Is There a Specific Executive Capacity for Dual Task Coordination? Evidence From Alzheimer's Disease

Distinct age-related brain activity patterns in the prefrontal cortex when increasing cognitive load: A functional near-infrared spectroscopy study

Researchers have long observed distinct brain activity patterns in older adults compared with younger adults that correlate with cognitive performance. Mainly, older adults tend to show over-recruitment of bilateral brain regions during lower task loads and improved performance interpreted as compensation, but not observed at higher loads. However, there are discrepancies about whether increases in activity are compensatory and whether older adults can show compensation at higher loads. Our aim was to examine age-related differences in prefrontal cortex (PFC) activity and cognitive performance using functional near-infrared spectroscopy (fNIRS) during single and dual N-back tasks. Twenty-seven young adults (18-27 years) and 31 older adults (64-84 yrs) took part in the study. We used a robust fNIRS data methodology consisting of channel and region of interest analyses. Results showed differences in performance between task load conditions and age-related differences in reaction times but no age-group effects for accuracy. Older adults exhibited more bilateral PFC activation compared with young adults across all tasks and showed increases in brain activity in high compared to low load conditions. Our findings further support previous reports showing that older adults use compensatory recruitment of additional brain regions in PFC to maintain cognitive performance but go against the notion that such compensation is not present at higher cognitive loads. Additionally, our results indicate that fNIRS is a sensitive tool that can characterize adaptive cortical changes in healthy aging.

The contribution of being physically active to successful aging

Growing old involves changes in physical, psychological, and cognitive functions. Promoting physical and mental health has become one of the priorities for an aging population. Studies have demonstrated the benefits of engaging in regular physical activity. Here, we aimed to understand the relationships between physical activity and working memory complaints in attention, memory storage, and executive functions. We hypothesized that physical activity was negatively associated with complaints in working memory domains after controlling for socio-demographics and distress factors, such as anxiety, stress, and depression. Two hundred and twenty-three individuals aged between 65 and 100 years (74.84; SD = 7.74; 133 males) without self-reported neurological and/or psychiatric disorders completed a questionnaire on socio-demographic, with questions on physical activity and the Italian version of the working memory questionnaire (WMQ) and the DASS-21 measuring anxiety, stress, and depression. Results from three linear regression models showed that low physical activity was associated with complaints in attention (R2 = 0.35) and executive functions (R2 = 0.37) but not in memory storage (R2 = 0.28). Notably, age, gender, and total emotional distress (DASS score) were significant in all regression models. Our results suggested regular physical activity, even just walking, is crucial for maintaining efficient cognitive function. Theoretical and practical implications for engaging in physical activity programs and social aggregation during exercise are considered. Limitations are also presented.

Intraindividual variability measured with dispersion across diagnostic groups in a memory clinic sample

Increased intraindividual variability (IIV) has been linked to outcomes such as cognitive decline and dementia, suggesting IIV might add valuable diagnostic information beyond traditional neuropsychological interpretation. We explored whether a subtype of IIV, dispersion, can provide additional information for dementia diagnosis. In a sample of memory clinic patients, three cognitive status groups were identified: subjective cognitive impairment (SCI; n = 85), amnestic mild cognitive impairment (a-MCI; n = 16), and dementia due to Alzheimer's disease (AD; n = 48). Dispersion was computed as intraindividual standard deviations across multiple neuropsychological measures within three cognitive domains (executive functioning; immediate and delayed memory) and was compared for each diagnostic group using profile analysis. Patients with AD and a-MCI demonstrated less dispersion than patients with SCI in delayed memory. Results support existing theoretic perspectives on cognitive variability and age-related cognitive decline but suggest floor effects underlie suppression of dispersion in amnestic cognitive presentations. Questions remain about the contribution of IIV beyond impressions of impairment versus no impairment in these constrained representations of cognitive domains. Future investigations should investigate variability in SCI groups against controls to examine whether observed dispersion similarities between SCI and a-MCI or AD in immediate memory and executive functioning are meaningful.

Scoping review of dual-task interference in individuals with intellectual disability

Dual-task paradigms can provide insights on the structures and mechanisms underlying information processing and hold diagnostic, prognostic, and rehabilitative value for populations with cognitive deficits such as in individuals with intellectual disability (ID). In this paradigm, two tasks are performed separately (single-task context) and concurrently (dual-task context). The change in performance from single- to dual-task context represents dual-task interference. Findings from dual-task studies have been largely inconsistent on whether individuals with ID present with dual-task-specific deficits. The current review aimed to map the published literature on dual-task methods and pattern of dual-task interference in individuals with ID. A scoping review based on Arksey and O'Malley's five-stage methodological framework was performed. Seventeen electronic databases and registries were searched to identify relevant studies, including gray literature. Charted data from included studies were analyzed quantitatively and qualitatively. PRISMA guidelines informed the reporting of this review. Twenty-two studies involving 1,102 participants (656 with ID and 446 without ID) met the review's inclusion criteria. Participants in the included studies were heterogeneous in sex, age (range 3-59 years), etiology and ID severity. Included studies characterized their ID-sample in different ways, most commonly using intelligence quotient (IQ) scores. Other measures of intellectual function (e.g., mental age, ID severity, verbal and/or visuospatial ability scores) were also used, either solely or in combination with IQ. Methods of dual-task testing varied across studies, particularly in relation to dual-task combinations, equation of single-task performance between groups, measurement and reporting of dual-task performance for each single-task, and task priority instructions. Thematic content of the included studies were: (1) structural interference to dual-tasking; (2) etiology-based differences in dual-tasking; (3) gait and balance dual-task performance; (4) testing executive function using dual-task paradigms; and (5) training effect on dual-task performance. Although the evidence consistently supported the intact dual-tasking ability of individuals with ID, the pattern of dual-task interference was inconsistent. Likewise, the evidence was inconclusive regarding dual-task deficit specific to individuals with ID because of heterogeneity in dual-task study designs among included studies.

Individual differences in everyday multitasking behavior and its relation to cognition and personality

Our ability to multitask-focus on multiple tasks simultaneously-is one of the most critical functions of our cognitive system. This capability has shown to have relations to cognition and personality in empirical studies, which have received much attention recently. This review article integrates the available findings to examine how individual differences in multitasking behavior are linked with different cognitive constructs and personality traits to conceptualize what multitasking behavior represents. In this review, we highlight the methodological differences and theoretical conceptions. Cognitive constructs including executive functions (i.e., shifting, updating, and inhibition), working memory, relational integration, divided attention, reasoning, and prospective memory were investigated. Concerning personality, the traits of polychronicity, impulsivity, and the five-factor model were considered. A total of 43 studies met the inclusion criteria and entered the review. The research synthesis directs us to propose two new conceptual models to explain multitasking behavior as a psychometric construct. The first model demonstrates that individual differences in multitasking behavior can be explained by cognitive abilities. The second model proposes that personality traits constitute a moderating effect on the relation between multitasking behavior and cognition. Finally, we provide possible future directions for the line of research.

