Attention in hyperactive children and the effect of methylphenidate (ritalin)

Which Measures From a Sustained Attention Task Best Predict ADHD Group Membership?

Difficulty with sustaining attention to a task is a hallmark of ADHD. It would be useful to know which measures of sustained attention best predict a diagnosis of ADHD. Participants were 129 children with a diagnosis of ADHD and 129 matched controls who completed the fixed Sustained Attention to Response Task (SART). The number of commission and omission errors, standard deviation of response time (SDRT), tau, fast and slow frequency variability, d-prime, and mu were able to successfully classify children with and without ADHD. The mean response time, criterion, and sigma were not able to classify participants. The best classifiers were d-prime (0.75 Area Under the Receiver Operated Characteristic), tau (.74), SDRT (0.74), omission errors (0.72), commission errors (0.71), and SFAUS (0.70). This list of the best classifier measures derived from the SART may prove useful for the planning of future studies.

ADHD severity as a predictor of cognitive task performance in children with Autism Spectrum Disorder (ASD)

BACKGROUND

In recent years, a number of studies have begun to explore the nature of Attention-Deficit/Hyperactivity Disorder (ADHD) in children with Autism Spectrum Disorder (ASD). In this study, we examined the relationship between both symptoms of ADHD and symptoms of ASD on cognitive task performance in a sample of higher-functioning children and adolescents with ASD. Participants completed cognitive tasks tapping aspects of attention, impulsivity/inhibition, and immediate memory.

AIMS

We hypothesized that children with ASD who had higher levels of ADHD symptom severity would be at higher risk for poorer sustained attention and selective attention, greater impulsivity/disinhibition, and weaker memory.

METHODS AND PROCEDURES

The sample included 92 children (73 males) diagnosed with ASD (Mean Age = 9.41 years; Mean Full Scale IQ = 84.2).

OUTCOMES AND RESULTS

Using regression analyses, more severe ADHD symptomatology was found to be significantly related to weaker performance on tasks measuring attention, immediate memory, and response inhibition. In contrast, increasing severity of ASD symptomatology was not associated with higher risk of poorer performance on any of the cognitive tasks assessed.

CONCLUSIONS AND IMPLICATIONS

These results suggest that children with ASD who have more severe ADHD symptoms are at higher risk for impairments in tasks assessing attention, immediate memory, and response inhibition-similar to ADHD-related impairments seen in the general pediatric population. As such, clinicians should assess various aspects of cognition in pediatric patients with ASD in order to facilitate optimal interventional and educational planning.

Neuropsychological Measures in the Diagnosis of ADHD in Preschool: Can Developmental Research Inform Diagnostic Practice?

Objective: The diagnosis of ADHD in preschool is challenging. Behavioral ratings are less reliable, but the value of neuropsychological tests in the diagnosis of ADHD has been debated. Method: This article provides an overview of neuropsychological measures utilized in preschoolers with ADHD (3-5 years). In addition, the manuscript discusses the extent to which these measures have been tested for their diagnostic capacity. Results: The diagnostic utility of computerized continuous performance tests and working memory subtests from IQ-batteries has been demonstrated in a number of studies by assessing their psychometric properties, sensitivity, and specificity. However, findings from developmental and basic research attempting to describe risk factors that explain variance in ADHD show the most consistent associations of ADHD with measures of delay aversion. Conclusion: Results from developmental research could benefit studies that improve ADHD diagnosis at the individual level. It might be helpful to consider testing as a structured situation for behavioral observation by the clinician.

