Age-related changes in task-switching components: the role of task uncertainty

The influence of interruptions and planning on serial everyday multitasking in older adults

Cognitive aging research has studied the influence of healthy aging on the ability to multitask. Yet, little is known about the factors that might improve or impair serial multitasking performance in older adults. Three experiments involving younger and older adults assessed the impact of interruptions and planning on a prop-based test of multitasking. In Experiment 1, 26 younger adults and 25 older adults' multitasking abilities were assessed; older adults performed significantly more poorly than younger adults. In Experiment 2, 19 younger and 22 older adults were randomly allocated to a group who experienced a one minute unexpected interruption while multitasking or a group with no interruption. The results showed that, when there was an interruption, the age difference disappeared. In Experiment 3, 32 younger and 30 older adults were randomly allocated to a group who were given 3 minutes to write an outline describing how they intended to approach the multitasking task, and another group who were given 3 minutes to label pictures of everyday objects prior to multitasking. Again, when participants were encouraged to plan, no age difference was found. These results highlight the advantage that interruptions and planning might have on serial everyday multitasking performance in older adults.

The effect of age on task switching: updated and extended meta-analyses

Cognitive flexibility is one of the crucial abilities for human survival. As people get older, whether their flexibility ability will be affected is one of the core research topics in aging research. Researchers have developed a task-switch paradigm in laboratories to mimic daily-life shifting task-set scenarios. However, the empirical evidence is equivocal. Considering every single study may have a biased sample; therefore, we hoped to combine smaller studies, making them into one extensive investigation, which may help show an actual effect. In the current study, we used two meta-analysis techniques, the Brinley plot (along with the State-trace plot) and conventional meta-analysis, to re-evaluate whether healthy aging influences cognitive flexibility. The results of the Brinley plot analysis showed no evidence of switch-specific age-related impairment as indexed by the local switch cost. Yet, older adults performed more slowly than younger adults across task conditions. The conventional meta-analysis further showed that the currently available findings were heterogenous and exhibited publication bias. Therefore, this study suggests that researchers should interpret their results cautiously while using a task-switching paradigm to address older adults' shifting abilities. More parametric variables must be considered and developed in a task-switching paradigm to enhance its sensitivity and reveal older adults' actual shifting ability.

Assessment of the Relationship Between Executive Function and Cardiorespiratory Fitness in Healthy Older Adults

Associations between cardiorespiratory fitness and brain health in healthy older adults have been reported using a variety of cardiorespiratory fitness estimates (CRFe). Using commonly used methods to determine CRF, we assessed the relationship between CRFe and executive function performance. Healthy older adults (n = 60, mean age 68 years, 77% women), underwent three CRF tests: a Maximal Graded Exercise Test performed on a cycle ergometer, the Rockport Fitness Walking Test, and a Non-Exercise Prediction Equation. Executive function was assessed by a computerized cognitive assessment using an N-Back task (updating cost) and a Stroop task (interference cost, global and local switch cost). Multiple hierarchical regression analyses were conducted to assess the relationship between different CRFe and executive function performance. Regardless of age and education, cardiorespiratory fitness estimated from the Maximal Graded Exercise Test and the Rockport Fitness Walking Test was significantly associated with the global switch cost. All CRFe were associated with the interference cost. No association was observed between CRFe and local switching costs or the updating costs. In the present study, not all subcomponents of executive function were related to CRFe. Interestingly, the executive functions that were associated with CRFe are those that are known to be the most affected by aging.

Functional brain changes associated with cognitive training in healthy older adults: A preliminary ALE meta-analysis

Accumulating evidence suggests that cognitive training (CT) programs may provide healthy older adults (OAs) with cognitive benefits that are accompanied by alterations in neural activity. The current review offers the first quantitative synthesis of the available literature on the neural effects of CT in healthy aging. It was hypothesized that OAs would evidence increased and decreased neural activations across various challenging CTs, and that these effects would be observed as significantly altered clusters within regions of the frontoparietal network (FPN). Online databases and reference lists were searched to identify peer-reviewed publications that reported assessment of neural changes associated with CT programs in healthy OAs. Among the 2097 candidate studies identified, 14 studies with a total of 238 participants met inclusionary criteria. GingerALE software was used to quantify neural effects in a whole-brain analysis. The activation likelihood estimation technique revealed significant increases in activation following CT in the left hemisphere middle frontal gyrus, precentral gyrus, and posterior parietal cortex, extending to the superior occipital gyrus. Two clusters of diminished neural activity following CT were identified within the right hemisphere middle frontal gyrus and supramarginal gyrus, extending to the superior temporal gyrus. These results provide preliminary evidence of common neural effects of different CT interventions within regions of the FPN. Findings may inform future investigations of neuroplasticity across the lifespan, including clinical applications of CT, such as assessing treatment outcomes.

Age Differences in the Subcomponents of Executive Functioning

OBJECTIVES

Across the life span, deficits in executive functioning (EF) are associated with poor behavioral control and failure to achieve goals. Though EF is often discussed as one broad construct, a prominent model of EF suggests that it is composed of three subdomains: inhibition, set shifting, and updating. These subdomains are seen in both younger (YA) and older adults (OA), with performance deficits across subdomains in OA. Therefore, our goal was to investigate whether subdomains of EF might be differentially affected by age, and how these differences may relate to broader global age differences in EF.

METHODS

To assess these age differences, we conducted a meta-analysis at multiple levels, including task level, subdomain level, and of global EF. Based on previous work, we hypothesized that there would be overall differences in EF in OA.

RESULTS

Using 1,268 effect sizes from 401 articles, we found overall differences in EF with age. Results suggested that differences in performance are not uniform, such that variability in age effects emerged at the task level, and updating was not as affected by age as other subdomains.

DISCUSSION

These findings advance our understanding of age differences in EF, and stand to inform early detection of EF decline.

