Atypical Arousal Regulation in Children With Autism but Not With Attention-Deficit/Hyperactivity Disorder as Indicated by Pupillometric Measures of Locus Coeruleus Activity

BACKGROUND

Atypical arousal regulation may explain slower mean reaction time (MRT) in autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder compared with typical development. The locus coeruleus-norepinephrine system (LC-NE) underlies arousal regulation and adapts its activity to the utility of a task. LC-NE tonic and phasic activity are indexed by baseline pupil size (BPS) and stimulus-evoked pupillary response (SEPR).

METHODS

The study assessed pupillometry in ASD (n = 31, 3 female/28 male), attention-deficit/hyperactivity disorder (n = 28, 3 female/25 male), and typically developing control subjects (n = 31, 16 female/15 male) during a visuospatial reaction-time task that manipulates arousal by conditions with low and high task utility. We estimated linear mixed models of BPS, SEPR, and MRT in a per-trial analysis to investigate arousal regulation of task performance.

RESULTS

Slower MRT occurred in the ASD group compared with the typically developing control group during low-utility conditions while controlling for dimensional ASD and attention-deficit/hyperactivity disorder symptoms. In low-utility conditions, BPS and SEPR were inversely related and both were associated with faster MRT. Increased ASD symptoms across groups were associated with higher BPS during low-utility conditions. Changes in BPS and SEPR between task-utility conditions were smaller in the ASD group.

CONCLUSIONS

Slower visuospatial task performance in ASD is specific to low task utility. Arousal was associated with task performance and showed altered activity in ASD. Increased BPS during low-utility conditions suggested increased LC-NE tonic activity as an ASD symptom marker in children. Smaller changes in BPS and SEPR in ASD indicated attenuated LC-NE activity adaptation in response to high-utility conditions. Slower performance and atypical arousal regulation are probably associated with attenuated LC-NE activity adaptation.

Multisensory Enhancement of Cognitive Control over Working Memory Capture of Attention in Children with ADHD

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in school-age children. Although it has been well documented that children with ADHD are associated with impairment of executive functions including working memory (WM) and inhibitory control, there is not yet a consensus as to the relationship between ADHD and memory-driven attentional capture (i.e., representations in WM bias attention toward the WM-matched distractors). The present study herein examined whether children with ADHD have sufficient cognitive control to modulate memory-driven attentional capture. 73 school-age children (36 with ADHD and 37 matched typically developing (TD) children) were instructed to perform a visual search task while actively maintaining an item in WM. In such a paradigm, the modality and the validity of the memory sample were manipulated. The results showed that under the visual WM encoding condition, no memory-driven attentional capture was observed in TD children, but significant capture was found in children with ADHD. In addition, under the audiovisual WM encoding condition, memory-matched distractors did not capture the attention of both groups. The results indicate a deficit of cognitive control over memory-driven attentional capture in children with ADHD, which can be improved by multisensory WM encoding. These findings enrich the relationship between ADHD and cognitive control and provide new insight into the influence of cross-modal processing on attentional guidance.

Inhibitory Control Development: A Network Neuroscience Perspective

As one of the core executive functions, inhibition plays an important role in human life through development. Inhibitory control is defined as the ability to suppress actions when they are unlikely to accomplish valuable results. Contemporary neuroscience has investigated the underlying neural mechanisms of inhibitory control. The controversy started to arise, which resulted in two schools of thought: a modulatory and a network account of inhibitory control. In this systematic review, we survey developmental mechanisms in inhibitory control as well as neurodevelopmental diseases related to inhibitory dysfunctions. This evidence stands against the modulatory perspective of inhibitory control: the development of inhibitory control does not depend on a dedicated region such as the right inferior frontal gyrus (rIFG) but relies on a more broadly distributed network.

Go/no-go task performance of Japanese children: Differences by sex, grade, and lifestyle habits

Background

Japanese children face critical psychological challenges that urgently need to be addressed.

Objective

This study aimed to clarify performance differences in go/no-go tasks among Japanese elementary and junior high students by sex and grade and comprehensively investigate the relationship between children's lifestyle habits and performance.