Effects of Extended-Release Methylphenidate Treatment on Cognitive Task Performance in Children with Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder

Objective: To examine the effectiveness of four doses of psychostimulant medication, combining extended-release methylphenidate (ER-MPH) in the morning with immediate-release MPH (IR-MPH) in the afternoon, on cognitive task performance. Method: The sample comprised 24 children (19 boys and 5 girls) who met the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition Text Revision (DSM-IV-TR) criteria for an autism spectrum disorder (ASD) on the Autism Diagnostic Interview-R and the Autism Diagnostic Observation Schedule, and had significant symptoms of attention-deficit/hyperactivity disorder (ADHD). This sample consisted of elementary school-age, community-based children (mean chronological age = 8.8 years, SD = 1.7; mean intelligence quotient = 85; SD = 16.8). Effects of placebo and three dose levels of ER-MPH (containing 0.21, 0.35, and 0.48 mg/kg equivalent of IR-MPH) on cognitive task performance were compared using a within-subject, crossover, placebo-controlled design. Each of the four MPH dosing regimens (placebo, low-dose MPH, medium-dose MPH, and high-dose MPH) was administered for 1 week; the dosing order was counterbalanced across children. Results: MPH treatment was associated with significant performance gains on cognitive tasks tapping sustained attention, selective attention, and impulsivity/inhibition. Dose/response was generally linear in the dose range studied, with no evidence of deterioration in performance at higher MPH doses in the dose range studied. Conclusion: The results of this study suggest that MPH formulations are associated with significant improvements on cognitive task performance in children with ASD and ADHD.

Cross-cultural study of the childhood developmental trajectory of attention and impulse control

The maturation lag model explains inattention and impulsivity in Attention Deficit Hyperactivity Disorder (ADHD) as delayed maturation along a normal developmental trajectory. The concept of a cross-culturally uniform developmental trajectory is tested by a comparison of the performance of 212 Mexican school children on the Test of Variable Attention (TOVA) with the performance of populations previously studied. An observed pattern of decreasing errors of omission (indicating improving ability to sustain attention) with increasing age did confirm the predictions of the existing developmental trajectory model, although the shape of this change was linear rather than curvilinear. A predicted age-related decrease in errors of commission (indicating improving impulse control) was not observed. Gender differences in attentional and impulse control measures among Mexican children, aged 6–12 years, were not significant, in contrast to the findings of previous US studies in which boys performed poorly compared with girls. Mexican children made significantly more errors of omission and commission than American children, indicating greater degrees of characteristic inattentive and impulsive behaviours in childhood. These results indicate that the assumption of a uniform developmental trajectory of these behaviours should be carefully considered before it is applied to understanding children’s behaviour in culturally diverse settings.

Continuous Performance Tasks: Not Just About Sustaining Attention

PURPOSE

Continuous performance tasks (CPTs) are used to measure individual differences in sustained attention. Many different stimuli have been used as response targets without consideration of their impact on task performance. Here, we compared CPT performance in typically developing adults and children to assess the role of stimulus processing on error rates and reaction times.

METHOD

Participants completed a CPT that was based on response to infrequent targets, while monitoring and withholding responses to regular nontargets. Performance on 3 stimulus conditions was compared: visual letters (X and O), their auditory analogs, and auditory pure tones.

RESULTS

Adults showed no difference in error propensity across the 3 conditions but had slower reaction times for auditory stimuli. Children had slower overall reaction times. They responded most quickly to the visual target and most slowly to the tone target. They also made more errors in the tone condition than in either the visual or the auditory spoken CPT conditions.

CONCLUSIONS

The results suggest error propensity and reaction time variations on CPTs cannot solely be interpreted as evidence of inattention. They also reflect stimulus-specific influences that must be considered when testing hypotheses about modality-specific deficits in sustained attention in populations with different developmental disorders.

Elevated background noise in adult attention deficit hyperactivity disorder is associated with inattention

Background

Inattention and distractibility are core symptoms of attention deficit hyperactivity disorder (ADHD). Still the neuronal organization is largely unknown. Previously we studied the electrophysiological activity of a distinct neuronal network—the retina—and found no change in stimulus-driven neural activity in patients with ADHD. However there is growing evidence for an elevated non stimulus-driven neural activity, or neuronal background noise, as underlying pathophysiological correlate. To further examine the biological bases that might underlie ADHD and problems with inattention, we performed a new analysis to test the hypothesis of an elevated background noise as underlying neuronal correlate for ADHD and problems with inattention in humans. A direct measure of background noise in patients with ADHD has not been described yet.

