involving shifting. However, musical training only predicted the latent variable of working memory updating, but not the latent variables of inhibition or shifting after controlling for IQ, socioeconomic status, and handedness. Although these data are correlational, they nonetheless suggest that musical experience places particularly strong demands specifically on working memory updating processes.     

The concurrent validity and test–retest reliability of a visuospatial working memory task

To determine whether the visuospatial n-back working memory task is a reliable and valid measure of cognitive processes believed to underlie intelligence, this study compared the reaction times and accuracy of performance of 70 participants, with performance on the Multidimensional Aptitude Battery (MAB). Testing was conducted over two sessions separated by 1 week. Participants completed the MAB during the second test session. Moderate test–retest reliability for percentage accuracy scores was found across the four levels of the n-back task, whilst reaction times were highly reliable. Furthermore, participants' performance on the MAB was negatively correlated with accuracy of performance at the easier levels of the n-back task and positively correlated with accuracy of performance at the harder task levels. These findings confirm previous research examining the cognitive basis of intelligence, and suggest that intelligence is the product of faster speed of information processing, as well as superior working memory capacity.     

Working memory training improvements and gains in non-trained cognitive tasks in young and older adults

Previous studies on working memory training have indicated that transfer to non-trained tasks of other cognitive domains may be possible. The aim of this study is to compare working memory training and transfer effects between younger and older adults (n = 60). A novel approach to adaptive n-back training (12 sessions) was implemented by varying the working memory load and the presentation speed. All participants completed a neuropsychological battery of tests before and after the training. On average, younger training participants achieved difficulty level 12 after training, while older training participants only reached difficulty level 5. In younger participants, transfer to Verbal Fluency and Digit Symbol Substitution test was found. In older participants, we observed a transfer to Digit Span Forward, CERAD Delayed Recall, and Digit Symbol Substitution test. Results suggest that working memory training may be a beneficial intervention for maintaining and improving cognitive functioning in old age.     

Executive Functions in Children and Adolescents with Turner Syndrome: A Systematic Review and Meta-Analysis

Turner syndrome (TS) is a genetic disorder, affecting 1/2500 to 1/3000 live female births, induced by partial or total deletion of one X chromosome. The neurocognitive profile of girls with TS is characterized by a normal Verbal IQ and weaknesses in visual-spatial, mathematics, and social cognitive domains. Executive functions (EFs) impairments have also been reported in these young patients. However, methodological differences across studies do not allow determination of which EFs are impaired and what is the magnitude of these impairments. The aim of this review was to clarify the EF profile of children and adolescents with TS. Sixteen samples, from thirteen studies, were included in the current meta-analysis. EFs measures used in these studies were classified into working memory, inhibitory control, cognitive flexibility, or higher-order EFs tasks in accordance with Diamond’s model, Annual Review of Psychology, 64, 135–168 (2013). Results confirmed that girls with TS had significant executive impairments with effect sizes varying from small (inhibitory control) to medium (cognitive flexibility) and large (working memory, higher-order EFs). Analyses by task revealed that cognitive inhibition may be more impaired than the other inhibitory control abilities. Heterogeneity across cognitive flexibility measures was also highlighted. Between-sample heterogeneity was observed for three tasks and the impact of participants’ characteristics on EFs was discussed. This meta-analysis confirms the necessity to assess, in patients living with TS, each EF by combining both visual and verbal tasks. Results also underline that, when studying girls with TS’ executive profile, it is important to explore the impact of moderator variables, such as IQ, parental socio-economic status, TS karyotype, psychiatric comorbidities, and hormonal treatment status.     

Dual n-back training increases the capacity of the focus of attention

Working memory (WM) training has been reported to benefit abilities as diverse as fluid intelligence (Jaeggi et al., Proceedings of the National Academy of Sciences of the United States of America, 105:6829–6833, 2008) and reading comprehension (Chein & Morrison, Psychonomic Bulletin & Review, 17:193–199, 2010), but transfer is not always observed (for reviews, see Morrison & Chein, Psychonomics Bulletin & Review, 18:46–60, 2011; Shipstead et al., Psychological Bulletin, 138:628–654, 2012). In contrast, recent WM training studies have consistently reported improvement on the trained tasks. The basis for these training benefits has received little attention, however, and it is not known which WM components and/or processes are being improved. Therefore, the goal of the present study was to investigate five possible mechanisms underlying the effects of adaptive dual n-back training on working memory (i.e., improvements in executive attention, updating, and focus switching, as well as increases in the capacity of the focus of attention and short-term memory). In addition to a no-contact control group, the present study also included an active control group whose members received nonadaptive training on the same task. All three groups showed significant improvements on the n-back task from pretest to posttest, but adaptive training produced larger improvements than did nonadaptive training, which in turn produced larger improvements than simply retesting. Adaptive, but not nonadaptive, training also resulted in improvements on an untrained running span task that measured the capacity of the focus of attention. No other differential improvements were observed, suggesting that increases in the capacity of the focus of attention underlie the benefits of adaptive dual n-back training.     