Cross-Modal Transfer Following Auditory Task-Switching Training in Old Adults

Maintaining and coordinating multiple task-sets is difficult and leads to costs, however task-switching training can reduce these deficits. A recent study in young adults demonstrated that this training effect occurs at an amodal processing level. Old age is associated with reduced cognitive plasticity and further increases the performance costs when mixing multiple tasks. Thus, cognitive aging might be a limiting factor for inducing cross-modal training effects in a task-switching environment. We trained participants, aged 62-83 years, with an auditory task-switching paradigm over four sessions (2880 total trials), to investigate whether training-related reductions in task-switching costs would also manifest in an untrained visual modality version of the task. Two control groups trained with single tasks (active control) or not trained (passive control) allowed us to identify improvements specific to task-switching training. To make statistical evaluations of any age differences in training and cross-modal transfer, the data from the Kattner cohort were incorporated into the present analysis. Despite the tendency for older adults to respond more cautiously, task-switching training specifically led to a mixing cost reduction in both trained and untrained modalities, the magnitude of which was statistically similar regardless of age. In line with a growing body of research, we failed to observe any far transfer effects in measures of inhibition, working memory or fluid intelligence. Overall, we conclude that any apparent cognitive limitations associated with aging do not prevent cognitive control processes which support set-shifting from improving at an amodal level.

The developmental trajectories of executive function from adolescence to old age

Executive functions demonstrate variable developmental and aging profiles, with protracted development into early adulthood and declines in older age. However, relatively few studies have specifically included middle-aged adults in investigations of age-related differences in executive functions. This study explored the age-related differences in executive function from late childhood through to old age, allowing a more informed understanding of executive functions across the lifespan. Three hundred and fifty participants aged 10 to 86 years-old completed a battery of tasks assessing the specific roles of inhibitory control, working memory, cognitive flexibility, and planning. Results highlighted continued improvement in working memory capacity across adolescence and into young adulthood, followed by declines in both working memory and inhibitory control, beginning from as early as 30-40 years old and continuing into older age. Analyses of planning abilities showed continued improvement across adolescence and into young adulthood, followed by a decline in abilities across adulthood, with a small (positive) change in older age. Interestingly, a dissociation was found for cognitive flexibility; switch costs decreased, yet mixing costs increased across the lifespan. The results provide a description of the developmental differences in inhibitory control, working memory, cognitive flexibility and planning, above any effects of IQ or SES, and highlight the importance of including middle-aged adults in studies seeking to establish a more comprehensive picture of age-related differences in executive function.

Effects of aging in a task-switch paradigm with the diffusion decision model

We investigated aging effects in a task-switch paradigm with degraded stimuli administered to college students, 61-74 year olds, and 75-89 year olds. We studied switch costs (the performance difference between task-repeat and task-switch trials) in terms of accuracy and mean reaction times (RTs). Previous aging research focused on switch costs in terms of mean RTs (with accuracy at ceiling). Our results emphasize the importance of distinguishing between switch costs indexed by accuracy and by RTs because these measures lead to different interpretations. We used the Diffusion Decision Model (DDM; Ratcliff, 1978) to study the cognitive components contributing to switch costs. The DDM decomposed the cognitive process of task switching into multiple components. Two parameters of the model, the quality of evidence on which decisions were based (drift rate) and the duration of processes outside the decision process (nondecision time component), indexed different sources of switch costs. We found that older participants had larger switch costs indexed by nondecision time component than younger participants. This result suggests age-related deficits in preparatory cognitive processes. We also found group differences in switch costs indexed by drift rate for switch trials with high stimulus interference (stimuli with features relevant for both tasks). This result suggests that older participants have less effective cognitive processes involved in resolving interference. Our findings show that age-related effects in separate components of switch costs can be studied with the DDM. Our results demonstrate the utility of using discrimination tasks with degraded stimuli in conjunction with model-based analyses. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Plasticity in brain activity dynamics after task-shifting training in older adults

Cognitive control is supported by a dynamic interplay of transient (i.e., trial-related) brain activation across fronto-parietal networks and sustained (i.e., block-related) activation across fronto-striatal networks. Older adults show disturbances in this dynamic functional recruitment. There is evidence suggesting that cognitive-control training may enable older adults to redistribute their brain activation across cortical and subcortical networks, which in turn can limit behavioral impairments. However, previous studies have only focused on spatial rather than on temporal aspects of changes in brain activation. In the present study, we examined training-related functional plasticity in old age by applying a hybrid fMRI design that sensitively tracks the spatio-temporal interactions underlying brain-activation changes. Fifty healthy seniors were assigned to a task-shifting training or an active-control group and their pretest/posttest activation-change maps were compared against 25 untrained younger adults. After training, older adults showed the same performance as untrained young adults. Compared to the control group, task-shifting training promoted proactive (i.e., early, cue-related) changes in transient mechanisms supporting the maintenance and top-down biasing of task-set representations in a specific prefrontal circuitry; reactive (i.e., late, probe-related) changes in transient mechanisms supporting response-selection processes in dissociable fronto-parietal networks; overall reductions of sustained activation in striatal circuits. Results highlight the importance of spatio-temporal interactions in training-induced neural changes in age.

Delayed reconfiguration of a non-emotional task set through reactivation of an emotional task set in task switching: an ageing study

In our everyday life, we frequently switch between different tasks, a faculty that changes with age. However, it is still not understood how emotion impacts on age-related changes in task switching. Using faces with emotional and neutral expressions, Experiment 1 investigated younger (n = 29; 18-38 years old) and older adults' (n = 32; 61-80 years old) ability to switch between an emotional and a non-emotional task (i.e. responding to the face's expression vs. age). In Experiment 2, younger and older adults also viewed emotional and neutral faces, but switched between two non-emotional tasks (i.e. responding to the face's age vs. gender). Data from Experiment 1 demonstrated that switching from an emotional to a non-emotional task was slower when the expression of the new face was emotional rather than neutral. This impairment was observed in both age groups. In contrast, Experiment 2 revealed that neither younger nor older adults were affected by block-wise irrelevant emotion when switching between two non-emotional tasks. Overall, the findings suggest that task-irrelevant emotion can impair task switching through reactivation of the competing emotional task set. They also suggest that this effect and the ability to shield task-switching performance from block-wise irrelevant emotion are preserved in ageing.