Methods

The retinal background noise was assessed based on pattern electroretinogram (PERG) data in 20 unmedicated ADHD patients and 20 healthy controls. The PERG is an electrophysiological measure for retinal ganglion cell function. ADHD severity was assessed by interview and questionnaire.

Results

Noise amplitude was significantly higher (138%) in patients with ADHD compared to the control group (p = 0.0047). Noise amplitude correlated significantly with psychometric measures for ADHD (CAARS) especially inattention (r = 0.44, p = 0.004).

Conclusions

The data provide evidence that an elevated background noise is associated with symptoms of inattention in ADHD and support the use of therapeutic interventions that reduce noise and distraction in patients with ADHD.

Temperament and minor physical anomalies

Minor physical anomalies (MPAs) are an index of deviant embryological development due to genetic defects of insults to the fetus. A brief 10-minute examination an an individual makes it possible to establish a count that shown highly stable individual differences from the newborn period up to age seven years, the latest age studied longitudinally. For males, high MPA counts in the newborn period have shown strong predictive relationships to preschool temperament factors such as short attention span, high activity level, and aggressive-impulsive behaviour. For females, high anomaly scores showed relationships to short attention span and to inhibition. Such findings are in contrast with inconsistent results from genetic studies and with infrequent, weak relationships of neonatal variables to later behaviour. These results from the Bethesda longitudinal study have been confirmed in most cases by several cross-sectional studies. Sex differences in behaviour, usually considered to result from differential sex-role training, disappear in preschool samples from which high MPA individuals have been removed, but are much more pronounced than usual in samples with high MPAs.

Medications do not necessarily normalize cognition in ADHD patients

OBJECTIVE

Although ADHD medications are effective for the behavioral components of the disorder, little information exists concerning their effects on cognition, especially in community samples.

METHOD

A cross-sectional study of ADHD patients treated with three different ADHD drugs was conducted. Patients' performance on a computerized neurocognitive screening battery was compared to untreated ADHD patients and normal controls (NML). A total of 177 ADHD patients aged 10 to 18, achieved a favorable response to one of the following medications: Adderall XR (AMP), atomoxetine (ATMX), and Concerta (MPH-OROS) compared to 95 untreated ADHD patients and 101 NML.

RESULTS

Significant differences were detected between normals and untreated ADHD patients. Treated patients performed better than untreated patients but remained significantly impaired compared to normal subjects.

CONCLUSION

Even with optimal treatment, based on parents' and teachers' opinions, subtle and not-so-subtle neurocognitive impairments persisted in the ADHD patients. Some ADHD patients may require additional educational assistance, even in the face of successful medication treatment.

Quantifying ADHD classroom inattentiveness, its moderators, and variability: a meta-analytic review

BACKGROUND

Most classroom observation studies have documented significant deficiencies in the classroom attention of children with attention-deficit/hyperactivity disorder (ADHD) compared to their typically developing peers. The magnitude of these differences, however, varies considerably and may be influenced by contextual, sampling, diagnostic, and observational differences.

METHODS

Meta-analysis of 23 between-group classroom observation studies using weighted regression, publication bias, goodness of fit, best case, and original metric analyses.

RESULTS

Across studies, a large effect size (ES = .73) was found prior to consideration of potential moderators. Weighted regression, best case, and original metric estimation indicate that this effect may be an underestimation of the classroom visual attention deficits of children with ADHD. Several methodological factors-classroom environment, sample characteristics, diagnostic procedures, and observational coding schema-differentially affect observed rates of classroom attentive behavior for children with ADHD and typically developing children. After accounting for these factors, children with ADHD were on-task approximately 75% of the time compared to 88% for their classroom peers (ES = 1.40). Children with ADHD were also more variable in their attentive behavior across studies.

CONCLUSIONS

The present study confirmed that children with ADHD exhibit deficient and more variable visual attending to required stimuli in classroom settings and provided an aggregate estimation of the magnitude of these deficits at the group level. It also demonstrated the impact of situational, sampling, diagnostic, and observational variables on observed rates of on-task behavior.