Methods

In total, 4,482 (2,289 males, 2,193 females) 1st grade elementary to 3rd grade junior high students (6-15 years old) participated. We conducted a survey and the go/no-go experiments in the participating schools on weekday mornings from November 2017 to February 2020. We collected data on the number of errors in the go/no-go tasks in response to visual stimuli (commission errors in the no-go tasks; omission errors in the go tasks); and on lifestyle habits (i.e., sleep, screen time, and physical activity) using questionnaires.

Results

For the commission errors, the results demonstrated differences by sex and grade; for the omission errors, differences were only observed by grade. Additionally, we analysed the relationship between both types of errors and sex, grade, sleep conditions, screen time, and physical activity using binomial logistic regression analysis. Commission errors were significantly related to sex and grade whereas omission errors were related to grade, bedtime, screen time, and physical activity.

Conclusions

Our results highlighted that children's cognitive functions are related to their lifestyle habits (i.e., sleep conditions, screen time, and physical activity) in addition to sex and grade.

Ignore the faces: Neural characterisation of emotional inhibition from childhood to adulthood using MEG

The ability to effectively and automatically regulate one's response to emotional information is a basic, fundamental skill for social functioning. The neural mechanisms underlying emotion regulation processing have been assessed, however few investigations have leveraged neurophysiological techniques, particularly magnetoencephalography (MEG) to determine the development of this critical ability. The current MEG study is the first to examine developmental changes in the neural mechanisms supporting automatic emotion regulation. We used an emotional go/no-go task with happy and angry faces in a single-site cohort of 97 healthy participants, 4-40 years of age. We found age-related changes as a function of emotion and condition in brain regions key to emotion regulation, including the right inferior frontal gyrus, orbitofrontal cortices and primarily right-lateralized temporal areas. Interaction effects, including an age by emotion and condition, were also found in the left angular gyrus, an area critical in emotion regulation and attention. Findings demonstrate protracted and nonlinear development, due to the adolescent group, of emotion regulation processing from child to adulthood, and highlight that age-related differences in emotion regulation are modulated by emotional face type.

Developmental Trajectories of Size Constancy as Implicitly Examined by Simple Reaction Times

It is still unclear whether size constancy is an innate ability or whether it develops with age. As many developmental studies are limited to the child's comprehension of the task instructions, here, an implicit measure of perceived size, namely, simple manual reaction time (RT), was opted for based on the assumption that perceptually bigger objects generate faster detection times. We examined size constancy in children (from 5 to 14 years of age) and adults using a simple RT approach. Participants were presented with pictures of tennis balls on a screen that was physically moved to two viewing distances. Visual stimuli were adjusted in physical size in order to subtend the same visual angle across distances, determining two conditions: a small-near tennis ball vs. a big-far tennis ball. Thanks to size constancy, the two tennis balls were perceived as different even though they were of equal size on the retina. Stimuli were also matched in terms of luminance. Participants were asked to react as fast as possible to the onset of the stimuli. The results show that the RTs reflected the perceived rather than the retinal size of the stimuli across the different age groups, such that participants responded faster to stimuli that were perceived as bigger than those perceived as smaller. Hence, these findings are consistent with the idea that size constancy is already present in early childhood, at least from the age of five, and does not require extensive visual learning.

The role of event rate, temporal expectancy, and sensory modality in continuous performance of children and adults

This study explored developmental differences in the effects of event rate, temporal expectancy, and sensory modality on continuous performance. Children (ages 7-8 years) and college-aged adults completed visual and auditory continuous performance tasks (CPTs) that were equated at an intermediate (20 events/min) rate using the perceptual sensitivity index (d') and then were compared at faster (40 events/min) and slower (10 events/min) rates to determine the influence of event rate on continuous performance of children and adults. To investigate the effects of temporal expectancy, 20% of the critical signals and neutral events occurred early or late relative to the regular rhythm of the task. The findings (a) suggest that event rate influences continuous performance differently for children and adults, (b) highlight the role of temporal expectancy in continuous performance, and (c) reveal differences in the effects of event rate and temporal expectancy on visual and auditory continuous performance.

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.