The SwAD-Task – An Innovative Paradigm for Measuring Costs of Switching Between Different Attentional Demands

Task switching paradigms are frequently used to identify costs of switching between modalities, spatiality, attributes, rules, etc., but switching between different attentional demands has been somehow neglected. The present study introduces an innovative paradigm, that allows to test single attentional demands (such as selective and divided attention), and more importantly the process of switching between these demands. We examined the feasibility of the paradigm by focusing on the demands of selective and divided attention with a sample of 94 people (age: M = 21.44 years, SD = 2.68; 76 women). In addition, we tested correlations between the implemented single attentional demands and commonly used measures of selective and divided attention. Results show no general difference between individual assessments under single demand conditions. Reaction times under divided attention are significantly higher compared to selective attention. In the switching condition, reaction times in both demands increase with increased switching. Furthermore, switching costs significantly increase in selective but not in divided attention. Means of selective and divided attention in single and switching conditions significantly correlate with a commonly used measure of selective attention. Means of divided attention under single demand significantly correlate with performance in a commonly used dual-task paradigm. Summarizing the present findings, it can be stated that the introduced paradigm comprises a feasible way for quantifying the process of switching attention between different demands.

Age-Based Differences in Task Switching Are Moderated by Executive Control Demands

Objectives

Recent work has identified different aspects of executive function that may underlie cognitive changes associated with age. The current study used a multifactorial design to investigate age sensitivity in the ability to shift between different task sets and the interaction of this ability with several specific aspects of executive control.

Method

A large, well-characterized sample of younger (n = 40) and clinically healthy older (n = 51) adults completed a task switching paradigm in which 3 aspects of executive control were manipulated between subjects: a) sensorimotor demand (the number of distinct stimulus-response options); b) stimulus-level interference (i.e., flanker effects); and c) updating/monitoring (the frequency of task switches).

Results

Unique age-related deficits were observed for different aspects of local task switching performance costs and updating/monitoring, but not for interference. Sensorimotor demand was also an important additional factor that interacted with task switching performance.

Discussion

Our findings suggest that task switching, coupled with infrequent and unexpected transitions from one task set to another, in the context of high motoric demands, is particularly difficult for older adults.

Neurocompensatory Effects of the Default Network in Older Adults

The hemispheric asymmetry reduction in older adults (HAROLD) is a neurocompensatory process that has been observed across several cognitive functions but has not yet been examined in relation to task-induced relative deactivations of the default mode network. The present study investigated the presence of HAROLD effects specific to neural activations and deactivations using a functional magnetic resonance imaging (fMRI) n-back paradigm. It was hypothesized that HAROLD effects would be identified in relative activations and deactivations during the paradigm, and that they would be associated with better 2-back performance. Forty-five older adults (M age = 63.8; range = 53-83) were administered a verbal n-back paradigm during fMRI. For each participant, the volume of brain response was summarized by left and right frontal regions of interest, and laterality indices (LI; i.e., left/right) were calculated to assess HAROLD effects. Group level results indicated that age was significantly and negatively correlated with LI (i.e., reduced left lateralization) for deactivations, but positively correlated with LI (i.e., increased left lateralization) for activations. The relationship between age and LI for deactivation was significantly moderated by performance level, revealing a stronger relationship between age and LI at higher levels of 2-back performance. Findings suggest that older adults may employ neurocompensatory processes specific to deactivations, and task-independent processes may be particularly sensitive to age-related neurocompensation.

Disordered Eating Attitudes and Behavioral and Neuroelectric Indices of Cognitive Flexibility in Individuals with Overweight and Obesity

Impairment in cognitive flexibility is a trait characteristic among individuals with diagnosed eating disorders. However, the extent to which these relationships exist in individuals with overweight or obesity remains unclear. Furthermore, there is a lack of knowledge characterizing the neural underpinnings of these relationships. The current study aimed to investigate disordered eating attitudes and cognitive flexibility among adults with overweight and obesity. The Eating Attitudes Test (EAT-26) and a task-switching paradigm were collected from 132 adults (50 males, Body Mass Index (BMI) = 32.0 ± 5.8 kg/m²). Behavioral measures (accuracy and reaction time (RT)) and neuroelectric indices (amplitude and latency) of the P3 component were assessed. Hierarchical linear regressions, following adjustment of age, sex, intelligence quotient (IQ), weight status, and diet quality were developed using summative and subscale scores of the EAT-26. Higher EAT-26 summative scores, and the Dieting subscale, were related to longer RT. Only the Bulimia and Food Preoccupation subscale was related to longer P3 latency. The relationship between disordered eating attitudes and cognitive flexibility extends to individuals with overweight and obesity and is independent of age, sex, IQ, weight status, and diet quality. These findings are important, as differences in cognitive flexibility can lead to behavioral rigidity. Future work should aim to examine other neuroelectric components to identify where differences driving behavioral latencies may be occurring.

The shifting self in aging

BACKGROUND AND AIMS

This study investigated the ability of older adults to shift between self-images.

METHODS

We designed a shifting-self task in which older adults and younger adults were invited to produce statements describing their physical self (e.g., "I am tall") and psychological self (e.g., "I am cheerful"). Participants were invited to shift between physical-self statements and psychological-self statements and, on a control task, to produce two blocks of physical-self statements and psychological-self statements. They also performed a typical shifting task (i.e., the plus-minus task).

RESULTS

Analysis showed slower completion time on the shifting-self task in older adults than in younger adults. Time to complete the shifting-self task was longer than that for the control task in both older and younger adults. Performances on the shifting-self task were significantly correlated with performances on the plus-minus task.

DISCUSSION

We hypothesized that older adults take more time to shift between self-images because they enjoy self-stability. In other words, the tendency of older adults to shift between self-images more slowly than younger adults might be because they have more consistent or stable self-concepts, and are therefore less inclined to "change" their self-images.

Effects of rule uncertainty on cognitive flexibility in a card-sorting paradigm

Cognitive flexibility has been studied in two separate research traditions. Neuropsychologists typically rely on rather complex assessment tools such as the Wisconsin Card Sorting Test (WCST). In contrast, task-switching paradigms are used in experimental psychology to obtain more specific measures of cognitive flexibility. We aim to contribute to the integration of these research traditions by examining the role of the key factor that differs between the WCST and experimental task-switching paradigms: rule uncertainty. In two experimental studies, we manipulated the degree of rule uncertainty after rule switches in a computerized version of the WCST. Across a variety of task parameters, reducing rule uncertainty consistently impaired the speed and accuracy of responses when the rule designated to be more likely turned out to be incorrect. Other performance measures such as the number of perseverative errors were not significantly affected by rule uncertainty. We conclude that a fine-grained analysis of WCST performance can dissociate behavioural indicators that are affected vs. unaffected by rule uncertainty. By this means, it is possible to integrate WCST results and findings obtained from task-switching paradigms that do not involve rule uncertainty.