Executive function abilities in cognitively healthy young and older adults-A cross-sectional study

A prominent feature of cognitive aging is the decline of executive function (EF) abilities. Numerous studies have reported that older adults perform poorer than younger adults in such tasks. In this cross-sectional study, the effect of age on four EFs, inhibition, shifting, updating, and dual-tasking, was examined in 26 young adults (mean 21.18  years) and 25 older adults (mean 71.56  years) with the utilization of a pair of tasks for each EF. The tasks employed for DT were the Psychological Refractory Period paradigm (PRP) and a modified test for everyday attention, for inhibition the Stroop and Hayling sentence completion test (HSCT), for shifting a task switching paradigm and the trail making test (TMT), and for updating the backward digit span (BDS) task and a n-back paradigm. As all participants performed all tasks, a further aim was to compare the size of the age-related cognitive decline among the four EFs. Age-related decline was observed in all four EFs in one or both of the tasks employed. The results revealed significantly poorer performance in the older adults in the response times (RTs) of the PRP effect, interference score of the Stroop, RT inhibition costs of the HSCT, RT and error-rate shifting costs of the task switching paradigm, and the error-rate updating costs of the n-back paradigm. A comparison between the rates of decline revealed numerical and statistically significant differences between the four EFs, with inhibition showing the greatest decline, followed by shifting, updating, and dual-tasking. Thus, we conclude that with age, these four EFs decline at different rates.

Executive function and effortful control-Similar and different evidence from big data analysis

Introduction

The current study explored commonalities and similarities between executive function (EF) and effortful control (EC).

Methods

The major empirical studies published between 2013 and 2022 in the World of Science (WoS) was collected. The bibliographic information was systematically analyzed.

Results and discussion

(1) EC is the efficiency of executive attention that incorporates inhibitory control (IC), attentional control, activation mainly related to temperament. On the other hand, EF is the efficiency of self-directed action that encompasses IC, working memory (WM), and shifting/cognitive flexibility in particular focuses on the cognitive aspect. (2) EF research has overwhelmingly outnumbered EC research (2,000 EF studies vs. 50 EC studies per year). (3) According to a co-word analysis with keyword co-occurrences, the subject of preschool students and individual differences co-occurred in EF studies. (4) EC usually occurs with working memory and early childhood. In the more detailed analysis of the articles, the EF and EC studies used younger subject groups than older subject groups. EC studies were especially likely to use subjects in early childhood. (5) The Delis-Kaplan Tests of Executive Functioning System (D-KEFS) was the most commonly used test for EF. In contrast, the EC used self-report surveys such as the Adolescent Temperament Questionnaire (ATQ). This research illustrates and discusses key findings in the EC and EF data and provides suggestions for future study directions.

Turning and multitask gait unmask gait disturbance in mild-to-moderate multiple sclerosis: Underlying specific cortical thinning and connecting fibers damage

Multiple sclerosis (MS) causes gait and cognitive impairments that are partially normalized by compensatory mechanisms. We aimed to identify the gait tasks that unmask gait disturbance and the underlying neural correlates in MS. We included 25 patients with MS (Expanded Disability Status Scale score: median 2.0, interquartile range 1.0-2.5) and 19 healthy controls. Fast-paced gait examinations with inertial measurement units were conducted, including straight or circular walking with or without cognitive/motor tasks, and the timed up and go test (TUG). Receiver operating characteristic curve analysis was performed to distinguish both groups by the gait parameters. The correlation between gait parameters and cortical thickness or fractional anisotropy values was examined by using three-dimensional T1-weighted imaging and diffusion tensor imaging, respectively (corrected p < .05). Total TUG duration (>6.0 s, sensitivity 88.0%, specificity 84.2%) and stride velocity during cognitive dual-task circular walking (<1.12 m/s, 84.0%, 84.2%) had the highest discriminative power of the two groups. Deterioration of these gait parameters was correlated with thinner cortical thickness in regional areas, including the left precuneus and left temporoparietal junction, overlapped with parts of the default mode network, ventral attention network, and frontoparietal network. Total TUG duration was negatively correlated with fractional anisotropy values in the deep cerebral white matter areas. Turning and multitask gait may be optimal to unveil partially compensated gait disturbance in patients with mild-to-moderate MS through dynamic balance control and multitask processing, based on the structural damage in functional networks.

Description of the Method for Evaluating Digital Endpoints in Alzheimer Disease Study: Protocol for an Exploratory, Cross-sectional Study

BACKGROUND

More sensitive and less burdensome efficacy end points are urgently needed to improve the effectiveness of clinical drug development for Alzheimer disease (AD). Although conventional end points lack sensitivity, digital technologies hold promise for amplifying the detection of treatment signals and capturing cognitive anomalies at earlier disease stages. Using digital technologies and combining several test modalities allow for the collection of richer information about cognitive and functional status, which is not ascertainable via conventional paper-and-pencil tests.

OBJECTIVE

This study aimed to assess the psychometric properties, operational feasibility, and patient acceptance of 10 promising technologies that are to be used as efficacy end points to measure cognition in future clinical drug trials.

METHODS

The Method for Evaluating Digital Endpoints in Alzheimer Disease study is an exploratory, cross-sectional, noninterventional study that will evaluate 10 digital technologies' ability to accurately classify participants into 4 cohorts according to the severity of cognitive impairment and dementia. Moreover, this study will assess the psychometric properties of each of the tested digital technologies, including the acceptable range to assess ceiling and floor effects, concurrent validity to correlate digital outcome measures to traditional paper-and-pencil tests in AD, reliability to compare test and retest, and responsiveness to evaluate the sensitivity to change in a mild cognitive challenge model. This study included 50 eligible male and female participants (aged between 60 and 80 years), of whom 13 (26%) were amyloid-negative, cognitively healthy participants (controls); 12 (24%) were amyloid-positive, cognitively healthy participants (presymptomatic); 13 (26%) had mild cognitive impairment (predementia); and 12 (24%) had mild AD (mild dementia). This study involved 4 in-clinic visits. During the initial visit, all participants completed all conventional paper-and-pencil assessments. During the following 3 visits, the participants underwent a series of novel digital assessments.

RESULTS

Participant recruitment and data collection began in June 2020 and continued until June 2021. Hence, the data collection occurred during the COVID-19 pandemic (SARS-CoV-2 virus pandemic). Data were successfully collected from all digital technologies to evaluate statistical and operational performance and patient acceptance. This paper reports the baseline demographics and characteristics of the population studied as well as the study's progress during the pandemic.

CONCLUSIONS

This study was designed to generate feasibility insights and validation data to help advance novel digital technologies in clinical drug development. The learnings from this study will help guide future methods for assessing novel digital technologies and inform clinical drug trials in early AD, aiming to enhance clinical end point strategies with digital technologies.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/35442.

Cognitive Control Challenge Task Across the Lifespan

Meeting everyday challenges and responding in a goal-directed manner requires both the ability to maintain the current task set in face of distractors-stable cognitive control, and the ability to flexibly generate or switch to a new task set when environmental requirements change-flexible cognitive control. While studies show that the development varies across individual component processes supporting cognitive control, little is known about changes in complex stable and flexible cognitive control across the lifespan. In the present study, we used the newly developed Cognitive Control Challenge Task (C3T) to examine the development of complex stable and flexible cognitive control across the lifespan and to gain insight into their interdependence. A total of 340 participants (229 women, age range 8-84 years) from two samples participated in the study, in which they were asked to complete the C3T along with a series of standard tests of individual components of cognitive control. The results showed that the development of both stable and flexible complex cognitive control follows the expected inverted U-curve. In contrast, the indeces of task set formation and task set switching cost increase linearly across the lifespan, suggesting that stable and flexible complex cognitive control are subserved by separable cognitive systems with different developmental trajectories. Correlations with standard cognitive tests indicate that complex cognitive control captured by the C3T engages a broad range of cognitive abilities, such as working memory and planning, and reflects global processing speed, jointly suggesting that the C3T is an effective test of complex cognitive control that has both research and diagnostic potential.

