Attention-Deficit/Hyperactivity Disorder and Working Memory: A Task Switching Paradigm

Examining Distinctive Working Memory Profiles in Chinese Children With Predominantly Inattentive Subtype of Attention-Deficit/Hyperactivity Disorder and/or Reading Difficulties

Although evidence has shown that both RD and ADHD-I children suffer from working memory problems, inconsistencies in impaired modalities have been reported. This study aimed to (1) compare the three WM domains (i.e., verbal WM, visual-spatial WM, and behavioral WM) among pure ADHD-I, pure RD, comorbid ADHD-I+RD, and typical control groups and (2) examine the impact of comorbidity on the three WM domains. A Chinese sample of participants from Hong Kong included 29 children in the ADHD-I group, 78 children in the RD group, 31 children in the comorbid group (ADHD-I+RD), and 64 children in the TD control group. All participants completed the assessments individually. The findings showed that the children with ADHD-I and/or RD exhibited diverse cognitive profiles. In particular, RD was associated with verbal and visual-spatial working memory deficits, while ADHD-I was associated with behavioral working memory deficits. Interestingly, the comorbid condition demonstrated additive deficits of the two disorders but with greater deficits in behavioral working memory. These findings support the cognitive subtype hypothesis and provide a clearer picture of the distinctive working memory profiles of different groups, allowing for the development of intervention programs in the future.

Impairments in resource allocation and executive control in children with ADHD

Children diagnosed with attention-deficit hyperactivity disorder (ADHD) show pronounced alterations in cognitive tasks, such as a highly variable mode of responding. There is an ongoing debate about the key driving mechanisms of such alterations (e.g. specific inhibition or working memory (WM) impairments or general impairments in the allocation of energetic resources). The aim of this study was to disentangle such process-specific versus general limitations in cognitive and energetic mechanisms in children with ADHD compared to typically developed (TD) children based on the performance in a task-switching paradigm. This paradigm allows for both a common measurement and a later segregation of different executive sub-processes. Task-switching performance, including performance variability, of 26 children diagnosed with combined-type ADHD (8-13 years) was compared against the performance of 26 age-matched/IQ-matched TD children. Results revealed that compared to TD children, ADHD-diagnosed children showed alterations in performance variability during task switching, both in general (indicating disturbances in resource allocation) and conditionally on WM demands (indicating a specific WM deficit). Hence, our study provides diagnostically relevant new insights into performance impairments in children with ADHD compared to TD children. Importantly, it seems mandatory to include information on performance variability when trying to phenotype alterations in cognitive performance in ADHD.

Inattention and task switching performance: the role of predictability, working memory load and goal neglect

Inattention is a symptom of many clinical disorders including attention deficit hyperactivity disorder (ADHD) and is thought to be primarily related to limitations in working memory. In two studies, we investigated the implications of inattention for task switching performance. In study one, we measured task switching performance using predictable and unpredictable conditions in adults who self-rated inattention and other ADHD-related tendencies. Tasks required proactive control and reactive control, respectively, under both high and low working memory loads. Results revealed that inattentive, but not hyperactive/impulsive traits, predicted switch costs when switching was predictable and working memory load was high. None of the ADHD traits were related to unpredictable switch costs. Study two was designed to: (1) de-confound the role of proactive control and the need to keep track of task order in the predictable task switching paradigm; (2) investigate whether goal neglect, an impairment related to working memory, could explain the relationship between inattention and predictable task switching. Results revealed that neither predictability nor the need to keep track of the task order led to the association between switch costs and inattention, but instead it was the tendency for those high in inattention to neglect preparatory proactive control, especially when reactive control options were available.