General Slowing and Education Mediate Task Switching Performance Across the Life-Span

Objective: This study considered the potential role of both protective factors (cognitive reserve, CR) and adverse ones (general slowing) in modulating cognitive flexibility in the adult life-span. Method: Ninety-eight individuals performed a task-switching (TS) paradigm in which we adopted a manipulation concerning the timing between the cue and the target. Working memory demands were minimized by using transparent cues. Additionally, indices of cognitive integrity, depression, processing speed and different CR dimensions were collected and used in linear models accounting for TS performance under the different time constraints. Results: The main results showed similar mixing costs and higher switching costs in older adults, with an overall age-dependent effect of general slowing on these costs. The link between processing speed and TS performance was attenuated when participants had more time to prepare. Among the different CR indices, formal education only was associated with reduced switch costs under time pressure. Discussion: Even though CR is often operationalized as a unitary construct, the present research confirms the benefits of using tools designed to distinguish between different CR dimensions. Furthermore, our results provide empirical support to the assumption that processing speed influence on executive performance depends on time constraints. Finally, it is suggested that whether age differences appear in terms of switch or mixing costs depends on working memory demands (which were low in our tasks with transparent cues).

Can Driving-Simulator Training Enhance Visual Attention, Cognition, and Physical Functioning in Older Adults?

Virtual reality offers a good possibility for the implementation of real-life tasks in a laboratory-based training or testing scenario. Thus, a computerized training in a driving simulator offers an ecological valid training approach. Visual attention had an influence on driving performance, so we used the reverse approach to test the influence of a driving training on visual attention and executive functions. Thirty-seven healthy older participants (mean age: 71.46 ± 4.09; gender: 17 men and 20 women) took part in our controlled experimental study. We examined transfer effects from a four-week driving training (three times per week) on visual attention, executive function, and motor skill. Effects were analyzed using an analysis of variance with repeated measurements. Therefore, main factors were group and time to show training-related benefits of our intervention. Results revealed improvements for the intervention group in divided visual attention; however, there were benefits neither in the other cognitive domains nor in the additional motor task. Thus, there are no broad training-induced transfer effects from such an ecologically valid training regime. This lack of findings could be addressed to insufficient training intensities or a participant-induced bias following the cancelled randomization process.

Differential age-related changes in localizing a target among distractors across an extended visual field

Age differences in the spatial distribution of attention over a wide field of view have only been described in terms of the spatial extent, leaving the topographical aspect unexplored. This study examined age differences between younger and older adults in good general health in an important topographical characteristic, the asymmetry between the upper and lower visual fields. In Experiment 1, we found age differences across the entire attentional visual field. In addition, age differences were greater in the upper compared to the lower field. In Experiment 2, we examined whether the finding of a greater age difference in the ability to localize a target among distractors in the upper visual field in Experiment 1 was a result of possible differential age differences between the upper and lower visual fields in the ability to localize a target even when there was no distractor competing for attention. Our results suggested that the age differences we observed were linked to age differences in the ability to filter out distractors that compete with the target for attention rather than the ability to process only the target over a wide field of view. While younger adults demonstrated an upper visual field advantage in the ability to localize a target among distractors, there was no such field advantage in older adults. We discuss this finding of diminished upper visual field advantage in older adults in light of an account of pervasive loss of neural specialization with age. We postulate that one possible explanation of age differences in the asymmetry between the upper and lower visual fields may be an adaptation to age-related physical decline. We also discuss important implications of our findings in risks of falls and vehicle crashes.

Development of an eye-tracking method to assess mental set switching in people with aphasia

BACKGROUND

Deficits in cognitive flexibility contribute to impaired functional communication in people with aphasia. Understanding the relationship between functional communication and cognitive flexibility in people with neurologic communication disorders is important. However, traditional methods to assess mental set switching pose significant linguistic, cognitive and motoric response confounds. Eye-tracking methods have great potential to address these challenges.

AIMS

The goal of this study was to develop and validate an eye-tracking method to index mental set switching in individuals without neurological impairment based upon performance on a nonlinguistic switching task.

METHODS

Eye movements of 20 adults without communication disorders were recorded as they completed a switching task, requiring participants to match stimuli to one or two search criteria (colour or shape) in single- and mixed-task conditions. Differences between single and mixed conditions were assessed with eye-tracking measures. Performance on the eye-tracking task was compared to standardized measures of cognitive flexibility.

RESULTS

Eye-tracking measures indexed significant differences between nonswitch and switch trials within and between single- and mixed-task condition. Some standardized assessment measures correlated significantly with the eye movement measures.

CONCLUSIONS

Results support the construct validity of the novel eye-tracking method for assessing cognitive switching in language-normal adults. Clinical and research implications are discussed.

Age Differences in the Transfer and Maintenance of Practice-Induced Improvements in Task Switching: The Impact of Working-Memory and Inhibition Demands

Recent aging studies on training in task switching found that older adults showed larger improvements to an untrained switching task as younger adults do. However, less clear is what type of cognitive control processes can explain these training gains as participants were trained with a particular type of switching task including bivalent stimuli, requiring high inhibition demands, and no task cues helping them keeping track of the task sequence, and by this, requiring high working-memory (WM) demands. The aims of this study were first to specify whether inhibition, WM, or switching demands are critical for the occurrence of transfer and whether this transfer depends on the degree of overlap between training and transfer situation; and second to assess whether practiced-induced gains in task switching can be maintained over a longer period of time. To this end, we created five training conditions that varied in switching (switching vs. single task training), inhibition (switching training with bivalent or univalent stimuli), and WM demands (switching training with or without task cues). We investigated 81 younger adults and 82 older adults with a pretest-training-posttest design and a follow-up measurement after 6 months. Results indicated that all training and age groups showed improvements in task switching and a differential effect of training condition on improvements to an untrained switching task in younger and older adults. For younger adults, we found larger improvements in task switching for the switching groups than the single-task training group independently of inhibition and WM demands, suggesting that practice in switching is most critical. However, these benefits disappeared after 6 months. In contrast, for older adults training groups practicing task switching under high inhibition demands showed larger improvements to untrained switching tasks than the other groups. Moreover, these benefits were maintained over time. We also found that the transfer of benefits in task switching was larger with greater overlap between training and transfer situation. However, results revealed no evidence for transfer to other untrained cognitive task. Overall, the findings suggest that training in resolving interference while switching between two tasks is most critical for the occurrence of transfer in the elderly.

