Karin C. Brocki

Executive Functions in Children Aged 6 to 13: A Dimensional and Developmental Study

A cross-sectional study using 92 children aged 6 to 13 years investigated the dimensionality and the development of executive functioning. The measures were drawn from developmentally relevant conceptualizations of executive functioning and included a go/no-go task, a verbal fluency task, a continuous performance task, a Stroop-like task, a hand movements task, and a digit span task. Analyses revealed 3 dimensions interpreted as Disinhibition, Speed/arousal, and Working memory/Fluency. Age and sex differences were analyzed for the delineated functions, which means that the results may be taken to represent age effects at the level of specific processes within the executive domain rather than on single tests. Age-dependent changes in childrens performance on all 3 dimensions were demonstrated, with 3 particularly active stages of maturation: early childhood (6-8 years of age), middle childhood (9-12 years of age), and during early adolescence. Sex differences were only found for the speed/arousal dimension. The results are discussed in terms of 2 developmental executive function frameworks (Barkley, 1997b; Roberts & Pennington, 1996), where inhibition and the interaction between inhibition and working memory, respectively, are seen as key in the development of executive functioning.

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.

Motor response inhibition and execution in the stop-signal task: development and relation to ADHD behaviors.

The main aim of this study was to investigate the developmental course of motor response inhibition and execution as measured by the stop-signal task in a population-based sample of 525 4- to 12-year-olds. A further aspiration of the study was to enhance the limited knowledge on how the various stop-signal measures relate to ADHD behaviors in a normal sample. We also wanted to contribute to the theoretical understanding of the various stop-signal measures by examining the relations between the stop-signal measures and performance on tasks reflecting other aspects of response inhibition and execution. Our results showed that the ability to inhibit as well as to execute a motor response as measured by the stop-signal task improved with age during childhood. Of specific interest are the findings suggesting that this task captures the development of motor response inhibition in the late preschool years (age 5 years). Both of the inhibition measures derived from the stop-signal task (i.e., SSRT and probability of inhibition) related significantly to teacher ratings of inattention as well as to performance on tasks tapping other aspects of inhibition. The data provided by this study have thus contributed to the scarce knowledge on early development of motor response inhibition, as well as suggested that the stop-signal task may be a valuable tool for capturing deficient motor response inhibition in ADHD behaviors in normal samples.

CPT performance, motor activity, and continuous relations to ADHD symptom domains: A developmental study

Using a population-based sample consisting of 401 6- to 12-year-olds, this study examined normative age and sex distributions on motor activity as measured in an actigraphic-based motion tracking system (MTS) and on attention-related functions derived from a Continuous Performance Test (CPT). Specific objectives were to present new knowledge on age-related change in motor activity and to study age effects on changes in motor activity and CPT performance as a function of time on task. Further, continuous relations between the two ADHD symptom domains and CPT performance and motor activity, and importantly, age effects in these relations were examined. CPT performance improved, and level of motor activity decreased with age. Linear associations between the two ADHD symptom domains and several of the CPT and MTS parameters support available research describing the nature of ADHD as a continuous dimension with variable expression throughout the general population. Further, our study is one of the first to provide developmental data using a time on task design, particularly with regard to motor activity. Imperative for ADHD future research are our results showing that age matters in the relation between ADHD behaviours and neuropsychological function.

ASSESSING THE MOLECULAR GENETICS OF THE DEVELOPMENT OF EXECUTIVE ATTENTION IN CHILDREN: FOCUS ON GENETIC PATHWAYS RELATED TO THE ANTERIOR CINGULATE CORTEX AND DOPAMINE

It is well known that children show gradual and protracted improvement in an array of behaviors involved in the conscious control of thought and emotion. Non-invasive neuroimaging in developing populations has revealed many neural correlates of behavior, particularly in the developing cingulate cortex and frontostriatal circuits. These brain regions, themselves, undergo protracted molecular and cellular change in the first two decades of human development and, as such, are ideal regions of interest for cognitive- and imaging-genetic studies that seek to link processes at the biochemical and synaptic levels to brain activity and behavior. We review our research to date that employs both adult and child-friendly versions of the attention network task (ANT) in an effort to begin to describe the role of specific genes in the assembly of a functional attention system. Presently, we constrain our predictions for genetic association studies by focusing on the role of the anterior cingulate cortex (ACC) and of dopamine in the development of executive attention.

