Impairment of executive functions in boys with attention deficit/hyperactivity disorder.

The main aim of the present study is to compare the efficiency of executive control processes in 24 boys with attention deficit/hyperactivity disorder (ADHD) and 58 normal controls of similar age (between 8 and 11 years). Three reaction time (RT) paradigms were utilized: a dual task that requires coordination of two tasks responses, a shift task that makes it necessary to disengage attention from one task and engage into another one, and a stimulus-response spatial compatibility task that requires participants to inhibit a prepotent response. Another purpose of the study is to examine whether Barkley's (1997) executive dysfunction or Sergeant et al.'s (1999) resource allocation/arousal model best account for the behavioral deficits associated with ADHD. Examination of raw RT data showed significantly poorer performance in ADHD children with respect to age-matched controls on both the higher-level cognitive functions of executive control and on lower-level abilities (e.g., speed of processing) of all tasks of this study. However, using proportional transformations of raw RT data, we could demonstrate that, in addition to differences in processing speed, also executive control processes were significantly impaired in children with ADHD.     

Biological and psychological development of executive functions.

The purpose of this overview is to provide a background for understanding the relation between the biological maturation of the frontal lobes and the development of the psychological concept of executive functions. In the first section, an interactive hierarchical feedback model is presented as a heuristic way of conceptualizing the relationship of the frontal lobes and executive functions to other brain regions and abilities. The following two sections present a synopsis of research on biological maturation and the psychological development of executive functions.     

Development of executive attention in preschool children

The development of self-regulatory systems during the preschool years is accompanied by a dramatic increase in the ability to inhibit actions based on the directions of others. Several tasks have shown evidence of changes in self-regulation during the fourth year of life. The current cross-sectional study used a Simple Simon task, in which 33 3- to 4-year-old children were asked to respond to the command of one large toy animal but not to the command of another. Three important aspects of self-regulation were examined: the ability to inhibit action in the face of conflict, error detection/correction and the use of verbal and physical control strategies. The ability to inhibit a response in this task increased from 22% to 90% between 36 and 48 months of age. Post error slowing of Reaction Time (RT) indicative of error detection emerged at about the same age as successful inhibition. Physical rather than verbal self-regulation strategies were spontaneously employed by children to aid in the process of inhibition.     

Before and after entering school: The development of attention and executive functions from 6 to 8 years in Finnish children

In this 2‐year prospective follow‐up study we examined typical and atypical development of attention and executive function (AEF) across the transition to school. The NEPSY‐battery was used to evaluate the AEFs of the children before school at 6 years of age. Two subgroups, typical AEF (n = 25) and atypical AEF (n = 25), were formed according to the performance in AEF tasks. Children were assessed again at 8 years, when they were at the 2nd grade. The same subtests of the NEPSY‐battery and the ATTEX behavioral rating completed by a teacher were used. The effects of AEF deficits were compared with and without controlling for IQ. The group effect was significant in four out of the six NEPSY subtests used. The atypical AEF group had problems especially on subtests measuring motor inhibition both at the age of 6 and 8. The group‐time interaction effect was found in the subtest measuring attentional shifting. A catch‐up effect on shifting skills was observed in the atypical AEF group by the age of 8 years. In school at the 2nd grade, the early AEF problems were still observable, and related especially to inattention problems. Our results support the interpretation that inhibitory problems are at the core of executive dysfunction, that the problems are stable from preschool to 2nd grade, and that the effects of early AEF problems go over and beyond intellectual deficits. Our results also support the use of performance based measures of inhibition as an important part of the neuropsychological evaluation for school readiness.     

Differential changes in the development of motor coordination and executive functions in children with motor coordination impairments

Cognitive and motor coordination skills of children with and without motor coordination impairments were examined with a one-year follow-up investigation. Initially, children were between 4 and 6 years old. Age-appropriate tests of executive functions (updating, switching, inhibition, interference control), motor coordination (the Movement Assessment Battery for Children-2) and fitness (the Körperkoordinations-Test für Kinder) were administered in two consecutive years. Several background variables (age, socioeconomic status, medical support, clinical interventions, leisure activities) and potential moderators (nonverbal intelligence, reaction time, visual perception) were controlled. The matched sample consisted of 48 control children and 48 children with motor coordination impairments. The children’s executive functions dramatically improved during the one-year period. With regard to motor coordination performance, half of the impaired children caught up to the control children’s level (“remission group”), while the remaining half showed no improvement (“persisting group”). Compared to the persisting group, the children in the remission group showed markedly better interference control at both measurement points. The correlation between executive functions and motor coordination is significant in the persisting group, but not in the remission group. The results of the study are discussed in the light of the role of executive functions, especially inhibition processes, for the automatization of motor coordination tasks.     

Attention problems and executive functions in children with spina bifida and hydrocephalus.