The effects of alcohol on laboratory-measured impulsivity after L: -Tryptophan depletion or loading

RATIONALE

Indirect evidence supports a link between serotonergic activity and individual differences in the behavioral response to alcohol, but few studies have experimentally demonstrated that an individual's biological state can influence the sensitivity to alcohol-induced behaviors.

OBJECTIVE

Our purpose was to temporarily modify serotonin synthesis in healthy individuals to determine how altered biological states may interact with alcohol administration to affect impulsive behavior.

MATERIALS AND METHODS

In a repeated-measures design, 18 normal controls consumed a 50-g L: -tryptophan (Trp) depleting (ATD) or loading (ATL) amino-acid beverage that temporarily decreased or increased (respectively) serotonin synthesis before receiving either a moderate dose of alcohol (0.65 g/kg) or placebo. All participants completed three impulsivity testing sessions on each of the five experimental days. Session one was a baseline session. Session two included testing after ATD-only or ATL-only. Session three included: (1) placebo after ATL (ATL+PBO); (2) placebo after ATD (ATD+PBO); (3) alcohol after ATL (ATL+ALC); (4) alcohol after ATD (ATD+ALC); and (5) Alcohol-only conditions. Impulsivity was assessed using the Immediate Memory Task (Dougherty et al., Behav Res Methods Instrum Comput 34:391-398, 2002), a continuous performance test yielding commission errors that have been previously validated as a component of impulsive behavior.

RESULTS

Primary findings were that ATD-only increased impulsive responding compared to ATL-only, and ATD+ALC increased commission errors to levels higher than either the ATL+ALC or Alcohol-only conditions.

CONCLUSIONS

These findings demonstrate that reduced serotonin synthesis can produce increased impulsivity even among non-impulsive normal controls, and that the behavioral effects of alcohol are, in part, dependent on this biological state.

Conduct Problems in Adolescence: Three Domains of Inhibition and Effect of Gender

Behavioral and neuropsychological evidence has often shown that children with conduct disorder drawn from clinical populations show problems with impulsivity and are impaired in motor tasks of inhibitory control. We explored the relation between conduct problems and inhibitory deficits in a community sample. Three domains of inhibition were explored in 54 adolescents with conduct problems compared to 53 age, IQ, sex, school, and ethnicity matched controls in 2 geographical areas. Motor response inhibition was assessed using the Stop task, verbal inhibition using the Hayling Sentence Completion test, and cognitive interference inhibition using the Stroop task. Adolescents with conduct problems showed deficits in executive and inhibitory processes of the motor response inhibition task, but were unimpaired in cognitive or verbal inhibitory control. No sex differences were observed and impairments were independent of IQ or geographical location. Findings suggest that motor deficits, rather than higher cognitive forms of inhibitory control, are a specific deficit in children with conduct problems, that girls are as affected as boys, and that motor impulsiveness is a dimensional trait associated with conduct problems, as it is also observed in the community.

Attention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): a neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity)

Most studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the combined type and emphasized a core problem in response inhibition. It is proposed here that the core problem in the truly inattentive type of ADHD (not simply the subthreshold combined type) is in working memory. It is further proposed that laboratory measures, such as complex-span and dual-task dichotic listening tasks, can detect this. Children with the truly inattentive type of ADHD, rather than being distractible, may instead be easily bored, their problem being more in motivation (underarousal) than in inhibitory control. Much converging evidence points to a primary disturbance in the striatum (a frontal-striatal loop) in the combined type of ADHD. It is proposed here that the primary disturbance in truly inattentive-type ADHD (ADD) is in the cortex (a frontal-parietal loop). Finally, it is posited that these are not two different types of ADHD, but two different disorders with different cognitive and behavioral profiles, different patterns of comorbidities, different responses to medication, and different underlying neurobiologies.

