Cynthia L. Huang-Pollock

Neuropsychological executive functions and DSM-IV ADHD subtypes.

OBJECTIVE To evaluate and compare a focused set of component neuropsychological executive functions in the DSM-IV attention-deficit/hyperactivity disorder combined (ADHD-C) and inattentive (ADHD-I) subtypes. METHOD The Stop task, Tower of London, Stroop task, Trailmaking Test, and output speed measures were completed by 105 boys and girls aged 7-12 classified as either DSM-IV ADHD-C (n = 46), ADHD-I (n = 18), or community control (n = 41). RESULTS Both subtypes had deficits on output speed. A group x gender interaction was observed on the Stop task: boys with ADHD-C were impaired versus boys with ADHD-I, whereas girls in the two subtypes did not differ. The ADHD-C type had a deficit in planning. Neither ADHD group had a deficit in interference control per se, although they were slower than controls on the Stroop tasks. CONCLUSIONS ADHD-I shares neuropsychological deficits with ADHD-C in the domain of output speed; on most domains the subtypes did not differ. Neuropsychological distinctions between these ADHD subtypes may be few, depending on which domain of executive functioning is assessed, and these distinctions differ by gender. In the case of boys, the two subtypes may be distinguished by the specificity of motor inhibition deficits to ADHD-C.

Big five dimensions and ADHD symptoms: Links between personality traits and clinical symptoms

Attention-deficit/hyperactivity disorder (ADHD) in adulthood is conceptualized as originating in childhood. Despite considerable theoretical interest, little is known about how ADHD symptoms relate to normal personality traits in adults. In 6 studies, the Big Five personality dimensions were related to ADHD symptoms that adults both recalled from childhood and reported concurrently (total N = 1,620). Substantial effects emerged that were replicated across samples. First, the ADHD symptom cluster of inattention-disorganization was substantially related to low Conscientiousness and, to a lesser extent, Neuroticism. Second, ADHD symptom clusters of hyperactivity-impulsivity and oppositional childhood and adult behaviors were associated with low Agreeableness. Results were replicated with self-reports and observer reports of personality in community and clinical samples. Findings support theoretical connections between personality traits and ADHD symptoms.

Searching for the attention deficit in attention deficit hyperactivity disorder: The case of visuospatial orienting

We review all 14 extant studies of covert visuospatial attention in attention deficit hyperactivity disorder (ADHD) (total N=248). Metaanalysis showed that intriguing but isolated findings of alerting or posterior disengage deficits were too small to reliably detect with the sample sizes typically employed. Posterior move and engage operations and the vigilance sustained attention process were normal in ADHD. For exogenous cues, effect sizes for group differences were homogeneously small across all repeated-measures conditions, as were calculations of cost, benefit, and validity effects. For endogenous cues, effect sizes were heterogeneous; however, calculations of cost, benefit, and validity effects were small and homogenous. The most parsimonious conclusion may be that ADHD is not characterized by significant visual orienting dysfunction, but questions remain about the extent of anterior lateralized effects in the combined subtype and about attentional functioning in the inattentive subtype.

Can Executive Functions Explain the Relationship between Attention Deficit Hyperactivity Disorder and Social Adjustment

This study examined the ability of executive functions (EF) to account for the relationship between Attention Deficit Hyperactivity Disorder (ADHD) status and social adjustment as indexed by parent and teacher report and by performance on a standardized observational “chat room” task. Children with the Combined subtype (ADHD-C; n = 23), the Primarily Inattentive Subtype (ADHD-I; n = 33), and non-ADHD controls (n = 36) participated. EF did not mediate the relationship between ADHD status and parent or teacher report of social adjustment. EF accounted for about 40–50% of the variance between ADHD status and the ability of children to detect subtle verbal cues as well as memory for the conversation in the chat room task, but did not mediate the relationship between ADHD and the number of prosocial, hostile, or on-topic statements that were made. Results are consistent with other recent reports, and suggest that the role of EF deficits in the production of social skill deficits in ADHD may not be as prominent as is typically assumed. The implications for the development of intervention programs designed to target core cognitive etiologic factors are discussed.

ADHD Subtype Differences in Motivational Responsivity but not Inhibitory Control: Evidence from a Reward-Based Variation of the Stop Signal Paradigm.

In this study we examined prepotent motor inhibition and responsiveness to reward using a variation of the stop signal reaction time (SSRT) task in clinic- and community-recruited children ages 7 to 12 with attention-deficit/hyperactivity disorder–inattentive type (ADHD–I), ADHD–combined type (ADHD–C), and non-ADHD controls. Contrary to theoretical expectations, we found evidence for inhibitory weaknesses in ADHD–I. We also found evidence that although children with ADHD–I were able to improve their inhibitory control given reward-based motivation, the improvement depended on the order of reward conditions. Results suggest that the 2 primary subtypes of ADHD share similar neuropsychological weaknesses in inhibitory control but that there are subtype differences in response to success and failure that contribute to a childs ultimate level of performance.

Development of Implicit and Explicit Category Learning.

