Attention-Deficit Hyperactivity Disorder and Event-Related Potentials: Evidence for Deficits in Allocating Attentional Resources to Relevant Stimuli

Current research on the nature of attentional deficits in attention-deficit hyperactivity disorder (ADHD) is reviewed with a focus on studies using event-related potentials (ERPs). A robust effect is the smaller amplitude of the P3 wave to both auditory and visual stimuli for individuals with ADHD than for normal controls. This effect is indicative of deficits in the allocation of attentional resources to task-relevant information. The Nd wave is also smaller for individuals with ADHD, an effect that suggests impairments in the discrimination and preferential processing of task-relevant information, rather than distractibility by irrelevant stimuli. Studies of the effects of methylphenidate on ERPs in ADHD indicate that this stimulant enhances the quality of stimulus evaluation and speeds response time. These specific effects support the view that ADHD involves deficits in energetic processes that are required for processing task-relevant stimuli.     

EDITORIAL

The aim of the present study was to evaluate the usefulness of Barkley’s (1997a) model of inhibition and executive functioning in describing the deficits associated with Attention Deficit Hyperactivity Disorder (ADHD). Besides group differences, the present study addressed the question of independent effects of inhibition and the other executive functions in discriminating between children with ADHD and controls and how well, in terms of sensitivity and specificity, these measures can classify the children into the correct group. The results showed that children with ADHD differed significantly from controls with regard to measures of inhibition as well as all other executive function measures, except repetition of hand movements. In logistic regression models, three different measures tapping inhibition, working memory and emotion regulation were shown to be significant independent predictors of group membership. The sensitivity for these three variables as a set was 76.2, the specificity was 90.5, with a total of 86% of the sample correctly classified. When excluding the parental rating of emotion regulation, the overall classification rate decreased some, but was still relatively high in comparison with previous studies within this area of research.     

The Effects of Cognitive Development on the Use of Cognitive Behavioral Techniques with Children

The present paper hypothesizes that, for children, cognitive behavior therapy techniques cannot be applied without first determining the cognitive developmental level of information processing that is being used by the client. Demand requirements of various cognitive behavioral techniques are compared with information processing limitations described by developmental theorists to hypothesize a continuum of cognitive behavioral interventions for children.     

A comparison of working memory profiles in school-aged children with Specific Language Impairment,Attention Deficit/Hyperactivity Disorder,Comorbid SLI and ADHD and their typically developing peers

The association between specific language impairment (SLI), attention deficit/hyperactivity disorder (ADHD), and working memory (WM) was examined. WM has been implicated in language acquisition and models of ADHD; however, evidence for WM deficits in SLI and ADHD has been inconsistent. The components of Baddeley's WM model were investigated in 18 children with SLI, 16 children with ADHD, 11 children with comorbid SLI+ADHD, and 24 typically developing (TD) children. The presence of SLI resulted in deficits in more components of WM than the presence of ADHD indicating that children with SLI are more vulnerable to WM deficits than those with ADHD.     

Decision Making with Uncertain Reinforcement in Children with Attention Deficit/Hyperactivity Disorder (ADHD)

Reward-related processes are impaired in children with ADHD. Whether these deficits can be ascribed to an aversion to delay or to an altered responsiveness to magnitude, frequency, valence, or the probability of rewards still needs to be explored. In the present study, children with ADHD and normal controls aged 7 to 10 years performed a simple probabilistic discounting task. They had to choose between alternatives where the magnitude of rewards was inversely related to the probability of outcomes. As a result, children with ADHD opted more frequently for less likely but larger rewards than normal controls. Shifts of the response category after positive or negative feedback, however, occurred as often in children with ADHD as in control children. In children with ADHD, the frequency of risky choices was correlated with neuropsychological measures of response time variability but unrelated to measures of inhibitory control. It is concluded that the tendency to select less likely but larger rewards possibly represents a separate facet of dysfunctional reward processing, independent of delay aversion or altered responsiveness to feedback.     