Attention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): a neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity)

Most studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the combined type and emphasized a core problem in response inhibition. It is proposed here that the core problem in the truly inattentive type of ADHD (not simply the subthreshold combined type) is in working memory. It is further proposed that laboratory measures, such as complex-span and dual-task dichotic listening tasks, can detect this. Children with the truly inattentive type of ADHD, rather than being distractible, may instead be easily bored, their problem being more in motivation (underarousal) than in inhibitory control. Much converging evidence points to a primary disturbance in the striatum (a frontal-striatal loop) in the combined type of ADHD. It is proposed here that the primary disturbance in truly inattentive-type ADHD (ADD) is in the cortex (a frontal-parietal loop). Finally, it is posited that these are not two different types of ADHD, but two different disorders with different cognitive and behavioral profiles, different patterns of comorbidities, different responses to medication, and different underlying neurobiologies.

Varieties of attention-deficit/hyperactivity disorder-related intra-individual variability

Intra-individual variability in behavior and functioning is ubiquitous among children with attention-deficit/hyperactivity disorder (ADHD), but it has not been systematically examined or integrated within causal models. This article seeks to provide a conceptual, methodologic, and analytic framework as a foundation for future research. We first identify five key research questions and methodologic issues. For illustration, we examine the periodic structure of Eriksen Flanker task reaction time (RT) data obtained from 24 boys with ADHD and 18 age-matched comparison boys. Reaction time variability in ADHD differed quantitatively from control subjects, particularly at a modal frequency around .05 Hz (cycle length approximately 20 sec). These oscillations in RT were unaffected by double-blind placebo and were suppressed by double-blind methylphenidate. Together with converging lines of basic and clinical evidence, these secondary data analyses support the speculative hypothesis that the increased power of multisecond oscillations in ADHD RT data, and by inference, in attentional performance, represents a catecholaminergic deficit in the ability to appropriately modulate such oscillations in neuronal activity. These results highlight the importance of retaining time-series data and quantitatively examining intra-subject measures of variability as a putative endophenotype for ADHD.

Laboratory measured behavioral impulsivity relates to suicide attempt history

The purpose of this study was to examine the relationship between laboratory behavioral measured impulsivity (using the Immediate and Delayed Memory Tasks) and suicidal attempt histories. Three groups of adults were recruited, those with either: no previous suicide attempts (Control, n = 20), only a single suicide attempt (Single, n = 20), or multiple suicidal attempts (Multiple, n = 10). As hypothesized, impulsive responses increased with the number of suicide attempts (Control < Single < Multiple). This study helps to demonstrate how laboratory behavioral measures of impulsivity can be used to discriminate groups based on suicidal histories among samples not currently exhibiting significant suicidal behaviors.

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.

Suicidal behaviors and drug abuse: impulsivity and its assessment

Impulsivity appears to play an important role in suicidal behaviors and drug abuse, which are two psychiatric problems that may interact with one another. Interpretation of the literature on impulsivity in these behaviors may be complicated by the variety of measurement techniques for the assessment of impulsivity. There are three general types of impulsivity assessment: self-report, biological, and laboratory behavioral. Because laboratory behavioral measures both meet an operational definition of impulsivity and are sensitive to state-dependent changes in impulsivity, this paper presents data that focuses on laboratory behavioral performance among samples emitting suicidal behaviors or substance abuse. To better account for influence of impulsivity in these psychiatric disturbances, no single source of measurement should be used without the consideration of other types of instruments.

Age at First Drink Relates to Behavioral Measures of Impulsivity: The Immediate and Delayed Memory Tasks

BACKGROUND

This study examined the relationship between laboratory-measured impulsivity and age at first drink.

METHODS

Using a laboratory behavioral measure of impulsivity [Immediate (IMT) and Delayed Memory Tasks (DMT)], we compared two groups of women differing in their self-reported age at first drink (early-onset drinking, age <18 years, n = 40; late-onset drinking, age > or =21 years, n = 23). It was expected that those who first consumed alcohol before the legal drinking age (i.e., early onset) would perform in a more impulsive manner on the laboratory behavioral measure than the late-onset drinkers.