Unraveling the Cognitive-Motor Interaction in Individuals With Amnestic Mild Cognitive Impairment

PURPOSE

This study aimed to determine whether increasing the contribution of executive functions worsens dual-task performance in individuals with amnestic mild cognitive impairment (aMCI).

METHODS

Fourteen individuals with aMCI (mean [SD]: 74 [4] years) and 19 control adults (71 [5] years) recalled a list of letters in the order of presentation (SPAN-O) or in alphabetic order (SPAN-A) while ascending or descending a 3-step staircase. Dual-task cost (DTC) represented the average decrement of motor and cognitive performances during dual tasks, with greater DTC indicating worse performance.

RESULTS

SPAN-A (P < 0.001) and stair descent (P = 0.023) increased the DTC in both groups compared with SPAN-O and stair ascent. Furthermore, individuals with aMCI had a greater DTC (93.4 [41.2]%) than the control group (48.3 [27.9]%) for SPAN-A (P < 0.001). Dual-task cost was also greater in descent (76.6 [42.1]%) than ascent (64.0 [34.5]%) in individuals with aMCI (P = 0.024) but not in the control group (P = 0.99). Significant negative partial correlations (β < -0.39; P < 0.05) were found between Montreal Cognitive Assessment score and DTC, while controlling for age and physical function.

DISCUSSION AND CONCLUSIONS

A greater DTC in individuals with aMCI when the cognitive task requires working memory (SPAN-A) or during complex locomotor task (descent) suggests that aMCI impedes the capacity to perform 2 tasks simultaneously when higher-order cognitive processes are challenged. Furthermore, a greater DTC in our dual-task situations appears to reflect cognitive decline, as assessed by the Montreal Cognitive Assessment score. Overall, this study indicates that increasing the contribution of executive functions worsens the cognitive-motor interaction in individuals with aMCI.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A375).

What affects the magnitude of age-related dual-task costs in working memory? The role of stimulus domain and access to semantic representations

Although there is evidence that the effect of including a concurrent processing demand on the storage of information in working memory is disproportionately larger for older than younger adults, not all studies show this age-related impairment, and the critical factors responsible for any such impairment remain elusive. Here we assess whether domain overlap between storage and processing activities, and access to semantic representations, are important determinants of performance in a sample of younger and older adults (N = 119). We developed four versions of a processing task by manipulating the type of stimuli involved (either verbal or non-verbal) and the decision that participants had to make about the stimuli presented on the screen. Participants either had to perform a spatial judgement, in deciding whether the verbal or non-verbal item was presented above or below the centre of the screen, or a semantic judgement, in deciding whether the stimulus refers to something living or not living. The memory task was serial-ordered recall of visually presented letters. The study revealed a large increase in age-related memory differences when concurrent processing was required. These differences were smaller when storage and processing activities both used verbal materials. Dual-task effects on processing were also disproportionate for older adults. Age differences in processing performance appeared larger for tasks requiring spatial decisions rather than semantic decisions. We discuss these findings in relation to three competing frameworks of working memory and the extant literature on cognitive ageing.

Effect of robot-assisted gait training on gait automaticity in Parkinson disease: A prospective, open-label, single-arm, pilot study

ABSTRACT

Gait automaticity is reduced in patients with Parkinson disease (PD) due to impaired habitual control. The aim of this study was to investigate the effect of robot-assisted gait training (RAGT) on gait automaticity as well as gait speed and balance in patients with PD.This study was a prospective, open-label, single-arm, pilot study. We planned to recruit 12 patients with idiopathic PD. Participants received 12 sessions of RAGT using exoskeleton-type robotic device. Sessions were 45-minute each, 3 days a week, for 4 consecutive weeks using an exoskeleton-type gait robot. The primary outcome was the percentage of dual-task interference measured by the 10-Meter Walk Test (10MWT) under single and dual-task (cognitive and physical) conditions. Secondary outcomes were the Berg Balance Scale and Korean version of the Falls Efficacy Scale-International. All measures were evaluated before treatment (T0), after treatment (T1), and 1-month post-treatment (T2).Twelve patients were enrolled and 1 dropped out. Finally, 11 patients with idiopathic PD were analyzed. The mean age of 11 patients (5 males) was 66.46 ± 5.66 years, and disease duration was 112.91 ± 50.19 months. The Hoehn and Yahr stages were 2.5 in 8 patients and 3 in 3 patients. Linear mixed-effect model analysis showed a significant change over time only in single-task gait speed of the 10MWT (P = .007), but not in dual-task gait speed, dual-task interferences, and Korean version of the Falls Efficacy Scale-International. Cognitive dual-task interference significantly increased (P = .026) at T1, but not at T2 (P = .203). No significant changes were observed for physical dual-task interference at T1 and T2. Single-task gait speed of the 10MWT was significantly increased at T1 (P = .041), but not at T2 (P = .445). There were no significant changes in the dual-task gait speed of 10MWT. A significant improvement was observed in Berg Balance Scale score at T1 and T2 (P = .004 and P = .024, respectively).In this pilot study, despite improvement in walking speed and balance, gait automaticity in patients with PD was not improved by RAGT using an exoskeleton-type robot. Additional therapeutic components may be needed to improve gait automaticity using RAGT in patients with PD.

The Number Symbol Coding Task: A brief measure of executive function to detect dementia and cognitive impairment

INTRODUCTION

Alzheimer's disease and related dementias (ADRD) affect over 5.7 million Americans and over 35 million people worldwide. Detection of mild cognitive impairment (MCI) and early ADRD is a challenge to clinicians and researchers. Brief assessment tools frequently emphasize memory impairment, however executive dysfunction may be one of the earliest signs of impairment. To address the need for a brief, easy-to-score, open-access test of executive function for use in clinical practice and research, we created the Number Symbol Coding Task (NSCT).

METHODS

This study analyzed 320 consecutive patient-caregiver dyads who underwent a comprehensive evaluation including the Clinical Dementia Rating (CDR), patient and caregiver versions of the Quick Dementia Rating System (QDRS), caregiver ratings of behavior and function, and neuropsychological testing, with a subset undergoing volumetric magnetic resonance imaging (MRI). Estimates of cognitive reserve were calculated using education, combined indices of education and occupation, and verbal IQ. Psychometric properties of the NSCT including data quality, data distribution, floor and ceiling effects, construct and known-groups validity, discriminability, and clinical profiles were determined.

RESULTS

The patients had a mean age of 75.3±9.2 years (range 38-98y) with a mean education of 15.7±2.8 years (range 6-26y) of education. The patients had a mean CDR-SB of 4.8±4.7 (range 0-18) and a mean MoCA score of 18.6±7.1 (range 1-30). The mean NSCT score was 30.1±13.8 and followed a normal distribution. All healthy controls and MCI cases were able to complete the NSCT. The NSCT showed moderate-to-strong correlations with clinical and neuropsychological measures with the strongest association (all p's < .001) for measures with executive components (e.g., Judgement and Problem Solving box of the CDR, Decision Making and Problem Solving domain of the QDRS, Trailmaking B, and Cognigram Attention and Executive Composite Scores). Women slightly outperformed men, and individuals with lower educational attainment and lower education-occupation indices had lower NSCT scores. Decreasing NSCT scores corresponded to older age, worse cognitive scores, higher CDR sum of boxes scores, worse caregiver ratings of function and behavior, worse patient and informant QDRS ratings, and smaller hippocampal volumes and hippocampal occupancy scores. The NSCT provided excellent discrimination (AUC: .866; 95% CI: .82-.91) with a cut-off score of 36 providing the best combination of sensitivity (0.880) and specificity (0.759). Combining the NSCT with patient QDRS and caregiver QDRS ratings improved discrimination (AUC: .908; 95% CI: .87-.94).