The role of working memory capacity and interference resolution mechanisms in task switching

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response-distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. A total of 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response-distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores, which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching.

The Roles for Prior Visual Experience and Age on the Extraction of Egocentric Distance

OBJECTIVES

In a well-lit room, observers can generate well-constrained estimates of the distance to an object on the floor even with just a fleeting glimpse. Performance under these conditions is typically characterized by some underestimation but improves when observers have previewed the room. Such evidence suggests that information extracted from longer durations may be stored to contribute to the perception of distance at limited time frames. Here, we examined the possibility that this stored information is used differentially across age. Specifically, we posited that older adults would rely more than younger adults on information gathered and stored at longer glimpses to judge the distance of briefly glimpsed objects.

METHOD

We collected distance judgments from younger and older adults after brief target glimpses. Half of the participants were provided 20-s previews of the testing room in advance; the other half received no preview.

RESULTS

Performance benefits were observed for all individuals with prior visual experience, and these were moderately more pronounced for the older adults.

DISCUSSION

The results suggest that observers store contextual information gained from longer viewing durations to aid in the perception of distance at brief glimpses, and that this memory becomes more important with age.

Task-Related Vigilance During Word Recognition in Noise for Older Adults with Hearing Loss

BACKGROUND/STUDY CONTEXT

Vigilance refers to the ability to sustain and adapt attentional focus in response to changing task demands. For older adults with hearing loss, vigilant listening may be particularly effortful and variable across individuals. This study examined the extent to which neural responses to sudden, unexpected changes in task structure (e.g., from rest to word recognition epochs) were related to pupillometry measures of listening effort.

METHODS

Individual differences in the task-evoked pupil response during word recognition were used to predict functional magnetic resonance imaging (MRI) estimates of neural responses to salient transitions between quiet rest, noisy rest, and word recognition in unintelligible, fluctuating background noise. Participants included 29 older adults (M = 70.2 years old) with hearing loss (pure tone average across all frequencies = 36.1 dB HL [hearing level], SD = 6.7).

RESULTS

Individuals with a greater average pupil response exhibited a more vigilant pattern of responding on a standardized continuous performance test (response time variability across varying interstimulus intervals r(27) = .38, p = .04). Across participants there was widespread engagement of attention- and sensory-related cortices in response to transitions between blocks of rest and word recognition conditions. Individuals who exhibited larger task-evoked pupil dilation also showed even greater activity in the right primary auditory cortex in response to changes in task structure.

CONCLUSION

Pupillometric estimates of word recognition effort predicted variation in activity within cortical regions that were responsive to salient changes in the environment for older adults with hearing loss. The results of the current study suggest that vigilant attention is increased amongst older adults who exert greater listening effort.

Positive explorers: modeling dynamic control in normal aging

Situations in which there are multiple changes occurring all at once and which demand complex decisions to be made are common throughout life, but little is known about how normal aging influences performance on these types of scenarios. To determine performance differences associated with normal aging, we test older and younger adults in a dynamic control task. The task involves the control of a single output variable over time via multiple and uncertain input controls. The Single Limited Input, Dynamic Exploratory Responses (SLIDER) computational model, is implemented to determine the behavioral characteristics associated with normal aging in a dynamic control task. Model-based analysis demonstrates a unique performance signature profile associated with normal aging. Specifically, older adults exhibit a positivity effect in which they are more influenced by positively valenced feedback, congruent with previous research, as well as enhanced exploratory behavior.

Dissociative global and local task-switching costs across younger adults, middle-aged adults, older adults, and very mild Alzheimer's disease individuals

A task-switching paradigm was used to examine differences in attentional control across younger adults, middle-aged adults, healthy older adults, and individuals classified in the earliest detectable stage of Alzheimer's disease (AD). A large sample of participants (570) completed a switching task in which participants were cued to classify the letter (consonant/vowel) or number (odd/even) task-set dimension of a bivalent stimulus (e.g., A 14), respectively. A pure block consisting of single-task trials and a switch block consisting of nonswitch and switch trials were completed. Local (switch vs. nonswitch trials) and global (nonswitch vs. pure trials) costs in mean error rates, mean response latencies, underlying reaction time (RT) distributions, along with stimulus-response congruency effects were computed. Local costs in errors were group invariant, but global costs in errors systematically increased as a function of age and AD. Response latencies yielded a strong dissociation: Local costs decreased across groups whereas global costs increased across groups. Vincentile distribution analyses revealed that the dissociation of local and global costs primarily occurred in the slowest response latencies. Stimulus-response congruency effects within the switch block were particularly robust in accuracy in participants in the very mild AD group. We argue that the results are consistent with the notion that the impaired groups show a reduced local cost because the task sets are not as well tuned, and hence produce minimal cost on switch trials. In contrast, global costs increase because of the additional burden on working memory of maintaining 2 task sets.

Relationships between strategy switching and strategy switch costs in young and older adults: a study in arithmetic problem solving

BACKGROUND/STUDY CONTEXT: This study investigated age-related differences in within-item strategy switching (i.e., revising initial strategy choices to select a better strategy while solving a given problem) and in strategy switch costs (i.e., longer latencies when participants switch strategies than when they do not switch strategy during strategy execution).

METHODS

In a computational estimation task, participants had to give approximate products to two-digit multiplication problems (e.g., 41×67) while rounding up (i.e., do 50×70 for 41×67) or rounding down (i.e., do 40×60 for 41×67) operands to their nearest decades. After executing a cued strategy during 1000 ms, participants had the possibility to switch to another strategy (or repeat the same strategy) in a selection condition. In an execution condition, participants were forced to repeat the same strategy or to switch to another strategy.

