Lisa B. Thorell

Training and Transfer Effects of Executive Functions in Preschool Children.

Executive functions, including working memory and inhibition, are of central importance to much of human behavior. Interventions intended to improve executive functions might therefore serve an important purpose. Previous studies show that working memory can be improved by training, but it is unknown if this also holds for inhibition, and whether it is possible to train executive functions in preschoolers. In the present study, preschool children received computerized training of either visuo-spatial working memory or inhibition for 5 weeks. An active control group played commercially available computer games, and a passive control group took part in only pre- and posttesting. Children trained on working memory improved significantly on trained tasks; they showed training effects on non-trained tests of spatial and verbal working memory, as well as transfer effects to attention. Children trained on inhibition showed a significant improvement over time on two out of three trained task paradigms, but no significant improvements relative to the control groups on tasks measuring working memory or attention. In neither of the two interventions were there effects on non-trained inhibitory tasks. The results suggest that working memory training can have significant effects also among preschool children. The finding that inhibition could not be improved by either one of the two training programs might be due to the particular training program used in the present study or possibly indicate that executive functions differ in how easily they can be improved by training, which in turn might relate to differences in their underlying psychological and neural processes.

Impact of executive functioning and symptoms of attention deficit hyperactivity disorder on children's peer relations and school performance.

This study examined the predictive relations from symptoms of Attention-deficit/hyperactivity disorder (ADHD) and executive functioning (EF) to social and school functioning in 112 (62 girls) school children. High levels of teacher and parent ratings of ADHD symptoms at the ages of 8–81/2 years, and poor EF measured at the age of 81/2, were associated with poor social functioning measured by peer nominations and poor teacher ratings of school functioning at the age of 91/2. ADHD symptoms independently predicted social and school functioning, whereas EF independently predicted only school functioning. Interaction effects between ADHD and EF and between EF and gender were found: At high levels of symptoms of inattention, the poorer the EF, the greater the need for special education. At high levels of symptoms of hyperactivity/impulsivity, the poorer the EF, the higher the levels of physical aggression. Girls with poor EF were less accepted by peers than equivalent boys.

Gains in fluid intelligence after training non-verbal reasoning in 4-year-old children: a controlled, randomized study.

Fluid intelligence (Gf) predicts performance on a wide range of cognitive activities, and children with impaired Gf often experience academic difficulties. Previous attempts to improve Gf have been hampered by poor control conditions and single outcome measures. It is thus still an open question whether Gf can be improved by training. This study included 4-year-old children (N = 101) who performed computerized training (15 min/day for 25 days) of either non-verbal reasoning, working memory, a combination of both, or a placebo version of the combined training. Compared to the placebo group, the non-verbal reasoning training group improved significantly on Gf when analysed as a latent variable of several reasoning tasks. Smaller gains on problem solving tests were seen in the combination training group. The group training working memory improved on measures of working memory, but not on problem solving tests. This study shows that it is possible to improve Gf with training, which could have implications for early interventions in children.

Multiple deficits in ADHD: executive dysfunction, delay aversion, reaction time variability, and emotional deficits

Background The notion that ADHD constitutes a heterogeneous disorder is well accepted. However, this study contributes with new important knowledge by examining independent effects of a large range of neuropsychological deficits. In addition, the study investigated whether deficits in emotional functioning constitute a dissociable component of ADHD. Method The study included children with ADHD (n = 102; 7–13 years) and a control sample individually matched with regard to age and gender. The administered tasks were designed to tap into three different neuropsychological domains: executive functions (i.e., working memory, inhibition, and shifting), delay aversion, and reaction time variability. Parent ratings of emotion regulation and a test of emotion recognition were also included. Results Children with ADHD differed significantly from controls on all measures, except for delay aversion and recognition of disgust. No main effects of gender or interaction effects of gender and group were found. More importantly, executive functioning, reaction time variability, and emotional functioning all contributed independently to distinguishing between children with ADHD and controls. Conclusions The current study supports the view of ADHD as a heterogeneous disorder related to multiple neuropsychological deficits. In addition, emotional functioning appears to be an area of importance for ADHD that needs to be incorporated into future theoretical models.

Common and unique components of inhibition and working memory : An fMRI, within-subjects investigation

Behavioural findings indicate that the core executive functions of inhibition and working memory are closely linked, and neuroimaging studies indicate overlap between their neural correlates. There has not, however, been a comprehensive study, including several inhibition tasks and several working memory tasks, performed by the same subjects. In the present study, 11 healthy adult subjects completed separate blocks of 3 inhibition tasks (a stop task, a go/no-go task and a flanker task), and 2 working memory tasks (one spatial and one verbal). Activation common to all 5 tasks was identified in the right inferior frontal gyrus, and, at a lower threshold, also the right middle frontal gyrus and right parietal regions (BA 40 and BA 7). Left inferior frontal regions of interest (ROIs) showed a significant conjunction between all tasks except the flanker task. The present study could not pinpoint the specific function of each common region, but the parietal region identified here has previously been consistently related to working memory storage and the right inferior frontal gyrus has been associated with inhibition in both lesion and imaging studies. These results support the notion that inhibitory and working memory tasks involve common neural components, which may provide a neural basis for the interrelationship between the two systems.