DISCUSSION

The NSCT is a brief, 90-second executive task that incorporates attention, planning and set-switching that can be completed by individuals into the moderate-to-severe stages of dementia. The NSCT may be a useful tool for dementia screening, case-ascertainment in epidemiological or community-based ADRD studies, and in busy primary care settings where time is limited. Combining the NSCT with a brief structured interview tool such as the QDRS may provide excellent power to detect cognitive impairment. The NSCT performed well in comparison to standardized scales of a comprehensive cognitive neurology evaluation across a wide array of sociodemographic variables in a brief fashion that could facilitate its use in clinical care and research.

Dual and triple tasks performance in institutionalized prefrail and frail older adults

OBJECTIVE

The aim of this pilot study was to investigate differences on dual- and triple-task performance in institutionalized prefrail and frail older adults. Performance on these tasks is relevant since many activities of daily living involve simultaneous motor and cognitive tasks.

METHODS

We used a phenotypic description of frailty based on the presence or absence of five criteria related to physical fitness and metabolism (unintentional weight loss, self-reported exhaustion, muscle weakness, low gait speed, and low physical activity). Thirty-three institutionalized older adults (≥ 65 years, 78.8% females) were divided according to their frailty status. Participants completed cognitive tasks (a phonemic verbal fluency task and a visuospatial tracking task) while cycling on a stationary cycle (upper- and lower-extremity function was assessed). Cycling (number of arm and foot cycles) and cognitive (number of correct answers) performances were measured during single-, dual-, and triple-task conditions. Performances and costs of dual -and triple- tasking on cycling and cognitive performances were compared between prefrail and frail groups.

RESULTS

Prefrail and frail older adults did not differ in their performance in dual-tasks; however, frail older adults showed a poorer performance in the triple-task.

CONCLUSIONS

Although future studies need to confirm our observations in larger samples, this pilot study suggests that developing new tools based on triple tasking could be useful for the comprehensive assessment of frailty.

How Do Scientific Views Change? Notes From an Extended Adversarial Collaboration

There are few examples of an extended adversarial collaboration, in which investigators committed to different theoretical views collaborate to test opposing predictions. Whereas previous adversarial collaborations have produced single research articles, here, we share our experience in programmatic, extended adversarial collaboration involving three laboratories in different countries with different theoretical views regarding working memory, the limited information retained in mind, serving ongoing thought and action. We have focused on short-term memory retention of items (letters) during a distracting task (arithmetic), and effects of aging on these tasks. Over several years, we have conducted and published joint research with preregistered predictions, methods, and analysis plans, with replication of each study across two laboratories concurrently. We argue that, although an adversarial collaboration will not usually induce senior researchers to abandon favored theoretical views and adopt opposing views, it will necessitate varieties of their views that are more similar to one another, in that they must account for a growing, common corpus of evidence. This approach promotes understanding of others' views and presents to the field research findings accepted as valid by researchers with opposing interpretations. We illustrate this process with our own research experiences and make recommendations applicable to diverse scientific areas.

Normative data and validation of the Italian translation of the Working Memory Questionnaire (WMQ)

Reliable and valid measures are necessary to assess subjective working memory complaints that can be distinct from objective memory performance. The Working Memory Questionnaire (WMQ) is a self-administered scale proposed by Vallat-Azouvi. It assesses the three different working memory domains (memory storage, attention, and executive functions) in accordance with Baddeley's working memory model. Our aim was to propose an Italian translation of the WMQ and provide normative data. We collected normative data from 697 healthy Italian participants aged between 18 and 88 years. Percentiles and cutoff scores, taking into consideration age, gender, and education, were provided for the WMQ total scores and the three separate domains. The performance on the WMQ was influenced by age and education. In particular, age and education affected self-perceived working memory efficacy. Our data demonstrate a significant correlation between the WMQ and paper-and-pencil tests assessing working memory, attention, and executive functions. This study provides normative data that have been adjusted for relevant demographics and percentile grids in an Italian population. The results are in line with a previous French study that also supported the use of the WMQ as a valid prescreening instrument for working memory deficits in clinical practice.

Psychosocial and Cognitive Performance Correlates of Subjective Cognitive Complaints in Help-Seeking Versus Non-Help-Seeking Community-Dwelling Adults

The clinical use of subjective cognitive complaints (SCCs) has been questioned, especially when considering the influence of depression. Further problems describe the registration of SCCs with a focus on memory and different sample selections, with only few studies that directly compare those who seek help because of SCCs and community-dwelling adults. The present study aimed to (1) evaluate differences in psychosocial variables in help-seeking adults and community-dwelling adults with a lower level of complaints and (2) to further explore the relationship between SCCs and cognitive performance in help-seekers. Fifty-five help-seeking adults (HS) were compared to 55 age-, sex-, and education-matched non-help-seeking adults (NHS). Multiple regression analyses revealed that depressive symptoms were linked to experiencing more SCCs mainly in NHS. Altogether, less variance was explained by psychosocial variables in HS, whereas adding cognitive variables-especially divided attention performance-led to a substantial increase in explained variance. Mediation analysis further revealed a possible mediation of depressive symptoms on SCC by divided attention performance. Taken together, our results underpin the importance of assessing SCCs comprehensively to detect a functional relationship between cognitive performance and complaints, especially in HS. In this group, it is likely that depression precedes problems in divided attention, which in turn lead to SCC. Therefore, future studies should further investigate the link between SCC and cognitive functions which rely on more cognitive resources, as these might be first to be affected by cognitive decline.

From short-term store to multicomponent working memory: The role of the modal model

The term "modal model" reflects the importance of Atkinson and Shiffrin's paper in capturing the major developments in the cognitive psychology of memory that were achieved over the previous decade, providing an integrated framework that has formed the basis for many future developments. The fact that it is still the most cited model from that period some 50 years later has, we suggest, implications for the model itself and for theorising in psychology more generally. We review the essential foundations of the model before going on to discuss briefly the way in which one of its components, the short-term store, had influenced our own concept of a multicomponent working memory. This is followed by a discussion of recent claims that the concept of a short-term store be replaced by an interpretation in terms of activated long-term memory. We present several reasons to question these proposals. We conclude with a brief discussion of the implications of the longevity of the modal model for styles of theorising in cognitive psychology.