This study addressed the incidence of Attention-Deficit/Hyperactivity Disorder (ADHD) subtypes in children with spina bifida meningomyelocele and shunted hydrocephalus (SBH) as well as differences in executive functions among these subtypes. Parent rating scales revealed that 31% of the group with SBH could be identified with AD/HD, mostly the Inattentive type (23%). The group with SBH differed from normal controls on cognitive measures of executive functions, but subtype differences were not significant. Multivariate tests showed that children with SBH were rated with greater difficulties on the Behavior Rating Inventory of Executive Function (BRIEF) compared to controls; those with SBH and any subtype of ADHD differed from those with SBH and no ADHD; and those with ADHD (Combined Type) differed significantly from those with ADHD (Predominantly Inattentive Type). Subtype differences on univariate tests in the latter comparison were significant on the BRIEF Inhibit scale, showing more disinhibition in those with SBH and ADHD (Combined Type), but no significant differences were apparent on the BRIEF Sustain, Shift, and Initiate scales. The results show that the incidence of ADHD in children with SBH exceeds the population rate, is represented by problems with inattention rather than with impulsivity and hyperactivity; and that as with non-brain injured individuals, subtype differences in cognitive function remain to more clearly delineated.     

Spatial memory and executive functions in children

A computerized hidden pathway maze-learning task was used to examine the development of spatial memory and executive functions in 6- to 9-year-olds. Pathway length was manipulated to investigate the impact of increases in maze matrix size on these abilities. Analysis showed that maze matrix size (and ipso facto pathway length) and age interacted to affect executive functions but not spatial memory. Executive errors differed as a function of age on the most difficult maze. Results are discussed in terms of factors affecting the development of executive functions and spatial memory.     

The development of analogy making in children: Cognitive load and executive functions

The aim of the current study was to investigate the performance of 6-, 8-, and 14-year-olds on an analogy-making task involving analogies in which there are competing perceptual and relational matches. We hypothesized that the selection of the common relational structure requires the inhibition of other salient features, in particular, perceptual matches. Using an A:B::C:D paradigm, we showed that children’s performance in analogy-making tasks depends crucially on the nature of the distractors. Children chose more perceptual distractors having a common feature with C compared with A or B (Experiment 1). In addition, they were also influenced by unstructured random textures. When measuring reaction times instead of accurate responses, only the 8-year-olds’ reaction times were significantly influenced by perceptual distractors. The 6-year-olds seemed to select the first match they noticed, and the 14-year-olds were not influenced (or much less influenced) by featural distractors. These results are compatible with an analogy-making account based on varying limitations in executive functioning at different ages.     

The development of and interaction among alerting,orienting, and executive attention in children

A sex-balanced sample (N = 96) of children from age 6.5 to age 12.5 completed a modified Attention Network Test. Across these ages, we found evidence for developmental changes to alerting and executive control but stable orienting. Additionally, we found that the youngest members of our sample manifested an interaction between alerting and executive control that is opposite to that typically found in adults; a reversal that diminishes with age to achieve the adult pattern by the older end of the age range of our sample.     

Selective attention and executive functions deficits among criminal psychopaths

The present study examined whether psychopaths exhibit deficits in selective attention and executive functions. Prison inmates were assigned to either a “psychopath” group or a “control” group according to their scores on the PCL‐R [Hare, 1991: Toronto, Multi‐Health Systems]. The two groups were compared in terms of performance on the following tests: (1) D‐II cancellation, (2) Porteus Maze, (3) Modified Wisconsin Card Sorting, (4) Stroop Color Word Interference, (5) Trail Making, and (6) Tower of London. The results support the hypothesis of selective attention and specific executive function deficits among psychopaths. Specifically, psychopaths' abilities to maintain a plan and to inhibit irrelevant information were inferior to those of control participants. Aggr. Behav. 29:393–405, 2003. © 2003 Wiley‐Liss, Inc.     

Common mechanisms of executive attention underlie executive function and effortful control in children

Executive Function (EF) and Effortful Control (EC) have traditionally been viewed as distinct constructs related to cognition and temperament during development. More recently, EF and EC have been implicated in top‐down self‐regulation ‐ the goal‐directed control of cognition, emotion, and behavior. We propose that executive attention, a limited‐capacity attentional resource subserving goal‐directed cognition and behavior, is the common cognitive mechanism underlying the self‐regulatory capacities captured by EF and EC. We addressed three related questions: (a) Do behavioral ratings of EF and EC represent the same self‐regulation construct? (b) Is this self‐regulation construct explained by a common executive attention factor as measured by performance on cognitive tasks? and (c) Does the executive attention factor explain additional variance in attention deficit hyperactivity disorder (ADHD) problems to behavioral ratings of self‐regulation? Measures of performance on complex span, general intelligence, and response inhibition tasks were obtained from 136 preadolescent children (M = 11 years, 10 months, SD = 8 months), along with self‐ and parent‐reported EC, and parent‐reported EF, and ADHD problems. Results from structural equation modeling demonstrated that behavioral ratings of EF and EC measured the same self‐regulation construct. Cognitive tasks measured a common executive attention factor that significantly explained 30% of the variance in behavioral ratings of self‐regulation. Executive attention failed to significantly explain additional variance in ADHD problems beyond that explained by behavioral ratings of self‐regulation. These findings raise questions about the utility of task‐based cognitive measures in research and clinical assessment of self‐regulation and psychopathology in developmental samples.     