N-backer: an auditory n-back task with automatic scoring of spoken responses

The n-back task is commonly used to load working memory (WM) in dual-task and neuroimaging experiments. However, it typically involves visual presentation and buttonpress responses, making it unsuitable for combination with primary tasks that involve vision and action, such as sequential object use and other tasks of daily living. The N-backer software presented here will automatically present and score auditory–verbal n-back sequences utilising the standard speech synthesis and recognition facilities that come with Microsoft Windows. Data are presented from an experiment in which 12 student participants carried out three tasks from the Naturalistic Action Test (NAT) while their attention was divided between the primary task and a continuous auditory–verbal 2-back secondary task. The participants’ 2-back performance was scored in two ways: by hand, from video recordings, and automatically, using the software, allowing us to evaluate the accuracy of N-backer. There was an extremely high correlation between these scores (.933). The videos were also used to obtain a comprehensive error score for the NAT. Significantly more errors were made in the more complex NAT tasks when participants were 2-backing, as compared with when they were not, showing that the auditory–verbal n-back task can be used to disrupt sequential object use. This dual-task method may simulate the attentional deficits of patients with brain injury, providing insights into the difficulties they face in tasks of daily living.     

3D Multiple Object Tracking Boosts Working Memory Span: Implications for Cognitive Training in Military Populations

Recently, there has been much theoretical and applied interest in the prospects of cognitive training for improving cognition. NeuroTracker is a relatively recent training device for improving dynamic attention in athletes by training 3D multiple-object tracking skills. We examined its effectiveness for improving working memory (WM) span in members of the Canadian Armed Forces (CAF) by randomly assigning participants to the experimental (NeuroTracker), active control (adaptive dual n-back task), or passive control (no contact) conditions. NeuroTracker training resulted in significant gains in verbal, visual, and matrix span. No gain was observed in the active or passive control group. These results suggest that NeuroTracker could be a useful training tool for increasing WM span in military samples. Future studies could examine the effects of NeuroTracker training on militarily relevant performance measures that draw on WM span.     

Capacity estimates in working memory: Reliability and interrelationships among tasks

The concept of capacity has become increasingly important in discussions of working memory (WM), in so far as most models of WM conceptualize it as a limited-capacity mechanism for maintaining information in an active state, and as capacity estimates from at least one type of WM task—complex span—are valid predictors of real-world cognitive performance. However, the term capacity is also often used in the context of a distinct set of WM tasks, change detection, and may or may not refer to the same cognitive capability. We here develop maximum-likelihood models of capacity from each of these tasks—as well as from a third WM task that places heavy demands on cognitive control, the self-ordered WM task (SOT)—and show that the capacity estimates from change detection and complex span tasks are not correlated with each other, although capacity estimates from change detection tasks do correlate with those from the SOT. Furthermore, exploratory factor analysis confirmed that performance on the SOT and change detection load on the same factor, with performance on our complex span task loading on its own factor. These findings suggest that at least two distinct cognitive capabilities underlie the concept of WM capacity as it applies to each of these three tasks.     

How am I doing? Performance feedback mitigates the effects of mental fatigue on endurance exercise performance

Mental fatigue induced by an earlier cognitive task can impair performance on a subsequent physical task. The current study investigated whether such performance impairment could be mitigated by performance feedback. In an experimental sequential-task design, 63 sport science students completed a series of three tasks: 5-min physical (pre-test), 20-min cognitive, 5-min physical (post-test). Participants were randomly allocated to one of three groups: feedback (n = 23), no feedback (n = 20), control (n = 20). The physical tasks, which assessed force production during a self-paced rhythmic handgrip task as a measure of physical endurance performance, were performed with (feedback group) or without (no feedback group, control group) visual performance feedback. The cognitive tasks involved either completing a 2-back memory task to induce mental fatigue (feedback and no feedback groups) or watching a didactic film (control group). Self-report measures (fatigue, exertion, vigor, motivation) were collected throughout. The 2-back cognitive task increased mental fatigue, mental exertion and general fatigue in the feedback and no feedback groups compared to the control group. Relative to the pre-test physical task, post-test endurance performance declined in the no feedback group (−14.4%) but did not change in the control (−2.6%) and feedback (−2.4%) groups. This mitigation of performance effect was not accompanied by parallel changes in fatigue, exertion, vigor, or motivation. In conclusion, visual performance feedback mitigates the negative effects of mental fatigue on physical endurance performance.     