Dual-task costs in working memory: An adversarial collaboration

[Correction Notice: An Erratum for this article was reported in Vol 45(9) of Journal of Experimental Psychology: Learning, Memory, and Cognition (see record 2019-48991-001). In the article, the copyright attribution was incorrectly listed and should have published under the Creative Commons CC-BY license. The correct copyright is "© 2018 The Author(s)." All versions of this article have been corrected.] Theories of working memory often disagree on the relationships between processing and storage, particularly on how heavily they rely on an attention-based limited resource. Some posit separation and specialization of resources resulting in minimal interference to memory when completing an ongoing processing task, while others argue for a greater overlap in the resources involved in concurrent tasks. Here, we present four experiments that investigated the presence or absence of dual-task costs for memory and processing. The experiments were carried in an adversarial collaboration in which researchers from three opposing theories collaboratively designed a set of experiments and provided differential predictions in line with each of their models. Participants performed delayed recall of aurally and visually presented letters and an arithmetic verification task either as single tasks or with the arithmetic verification task between presentation and recall of letter sequences. Single- and dual-task conditions were completed with and without concurrent articulatory suppression. A consistent pattern of dual-task and suppression costs was observed for memory, with smaller or null effects on processing. The observed data did not fit perfectly with any one framework, with each model having partial success in predicting data patterns. Implications for each of the models are discussed, with an aim for future research to investigate whether some combination of the models and their assumptions can provide a more comprehensive interpretation of the pattern of effects observed here and in relevant previous studies associated with each theoretical framework. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

A fractionated analysis of hot and cool self-regulation in cigarette smokers from different socioeconomic backgrounds

Smoking cigarettes and low socioeconomic status (SES) are both related to impaired cognition. However, it is unknown whether people of lower SES, who comprise most tobacco smokers worldwide, are more susceptible to cognitive impairment associated with smoking. In this non-randomized, cross-sectional study we investigated the effects of cigarette smoking, SES and their interaction on dissociable executive or “cool” and “hot” measures of behavioural self-regulation. Participants (n = 80) were selected among young physically and mentally healthy smokers and non-smokers who had graduated high school and were from different SES backgrounds. Cool self-regulation was measured by executive function tasks that tap inhibition, updating, shifting, dual tasking, planning, access to long-term memory (semantic fluency), and working memory capacity. Hot measures assessed self-reported impulsivity, delay discounting and risk taking. Exposure to tobacco (cotinine, exhaled carbon monoxide, tobacco dependence, cigarette consumption) was assessed to determine to what extent it mediated the cognitive effects of smoking. Nicotine abstinence and its acute effects were controlled, as were sex, age, schooling, and psychiatric symptoms despite the fact that smokers and non-smokers were selected as being as similar as possible in these demographic characteristics. Lower SES (less years of parental schooling) was associated with worse performance on tasks that measured all cool domains except dual tasking and fluency, while smoking status was related to impaired delayed discounting and impulsivity (hot domains), effects that were not mediated by tobacco exposure. Smoking and SES, however, did not interact. In short, impaired performance in measures of most cool skills was associated with SES irrespective of smoking status; in contrast, regardless of SES, smokers showed specific impairment in hot self-regulation domains (more difficulty resisting immediate temptations and weighing future consequences of actions). Possible explanations for the lack of mediation of tobacco exposure on hot skills of smokers are discussed.

Monitoring Multiple Deadlines Relies on Spatial Processing in Posterior Parietal Cortex

Proactively coordinating one's actions is an important aspect of multitasking performance due to overlapping task sequences. In this study, we used fMRI to investigate neural mechanisms underlying monitoring of multiple overlapping task sequences. We tested the hypothesis that temporal control demands in multiple-task monitoring are offloaded onto spatial processes by representing patterns of temporal deadlines in spatial terms. Results showed that increased demands on time monitoring (i.e., responding to concurrent deadlines of one to four component tasks) increasingly activated regions in the left inferior parietal lobe and the precuneus. Moreover, independent measures of spatial abilities correlated with multiple-task performance beyond the contribution of working memory. Together, these findings suggest that monitoring and coordination of temporally overlapping task timelines rely on cortical processes involved in spatial information processing. We suggest that the precuneus is involved in tracking of multiple task timelines, whereas the inferior parietal lobe constructs spatial representations of the temporal relations of these overlapping timelines. These findings are consistent with the spatial offloading hypothesis and add new insights into the neurocognitive mechanisms underlying the coordination of multiple tasks.

Multitasking behavior and its related constructs: Executive functions, working memory capacity, relational integration, and divided attention

Although prior investigations have revealed cognitive abilities to be important predictors of multitasking behavior, few investigations have been conducted on the relation between executive functions (EFs) and multitasking behavior. The current study examines the underlying cognitive constructs associated with the concept of multitasking behavior. A sample of 202 young adults completed a battery of EFs (shifting, updating, and inhibition), three working memory capacity (WMC) tests, three relational integration tests, two divided attention tests, and a multitasking scenario (Simultaneous Capacity). First, in direct replication attempts, the results replicated the multitasking behavior model (Bühner, König, Pick, & Krumm, 2006) and partially replicated the three-factor and nested factors EFs models (Friedman et al., 2016). Second, hierarchical multiple regression analyses and relative weight analyses revealed that updating, inhibition, relational integration, and divided attention had strong contributions in explaining multitasking behavior variance, whereas shifting and WMC did not show any explanatory power beyond these constructs. Finally, using structural equation modeling, we found that the general EF ability (common EF) representing variance common to shifting, updating, and inhibition highly overlapped with multitasking behavior. Our results are of value not only to shed light on the relevant cognitive correlates of multitasking behavior but also to position multitasking behavior in an established framework of cognitive abilities.

Effects of Dance/Movement Training vs. Aerobic Exercise Training on cognition, physical fitness and quality of life in older adults: A randomized controlled trial

INTRODUCTION

It is generally accepted that physical activity promotes healthy aging. Recent studies suggest dance could also benefit cognition and physical health in seniors, but many styles and approaches of dance exist and rigorous designs for intervention studies are still scarce. The aim of this study was to compare the effects of Dance/Movement Training (DMT) to Aerobic Exercise Training (AET) on cognition, physical fitness and health-related quality of life in healthy inactive elderly.

METHODS

A single-center, randomized, parallel assignment, open label trial was conducted with 62 older adults (mean age = 67.48 ± 5.37 years) recruited from the community. Participants were randomly assigned to a 12-week (3x/week, 1hr/session) DMT program, AET program or control group. Cognitive functioning, physical fitness and health-related quality of life were assessed at baseline (T-0), and post-training (T-12 weeks).

RESULTS

41 participants completed the study. Executive and non-executive composite scores showed a significant increase post-training (F_(1,37) = 4.35, p = .04; F_(1,37) = 7.01, p = .01). Cardiovascular fitness improvements were specific to the AET group (F_(2,38) = 16.40, p < .001) while mobility improvements were not group-dependent (10 m walk: F_(1,38) = 11.67, p = .002; Timed up and go: F_(1,38) = 22.07, p < .001).

CONCLUSIONS

Results suggest that DMT may have a positive impact on cognition and physical functioning in older adults however further research is needed. This study could serve as a model for designing future RCTs with dance-related interventions. REGISTRATION: clinicaltrials. gov Identifier NCT02455258.

The Effect of a Verbal Concurrent Task on Visual Precision in Working Memory

By investigating the effect of individualized verbal load on a visual working memory task, we investigated whether working memory is better captured by modality-specific stores or a general attentional resource. A visual measure was used that allows for the precision of representations in working memory to be quantified. Bayesian analyses were employed to contrast the likelihood of our data assuming a small versus a large effect, as predicted by the differing accounts. We found evidence that the effect of verbal load on visual precision and binary feature recall was small. The results were indeterminate for the size of the dual task effect on verbal accuracy and the probability of recalling a continuous target feature. These results, in part, support a multiple component account of working memory. An analysis of how the chosen effect intervals affect the results is also reported, highlighting the importance of making specific predictions in the literature.