RESULTS

The main finding was that the early-onset group (IMT: mean, 28.7%; DMT: mean, 30.4%) had increased commission error rates compared with the late-onset group (IMT: mean, 21.2%; DMT: mean, 15.5%) during both the IMT [ANOVA:F (1,61) = 4.30; p = 0.042; f = 0.27] and DMT [F (1,61) = 10.76; p = 0.002; f = 0.42]. Age at first drink was significantly correlated with DMT commission errors (r = -0.23; p = 0.037), although this was only at the trend level for IMT commission errors (r = -0.20; p = 0.062); these correlations are likely to be underestimates because of range restriction of the age variable.

CONCLUSIONS

These results demonstrate that differences in impulsive behavioral responding are distinguishable even between groups of alcohol drinkers who are not experiencing clinically significant problems with alcohol.

Continuous performance test performance in a normative epidemiological sample

A 14-min continuous performance test (CPT) requiring a high rate of responding was administered to a probability-weighted random sample of 816 9-17-year-old children drawn from a population of 17,117 children in an ongoing epidemiological and longitudinal study in Western North Carolina. Systematic main effects of improved performance with older age were found in this age range for all variables, including reaction time (RT), RT standard error, errors of omission, errors of commission, and signal detection parameters (d' and beta). Significant gender main effects included more impulsive errors, less variability, and faster RT by males, with no interactions between age and gender. There were no main effects of ethnicity or interactions of ethnicity with age and/or gender. Large main effects of interstimulus interval (ISI; 1, 2, or 4-s intervals) and time block were present for most CPT performance measures. The normative data from the CPT should provide a useful framework for interpreting similar data in future studies of child and adolescent psychopathology.

The top and the bottom of ADHD: a neuropsychological perspective

Five models of attention deficit/hyperactivity disorder (ADHD) are reviewed. It is proposed that the cognitive-energetic model provides a reasonably comprehensive account of ADHD by incorporating the features of both the inhibition and delay aversion models. It is suggested that ADHD can only be accounted for by an analysis at three levels: top-down control, specific cognitive processes and energetic factors. It is argued that a refined and conceptually comprehensive neuropsychological battery is needed to advance research in ADHD. A widely distributed neural network involving frontal, basal ganglia, limbic and cerebellar loci seem implicated in ADHD.

Behavioral impulsivity paradigms: a comparison in hospitalized adolescents with disruptive behavior disorders

BACKGROUND

Behavioral impulsivity paradigms vary widely and studies using these measures have typically relied on a single measure used in isolation. As a result, comparisons between measures are difficult, with little consensus regarding which method may be most sensitive to individual impulsivity differences of different populations.

METHOD

A single testing session of each of four different impulsivity tasks was completed by two groups of adolescents aged 13-17: hospitalized inpatients with disruptive behavior disorders (DBD; n = 22) and controls (n = 22). Tasks included two rapid-decision (IMT/DMT and GoStop) and two reward-directed (TC and SKIP) impulsivity paradigms. Behavioral testing took place within 3 days of hospitalization for the adolescents with DBD.

RESULTS

Compared to controls, the DBD group exhibited higher commission error rates, lower inhibited response rates after a stop-signal, and twice as many reward-directed responses even after IQ differences between the groups were taken into account. When the four paradigms were compared, effect-size calculations indicated that the two rapid-decision paradigms were more sensitive to group differences than the reward-directed tasks.

CONCLUSIONS

Despite the initiation of pharmacotherapy within the first 3 days of hospitalization, in contrast to the control group, the adolescents with DBD performed consistently with what has been operationally defined as impulsivity. Based on these results, these tasks appear to measure similar, but unique components of the impulsivity construct. With further study, laboratory behavioral paradigms may prove to be useful additions to current clinical diagnostic and treatment procedures in a variety of psychiatric populations.