An update on the debated association between ADHD and bipolar disorder across the lifespan

Diagnostic formulations for attention deficit hyperactivity disorder (ADHD) and bipolar disorder (BD) both include symptoms of distractibility, psychomotor agitation and talkativeness, alongside associated emotional features (irritability and emotional lability). Treatment studies suggest the importance of accurate delineation of ADHD and BD. However, boundaries between the two disorders are blurred by the introduction of broader conceptualisations of BD. This review attempts to elucidate whether associations between ADHD and BD are likely to be driven by superficial symptomatological similarities or by a more meaningful etiological relationship between the disorders. This is achieved by outlining findings on comorbidity, temporal progression of the disorders, familial co-variation, and neurobiology in ADHD and BD across the lifespan. Longitudinal studies fail to consistently show developmental trajectories between ADHD and BD. Comparative research investigating neurobiology is in its infancy, and although some similarities are seen between ADHD and BD, studies also emphasise differences between the two disorders. However, comorbidity and family studies appear to show that the two disorders occur together and aggregate in families at higher than expected rates. Furthermore close inspection of results from population studies reveals heightened co-occurrence of ADHD and BD even in the context of high comorbidity commonly noted in psychopathology. These results point towards a meaningful association between ADHD and BD, going beyond symptomatic similarities. However, future research needs to account for heterogeneity of BD, making clear distinctions between classical episodic forms of BD, and broader conceptualisations of the disorder characterised by irritability and emotional lability, when evaluating the relationship with ADHD.

Methylphenidate, interstimulus interval, and reaction time performance of children with attention deficit/hyperactivity disorder: a pilot study

Thirteen children with attention deficit/hyperactivity disorder (ADHD: DSM-IV-TR) participated in the pilot study. They carried out a Go/No-Go test with a short (2 seconds) and long (6 seconds) interstimulus interval (ISI) when on placebo and a therapeutic dose of methylphenidate (MPH). For the long-ISI placebo condition the responses were slow and inaccurate. This pattern of response may be due to underactivation of the readiness-to-respond state that is not fully controlled by effort allocation. Speed of response and accuracy were enhanced during the short-ISI placebo condition and the long-ISI MPH condition. However, the combined effect (short ISI and MPH) resulted in a fast but inaccurate response style. This pattern of response may be due to overactivation of the readiness-to-respond state. The data of the pilot study support the stimulus shift hypothesis: MPH administration result in deterioration on tests on which children had previously done well (short ISI plus placebo versus short ISI plus MPH). In addition, the data support the idea that ADHD is associated with poor state regulation rather than motivational (delay aversion) theories or temporal-processing/time-estimation theories of ADHD. The pilot study defined empirically an issue for further study with the larger controlled sample.

Cool and hot executive functions in medication-naive attention deficit hyperactivity disorder children

BACKGROUND

This study aimed to compare 'cool' [working memory (WM) and response inhibition] and 'hot' (delay aversion) executive functions (EFs) in children with and without attention deficit hyperactivity disorder (ADHD).

METHOD

A total of 100 ADHD children (45 with family history of ADHD and 55 with no family history) and 100 healthy controls, all medication free, were tested on tasks related to the 'hot' (i.e. two choice-delay tasks) and 'cool' domains of EF (i.e. Digits backward, Corsi Block Task backward, Go/No-Go Task, Stop-Signal Task, and the Stroop).

RESULTS

Compared with the controls, children with ADHD were found to perform significantly worse on one or more measures of response inhibition, WM, and delay aversion after controlling for co-morbidities and estimated IQ. In addition, comparisons between ADHD children with family history of ADHD and those with no family history found significant differences on measures of response inhibition and WM but not delay aversion. These results are largely supported by results of two logistic regressions.

CONCLUSIONS

ADHD was found to be associated with deficits on both cool and hot EFs. There is also evidence to suggest that cool EFs impairment is related to a family history of ADHD. Findings of this study have helped to elucidate the nature and extent of EF deficits in children with ADHD.

Self-regulation in ADHD: the role of error processing

Attention-deficit hyperactivity disorder (ADHD) is characterized by persistent and impairing developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. Such behavioral dysregulation may be a consequence of deficits in self-monitoring or adaptive control, both of which are required for adaptive behavior. Processing of contextual demands, ongoing monitoring of one's behavior to evaluate whether it is appropriate for a particular situation, and adjusting behavior when it is suboptimal are components of self-regulation. This review examines and integrates the emerging literature on error-processing and adaptive control as components of self-regulation into the prominent etiological theories of ADHD. Available data on error-processing, as reflected in event-related potentials (ERN and Pe) and behavioral performance, suggest that both early error detection and later error-evaluation may be diminished in ADHD, thereby interfering with adaptive control processes. However, variability in results limit broad conclusions, particularly for early error detection. A range of methodological issues, including ERP parameters and sample and task characteristics, likely contribute to this variability, and recommendations for future work are presented. The emerging literature on error-processing and adaptive control informs etiological theories of ADHD in general and may provide a method for testing self-regulation models in particular.