Storage and processing in working memory: Assessing dual-task performance and task prioritization across the adult lifespan

There is a theoretical disagreement in the working memory literature, with some proposing that the storage and processing of information rely on distinct parts of the cognitive system and others who posit that they rely, to some extent, on a shared attentional capacity. This debate is mirrored in the literature on working memory and aging, where there have been mixed findings on the ability of older adults to perform simultaneous storage and processing tasks. We assess the overlap between storage and processing and how this changes with age using a procedure in which both tasks have been carefully adjusted to produce comparable levels of single-task performance across a sample (N = 164) of participants aged 18-81. By manipulating incentives to perform one task over the other, this procedure was also capable of disentangling concurrence costs (single- vs. dual-task performance) from prioritization costs (relative payoffs for storage vs. processing performance) in a theoretically meaningful manner. The study revealed a large general cost to serial letter recall performance associated with concurrent performance of an arithmetic verification processing task, a concurrence cost that increased with age. For the processing task, there was no such general concurrence cost. Rather, there was a prioritization effect in dual-task performance for both tasks, irrespective of age, in which performance levels depended on the relative emphasis assigned to memory versus processing. This prioritization effect was large, albeit with a large residual in performance. The findings place important constraints on both working memory theory and our understanding of how working memory changes across the adult lifespan. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The quest for synergy between physical exercise and cognitive stimulation via exergaming in people with dementia: a randomized controlled trial

Background

Exercise is often proposed as a non-pharmacological intervention to delay cognitive decline in people with dementia, but evidence remains inconclusive. Previous studies suggest that combining physical exercise with cognitive stimulation may be more successful in this respect. Exergaming is a promising intervention in which physical exercise is combined with cognitively challenging tasks in a single session. The aim of this study was to investigate the effect of exergame training and aerobic training on cognitive functioning in older adults with dementia.

Methods

A three-armed randomized controlled trial (RCT) compared exergame training, aerobic training and an active control intervention consisting of relaxation and flexibility exercises. Individuals with dementia were randomized and individually trained three times a week during 12 weeks. Cognitive functioning was measured at baseline, after the 12-week intervention period and at 24-week follow-up by neuropsychological assessment. The domains of executive function, episodic memory, working memory and psychomotor speed were evaluated. Test scores were converted into standardized z-scores that were averaged per domain. Between-group differences were analysed with analysis of covariance.

Results

Data from 115 people with dementia (mean (SD) age = 79.2 (6.9) years; mean (SD) MMSE score = 22.9 (3.4)) were analysed. There was a significant improvement in psychomotor speed in the aerobic and exergame groups compared to the active control group (mean difference domain score (95% CI) aerobic versus control 0.370 (0.103–0.637), p = 0.007; exergame versus control 0.326 (0.081–0.571), p = 0.009). The effect size was moderate (partial η² = 0.102). No significant differences between the intervention and control groups were found for executive functioning, episodic memory and working memory.

Conclusions

To our knowledge, this is the first RCT evaluating the effects of exergame training and aerobic training on cognitive functioning in people with dementia. We found that both exergame training and aerobic training improve psychomotor speed, compared to an active control group. This finding may be clinically relevant as psychomotor speed is an important predictor for functional decline. No effects were found on executive function, episodic memory and working memory.

Trial registration

Netherlands Trial Register, NTR5581. Registered on 7 October 2015.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0454-z) contains supplementary material, which is available to authorized users.

The Sources of Dual-task Costs in Multisensory Working Memory Tasks

We investigated the sources of dual-task costs arising in multisensory working memory (WM) tasks, where stimuli from different modalities have to be simultaneously maintained. Performance decrements relative to unimodal single-task baselines have been attributed to a modality-unspecific central WM store, but such costs could also reflect increased demands on central executive processes involved in dual-task coordination. To compare these hypotheses, we asked participants to maintain two, three, or four visual items. Unimodal trials, where only this visual task was performed, and bimodal trials, where a concurrent tactile WM task required the additional maintenance of two tactile items, were randomly intermixed. We measured the visual and tactile contralateral delay activity (CDA/tCDA components) as markers of WM maintenance in visual and somatosensory areas. There were reliable dual-task costs, as visual CDA components were reduced in size and visual WM accuracy was impaired on bimodal relative to unimodal trials. However, these costs did not depend on visual load, which caused identical CDA modulations in unimodal and bimodal trials, suggesting that memorizing tactile items did not reduce the number of visual items that could be maintained. Visual load did not also affect tCDA amplitudes. These findings indicate that bimodal dual-task costs do not result from a competition between multisensory items for shared storage capacity. Instead, these costs reflect generic limitations of executive control mechanisms that coordinate multiple cognitive processes in dual tasks. Our results support hierarchical models of WM, where distributed maintenance processes with modality-specific capacity limitations are controlled by a central executive mechanism.

A transcultural cognitive marker of Alzheimer's Disease

OBJECTIVE

Temporary binding (TB) is sensitive and specific to Alzheimer's Disease (AD), is not affected by age, repeated testing or level of education. Hence, TB is useful to assess patients with very different socio-cultural backgrounds. However, the current computerised version of the test is not suitable for use in clinical settings. The aim of this study was to investigate whether a clinically friendly version of the TB task results in overlapping outcomes compared to the computerised version.

METHODS

A newly devised Flash-card version of the TB assesses temporary visual binding for arrays of stimuli such as shapes (polygons), colours, or combinations of shapes and colours. In Experiment 1, this version was compared with the laboratory computerised version. In Experiment 2, 33 AD patients and 33 matched controls, recruited from various geriatric centres in Romania, were assessed with the new TB test and with Free and Cued Selective Reminding test.

RESULTS

The results with the Flash-card version of the TB test were comparable to those obtained with the computerised version. TB was not affected by age, but it was impaired by AD. The sensitivity and specificity of the new TB test were found to be greater than those achieved by a Selective Reminding test.

CONCLUSIONS

TB deficits may be conceived as a fundamental marker of AD. The Flash-card version is suitable for clinical use also in primary care facilities and in intervention trials, requires minimal training for administration and scoring, is quick to administer, non-invasive, inexpensive, and facilitates cross-cultural studies. Copyright © 2016 John Wiley & Sons, Ltd.

When children forget to remember: Effects of reduced working memory availability on prospective memory performance

The preparatory attentional and memory processes theory (PAM) of prospective memory (PM) proposes that prospective remembering is influenced by the variation in the availability of WM resources. Consequently, PM should be impaired when WM resources are reduced either by direct WM manipulation or by individual differences associated with restricted WM performance. Our study tested this prediction in school-age children by examining the independent and interactive effects of three factors known to deplete availability of WM resources: increased processing demands of a concurrent arithmetic task, additional WM span requirements, and high trait anxiety. A sample of 10-year-old children (N = 128) performed a PM task, embedded in an ongoing arithmetic task, which progressively imposed greater WM processing demands. Half of these participants also concurrently carried out an embedded WM span task. The results supported the PAM hypothesis, showing that children's PM was compromised by the restriction of WM resources, whether this resulted from increasing the processing demands on the ongoing task, from imposing additional WM span requirements, or from high trait anxiety. However, these WM-depleting factors exerted additive effects rather than an interactive impact, suggesting that they might each deplete different aspects of WM resource availability necessary for prospective remembering. Overall findings imply that children's PM success is not only associated to their WM capacity but it mostly depends upon how many of those WM resources are available to be devoted to the PM requirement.

