Petra P. M. Hurks

Verbal fluency over time as a measure of automatic and controlled processing in children with ADHD

The performance of ADHD children on semantic category fluency (SCF) versus initial letter fluency (ILF) tasks was examined. For each participant, word production was recorded for each 15-s time slice on each task. Performance on both fluency tasks was compared to test the hypothesis that children with ADHD are characterized by a performance deficit on the ILF task because performance on this task is less automated than performance on the SCF. Children classified with ADHD (N = 20) were compared to children with other psychopathology (N = 118) and healthy controls (N = 130). Results indicated that the groups could not be differentiated by the total number of words produced in 60 s in either fluency task. As hypothesized, a significant interaction of group by productivity over time by type of fluency task was found: ADHD children had more problems finding words in the first 15 s of the IFL than did children in the other two groups, and as compared with their performance on the SCF. Results were taken to indicate that children with ADHD symptoms show a delay in the development of automating skills for processing abstract verbal information.

Child Psychiatric Diagnoses in a Population of Dutch Schoolchildren Aged 6 to 8 Years

OBJECTIVE To determine the prevalence rates of child psychiatric diagnoses in a school-based population of children aged 6 to 8 years in the south of the province of Limburg (The Netherlands). METHOD In a two-stage design 1,317 children were screened with the Child Behavior Checklist. From 403 of these children, child psychiatric information was obtained with the Amsterdam Diagnostic Interview for Children and Adolescents (ADIKA, DSM-III-R/IV). Data were generalized to the responder group (n = 1,317) and to the entire cohort (N = 2,290). For the latter procedure, a prediction model was used to generalize ADIKA results to the nonresponders (n = 973). RESULTS Estimates of the prevalence of different ADIKA diagnoses in the responder group were quite comparable with those for the entire cohort. Twenty-four percent of the entire cohort met criteria for a single disorder, and 21.0% met criteria for two or more disorders. However, in only 5.7% of the cases parents did report a need for help. CONCLUSIONS Where other studies generalize psychiatric diagnoses to the responder group only, this report adds new information by generalizing the prevalence to a school-based cohort of children aged 6 to 8 years. These prevalence estimates are of importance with regard to the demand for care for child psychopathology.

Semantic category fluency versus initial letter fluency over 60 seconds as a measure of automatic and controlled processing in healthy school-aged children

Verbal fluency was operationalized as the number of words produced in a restricted category (i.e., semantic category [SCF] and words beginning with a given letter [ILF]) in 60 seconds. Word production in the first 15 seconds of either type of fluency task was defined as a measure of automatic information processing, whereas word production in the remaining 45 seconds (in 15-second periods) was taken as a measure of controlled information processing. Data revealed that over 60 seconds healthy children aged 8.4–9.7 years (n = 91) produced significantly more words and less incorrect responses on the SCF task than on the ILF task. Although word production was a function of both type of task and time, it was highest in the initial time slice of either type of fluency and decreased as time on task increased. Finally, no sex differences were found for any measure of performance on either type of fluency task. In contrast, the level of occupational achievement of the caregiver (LOA) appeared to be a determinant of the child’s performance on either type of fluency task, indicating that LOA affects higher-order processes, such as the automation of newly learned verbal skills and effortful processing.

Speed, speed variability, and accuracy of information processing in 5 to 6-year-old children at risk of ADHD

The early assessment of Attention-Deficit/Hyperactivity Disorder (ADHD) children has mainly focused on the behavioral, social, and pre-academic impairments. This study examined whether 5 to 6-year-old children at risk of ADHD are characterized by information-processing deficits. By screening 1317 children in Southern Limburg (the Netherlands) with the Child Behavior Checklist, 363 were selected and underwent a computerized examination. Eighteen months later, standardized psychiatric information was obtained. Thirty-three ADHD children were compared with 75 borderline ADHD children, 122 pathological controls, and 133 healthy controls. ADHD and borderline ADHD children were slower and more variable in their processing speed on all tasks than children with no or other pathology. These differences were most pronounced for the divided and focused attention tasks. Furthermore, one measure of a state regulation deficit discriminated between groups. With regard to accuracy, only the proportion of misses on a go-no-go task was higher in the ADHD group than in the other groups. Evidence was found that ADHD is better seen as a continuum rather than a discrete category. Already at a young age, children at risk of ADHD show specific information-processing deficits. Deficits in time perception and/or energetic state control in children with ADHD may possibly account for subnormal task performance.

Developmental changes in semantic verbal fluency: Analyses of word productivity as a function of time, clustering and switching

We investigated age-related improvement in semantic category verbal fluency (VF) in 309 Dutch schoolchildren attending first to ninth grade. Quantitative analyses of number of correct responses as a function of time as well as qualitative analyses of clustering and switching were conducted. Overall, Dutch VF task performance, i.e., number of correct responses over 60 seconds, was not established before mid-adolescence. This is in line with previously published studies, using VF number of correct responses over 60 seconds as the main outcome measure and examining VF task performance across other cultures and languages (e.g., Italian, French, Hebrew). Next, mean cluster size, a measure of lexico-semantic knowledge, was not established until at least grade 3. In contrast, performance on the VF outcome measures “number of switches/clusters” was established at least 4 years later. Qualitative and quantitative Design Fluency (DF) outcome measures support the notion that the numbers of switches/clusters are valid measures of higher order cognitive functions, such as strategy use and cognitive flexibility. In line of this, VF number of correct responses during 16–60 seconds, a measure of controlled information processing, is established at least 2 years later (i.e., grades 7–8) than number of correct responses during the first 15 seconds time slide, a measure of automatic processing. Finally, environment, i.e., the level of parental education, primarily affected automatic and lexico-semantic knowledge. No effects of sex on VF performance were found. These data suggest that the alternative scoring methods of VF tasks can be used to acquire knowledge on development of lower and higher order cognitive functions in healthy children and the influence of the environment on it.