Coordination of executive functions in monolingual and bilingual children

Two groups of 8-year-old children who were monolingual or bilingual completed a complex classification task in which they made semantic judgments on stimuli that were presented either visually or auditorily. The task requires coordinating a variety of executive control components, specifically working memory, inhibition, and shifting. When each of the visual and auditory tasks was presented alone, performance was comparable for children in the two groups. Combining the two modalities into a dual-task paradigm made the task more difficult, and on this combined task bilingual children maintained better accuracy than monolingual children, especially on the visual task. The results are interpreted in terms of the enhanced ability of bilingual children to coordinate the executive control components required in performing this complex task.     

Evaluation of executive functions in children and adolescents with familial Mediterranean fever

The aim of the present study was to investigate neuropsychological test performance in children and adolescents with familial Mediterranean fever (FMF). A total of 88 children and adolescents aged 8 to 17 years were included, 52 with FMF and 36 healthy controls. After the participants were administered the Children Depression Inventory (CDI) and the Screen for Child Anxiety Related Emotional Disorders (SCARED), they completed the battery tests of the Central Nervous System Vital Signs (CNSVS), a neurocognitive test battery, via computer. The battery calculates seven domain scores (Memory, Psychomotor Speed, Processing Speed, Reaction Time, Complex Attention, Executive Function, and Cognitive Flexibility) and a summary score (Neurocognition Index [NCI]). A statistically significant difference between the FMF and control groups was found in six out of seven domains, where the scores of the participants with FMF were found to be significantly lower than those of the control participants (p < .05). Although the mean Reaction Time score of the participants with FMF was found to be lower than that of the control participants, the finding was not statistically significant (p > .05). The mean CDI and SCARED scores of the participants with FMF were found to be significantly higher than those of the control participants (p < .05). Low scores in the Processing Speed and Psychomotor Speed domains of the CNSVS were significantly correlated with higher SCARED scores (r = ?.37, p = .01). Impaired cognitive functions should be taken into consideration in children and adolescents with FMF when assessing and managing this population.     

The role of executive functions in bilingual children with reading difficulties

To explore the joint effect of reading difficulties (RD) and bilingualism on executive functions, 190 children of four groups of 9–12 year‐olds (41 bilinguals with RD, 45 monolinguals with RD, 45 bilinguals without RD, and 59 monolinguals without RD) were examined on the Concentration game, Tower of Hanoi, and Stroop as measures of executive functioning tapping into inhibitory/attentional control, working memory and planning ability. The most prominent finding was that in terms of RD, the speed of performances decreased dramatically. This general decrease was more pronounced for bilingual children with RD than for their monolingual counterparts. In conclusion, the findings suggest that while bilinguals gain more from executive functions in normal reading, they lose in terms of RD. Such an outcome confirms that executive functions are essential components of both reading and bilingualism, which depending on whether reading conditions are normal or difficult will produce cognitive advantages or disadvantages. Further, it is argued that dissimilarity between the Farsi and Swedish languages may complicate handling of such a situation.     

The vigilance, orienting, and executive attention networks in 4-year-old children.

The present study examined the development of lower and higher order forms of attention during the preschool years. Lower forms of attention were assessed with tasks that primarily engaged the attention functions of vigilance and orienting. Higher, executive forms of attention were assessed with tasks that involved inhibition and working memory. The findings revealed that performance improved significantly with age on measures of inhibition and orienting. Results are discussed in the context of the development of attentional networks.     

Infants' fast saccades in the gap paradigm and development of visual attention

The saccadic reaction times (SRTs) in the overlap, no-overlap, and gap conditions of 2.5- to 12-month-old infants and adults were measured. In the overlap condition, the SRTs of younger infants were over 600 ms longer than those of older infants, whereas the SRTs in the gap condition of the younger infants were 300–350 ms, much faster than reported hitherto, and were shortened only by about 100 ms. The results indicate that the oculo-motor system and attention process for disengagement in the gap condition mature earlier than the attention process for disengagement in the overlap condition.     

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.     

Interaction between the development of postural control and the executive function of attention

The authors examined the interaction between the development of postural control and the development of the executive function of attention in 13 children and 6 adults in dual-task conditions. Participants performed an attentionally demanding cognitive task and a postural task simultaneously. The authors equalized the attentional load of the cognitive task across age groups. Comparative changes in the center of pressure in dual- and single-task conditions indicated that dual tasks interfered with postural performance in the wide stance (WS) and the modified Romberg stance (RS). Children at 4-6 years of age (but not children at ages 7-12 years of age or adults) experienced postural control interference in both stance positions, but interference was greater in the RS (p = .018). For all participants, cognitive task performance in RS was unchanged from that in WS. The knowledge gained from the results of this study will contribute to the design and implementation of academic and preacademic programming for young children. Their performance of an intentionally demanding cognitive task would be enhanced by the provision of appropriately sized desks and chairs or their use of an alternate, less demanding position.