Investigating the Relationship Between Attention and Working Memory in Clinical and Community Samples

The first aim of the present study was to investigate whether differences in core deficits in ADHD subtypes lead to dissociable working memory profiles. The second aim was to compare the working memory profiles of inattentive students with those identified as having poor working memory, as they exhibit very similar behavioral profiles. Finally, the relationship between working memory and academic attainment in these groups were also of interest. Four groups of 9-year-olds were recruited: a community sample of children with inattentive symptoms, a clinically diagnosed group of children with ADHD-Combined, children with low working memory, and a healthy comparison group. They were assessed on measures of working memory, IQ, academic attainment, and sustained attention. The findings indicated that the combined and inattentive subtypes could not be distinguished on the basis of their working memory profile. In contrast, those with inattentive symptoms did better on the short-term memory tasks than the low working memory group. The majority of all three atypical groups performed very poorly in reading and math. This pattern can be interpreted as reflecting the link between working memory and academic attainment, even in those with attention problems.     

Verbal learning and memory as measured by the Rey-Auditory Verbal Learning Test: ADHD with and without learning disabilities

The primary purpose of the present study is to examine the effects of attention deficits, learning disability, and the combined effects of both on the learning and memory processes, as measured by the Rey Auditory Verbal Learning Test (AVLT). Thirty children (age range 12–17) diagnosed with attention deficit/hyperactivity disorder (ADHD), 18 children (age range 11–17) diagnosed with learning disabilities (LD), and 64 children (age range 12–17) diagnosed with ADHD as well as with LD, and 28, 18, and 62 matched controls, respectively, participated in this study. It was found that the children diagnosed with ADHD did not differ in any of the verbal learning and memory measures derived from the Rey AVLT. The group with LD was impaired in the overall number of words recalled across the learning phase. Performance of the children diagnosed with ADHD +LD showed a similar impairment as the group with LD (i.e., overall amount of words learned) and, in addition, their retrieval efficiency was also impaired. In conclusion, this study indicates that verbal memory is preserved in children with ADHD if they have no LD and their intelligence is in the normal range or above. LD by itself leads to difficulties in acquisition, but the combination of ADHD+LD leads to additional impairment in retrieval processes.     

Intra-Individual Variability Among Children with ADHD on a Working Memory Task: An Ex-Gaussian Approach

Intra-individual variability on a computer-based working memory task was examined among 25 children/adolescents with ADHD and 24 typically developing peers. Participants completed the Visual Serial Addition Task (VSAT) and reaction time data were fit to an ex-Gaussian distribution. ADHD participants demonstrated significantly more variable performance than controls, and effects of working memory load were observed. Event rate, however, had no influence on group differences in performance. Follow-up correlations revealed associations between VSAT performance and ADHD symptomatology. This study supports intra-individual variability as a hallmark feature of ADHD beyond the domain of response inhibition and reinforces the need to consider variability in ADHD more broadly.     

The Test of Variables of Attention (TOVA): Internal Consistency (Q1 vs. Q2 and Q3 vs. Q4) in Children with Attention Deficit/Hyperactivity Disorder (ADHD)

The internal consistency of the Test of Variables of Attention (TOVA) was examined in a cohort of 6- to 12-year-old children (N = 63) strictly diagnosed with ADHD. The internal consistency of errors of omission (OMM), errors of commission (COM), response time (RT), and response time variability (RTV) of different test conditions (stimulus infrequent condition [Q₁ vs. Q₂] and stimulus frequent condition [Q₃ vs. Q₄]) was assessed via correlation analyses. All TOVA index scores under investigation assessing its internal consistency exhibited statistically significant correlations. All correlations fell in the moderate-high range.     

Time-Based Prospective Memory Performance and Time-Monitoring in Children with ADHD

The current study investigated prospective memory (PM) performance in children with attention deficit/hyperactivity disorder (ADHD) and controls and aimed at exploring possible underlying factors of PM performance. Twenty-two children with ADHD and 39 age- and ability-matched typically developing children performed a computerized time-based PM task. As predicted, children with ADHD had fewer correct PM responses than controls. Neither differences in overall ongoing task performance nor, remarkably, differences in overall frequency and accuracy of time monitoring were found. Exploratory analyses suggest that individual differences in time monitoring in the final interval before target times may be related to PM performance in ADHD.