Forethought in Youth with Attention Deficit/Hyperactivity Disorder: An fMRI Study of Sex-Specific Differences.

Objective. The majority of studies investigating neurocognitive processing in attention deficit/hyperactivity disorder (ADHD) have been conducted on male participants. Few studies evaluated females or examined sex differences. Among various cognitive anomalies in ADHD, deficit in forethought seems particularly important as children with ADHD often fail to adequately use previous information in order to prepare for responses. The main goal of this study was to assess sex-specific differences in behavioral and neural correlates of forethought in youth with ADHD. Methods. 21 typically developing (TD) youth and 23 youth with ADHD were asked to judge whether two pictures told a congruent or incongruent story. Reaction time, performance accuracy, and cerebral activations were recorded during functional magnetic resonance imaging (fMRI). Results. Significant sex-specific differences in cerebral activations appeared, despite equivalent performance. Relative to the boys TD participants, boys with ADHD had extensive bilateral frontal and parietal hypoactivations, while girls with ADHD demonstrated more scattered hypoactivations in the right cerebral regions. Conclusion. Present results revealed that youth with ADHD exhibit reduced cerebral activations during forethought. Nevertheless, the pattern of deficits differed between boys and girls, suggesting the use of a different neurocognitive strategy. This emphasizes the importance of including both genders in the investigations of ADHD.

[Learning disorders in ADHD: How are they related?] / Troubles d'apprentissage dans le trouble de déficit de l'attention avec ou sans hyperactivité : quelle est la nature du lien ?

Learning difficulties in general and learning disabilities in particular are almost constant in attention deficit disorder with or without hyperactivity (ADHD). Despite a major research effort, the extent and diversity of these comorbid events still raise many questions about the exact nature of their pathogenetic condition (simple consequences of ADHD or specific related disorders?) and consequently the best way to support them. This article aims to present a brief review of the current data.

[Structural and functional neuroanatomy of attention-deficit hyperactivity disorder (ADHD)]. / Neuroanatomie structurelle et fonctionnelle du trouble déficitaire d'attention avec ou sans hyperactivité (TDAH).

INTRODUCTION: Attention-deficit hyperactivity disorder (ADHD) is a common and impairing neuropsychiatric disorder with preschool onset. ADHD occurs in approximately 3-9% of the childhood population. There is a much higher incidence rate in boys who are around three times more likely than girls to be diagnosed. Approximately 30-60% of individuals diagnosed with ADHD in youth have symptoms that persist into adulthood. LITERATURE FINDINGS: Three subtypes of the disorder have been proposed in the current clinical view of ADHD: inattentive, hyperactive-impulsive and combined type. Numerous problems are associated with ADHD: poor academic performance, learning disorders, subtle cognitive deficits, conduct disorders, antisocial personality disorder, poor social relationships, and a higher incidence of anxiety and depression symptoms into adulthood. Researchers have emphasized poor behavioural inhibition as the central impairment of the disorder. From the neuropsychological viewpoint, impairment of the "hot" affective aspects of executive functions, like behavioural inhibition and attention and the more cognitive, "cool" aspects of executive functions like self-regulation, working memory, planning, and cognitive flexibility, are often reported by studies on ADHD. The hot executive functions are associated with ventral and medial regions of the prefrontal cortex (including the anterior cingulated cortex) and named "hotbrain" and the cool executive functions are associated with the dorsolateral prefrontal cortex and are called "coolbrain". DISCUSSION: Convergent data from neuroimaging, neuropsychology, genetics and neurochemical studies consistently point to the involvement of the frontostriatal network as a likely contributor to the pathophysiology of ADHD. This network involves the lateral prefrontal cortex, the dorsal anterior cingulate cortex, the caudate nucleus and putamen. Moreover, a growing literature demonstrates abnormalities affecting other cortical regions and the cerebellum. The exploratory brain regions of interest in which abnormalities have been identified, but that were not predicted by cognitive models of ADHD, are the temporal lobe, parietal lobe, occipital lobe and lateral ventricles. 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. More precisely, reductions in volume have been observed in the total cerebral volume, the prefrontal cortex, the basal ganglia (striatum), the dorsal anterior cingulate cortex, the corpus callosum and the cerebellum. Furthermore, hypoactivation of the dorsal anterior cingulate cortex, the frontal cortex and the basal ganglia (striatum) have also been reported. The paradigms mostly used in functional magnetic resonance imaging (fMRI) are tasks of motor inhibition, interference and attention such as the go/no-go, "stop-signal" and the Stroop. CONCLUSION: This review provides an overview of the main imaging studies that investigated the neurobiological substrate of ADHD. Some guidelines for future functional magnetic imaging studies are also suggested.

[Development of self-regulation and inhibition in children exhibiting attention deficit disorder with or without hyperactivity (ADHD)]. / Développement de l'autorégulation et de l'inhibition chez des enfants présentant un trouble déficitaire de l'attention avec ou sans hyperactivité (TDAH).

INTRODUCTION: Self-regulation shares several affinities with executive functions. However, the specificity of self-regulation deficits in attention deficit/hyperactivity disorder (ADHD) remains unclear. The typical child starts around the age of four to develop a self-control mechanism along with an internal language that allows the child to modulate impulsively. Conversely, a child with ADHD seems to have greater difficulties delaying or retaining an action or response. OBJECTIVE: In this study we aim to evaluate self-regulation of comprehension in ADHD. RESULTS: Our results show that children with ADHD fail to recognize inconsistencies in presented stories at a rate ranging between 72 (eight years) and 54% (ten years). We also found a positive correlation between a better control of self-regulation and our behavioral inhibition measurement. The attentional deficits exhibited through markedly longer reaction times to continuous performance test (CPT) could be responsible for a poor ability to self-regulate. Fast reaction times were found to be associated with increased vigilance/attention that in turn would permit better self-regulation. Furthermore, our findings show that older subjects with ADHD have shorter reaction times to CPT approaching this group to the typical children. DISCUSSION: This suggests that improvement overtime in self-regulation processes may be attributed to the associated development of vigilance/attention in children with ADHD. Improved vigilance/attention would result in optimal reaction times during tasks that require self-regulation. In addition, our findings suggest that subjects with ADHD have developmental trajectories similar to those observed in healthy subjects. CONCLUSION: In the present study, the lack of a comparison group does not allow us to conclude if such trajectory is delayed compared to typical subjects. Finally, there was no significant relation between the degree of intelligence and the rate of self-regulation, which makes it possible to distinguish the two functions. However, in ADHD self-regulation is favourably influenced by age as observed in developmental studies on typical children. Thus, maturation independent of intelligence, influences self-regulation processes.