Novel n-back spatial working memory task using eye movement response

We created a novel eye movement version of the n-back task to measure spatial working memory (WM). Rather than one continuous trial, discrete trials were presented in order to develop a simpler WM task. In Experiment 1, we varied the visibility of the final stimulus to maximize the difference in performance between 0-back and 1-back tasks (WM effect). In Experiment 2, we administered the optimized task to children. In Experiment 3, we further simplified the task. Both adults and children easily completed our task, displaying significant WM effects. Further, similar WM effects were obtained in our original and simplified n-back spatial WM tasks, demonstrating flexibility. Because WM deficits are often an early feature of disease and a marker of disease progression, our saccadic measure of spatial WM may be particularly useful in hard-to-test populations, such as patients and children, and may have application in brain-imaging studies that require discrete trials.     

The impact of achievement goal states on working memory

The present study examines the influence of achievement goal states on working memory under varying executive load. Seventy-six undergraduate students were randomly assigned to either a mastery-approach condition (goal was to develop self-referential competence), a performance-approach condition (goal was to demonstrate normative competence) or a control condition (no goal assigned) prior to completing the N-Back working memory task. Analyses revealed achievement goal effects on working memory under high executive load (3-back) but not under the less demanding loads (1-back, 2-back). Under high load, pursuit of a performance-approach goal resulted in poorer working memory processing than pursuit of a mastery-approach goal or no-goal control. Findings are unlikely to be confounded by cognitive ability, working memory capacity or state-anxiety. Contributions to the motivation–cognition interface and suggestions for future research are discussed.     

Complex span tasks, simple span tasks, and cognitive abilities: A reanalysis of key studies

There is great interest in the relationships between memory span tasks and cognitive abilities. However, the causes underlying their correlation remain unknown. In the present article, five key data sets were reanalyzed according to two criteria: They must consider complex span tasks (so-called working memory [WM] tasks) and simple span tasks (so-called short-term memory [STM] tasks), and they must comprise cognitive ability measures. The obtained results offer several points of interest. First, memory span tasks should be conceived from a hierarchical perspective: They comprise both general and specific components. Second, the general component explains about four times the variance explained by the specific components. Third, STM and WM measures are closely related. Fourth, STM and WM measures share the same common variance with cognitive abilities. Finally, the strong relationship usually found between memory span tasks and cognitive abilities could be tentatively interpreted by the component shared by STM and WM--namely, the capacity for temporarily preserving a reliable memory representation of any given information.     

On the division of short-term and working memory: an examination of simple and complex span and their relation to higher order abilities

Research has suggested that short-term memory and working memory (as measured by simple and complex span tasks, respectively) are separate constructs that are differentially related to higher order cognitive abilities. This claim is critically evaluated by reviewing research that has compared simple and complex span tasks in both experimental and correlational studies. In addition, a meta-analysis and re-analyses of key data sets were conducted. The review and analyses suggest that simple and complex span tasks largely measure the same basic subcomponent processes (e.g., rehearsal, maintenance, updating, controlled search) but differ in the extent to which these processes operate in a particular task. These differences largely depend on the extent to which phonological processes are maximized and variability from long list lengths is present. Potential methodological, psychometric, and assessment implications are discussed and a theoretical account of the data is proposed.     

Working memory, attention control, and the N-back task: a question of construct validity

The N-back task requires participants to decide whether each stimulus in a sequence matches the one that appeared n items ago. Although N-back has become a standard "executive" working memory (WM) measure in cognitive neuroscience, it has been subjected to few behavioral tests of construct validity. A combined experimental- correlational study tested the attention-control demands of verbal 2- and 3-back tasks by presenting n = 1 "lure" foils. Lures elicited more false alarms than control foils in both 2- and 3-back tasks, and lures caused more misses to targets that immediately followed them compared with control targets, but only in 3-back tasks. N-back thus challenges control over familiarity-based responding. Participants also completed a verbal WM span task (operation span task) and a marker test of general fluid intelligence (Gf; Ravens Advanced Progressive Matrices Test; J. C. Raven, J. E. Raven, & J. H. Court, 1998). N-back and WM span correlated weakly, suggesting they do not reflect primarily a single construct; moreover, both accounted for independent variance in Gf. N-back has face validity as a WM task, but it does not demonstrate convergent validity with at least 1 established WM measure.