RESULTS

It was found that (1) older adults were less able than young adults to switch strategy after starting to execute a cued strategy (36.1% vs. 45.8%); (2) older adults showed larger switch costs than young adults (422 vs. 223 ms); and (3) strategy switches and strategy switch costs correlated in older adults but not in young adults.

CONCLUSION

These findings have important implications for our understanding of the mechanisms underlying within-item strategy switching and aging effects on these mechanisms as well as, more generally, of strategic variations during cognitive aging.

Latent profiles of executive functioning in healthy young adults: evidence of individual differences in hemispheric asymmetry

Two competing theoretical models of individual differences in executive functioning (EF) were examined: the Prefrontal Convexity Model and the Hemispheric Asymmetry Model. Neurologically healthy individuals (N = 315; mean age 20.8) completed a modified switching task (MST) and the Attention Network Test (ANT) in a single testing session. Data analysis was conducted in two phases. In the first phase (model identification), latent profile analysis was applied to MST variables measuring the abilities to form, switch, and maintain mental sets under conditions designed to tax left or right hemisphere resources. In the second phase (model validation), participant clusters obtained from the first phase were compared on the ANT. The Model Identification phase yielded a 3-profile solution consistent with the Hemispheric Asymmetry Model. Profile 1 (N = 203) was characterized by average EF performances. Profile 2 (N = 43) revealed a set maintenance weakness under non-verbal conditions. Profile 3 (N = 38) demonstrated weaknesses in cognitive flexibility combined with poor executive performances under verbal conditions. The Model Validation phase confirmed group differences. Profile 1 demonstrated average EF performances. Profile 2 demonstrated distractibility and decreased alertness, consistent with a right hemisphere weakness. Profile 3 demonstrated cognitive rigidity in the absence of external cues, consistent with a left hemisphere weakness. Individual differences in EF appear to follow a Hemispheric Asymmetry Model of EF among neurologically healthy adults. Investigating the relationship between hemispherically mediated executive functions and other individual difference factors known to confer health risk or resilience could inform numerous disciplines within the field of psychology.

Response-Conflict Moderates the Cognitive Control of Episodic and Contextual Load in Older Adults

OBJECTIVES

Decline in cognitive control is one of the primary cognitive changes in normal aging. Reaching a consensus regarding the nature of these age-related changes, however, is complicated by the complexity of cognitive control as a construct.

METHODS

Healthy older and younger adults participated in a multifactorial test of cognitive control. Within participants, the procedure varied as a function of the amount contextual load, episodic load, and response-conflict load present.

RESULTS

We found that older adults showed impaired performance relative to younger adults. We also found, however, that the response selection process underlying the response-conflict manipulation was a major moderator of age-related differences in both the contextual and episodic load conditions-suggesting a hierarchical organization.

DISCUSSION

These findings are consistent with previous findings, suggesting that deficits in cognitive control in older adults are directly related to the resolution of response-conflict and that other apparent deficits may be derivative upon the more basic response-conflict related deficit.

Aging and random task switching: the role of endogenous versus exogenous task selection

BACKGROUND/STUDY CONTEXT: Task switching research typically emphasizes two robust shifting effects between competing tasks: mixing costs (MCs), which indicate less efficient performance in mixed-task versus single-task conditions, and switch costs (SCs), which reflect differences between switch trials and repetition trials within mixed-task conditions. The current study examined age-related MC and SC influenced by the method of task selection in two procedures.

METHODS

Twenty-six young adults, 18 to 21 years of age (M = 18.4, SD = 1.1), and 25 older adults, 74 to 87 years of age (M = 80.3, SD = 5.4), participated as part of the Cognition, Health, and Aging Project (CHAP). Younger and older adults' performed cued and voluntary task switching, requiring a random sequence of task changes, placing demands on externally versus internally directed processes.

RESULTS

Results indicated that SCs were not disproportionately larger for older adults during an exogenous switching condition, but large age differences in MCs were present beyond the degree predicted by differences in baseline speed. In an endogenous switching condition, small age differences were present both for MCs and SCs, although further age differences were evident in older adults' reduced switch rates.

CONCLUSION

These findings suggest that older adults are substantially slower at updating repeated task sets during exogenous switching, but partially counter these effects by adopting a more persistent within-set mode of processing during endogenous switching.

Task uncertainty can account for mixing and switch costs in task-switching

Cognitive control is required in situations that involve uncertainty or change, such as when resolving conflict, selecting responses and switching tasks. Recently, it has been suggested that cognitive control can be conceptualised as a mechanism which prioritises goal-relevant information to deal with uncertainty. This hypothesis has been supported using a paradigm that requires conflict resolution. In this study, we examine whether cognitive control during task switching is also consistent with this notion. We used information theory to quantify the level of uncertainty in different trial types during a cued task-switching paradigm. We test the hypothesis that differences in uncertainty between task repeat and task switch trials can account for typical behavioural effects in task-switching. Increasing uncertainty was associated with less efficient performance (i.e., slower and less accurate), particularly on switch trials and trials that afford little opportunity for advance preparation. Interestingly, both mixing and switch costs were associated with a common episodic control process. These results support the notion that cognitive control may be conceptualised as an information processor that serves to resolve uncertainty in the environment.

Age Differences in Memory-Based Task Switching With and Without Cues

The study investigated the neuronal mechanisms of age-related changes in mixing costs during memory-based task switching with two levels of working memory (WM) load. Forty-eight healthy younger and 45 healthy older participants performed a memory based (high WM load) and a memory plus cue based (low WM load) switching task while event-related brain potentials (ERPs) were registered. Older adults revealed larger mixing costs in both reaction time (RT) and accuracy at higher WM loads than younger adults. The presence of explicit cues substantially reduced age differences in mixing costs for accuracy but not for RT. Similarly, no age differences regarding local switch costs were found at lower WM load. Surprisingly, larger RT local costs in younger adults than in older adults were found in the memory-based block. The CNV was reduced under high WM load and positively correlated with accuracy mixing costs in older adults. The target-locked occipital N1 and fronto-central P2 were larger in older adults relative to younger adults irrespective of WM load. The P2 latency reflected the pattern of switch costs observed in behavioral data. Moreover, P2 latency positively correlated with RT mixing costs in older adults. Elderly also showed a delayed N2 and a delayed and reduced P3b. The results suggest that age-related differences in mixing costs may be partially due to a less efficient task preparation and task set maintenance (CNV) in elderly. However, elderly attempted to compensate for these deficits by permanent activation of mechanisms relating to stimulus encoding (N1) and task-set retrieval (P2). Finally, the delayed fronto-central N2 as well as the delayed and reduced parietal P3b strongly suggest delays of response selection and working memory updating in elderly due to an increase in selection threshold or in response selection variability constituting the performance decline.