Independent contributions of cognitive functioning and social risk factors to symptoms of ADHD in two nordic populations-based cohorts

This study examined independent contributions of executive functioning (EF), state regulation (SR), and social risk factors to symptom dimensions of attention deficit hyperactivity disorder (ADHD) in two cohorts, which included 221 Norwegian children and 294 Finnish adolescents. Independent contributions of EF and SR were shown in the Norwegian cohort and EF contributed independently in the Finnish cohort. When controlling for each symptom dimension, cognitive functioning and social risk factors were differentially associated with inattention and hyperactivity/impulsivity symptoms. The results show the need to include both social risk factors and cognitive functioning to obtain a better understanding of ADHD symptoms.

Inhibition and object relations in borderline personality traits after traumatic brain injury

This study aims to assess the nature and severity of borderline traits after traumatic brain injury (TBI). Thirty subjects with moderate or severe TBI were compared to 30 normal controls on the Revised Diagnostic Interview for Borderlines (DIB-R), a dimensional measure of borderline traits, the Go-no go inhibition task, the Complexity of Representations of People and Affect-Tone Relationships Paradigms, two scales from the Social Cognition and Object Relations Scale (SCORS) evaluating the quality of object relations, an estimation of pre-morbid borderline severity, the Beck Depression Inventory (BDI) and various neuropsychological measures. Results indicate that TBIs present more borderline symptoms and traits than controls. However, the severity of borderline symptomatology remains comparatively low for the vast majority. As expected, the TBI group showed a poorer performance on the Go-no go task, a characteristic neuropsychological inhibition deficit. Yet, both samples present similar profiles on the SCORS. Finally, the DIB-R was correlated with the Affect-Tone scale, the BDI and with the pre-morbid severity estimation. Results suggest that post-TBI borderline traits remain rare and relate more to the affective quality of object relations, negative affects and pre-morbid borderline pathology than inhibition deficits.

Do motivational incentives reduce the inhibition deficit in ADHD?

The primary goal of this study was to test three competing theories of ADHD: the inhibition theory, the motivational theory, and a dual deficit theory. Previous studies have produced conflicting findings about the effects of incentives on executive processes in ADHD. In the present study of 25 children with ADHD and 30 typically developing controls, motivation was manipulated within the Stop Task. Stop signal reaction time was examined, as well as reaction time, its variability, and the number of errors in the primary choice reaction time task. Overall, the pattern of results supported the inhibition theory over the motivational or dual deficit hypotheses, as main effects of group were found for most key variables (ADHD group was worse), whereas the group by reward interaction predicted by the motivational and dual deficit accounts was not found. Hence, as predicted by the inhibition theory, children with ADHD performed worse than controls irrespective of incentives.

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.

Multidisciplinary perspectives on attention and the development of self-regulation

During infancy and early childhood, children develop their ability to regulate their own emotions and behavior. This development of self-regulatory mechanisms has been considered to be the crucial link between genetic predisposition, early experience, and later adult functioning in society. This paper brings together the updated empirical findings related to the role of attention and the maturation of brain frontal areas in self-regulation. It reviews viewpoints and evidence of disciplines such as developmental psychology, cognitive neuroscience, social psychology, and neurobiology. It examines the causes of individual differences in self-regulation and the effects of those differences on the social and academic functioning of the individual. The consequences of failure in self-regulation are illustrated by focusing on the attention deficit/hyperactivity disorder (ADHD), including a detailed review of the animal models related to this disorder. Finally, some initial evidence suggesting the possibility of fostering self-regulation through training of attention is presented.