Neuroelectric and Behavioral Effects of Acute Exercise on Task Switching in Children with Attention-Deficit/Hyperactivity Disorder

The main purpose of this two-part study was to examine the effects of acute, moderate intensity exercise on task switching in children with attention-deficit/hyperactivity disorder (ADHD). In Study 1, we compared the task switching performance of children with and without ADHD. Twenty children with ADHD and 20 matched controls performed the task switching paradigm, in which the behavioral indices and P3 component of event-related potentials elicited by task-switching were assessed simultaneously. The amplitude and latency of P3 reflected the amount of attention resource allocated to task-relevant stimulus in the environment and the efficiency of stimulus detection and evaluation, respectively. The task switching included two conditions; the pure condition required participants to perform the task on the same rule (e.g., AAAA or BBBB) whereas the mixed condition required participants to perform the task on two alternating rules (e.g., AABBAA…). The results indicated that children with ADHD had significantly longer RTs, less accuracy, and larger global switch cost for accuracy than controls. Additionally, ADHD participants showed smaller amplitudes and longer P3 latencies in global switch effects. In Study 2, we further examined the effects of an acute aerobic exercise session on task switching in children with ADHD. Thirty-four children with ADHD performed a task switching paradigm after 30 min of moderate-intensity aerobic exercise on a treadmill and after control sessions (watching videos while seated). The results revealed that following exercise, children with ADHD exhibited smaller global switch costs in RT compared with after control sessions. The P3 amplitude only increased following exercise in the mixed condition relative to the pure condition, whereas no effects were found in the control session. These findings suggest that single bouts of moderate intensity aerobic exercise may have positive effects on the working memory of children with ADHD.

A pilot study of the efficacy of a computerized executive functioning remediation training with game elements for children with ADHD in an outpatient setting: outcome on parent- and teacher-rated executive functioning and ADHD behavior

OBJECTIVE

This pilot study tested the short- and long-term efficacy (9 weeks follow-up) of an executive functioning (EF) remediation training with game elements for children with ADHD in an outpatient clinical setting, using a randomized controlled wait-list design. Furthermore, in a subsample, that is, those treated with methylphenidate, additive effects of the EF training were assessed.

METHOD

A total of 40 children (aged 8-12 years) were randomized to the EF training or wait-list. The training consisted of a 25-session training of inhibition, cognitive flexibility, and working memory. Treatment outcome was assessed by parent- and teacher-rated EF, ADHD, oppositional deviant disorder, and conduct disorder symptoms.

RESULTS

Children in the EF training showed significantly more improvement than those in the wait-list condition on parent-rated EF and ADHD behavior in the total sample and in the subsample treated with methylphenidate. Effects were maintained at follow-up.

CONCLUSION

This pilot study shows promising evidence for the efficacy of an EF training with game elements.

The utility of Stroop task switching as a marker for early-stage Alzheimer's disease

Past studies have suggested attentional control tasks such as the Stroop task and the task-switching paradigm may be sensitive for the early detection of dementia of the Alzheimer's type (DAT). The authors of the current study combined these tasks to create a Stroop switching task. Performance was compared across young adults, older adults, and individuals diagnosed with very mild dementia. Results indicated that this task strongly discriminated individuals with healthy aging from those with early-stage DAT. In a logistic regression analysis, incongruent error rates from the Stroop switching task discriminated healthy aging from DAT better than any of the other 18 cognitive tasks given in a psychometric battery.

Executive function profile of Chinese boys with attention-deficit hyperactivity disorder: different subtypes and comorbidity

This study examined the executive function (EF) profile of Chinese boys with attention-deficit hyperactivity disorder (ADHD) using a large sample. Executive function performance within the ADHD subtypes and the effects of comorbidity were also investigated. Five hundred Chinese boys (375 with ADHD and 125 controls) aged 6-15 completed a battery of EF tests. Boys with all types of ADHD performed worse in all of the EF tests than age- and intelligence quotient-matched healthy controls. The boys with the inattention ADHD subtype and the combined subtype showed similar impairments across different EF tasks, whereas the boys with the hyperactive-impulsive ADHD subtype primarily displayed deficits in theory of mind and visual memory. Comorbid oppositional defiant disorder/conduct disorder had no additional influence on the EF characteristics of the boys with ADHD only, whereas comorbid learning disorder increased the severity of inhibition and shifting impairments.