We present two studies that examined developmental differences in the implicit and explicit acquisition of category knowledge. College-attending adults consistently outperformed school-age children on two separate information-integration paradigms due to childrens more frequent use of an explicit rule-based strategy. Accuracy rates were also higher for adults on a unidimensional rule-based task due to childrens more frequent use of the irrelevant dimension to guide their behavior. Results across these two studies suggest that the ability to learn categorization structures may be dependent on a childs ability to inhibit output from the explicit system.

Decomposing attention-deficit/hyperactivity disorder (ADHD)-related effects in response speed and variability.

OBJECTIVE Slow and variable reaction times (RTs) on fast tasks are such a prominent feature of attention-deficit/hyperactivity disorder (ADHD) that any theory must account for them. However, this has proven difficult because the cognitive mechanisms responsible for this effect remain unexplained. Although speed and variability are typically correlated, it is unclear whether single or multiple mechanisms are responsible for group differences in each. RTs are a result of several semi-independent processes, including stimulus encoding, rate of information processing, speed-accuracy trade-offs, and motor response, which have not been previously well characterized. METHOD A diffusion model was applied to RTs from a forced-choice RT paradigm in two large, independent case-control samples (NCohort 1 = 214 and NCohort 2 = 172). The decomposition measured three validated parameters that account for the full RT distribution and assessed reproducibility of ADHD effects. RESULTS In both samples, group differences in traditional RT variables were explained by slow information processing speed, and unrelated to speed-accuracy trade-offs or nondecisional processes (e.g., encoding, motor response). CONCLUSIONS RT speed and variability in ADHD may be explained by a single information processing parameter, potentially simplifying explanations that assume different mechanisms are required to account for group differences in the mean and variability of RTs.

Working Memory Demands Impair Skill Acquisition in Children With ADHD

This study examined the process of cognitive skill acquisition under differential working memory (WM) load conditions in children with the primarily inattentive (n = 21) and the combined (n = 32) subtypes of childhood attention-deficit/hyperactivity disorder (ADHD) and compared the results with those of non-ADHD controls (n = 48). Children completed 2 tasks of cognitive skill acquisition: alphabet arithmetic and finger math. The tasks differed in the amount of WM required for execution (alphabet arithmetic required more) but were otherwise matched with respect to logical structure, design, and discriminatory power. As would be predicted if the WM of the to-be-learned task affected the ability of children with ADHD to develop automaticity for a complex cognitive skill, ADHD-related impairments in the development of automaticity were seen for alphabet arithmetic but not for finger math. Results not only are relevant to ongoing debate regarding the presence of effortful versus automatic cognitive deficits in ADHD but also have implications for the development of new psychoeducational interventions for children with ADHD.

Abnormal spatial asymmetry of selective attention in ADHD

BACKGROUND Evidence for a selective attention abnormality in children with attention deficit hyperactivity disorder (ADHD) has been hard to identify using conventional methods from cognitive science. This study tested whether the presence of selective attention abnormalities in ADHD may vary as a function of perceptual load and target lateralisation. Given evidence of right-hemisphere dysfunction in ADHD we predicted increased interference effects for right, but not left-sided target displays, particularly under low perceptual load. METHOD Fourteen children with ADHD-C and 14 typically developing children were tested on a modified flanker task under low and high perceptual load. We also sought evidence for our hypothesis in a re-analysis of an independent data set (42 ADHD; 34 typically developing) in which load effects on selective attention in ADHD were previously examined (Huang-Pollock, Nigg, & Carr, 2005). RESULTS As predicted, all children showed evidence of greater interference by flankers under low compared with high perceptual load conditions. Crucially, however, children with ADHD showed the greatest interference effect for right-sided target displays under low but not high perceptual load. In contrast, typically developing children showed the greatest interference for left-sided target displays. The magnitude of interference for right-sided targets was also positively correlated with ADHD symptom levels. Re-analysis of an independent data set (Huang-Pollock et al., 2005) further confirmed our findings. CONCLUSIONS This study demonstrates that interference effects in children with ADHD and typically developing children are spatially asymmetrical but opposite in direction. The pattern of right-sided interference effects in children with ADHD suggests disruption within right hemisphere attentional networks in ADHD.

Examining Relationships Between Executive Functioning and Delay Aversion in Attention Deficit Hyperactivity Disorder

Although motivation and cognition are often examined separately, recent theory suggests that a delay-averse motivational style may negatively impact development of executive functions (EFs), such as working memory (WM) and response inhibition (RI) for children with Attention Deficit Hyperactivity Disorder (ADHD; Sonuga-Barke, 2002). This model predicts that performance on delay aversion and EF tasks should be correlated for school-age children with ADHD. However, tests of these relationships remain sparse. Forty-five children ages 8 to 12 with ADHD and 46 non-ADHD controls completed tasks measuring EFs and delay aversion. Children with ADHD had poorer WM and RI than non-ADHD controls, as well as nonsignificantly worse delay aversion. Consistent with previous research, RI was not related to delay aversion. However, delay aversion did predict WM scores for children with and without ADHD. Implications for the dual-pathway hypothesis and future research on cognitive and motivational processing in ADHD are discussed.