Processing speed deficits in attention deficit/hyperactivity disorder and reading disability

The goal of the current study was to test whether deficits in processing speed (PS) may be a shared cognitive risk factor in reading disability (RD) and Attention Deficit/Hyperactivity Disorder (ADHD), which are known to be comorbid. Literature on ADHD and RD suggests that deficits on tasks with a speeded component are seen in both of these disorders individually. The current study examined a wide range of speeded tasks in RD, ADHD, comorbid RD+ADHD, and a control group to test whether RD and ADHD have similar profiles of PS deficits, and whether these deficits are shared by the two disorders. The results suggest that a general PS deficit exists in both clinical groups compared to controls, although children with RD demonstrate greater PS deficits than children with ADHD. Two tests (underadditivity and partial correlations) were conducted to test whether these PS deficits are shared. Since we found that PS deficits were underadditive in the comorbid group and that partialling PS reduced the correlation between RD and ADHD, it appears that PS is a shared cognitive risk factor that may help explain the comorbidity of these two disorders.

Developmental changes in error monitoring: an event-related potential study

The aim of the study was to investigate the developmental trajectory of error monitoring. For this purpose, children (age 7-8), young adolescents (age 13-14) and adults (age 23-24) performed a Go/No-Go task and were compared on overt reaction time (RT) performance and on event-related potentials (ERPs), thought to reflect error detection (error-related negativity: ERN) and conscious evaluation (error positivity: Pe) of the error. RT on correct trials, variability of responding and percentage of errors decreased with age. The latencies of incorrect responses, compared to correct responses, were shorter in children and adolescents than in adults, indicative of developmental changes in impulsive response style. Groups did not differ in the ability to adjust response strategies after making an error (post-error slowing). The ERN amplitude increased with age, the Pe amplitude did not change with age. Possible explanations for the developmental changes in ERN are discussed.

State regulation in adult ADHD: an event-related potential study

The state regulation hypothesis postulates that poor task performance of children with ADHD is related to poor energetical state control. The current study aimed to investigate whether such a deficit persists in adult ADHD. Event-related potentials (ERPs) were recorded during administration of a Go/No-Go task that incorporated the stressor presentation rate of stimuli. It was found that males with ADHD responded slower than control males in the slow condition, which was accompanied by smaller parietal P3s, suggesting less effort allocation. No group differences were found with respect to the response inhibition measures (errors of commission and the N2 effect). In conclusion, problems in state regulation seem to persist in male adults with ADHD.

What have we learned about cognitive development from neuroimaging?

Changes in many domains of cognition occur with development. In this paper, we discuss neuroimaging approaches to understanding these changes at a neural level. We highlight how modern imaging methods such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are being used to examine how cognitive development is supported by the maturation of the brain. Some reports suggest developmental changes in patterns of brain activity appear to involve a shift from diffuse to more focal activation, likely representing a fine-tuning of relevant neural systems with experience. One of the challenges in investigating the interplay between cognitive development and maturation of the brain is to separate the contributions of neural changes specific to development and learning. Examples are given from the developmental neuroimaging literature. The focus is on the development of cognitive control, as the protracted developmental course of this ability into adolescence raises key issues. Finally, the relevance of normative studies for understanding neural and cognitive changes in developmental disorders is discussed.

The course of neuropsychological functions in children with attention deficit hyperactivity disorder from late childhood to early adolescence

OBJECTIVE

The aim of this follow-up study was to investigate the course of performance in attentional tasks in children with ADHD and normal controls in late childhood and preadolescence over short periods of time. The development of two dimensions of attention was compared: alertness/arousal and inhibitory control.

METHOD

Children with ADHD (N=28) and normal controls (N=25) were examined at three times: at baseline (age mean=10.8 years, SD=1.5), after one year (age mean=12.0 years, SD=1.6), and after 2.6 years (age mean=13.3 years, SD=1.6). They performed two tasks of a computerized battery for attentional performance: Alertness--a test of simple reaction time to visual stimuli contrasting a condition with and without auditory warning signal, and Incompatibility--a test of spatial interference/inhibitory control. Clinical diagnosis according to DSM-III-R criteria was established at time 1 and time 3 by structured diagnostic interviews.

RESULTS

In the Alertness task significant group differences regarding increased reaction time variability in ADHD, but not for reaction time itself, were found at time 1 and more pronounced at time 2. At time 3 group differences had disappeared. In the Incompatibility task group differences in number of errors were not observed at time 1, whereas children with ADHD made significantly more errors at time 2 and less pronounced at time 3. The degree of clinical symptom remission after 2.6 years was not related to changes in neuropsychological performance.