Influence of working memory and executive function on stair ascent and descent in young and older adults

This study assessed the influence of attention division, working memory and executive function on stair ascent and descent in young and older adults. Twenty young (25.5 ± 2.1 yrs) and 20 older adults (68.4 ± 5.4 yrs) ascended and descended a 3-step staircase with no simultaneous cognitive task (single-motor task) or while performing a cognitive task (dual-task condition). The cognitive task involved either 1) recalling a word list of the subject's word-span minus 2 words (SPAN-2) to assess the attention division effect, 2) a word list of subject's word-span (SPAN-O) to assess the working memory effect, or 3) recalling in alphabetical order, a word list of the subject's word-span (SPAN-A) to assess the executive function effect. Word-span corresponds to the longest string of words that can be recalled correctly. The duration of ascent and descent of stairs was used to assess the cognitive-motor interaction. Stair ascent and descent duration did not differ between age groups for the single-motor task, and was similar between single-motor task and SPAN-2 in both groups (p > 0.05). In contrast, stair ascent and descent duration increased with SPAN-O compared with SPAN-2 for both groups (p < 0.01). Stair ascent (p = 0.017) and descent (p = 0.008) were longer in SPAN-A than SPAN-O only in older adults. Healthy aging was not associated with a decrease in the capacity to perform motor-cognitive dual tasks that involved ascending and descending of stairs when the cognitive task only required working memory. However, the decrease in dual-task performance involving executive functioning may reflect a subclinical cognitive decline in healthy older adults.

Impaired math achievement in patients with acute vestibular neuritis

Broad cognitive difficulties have been reported in patients with peripheral vestibular deficit, especially in the domain of spatial cognition. Processing and manipulating numbers relies on the ability to use the inherent spatial features of numbers. It is thus conceivable that patients with acute peripheral vestibular deficit show impaired numerical cognition. Using the number Stroop task and a short math achievement test, we tested 20 patients with acute vestibular neuritis and 20 healthy, age-matched controls. On the one hand, patients showed normal congruency and distance effects in the number Stroop task, which is indicative of normal number magnitude processing. On the other hand, patients scored lower than healthy controls in the math achievement test. We provide evidence that the lower performance cannot be explained by either differences in prior math knowledge (i.e., education) or slower processing speed. Our results suggest that peripheral vestibular deficit negatively affects numerical cognition in terms of the efficient manipulation of numbers. We discuss the role of executive functions in math performance and argue that previously reported executive deficits in patients with peripheral vestibular deficit provide a plausible explanation for the lower math achievement scores. In light of the handicapping effects of impaired numerical cognition in daily living, it is crucial to further investigate the mechanisms that cause mathematical deficits in acute PVD and eventually develop adequate means for cognitive interventions.

Fractionating Executive Functions of Adults With ADHD

OBJECTIVE

To evaluate the performance of adults with ADHD considering the fractionation of executive functions into six different domains.

METHOD

Participants were adult ADHD patients who were not under the acute effects of medication ( n = 48). Their performance was compared with that of a healthy control group ( n = 20) of comparable age, education, and nonverbal intelligence quotient. The cognitive domains assessed were executive shifting, updating, inhibition of prepotent responses, dual-task performance, planning, and access to long-term memory. We also assessed the symptoms of inattention, hyperactivity/impulsivity, anxiety, and depression by validated questionnaires.

RESULTS

Compared with controls, patients reported more symptoms related to ADHD, anxiety and depression symptoms and were impaired in the shifting cost measure and phonemic fluency (measure of access to long-term memory).

CONCLUSION

ADHD in adults selectively impaired executive shifting and access to long-term memory, domains that may alter performance in a wide range of daily tasks.

Semantic control deficits impair understanding of thematic relationships more than object identity

Recent work has suggested a potential link between the neurocognitive mechanisms supporting the retrieval of events and thematic associations (i.e., knowledge about how concepts relate in a meaningful context) and semantic control processes that support the capacity to shape retrieval to suit the circumstances. Thematic associations and events are inherently flexible: the meaning of an item changes depending on the context (for example, lamp goes with reading, bicycle and police). Control processes might stabilise weak yet currently-relevant interpretations during event understanding. In contrast, semantic retrieval for objects (to understand what items are, and the categories they belong to) is potentially constrained by sensory-motor features (e.g., bright light) that change less across contexts. Semantic control and event understanding produce overlapping patterns of activation in healthy participants in left prefrontal and temporoparietal regions, but the potential causal link between these aspects of semantic cognition has not been examined. We predict that event understanding relies on semantic control, due to associations being necessarily context-dependent and variable. We tested this hypothesis in two ways: (i) by examining thematic associations and object identity in patients with semantic aphasia, who have well-documented deficits of semantic control following left frontoparietal stroke and (ii) using the same tasks in healthy controls under dual-task conditions that depleted the capacity for cognitive control. The patients were impaired on both identity and thematic matching tasks, and they showed particular difficulty on non-dominant thematic associations which required greater control over semantic retrieval. Healthy participants showed the same pattern under conditions of divided attention. These findings support the view that semantic control is necessary for organising and constraining the retrieval of thematic associations.

The Neuroanatomical, Neurophysiological and Psychological Basis of Memory: Current Models and Their Origins

This review aims to classify and clarify, from a neuroanatomical, neurophysiological, and psychological perspective, different memory models that are currently widespread in the literature as well as to describe their origins. We believe it is important to consider previous developments without which one cannot adequately understand the kinds of models that are now current in the scientific literature. This article intends to provide a comprehensive and rigorous overview for understanding and ordering the latest scientific advances related to this subject. The main forms of memory presented include sensory memory, short-term memory, and long-term memory. Information from the world around us is first stored by sensory memory, thus enabling the storage and future use of such information. Short-term memory (or memory) refers to information processed in a short period of time. Long-term memory allows us to store information for long periods of time, including information that can be retrieved consciously (explicit memory) or unconsciously (implicit memory).

The residual protective effects of enactment

Research has demonstrated the importance of the quality of initial retrieval events (Test 1) for performance on later memory tests (Test 2). We explored whether enacting words at encoding, relative to simply reading them, provided protection against the detrimental effects of a degraded retrieval experience, through the addition of motor processing to the extant memory representation. Participants encoded a mixed list of enacted and read words, then completed Test 1, and a later Test 2. Encoding and Test 2 were always completed under full attention (FA). Critically though, Test 1 was completed either under FA, or under divided attention (DA) with a distracting task requiring semantic and phonological processing. We predicted a larger enactment effect following DA relative to FA, indicating greater preservation of enacted words from dual-task interference. In Experiment 1, we demonstrated that the enactment effect was indeed larger following DA than FA, indicating greater preservation of enacted words after dual-task interference. In Experiment 2, we showed that this effect was even more potent over longer time scales, which served as a conceptual replication. In Experiment 3, we showed that enactment provides little to no protection when the distracting task requires motor processing, and in Experiment 4, we returned to the phonological distracting task and showed that in contrast with enactment, generation at encoding does not afford the same protection to memory. Taken together, these finding suggest that enactment renders words relatively immune to the detrimental effects of dual-tasking during testing, through the addition of a different kind, rather than a greater degree, of processing to the memory trace at encoding.

Perspectives on working memory: introduction to the special issue

More than 40 years ago, Baddeley and Hitch (1974) published an article with a wealth of experimentation and theorization on working memory, the small amount of information held in mind and often used within cognitive processes such as language comprehension and production, reasoning, and problem solving. We honor this seminal accomplishment in the present special issue, and take this opportunity to provide an introduction to our perspectives on the origin of the theory of working memory, how it has affected our work, what may be coming in the near future, and how the research articles in the present issue contribute to several related themes within the clearly thriving field of working memory.