Reactive control processes contributing to residual switch cost and mixing cost across the adult lifespan

In task-switching paradigms, performance is better when repeating the same task than when alternating between tasks (switch cost) and when repeating a task alone rather than intermixed with another task (mixing cost). These costs remain even after extensive practice and when task cues enable advanced preparation (residual costs). Moreover, residual reaction time mixing cost has been consistently shown to increase with age. Residual switch and mixing costs modulate the amplitude of the stimulus-locked P3b. This mixing effect is disproportionately larger in older adults who also prepare more for and respond more cautiously on these “mixed” repeat trials (Karayanidis et al., 2011). In this paper, we analyze stimulus-locked and response-locked P3 and lateralized readiness potentials to identify whether residual switch and mixing cost arise from the need to control interference at the level of stimulus processing or response processing. Residual mixing cost was associated with control of stimulus-level interference, whereas residual switch cost was also associated with a delay in response selection. In older adults, the disproportionate increase in mixing cost was associated with greater interference at the level of decision-response mapping and response programming for repeat trials in mixed-task blocks. These findings suggest that older adults strategically recruit greater proactive and reactive control to overcome increased susceptibility to post-stimulus interference. This interpretation is consistent with recruitment of compensatory strategies to compensate for reduced repetition benefit rather than an overall decline on cognitive flexibility.

Age-related decline in divided-attention: from theoretical lab research to practical real-life situations

The purpose of this advanced review is to provide readers with an up-to-date synopsis of age-related changes in divided-attention abilities. An interdisciplinary approach is taken, supplying readers with evidence from very structured laboratory studies and findings from more ecological research studies that target real-life divided-attention situations (i.e., walking and talking). The review goes beyond the reported age-related declines in divided-attention abilities and offers the reader an overview of current cognitive (dual-task) training findings which suggest that these declines can be diminished with training. The contents of this review and the future directions proposed demonstrate that divided-attention research and its recent application to aging and mobility has become a major and fast growing scientific field of investigation. WIREs Cogn Sci 2013, 4:623-640. doi: 10.1002/wcs.1252 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

Reconciling the influence of task-set switching and motor inhibition processes on stop signal after-effects

Executive response functions can be affected by preceding events, even if they are no longer associated with the current task at hand. For example, studies utilizing the stop signal task have reported slower response times to “GO” stimuli when the preceding trial involved the presentation of a “STOP” signal. However, the neural mechanisms that underlie this behavioral after-effect are unclear. To address this, behavioral and electroencephalography (EEG) measures were examined in 18 young adults (18–30 years) on “GO” trials following a previously “Successful Inhibition” trial (pSI), a previously “Failed Inhibition” trial (pFI), and a previous “GO” trial (pGO). Like previous research, slower response times were observed during both pSI and pFI trials (i.e., “GO” trials that were preceded by a successful and unsuccessful inhibition trial, respectively) compared to pGO trials (i.e., “GO” trials that were preceded by another “GO” trial). Interestingly, response time slowing was greater during pSI trials compared to pFI trials, suggesting executive control is influenced by both task set switching and persisting motor inhibition processes. Follow-up behavioral analyses indicated that these effects resulted from between-trial control adjustments rather than repetition priming effects. Analyses of inter-electrode coherence (IEC) and inter-trial coherence (ITC) indicated that both pSI and pFI trials showed greater phase synchrony during the inter-trial interval compared to pGO trials. Unlike the IEC findings, differential ITC was present within the beta and alpha frequency bands in line with the observed behavior (pSI > pFI > pGO), suggestive of more consistent phase synchrony involving motor inhibition processes during the ITI at a regional level. These findings suggest that between-trial control adjustments involved with task-set switching and motor inhibition processes influence subsequent performance, providing new insights into the dynamic nature of executive control.

Cognitive control and the COMT Val¹⁵⁸Met polymorphism: genetic modulation of videogame training and transfer to task-switching efficiency

The study investigated whether successful transfer of game-based cognitive improvements to untrained tasks might be modulated by preexisting neuro-developmental factors, such as genetic variability related to the catechol-O-methyltransferase (COMT)-an enzyme responsible for the degradation of dopamine. The COMT Val(158)Met genotype may differentially affect cognitive stability and flexibility, and we hypothesized that Val/Val homozygous individuals (who possess low prefrontal dopamine levels) show more pronounced cognitive flexibility than Met/-carriers (who possess high prefrontal dopamine levels). We trained participants, genotyped for the COMT Val(158)Met polymorphism on playing "Half-Life 2", a first-person shooter game which has been shown to improve cognitive flexibility. Pre-training (baseline) and post-training measures of cognitive flexibility were acquired by means of a task-switching paradigm. As expected, Val/Val homozygous individuals showed larger beneficial transfer effects than Met/-carriers. Our findings support the idea that genetic predisposition modulates transfer effects and that playing first-person shooter games promotes cognitive flexibility in individuals with a suitable genetic predisposition.

Impact of five SNPs in dopamine-related genes on executive function

OBJECTIVES

Dopamine neurotransmission is a critical factor for executive function, which is controlled by the prefrontal cortex in humans. Although the contribution of genetic factors to the regulation of brain dopaminergic activity is widely acknowledged, identification of a genotype-phenotype association has not yet been clearly established. In this study, we therefore evaluated the effects of five functional single-nucleotide polymorphisms (SNPs) in specific genes related to dopamine neurotransmission on executive function in a general population.