Heterogeneity in ADHD: neuropsychological pathways, comorbidity and symptom domains.

The aim of the present study was to investigate different neuropsychological impairments and comorbid behavioral problems in relation to symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD), studying the independent effects of different functions as well as specific relations to symptoms of hyperactivity/impulsivity and inattention. A community-based sample of school children (n = 182; the higher end of the ADHD symptom range was oversampled) completed neuropsychological tasks designed to measure executive function (EF), state regulation and delay aversion. Behavioral symptoms were measured through parental and teacher ratings of the DSM-IV criteria for ADHD and Oppositional Defiant Disorder (ODD). Both categorical and dimensional analyses were used to acquire a deeper understanding of ADHD. The results supported the notion that EF and state regulation constitute independent pathways to ADHD, primarily to symptoms of inattention. In addition, the present study points to the importance of viewing ADHD as a heterogeneous condition also with regard to the differential impact of neuropsychological functioning and comorbidity on different ADHD symptom groups and the two ADHD symptom domains.

Representations of attachment to parents and shyness as predictors of children's relationships with teachers and peer competence in preschool

In a group of 112 children (46% boys), representations of attachment to parents and shyness at age 5 were used as predictors of social relationships in preschool at age 6. A Story Completion task was used to assess attachment representations and shyness was assessed through parent ratings and observations. Preschool teachers rated the child – teacher relationship and the childs peer competence. Children with avoidant representations had more conflictual and less close teacher relationships, and showed less prosocial orientation with peers than did children with secure attachment representations. Children with bizarre-ambivalent representations had somewhat less intimate teacher relationships and less social initiative with peers than did children with secure representations. Shy children had less close and less conflictual teacher relationships and somewhat less social initiative with peers than did non-shy children. There was one marginally significant interaction effect of the quality of attachment representations and shyness on social relationships.

ADHD Symptoms and Executive Function Impairment: Early Predictors of Later Behavioral Problems

This longitudinal study investigated ADHD symptoms and EF impairments in terms of continuity and cross-domain associations, as well as their predictive relations to a range of socioemotional problem behaviors. We applied a factorial ANOVA design to study additive and interactive effects in a sample of non-clinical preschool children (N = 87) and complemented these analyses with group contrasts. The results showed that early ADHD symptoms and EF impairments acted as predictors of continuing problems within each domain. However, it was only ADHD symptoms that predicted other aspects of socioemotional functioning such as dysfunctional emotional regulation and lower levels of social competence. There was no indication of interactive effects on any measure. In conclusion, our results showed that both ADHD symptoms and impaired EF act as early predictors of problem behaviors, although it is clear that predictions based on ADHD symptoms encompass a wider range of problems in early school age children.

Interrelations Between Executive Function and Symptoms of Hyperactivity/Impulsivity and Inattention in Preschoolers: A Two Year Longitudinal Study

The present study, including children at risk for developing Attention Deficit Hyperactivity Disorder (ADHD), examined the idea that complex executive functions (EFs) build upon more simple ones. This notion was applied in the study of longitudinal interrelations between core EF components — simple and complex inhibition, selective attention, and working memory (WM) — at age 5 and 6 as well as their predictive relations to ADHD symptoms at age 7. The results showed that simple inhibition and selective attention at age 5 independently predicted complex inhibition and WM at age 6. In addition, EFs primarily predicted symptoms of inattention rather than hyperactivity/impulsivity even at this young age. Finally, age 6 complex inhibition was shown to act as a mediator in the relations between simple inhibition and selective attention at age 5 and symptoms of inattention at age 7. These findings provide novel longitudinal support for the theory that fundamental EF components show a progression with age toward more complex executive control (see Garon et al. Psychological Bulletin 134(1):31–60 2008). Further, complex inhibition, implicating both inhibition and WM, seems to be a particularly strong correlate of ADHD symptoms in young children and should as such be the focus of future studies examining the relation between cognitive function and ADHD symptoms from a developmental perspective.

Disorganized Attachment and Inhibitory Capacity: Predicting Externalizing Problem Behaviors.

The aim of the present study was to investigate whether attachment insecurity, focusing on disorganized attachment, and the executive function (EF) component of inhibition, assessed at age 5, were longitudinally related to general externalizing problem behaviors as well as to specific symptoms of ADHD and Autism spectrum disorder (ASD), and callous-unemotional (CU) traits. General externalizing problem behaviors were also measured at age 5 to allow for a developmental analysis. Outcome variables were rated by parents and teachers. The sample consisted of 65 children with an oversampling of children with high levels of externalizing behaviors. Attachment was evaluated using a story stem attachment doll play procedure. Inhibition was measured using four different tasks. The results showed that both disorganized attachment and poor inhibition were longitudinally related to all outcome variables. Controlling for initial level of externalizing problem behavior, poor inhibition predicted ADHD symptoms and externalizing problem behaviors, independent of disorganized attachment, whereas for ASD symptoms no predictive relations remained. Disorganized attachment independently predicted CU traits.