CONCLUSION

When measuring attentional functions, the selection of an appropriate time window seems to be essential for the detection of group differences between ADHD children and controls, because group differences are most pronounced before adolescence. The different developmental course of selective components of attention should be taken into account.

Association and linkage of alpha-2A adrenergic receptor gene polymorphisms with childhood ADHD

Attention-deficit hyperactivity disorder (ADHD) is a heritable disorder, prevalent from childhood through adulthood. Although the noradrenergic (NA) system is thought to mediate a portion of the pathophysiology of ADHD, genes in this pathway have not been investigated as frequently as those in the dopaminergic system. Previous association studies of one candidate gene in the NA system, ADRA2A, showed inconsistent results with regard to an MspI polymorphism. In the current study, two nearby single-nucleotide polymorphisms, which define HhaI and DraI restriction fragment length polymorphisms, were also genotyped and were in significant linkage disequilibrium with the MspI RFLP. Transmission disequilibrium tests (TDTs) in a sample of 177 nuclear families showed significant association and linkage of the DraI polymorphism with the ADHD combined subtype (P=0.03), and the quantitative TDT showed association of this polymorphism with the inattentive (P=0.003) and hyperactive-impulsive (P=0.015) symptom dimensions. The haplotype that contained the less common allele of the DraI polymorphism likewise showed a strong relationship with the inattentive (P=0.001) and hyperactive-impulsive (P=0.004) symptom dimensions. This study supports the hypothesis that an allele of the ADRA2A gene is associated and linked with the ADHD combined subtype and suggests that the DraI polymorphism of ADRA2A is linked to a causative polymorphism.

Neuropsychologic theory and findings in attention-deficit/hyperactivity disorder: the state of the field and salient challenges for the coming decade

The past decade has witnessed the establishment of several now well-replicated findings in the neuropsychology of attention-deficit/hyperactivity disorder (ADHD), which have been confirmed by meta-analyses. Progress has been notable from the importing of cognitive science and neuroscience paradigms. Yet these findings point to many neural networks being involved in the syndrome and to modest effect sizes suggesting that any one neuropsychologic deficit will not be able to explain the disorder. In this article, leading theories and key findings are briefly reviewed in four key domains: attention, executive functions, state regulation and motivation, and temporal information processing. Key issues facing the field of neuropsychologic research and theory in ADHD include 1) the need for more integrative developmental accounts that address both multiple neural systems and the socialization processes that assure their development; 2) consideration of multiple models/measures in the same study so as to examine relative contributions, within-group heterogeneity, and differential deficit; and 3) better integration of cognitive process models with affective and temperament theories so that early precursors to ADHD can be better understood. Overall, the field has witnessed notable progress as it converges on an understanding of ADHD in relation to disruption of a multicomponent self-regulatory system. The next era must articulate multipathway, multilevel developmental accounts of ADHD that incorporate neuropsychologic effects.

Equating tasks and sustaining attention in children and adults: The methodological and theoretical utility ofd’ matching

The present study develops a method to create task equivalency for children and adults in vigilance research. Experiment 1 employed the signal detection index of perceptual sensitivity (d') to calibrate vigilance tasks for 32 children (ages 7-8) and 32 adults. The results of Experiment 1 suggest that task equivalency across groups can be attained, and a vigilance decrement was observed for children. In Experiment 2, the task parameter of event rate was manipulated across two vigils. Again, 32 children (ages 7-8) and 32 adults participated. The results suggest that a reverse event rate effect emerged for both children and adults. In addition, developmental differences in response to the event rate manipulation and with respect to the vigilance decrement emerged: Children benefited less from the manipulation and were more likely to demonstrate a vigilance decrement than were adults. No developmental differences emerged for the sensitivity decrement. The results are explained with reference to how task demands interact with participant arousal, and implications for development and for future research are discussed.

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 children's 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.

A review of the biological bases of ADHD: what have we learned from imaging studies?