MATERIALS AND METHODS

Participants of the health examination at the Shimane Institute of Health Science were recruited for this study (n = 964). To evaluate executive function, the Frontal Assessment Battery (FAB) was administered. SNPs were genotyped using the TaqMan method.

RESULTS

A significant association was found between an SNP in the catechol-O-methyltransferase (COMT) gene (rs4680) encoding the low-activity Met allele and FAB score (P = 0.003). Of note, the flexibility subset of the FAB was associated with the SNP in COMT (P = 0.003) after adjustment for confounding factors. The generalized multifactor dimensionality reduction method identified that the combination of two SNPs in the COMT gene (rs4680) and the dopamine D4 receptor gene (rs1800955) had a significant effect on FAB score.

CONCLUSIONS

Our study indicates a contribution of rs4680 in the COMT gene to the variability in executive function, as assessed by the FAB. In addition, we have indicated that a complex gene-gene interaction between SNPs in the genes related to dopamine neurotransmission may influence executive function in a general population.

Partially overlapping mechanisms of language and task control in young and older bilinguals

The current study tested the hypothesis that bilinguals rely on domain-general mechanisms of executive control to achieve language control by asking if linguistic and nonlinguistic switching tasks exhibit similar patterns of aging-related decline. Thirty young and 30 aging bilinguals completed a cued language-switching task and a cued color-shape switching task. Both tasks demonstrated significant aging effects, but aging-related slowing and the aging-related increase in errors were significantly larger on the color-shape than on the language task. In the language task, aging increased language-switching costs in both response times and errors, and language-mixing costs only in response times. In contrast, the color-shape task exhibited an aging-related increase in costs only in mixing errors. Additionally, a subset of the older bilinguals could not do the color-shape task, but were able to do the language task, and exhibited significantly larger language-switching costs than matched controls. These differences, and some subtle similarities, in aging effects observed across tasks imply that mechanisms of nonlinguistic task and language control are only partly shared and demonstrate relatively preserved language control in aging. More broadly, these data suggest that age deficits in switching and mixing costs may depend on task expertise, with mixing deficits emerging for less-practiced tasks and switching deficits for highly practiced, possibly "expert" tasks (i.e., language).

A review of intentional and cognitive control in autism

Different clinical studies have provided empirical evidence for impairments in cognitive control in individuals with autism spectrum disorders (ASD). The challenge arises, however, when trying to specify the neurocognitive mechanisms behind the reported observations of deviant patterns of goal-directed behavior in ASD. Studies trying to test specific assumptions by applying designs that are based on a more controlled experimental conditions often fail in providing strong evidence for an impairment in specific cognitive functions. In this review, we summarize and critically reflect on behavioral findings and their theoretical explanations regarding cognitive control processing in autism, also from a developmental perspective. The specific focus of this review is the recent evidence of deficits in intentional control – a specific subset of cognitive control processes that biases the choice of our behavioral goals – coming from different research fields. We relate this evidence to the cognitive rigidity observed in ASD and argue that individuals with ASD experience problems at the intentional level rather than at the level of implementation of intentions. Both these processes are related to cognitive control mechanisms but in different ways. Finally, we discuss new directions in studying cognitive control in ASD and how these relate to adaptive cognition.

Beyond feature binding: interference from episodic context binding creates the bivalency effect in task-switching

When switching between different tasks and bivalent stimuli occur only occasionally on one of them, performance is slowed on subsequent univalent trials even if they have no overlapping features with the bivalent stimulus. This phenomenon has been labeled the "bivalency effect." Recent evidence has revealed that this effect is robust, general, and enduring. Moreover, it challenges current theories of task-switching and cognitive control. Here, we review these theories and propose a new, episodic context binding account. According to this account, binding does not only occur between stimuli, responses, and tasks, but also for the more general context in which the stimuli occur. The result of this binding process is a complex representation that includes each of these components. When bivalent stimuli occur, the resulting conflict is associated with the general context, creating a new conflict-loaded representation. The reactivation of this representation causes interference on subsequent trials, that is, the bivalency effect. We evaluate this account in light of the empirical evidence.

Predictors of semantic categorical flexibility in older adults

This study investigated the processes involved in the aging of semantic categorical flexibility. A previous study revealed the effects of aging on the flexible use of taxonomic relations. We aimed to explain our previous results regarding the performance of older adults; we carried out investigations into the respective roles of executive and conceptual factors in semantic categorical flexibility. Fifty older adults carried out a semantic categorical flexibility task alongside conceptual and executive measures. The results replicate our previous findings and indicate that the predictors of the maintenance of the use of taxonomic relations are conceptual and the predictors of the switching from thematic to taxonomic relations are executive.

Processing of representations in declarative and procedural working memory

The article investigates the relation between declarative and procedural working memory (WM; Oberauer, 2009). Two experiments test the assumption that representations in the two subsystems are selected for processing in analogous ways. Participants carried out a series of decisions on memorized lists of digits. For each decision, they had to select declarative and procedural representations. Regarding declarative representations, participants selected a memory set and a digit within this set as the input to each decision. With respect to the procedural representations, they selected a task set to be applied to the selected digit and a response within that task set. We independently manipulated the number of lists and the number of tasks to be switched among (one, two, or three; Experiment 1) and preparation time for a list switch (Experiment 2). For three effects commonly observed in task-switch studies, analogues in declarative WM were found: list-switch costs, mixing costs, and residual switch costs. List- and task-switch costs were underadditive, suggesting that declarative and procedural representations are selected separately and in parallel. The findings support the hypothesis of two analogous WM subsystems.

The Association between Routinization and Cognitive Resources in Later Life

The aim of this study was to investigate the association between routinization of daily life activities and cognitive resources during aging. Routinization could increase excessively during aging and become maladaptative in reducing individual resources. Fifty-two young participants ( M = 20.8 years) and 62 older participants ( M = 66.9 years) underwent a routinization scale and cognitive tasks of working memory, speed of processing, and attention. Results revealed that older adults presented a decrease on the three cognitive measures but no change on the routinization score. While no association was observed between routinization and cognitive measures for the young adults, a high routinization was associated with lower cognitive flexibility in the older adults. These findings are interpreted in the light of theories about the positive impact of variety in daily life environment on cognitive functions.