Motor timing deficits in community and clinical boys with hyperactive behavior: the effect of methylphenidate on motor timing

In a previous paper we showed that community children with hyperactive behavior were more inconsistent than controls in the temporal organization of their motor output. In this study we investigated: (1) various aspects of motor timing processes in 13 clinically diagnosed boys with attention deficit hyperactivity disorder (ADHD) who were compared to 11 community boys with hyperactive behavior and to a control group and (2) the effect of methylphenidate on the motor timing processes in the clinical group with ADHD in a double blind, cross-over, medication-placebo design, including 4 weeks of medication. The clinical group with ADHD, like the community group with hyperactivity, showed greater variability in sensorimotor synchronization and in sensorimotor anticipation relative to controls. The clinical group was also impaired in time perception, which was spared in the community group with hyperactivity. The persistent, but not the acute dose, of methylphenidate reduced the variability of sensorimotor synchronization and anticipation, but had no effect on time perception. This study shows that motor timing functions are impaired in both clinical and community children with hyperactivity. It is the first study to show the effectiveness of persistent administration of methylphenidate on deficits in motor timing in ADHD children and extends the use of methylphenidate from the domain of attentional and inhibitory functions to the domain of executive motor timing.

Relations between visual and auditory continuous performance tests in a clinical population: a descriptive study

Increased interest in auditory continuous performance tests (CPTs) exists despite the absence of a clear understanding about this procedure. The relation between auditory and visual CPTs and associations with IQ, achievement, and memory are evaluated in a referred sample of 634 children, ages 5.5 to 17.9. Age effects are found with CPT performance, regardless of modality. Total number correct or number of commissions correlations across tasks were greater than within-task number correct-number of commissions relations. The mean visual minus auditory correct difference score was 7.01; the mean commission difference score was -.85. Difference scores decreased with age and were not consistently related to other measures. Those with the lowest number correct on both CPTs (<25th percentile) were younger and had weaker short-term auditory memory and verbal learning skills; those falling in the problem quartile on commissions (>75th percentile) were younger and had poorer reading, verbal memory, and verbal learning. Total error scores (omissions + commissions) were inversely related to age. The auditory CPT has clinical utility, but other factors must be considered.

Brain sites of movement disorder: genetic and environmental agents in neurodevelopmental perturbations

In assessing and assimilating the neurodevelopmental basis of the so-called movement disorders it is probably useful to establish certain concepts that will modulate both the variation and selection of affliction, mechanisms-processes and diversity of disease states. Both genetic, developmental and degenerative aberrations are to be encompassed within such an approach, as well as all deviations from the necessary components of behaviour that are generally understood to incorporate "normal" functioning. In the present treatise, both conditions of hyperactivity/hypoactivity, akinesia and bradykinesia together with a constellation of other symptoms and syndromes are considered in conjunction with the neuropharmacological and brain morphological alterations that may or may not accompany them, e.g. following neonatal denervation. As a case in point, the neuroanatomical and neurochemical points of interaction in Attention Deficit and Hyperactivity disorder (ADHD) are examined with reference to both the perinatal metallic and organic environment and genetic backgrounds. The role of apoptosis, as opposed to necrosis, in cell death during brain development necessitates careful considerations of the current explosion of evidence for brain nerve growth factors, neurotrophins and cytokines, and the processes regulating their appearance, release and fate. Some of these processes may possess putative inherited characteristics, like alpha-synuclein, others may to greater or lesser extents be endogenous or semi-endogenous (in food), like the tetrahydroisoquinolines, others exogenous until inhaled or injested through environmental accident, like heavy metals, e.g. mercury. Another central concept of neurodevelopment is cellular plasticity, thereby underlining the essential involvement of glutamate systems and N-methyl-D-aspartate receptor configurations. Finally, an essential assimilation of brain development in disease must delineate the relative merits of inherited as opposed to environmental risks not only for the commonly-regarded movement disorders, like Parkinson's disease, Huntington's disease and epilepsy, but also for afflictions bearing strong elements of psychosocial tragedy, like ADHD, autism and Savantism.