Childhood Executive Function Inventory (CHEXI): A promising measure for identifying young children with ADHD?

The present study investigated whether the Childhood Executive Function Inventory (CHEXI) can discriminate between young children fulfilling the diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) and normally developing children. Unlike other executive function rating instruments, the CHEXI focuses specifically on inhibitory control and working memory, without including items that overlap with the diagnostic criteria of ADHD. The CHEXI was found to discriminate very well between children fulfilling the criteria for ADHD and normally developing children, also when controlling for the effect of IQ and socioeconomic status (SES). Both sensitivity and specificity of the two CHEXI subscales were shown to be high using either parent or teacher ratings. The highest overall classification rate was found for parent ratings on the inhibition subscale, with sensitivity and specificity reaching 93.3. To summarize, the CHEXI should be considered a promising measure for identifying young children with ADHD, although it is for future research to determine whether the CHEXI can be successfully used to also discriminate between different psychopathological groups.

Placing Neuroanatomical Models of Executive Function in a Developmental Context Imaging and Imaging-Genetic Strategies

Children show gradual and protracted improvement in an array of behaviors involved in the conscious control of thought and emotion. Behavioral research has shown that these abilities, collectively referred to as executive functions (EF), can be dissociated into separable processes, such as inhibition and working memory. Furthermore, noninvasive neuroimaging shows that these component processes often rely on separable neural circuits involving areas of the frontal cortex and nuclei of the basal ganglia. As additional noninvasive methodologies become available, it is increasingly possible to continue to dissect and dissociate components of EF and also test predictions made by a number of theoretical neuroanatomical models. One method of late is genetics, which is noninvasive and readily used in concert with neuroimaging. The biological data obtained with neuroimaging and genetics is particularly able to inform neuroanatomical models that link specific brain systems with higher more abstract process models derived from purely behavioral work. As much progress in this area continues to occur, we seek to evaluate the age dependency and manner in which certain aspects of EF and certain anatomical circuits show changes and interactions as children develop. Some examples are taken from research on children with the developmental disability attention deficit hyperactivity disorder. A review of selected developmental research shows that current cognitive and neuroanatomical models of EF offer a great many system‐ and synaptic‐level hypotheses that can be tested using imaging and imaging genetics in longitudinal and cross‐sectional study designs. Here, we focus on age‐related changes in inhibition and working memory.

The proposed interaction between working memory and inhibition

Two experiments investigated the determinants of performance on a go/no-go task by studying the interplay of two executive function components, working memory (WM) and inhibition. Systematically varied task demands on WM and inhibition were used in the analysis of performance together with individual capacity measures of both functions, thereby investigating an interactive view of WM and inhibition. Further analyses were conducted with individual differences in general fluid intelligence (gF), in an attempt to study the role of higher order cognition in handling task demands. The results are new in presenting empirical evidence for interactive effects of the task demand variables in concert with individual WM capacity as well as with gF, suggesting that executive processes common to WM and gF are involved in inhibitory performance, whereas gF appears to reflect a broader function in controlling behaviour in relation to task goals, whether it involves active responding or not.

A Longitudinal Examination of the Developmental Executive Function Hierarchy in Children With Externalizing Behavior Problems

Objective: Using a 4-year longitudinal design, we evaluated two hypotheses based on developmental executive function (EF) hierarchy accounts in a sample of children with externalizing problems. Method: The participants performed EF tasks when they were between 8 and 12 years (M = 9.93), and again approximately 4 years later when they were between 12 and 15 years (M = 13.36). Results: Inhibition in middle childhood predicted working memory (WM) 4 years later. Further, deficits in inhibition and sustained attention were more prominent in middle rather than late childhood, whereas poor WM was salient throughout these periods. Conclusions: These findings support the hypotheses that EFs develop hierarchically and that EF deficits in ADHD are more prominent in actively developing EFs. They also emphasize ADHD as a developmental disorder.