Resource-sharing in multiple-component working memory

Working memory research often focuses on measuring the capacity of the system and how it relates to other cognitive abilities. However, research into the structure of working memory is less concerned with an overall capacity measure but rather with the intricacies of underlying components and their contribution to different tasks. A number of models of working memory structure have been proposed, each with different assumptions and predictions, but none of which adequately accounts for the full range of data in the working memory literature. We report 2 experiments that investigated the effects of load manipulations on dual-task verbal temporary memory and spatial processing. Crucially, we manipulated cognitive load around the measured memory span of each individual participant. We report a clear effect of increasing memory load on processing accuracy, but only when memory load is increased above each participant’s measured memory span. However, increasing processing load did not affect memory performance. We argue that immediate verbal memory may rely both on a temporary phonological store and on activated traces in long-term memory, with the latter deployed to support memory performance for supraspan lists and when a high memory load is coupled with a processing task. We propose that future research should tailor the load manipulations to the capacities of individual participants and suggest that contrasts between models of working memory may be more apparent than real.

Specific Features of Executive Dysfunction in Alzheimer-Type Mild Dementia Based on Computerized Cambridge Neuropsychological Test Automated Battery (CANTAB) Test Results

BACKGROUND The primary manifestation of Alzheimer's disease (AD) is decline in memory. Dysexecutive symptoms have tremendous impact on functional activities and quality of life. Data regarding frontal-executive dysfunction in mild AD are controversial. The aim of this study was to assess the presence and specific features of executive dysfunction in mild AD based on Cambridge Neuropsychological Test Automated Battery (CANTAB) results. MATERIAL AND METHODS Fifty newly diagnosed, treatment-naïve, mild, late-onset AD patients (MMSE ≥20, AD group) and 25 control subjects (CG group) were recruited in this prospective, cross-sectional study. The CANTAB tests CRT, SOC, PAL, SWM were used for in-depth cognitive assessment. Comparisons were performed using the t test or Mann-Whitney U test, as appropriate. Correlations were evaluated by Pearson r or Spearman R. Statistical significance was set at p<0.05. RESULTS AD and CG groups did not differ according to age, education, gender, or depression. Few differences were found between groups in the SOC test for performance measures: Mean moves (minimum 3 moves): AD (Rank Sum=2227), CG (Rank Sum=623), p<0.001. However, all SOC test time measures differed significantly between groups: SOC Mean subsequent thinking time (4 moves): AD (Rank Sum=2406), CG (Rank Sum=444), p<0.001. Correlations were weak between executive function (SOC) and episodic/working memory (PAL, SWM) (R=0.01-0.38) or attention/psychomotor speed (CRT) (R=0.02-0.37). CONCLUSIONS Frontal-executive functions are impaired in mild AD patients. Executive dysfunction is highly prominent in time measures, but minimal in performance measures. Executive disorders do not correlate with a decline in episodic and working memory or psychomotor speed in mild AD.

Retiring the Central Executive

Reasoning, problem solving, comprehension, learning and retrieval, inhibition, switching, updating, or multitasking are often referred to as higher cognition, thought to require control processes or the use of a central executive. However, the concept of an executive controller begs the question of what is controlling the controller and so on, leading to an infinite hierarchy of executives or “homunculi”. In what is now a QJEP citation classic, Baddeley [Baddeley, A. D. (1996). Exploring the central executive. Quarterly Journal of Experimental Psychology, 49A, 5–28] referred to the concept of a central executive in cognition as a “conceptual ragbag” that acted as a placeholder umbrella term for aspects of cognition that are complex, were poorly understood at the time, and most likely involve several different cognitive functions working in concert. He suggested that with systematic empirical research, advances in understanding might progress sufficiently to allow the executive concept to be “sacked”. This article offers an overview of the 1996 article and of some subsequent systematic research and argues that after two decades of research, there is sufficient advance in understanding to suggest that executive control might arise from the interaction among multiple different functions in cognition that use different, but overlapping, brain networks. The article concludes that the central executive concept might now be offered a dignified retirement.

Poor executive functioning in children born very preterm: Using dual-task methodology to untangle alternative theoretical interpretations

Two alternative theoretical explanations have been proposed for the difficulties with executive functioning observed in children born very preterm (VP; ⩽32 weeks): a general vulnerability (i.e., in attentional and processing capacities), which has a cascading impact on increasingly complex cognitive functions, and a selective vulnerability in executive-level cognitive processes. It is difficult to tease apart this important theoretical distinction because executive functioning tasks are, by default, complex tasks. In the current study, an experimental dual-task design was employed to control for differences in task difficulty in order to isolate executive control. Participants included 50 VP children (mean age=7.29 years) and 39 term peer controls (mean age=7.28 years). The VP group exhibited a greater dual-task cost relative to controls despite experimental control for individual differences in baseline ability on the component single tasks. This group difference also remained under a condition of reduced task difficulty. These results suggest a selective vulnerability in executive-level processes that can be separated from any general vulnerability.

Musical expertise has minimal impact on dual task performance

Studies investigating effect of practice on dual task performance have yielded conflicting findings, thus supporting different theoretical accounts about the organisation of attentional resources when tasks are performed simultaneously. Because practice has been proven to reduce the demand of attention for the trained task, the impact of long-lasting training on one task is an ideal way to better understand the mechanisms underlying dual task decline in performance. Our study compared performance during dual task execution in expert musicians compared to controls with little if any musical experience. Participants performed a music recognition task and a visuo-spatial task separately (single task) or simultaneously (dual task). Both groups showed a significant but similar performance decline during dual tasks. In addition, the two groups showed a similar decline of dual task performance during encoding and retrieval of the musical information, mainly attributed to a decline in sensitivity. Our results suggest that attention during dual tasks is similarly distributed by expert and non-experts. These findings are in line with previous studies showing a lack of sensitivity to difficulty and lack of practice effect during dual tasks, supporting the idea that different tasks may rely on different and not-sharable attentional resources.

Feature Binding Deficits in Subjective Cognitive Decline and in Mild Cognitive Impairment

BACKGROUND

Feature binding is a sensitive and specific cognitive marker for Alzheimer's disease (AD). Subjective cognitive decline (SCD) and mild cognitive impairment (MCI) are clinical categories associated with an increased risk for AD.

OBJECTIVE

To investigate whether the SCD and MCI group are impaired with regard to feature binding.

METHODS

The feature binding test was administered to memory clinic patients with either SCD (n = 19, mean MMSE: 29.2) or with MCI (n = 23, mean MMSE: 26.5), and to a group of healthy controls (HC, n = 23, mean MMSE: 29.0). Participants were assessed with the CERAD Plus neuropsychological test battery. Cognitive performance of the three groups was compared by ANCOVA with age, gender and education as covariates and planned contrasts.

RESULTS

Groups differed in the binding condition. Planned contrasts showed significant differences in adjusted means between HC and SCD (p = 0.003), as well as between HC and MCI (p <  0.0001).

DISCUSSION

The feature binding task detects subtle cognitive impairments in participants with SCD, who are unimpaired in traditional neuropsychological testing. This corroborates the use of feature binding tests in preclinical AD studies and suggests that specific cognitive deficits can be found in SCD. Future studies incorporating AD biomarkers and longitudinal follow-up are needed to further establish the clinical utility of feature binding.