Attention Deficit Hyperactivity Disorder (ADHD) is a common and impairing neuropsychiatric disorder with onset at preschool age. Although a significant amount of progress has been made investigating the neurobiology of this disorder, its precise etiology still remains unclear. Converging evidence from studies of the neuropharmacology, genetics, neuropsychology, and neuroimaging of ADHD imply the involvement of fronto-striatal circuitry in ADHD. However, while it does appear that poor inhibitory control and the deficits in fronto-striatal circuitry associated with it are central, there is evidence to suggest that more posterior cerebral areas are also implicated in this disorder. Anatomical studies suggest widespread reductions in volume throughout the cerebrum and cerebellum, while functional imaging studies suggest that affected individuals activate more diffuse areas than controls during the performance of cognitive tasks. The future impact of new MR imaging methodologies on the field is discussed.

Differential patterns of striatal activation in young children with and without ADHD

BACKGROUND

Cognitive control, defined as the ability to suppress inappropriate thoughts and actions, is compromised in attention-deficit/hyperactivity disorder (ADHD). This study examines the neural basis of this deficit.

METHODS

We used a paradigm that incorporates a parametric manipulation within a go/nogo task, so that the number of go trials preceding a nogo trial is varied to tax the neural systems underlying cognitive control with increasing levels of interference.

RESULTS

Using this paradigm in combination with event-related functional magnetic resonance imaging (fMRI), we show that children without ADHD have increased susceptibility to interference with increasing numbers of go trials preceding a nogo trial, but children with ADHD have difficulty even with a single go trial preceding a nogo trial. In addition, children with ADHD do not activate frontostriatal regions in the same manner as normally developing children, but rather rely on a more diffuse network of regions, including more posterior and dorsolateral prefrontal regions.

CONCLUSIONS

Normal immature cognition may be characterized as being susceptible to interference and supported by the maturation of frontostriatal circuitry. ADHD children show a slightly different cognitive profile at 6 to 10 years of age that is paralleled by a relative lack of or delay in the maturation of ventral frontostriatal circuitry.

Is ADHD a disinhibitory disorder?

Attention deficit hyperactivity disorder (ADHD) is widely theorized to stem from dysfunctional inhibitory processes. However, the definition of inhibition is imprecisely distinguished across theories. To clarify the evidence for this conception, the author relies on a heuristic distinction between inhibition that is under executive control and inhibition that is under motivational control (anxiety or fear). It is argued that ADHD is unlikely to be due to a motivational inhibitory control deficit, although suggestions are made for additional studies that could overturn that conclusion. Evidence for a deficit in an executive motor inhibition process for the ADHD combined type is more compelling but is not equally strong for all forms of executive inhibitory control. Remaining issues include specificity to ADHD, whether inhibitory problems are primary or secondary in causing ADHD, role of comorbid anxiety and conduct disorder, and functional deficits in the inattentive ADHD subtype.

Motor control and state regulation in children with ADHD: a cardiac response study

The goal of the current study was to investigate whether poor motor control in children with Attention-Deficit Hyperactivity Disorder (ADHD) was associated with a state regulation deficit. For this purpose, 28 ADHD and 22 healthy children carried out two Go No-Go tests: one with a fast stimulus presentation rate, and the other with a slow stimulus presentation rate. Groups were compared on RT performance and on specific cardiac measures, reflecting arousal, motor activation/inhibition, and effort allocation. No group difference in the arousal measure (mean heart rate) was found. Further, groups did not differ with respect to response inhibition: in both the fast and slow condition, ADHD children made comparable numbers of errors of commission to the control group, and the groups did not differ with respect to the heart rate deceleration after the onset of the No-Go signal, reflecting motor inhibition. Group differences were found with respect to motor activation and effort allocation in the condition with a slow presentation rate. In this condition: (1) ADHD children reacted more slowly to Go signals than control children, suggesting poor motor activation; (2) the heart rate deceleration before the onset of Go signals, which is believed to reflect motor preparation, was less pronounced in the ADHD children; (3) after Go signals, where a response was given, the cardiac shift from deceleration to acceleration, indicating response initiation, was delayed in ADHD children; and (4) ADHD children had greater heart rate variability (0.10 Hz component) than the control group, indicating that less effort was allocated. No group differences in motor activation and effort allocation were found in the condition with a fast presentation rate of stimuli. We conclude, therefore, that a slow presentation rate of stimuli brings the ADHD child in a non-optimal activation state.