Differences in feedback- and inhibition-related neural activity in adult ADHD.

The objective of this study was to examine response inhibition- and feedback-related neural activity in adults with attention deficit hyperactivity disorder (ADHD) using event-related functional MRI. Sixteen male adults with ADHD and 13 healthy/normal controls participated in this study and performed a modified Go/NoGo task. Behaviourally, attention and inhibition problems in the ADHD group were observed; no feedback-related differences between the groups were detected. The neuroimaging data showed that the ADHD group displayed more activation in the inferior frontal gyrus and putamen during response inhibition. During feedback-related processes, the ADHD group displayed less activation in the inferior frontal/orbitofrontal cortex, hippocampus/nucleus accumbens, and caudate nucleus, but more activity in the inferior frontal gyrus. These results indicate that at least two distinguishable underlying brain networks related to response inhibition and feedback are altered in adults with ADHD.

Sustained and focused attention deficits in adult ADHD

Objective: To examine the specificity of deficits in focused attention and sustained attention in adults with ADHD and to evaluate the effect of comorbidity. Method: Twenty-eight adults with ADHD without comorbidity were compared with 28 ADHD outpatients with comorbidity. Two control groups were used: 68 adults referred for ADHD but with another psychopathology rather than ADHD (non-ADHD) and 28 healthy controls. All participants completed attention tests of the Amsterdam Neuropsychological Tasks program. Results: Both ADHD groups demonstrated a sustained attention deficit relative to the control groups, as indicated by a disproportionate deterioration of speed fluctuation with time-on-task reflecting temporal lapses in attention. Only the ADHD+ group showed focused attention deficits in that they were less able to ignore irrelevant information. Conclusion: These findings show that adults with ADHD have specific deficits in sustained attention. Additional deficits in focused attention are confined to outpatients with ADHD and comorbidity. (J. of Att. Dis. 2008; 11(6) 664-676)

Differential brain activation patterns in adult attention-deficit hyperactivity disorder (ADHD) associated with task switching.

OBJECTIVE The main aim of the study was to examine blood oxygen level-dependent response during task switching in adults with attention-deficit/hyperactivity disorder (ADHD). METHOD Fifteen male adults with ADHD and 14 controls participated and performed a task-switching paradigm. RESULTS Behaviorally, no specific executive control problems were observed in the ADHD participants, although they did display more errors in general. The neuroimaging data did show remarkable differences between the ADHD and control adults: Adults with ADHD engaged more strongly the dorsal anterior cingulate cortex, middle temporal gyrus, precuneus, lingual gyrus, precentral gyrus, and insula than did the healthy controls during task switching. Controls displayed more task-related activity in the putamen, posterior cingulate gyrus, medial frontal gyrus, thalamus, orbitofrontal cortex, and postcentral gyrus. CONCLUSIONS ADHD adults did not display specific executive control problems at a behavioral level, but did engage different brain areas during task switching compared with healthy controls. The results are discussed in the framework of the executive frontostriatal circuitry, conflict detection, and attentional networks.

Animal Verbal Fluency and Design Fluency in school-aged children: Effects of age, sex, and mean level of parental education, and regression-based normative data.

The Animal Verbal Fluency (AVF) and Design Fluency (DF) structured and unstructured test versions were administered to N = 294 healthy native Dutch-speaking children who were aged between 6.56 and 15.85 years. The AVF and DF structured test scores increased linearly as a function of age, whilst the relation between age and the DF unstructured test score was curvilinear (i.e., the improvement in test scores was much more pronounced for younger children than for older children). A higher mean level of parental education was associated with significantly higher AVF and DF structured test scores. Sex was not associated with any of the outcomes. Demographically corrected norms for the AVF and DF tests were established, and an automatic scoring program was provided.

Retrospective and Prospective Time Deficits in Childhood ADHD: The Effects of Task Modality, Duration, and Symptom Dimensions

Time estimation is believed to be an adaptive function in human life. In the present study, prospective and retrospective time estimation are studied in both clinical-referred school-aged children with ADHD-C and healthy community control children, while examining more specifically the effects of type of time estimation task, length of time intervals (i.e., ranging from 3–90 s), and continuous scaling of the main ADHD symptom clusters (i.e., inattention vs. hyperactivity/impulsiveness). On a prospective verbal time estimation test, children with ADHD-C showed significant more overestimation compared to controls. For the majority of short-to-medium time intervals, this overestimation was predicted only by the continuous levels of impulsiveness or a disturbed self-regulation, indicating a dysregulation of the internal clock in ADHD. The same holds for the retrospective time estimation task. In contrast, an ADHD-related underestimation on the prospective time reproduction task was found for the longer intervals. In contrast to verbal time estimation, levels of inattention, and not the levels of impulsiveness, predicted underestimation on the time reproduction task. Our results point thereby towards parallel networks for regulating attention/working memory versus impulse regulation/inhibition as potential loci for dysfunction. These results are in contrast to the frequently cited global inhibitory executive function deficit hypothesis.