Familial transmission of Continuous Performance Test behavior: attentional and impulsive response characteristics

Continuous Performance Tests (CPTs) provide information on attentional processing and impulsive behavior. The results of previous research that used self-report measures have provided evidence for familial transmission (through genetic and/or environmental influences) of impulsive characteristics. The authors of the present study examined whether the impulsive behavioral parameters that are measured by the CPT also share familial relationships. The researchers asked 26 healthy parent-adolescent pairs to complete the Immediate and Delayed Memory Tasks (IMT/DMT; D. M. Dougherty, 1999; D. M. Dougherty, D. M. Marsh, & C. W. Mathias, 2002), a modified CPT (B. A. Cornblatt, N. J. Risch, G. Faris, D. Friedman, & L. Erlenmeyer-Kimling, 1988; H. E. Rosvold, A. Mirsky, I. Sarason, E. D. Breansome, Jr., & L. H. Beck, 1956), and the Barratt Impulsiveness Scale (BIS; J. H. Patton, M. S. Stanford, & E. S. Barratt, 1995), a self-report measure. The main findings can be summarized as follows: (a) commission errors (but not correct detections) on the IMT and DMT were correlated between parents and their adolescent children, (b) adolescents emitted a higher proportion of commission errors than did their parents, and (c) self-reported impulsivity (i.e., BIS) was correlated with commission errors for parents, but not for adolescents. The findings of this study support the use of an objective behavioral measure of impulsivity to assess familial relationships of impulsivity.

Immediate and delayed memory tasks: a computerized behavioral measure of memory, attention, and impulsivity

The Immediate and Delayed Memory Task (IMT/DMT), a variant of the Continuous Performance Test (CPT), is a new software package designed to be a flexible research tool for the study of attention, memory, and impulsivity. This package allows researchers to determine the design to be used during a testing session and to manipulate many of the parameters. It features two components: the IMT and the DMT, both of which present sequential 2- to 7-digit stimuli with variable presentation rates and intertrial intervals. Subjects respond to identically matched stimuli presented consecutively, spanning a brief period of time (IMT), or to stimuli spanning a greater period of time (during which intervening stimuli to be ignored appear; DMT). Task complexity can be adjusted to suit applications for both children and adults. Preliminary studies have demonstrated that these laboratory tasks are sensitive to group differences, produce stable baselines of performance, and are sensitive to drug-induced performance decrements.

Behavioural and pharmacological relevance of stroke-prone spontaneously hypertensive rats as an animal model of a developmental disorder

The present study evaluates juvenile stroke-prone spontaneously hypertensive rats (SHRSP) as an animal model of a developmental disorder, which is diagnosed according to hyperactivity-impulsivity and/or inattention. To characterize behavioural alterations, we studied motor activity, as well as emotional and cognitive behaviours in juvenile SHRSP, with and without methylphenidate, a psychostimulant. Ambulatory and rearing activities in the open-field environment were significantly higher in SHRSP than in Wistar-Kyoto rats (WKY). In the elevated plus maze task, the entries into open arms, as an index of impulsivity, were significantly increased in SHRSP. In the Y-maze task, spontaneous alternation behaviour, as an index of attention, was significantly lowered in the male SHRSP, but not in the female SHRSP, indicating that spontaneous alternation deficit is gender specific. Methylphenidate (0.01-1 mg/kg, i.p.) significantly attenuated locomotor hyperactivity at low doses and dose-dependently improved the spontaneous alternation deficit in SHRSP. Our findings reveal that juvenile SHRSP manifest problematic behaviours resembling a developmental disorder, attention-deficit/hyperactivity disorder (ADHD), namely hyperactivity-impulsivity and/or inattention. Methylphenidate alleviated the behavioural symptoms of hyperactivity and inattention. We propose that juvenile SHRSP are an appropriate animal model of a developmental disorder resembling ADHD, from behavioural and pharmacological perspectives.

Visual sustained attention in a child psychiatric population

OBJECTIVE

To increase knowledge of the diversity and specificity of sustained attention deficits in children with attention-deficit hyperactivity disorder (ADHD), with special reference to the issue of distinguishing between children with ADHD and children with other psychiatric diagnoses.

METHOD

A visual sustained attention task was used to compare 52 boys with ADHD with 55 normal controls, 29 boys with oppositional defiant disorder or conduct disorder (ODD/CD), 29 boys with anxiety or dysthymia (ANX/DYS), 43 boys with pervasive developmental disorder, 24 boys with ADHD plus ODD/CD, and 14 boys with ADHD plus ANX/DYS.

RESULTS

Compared with normal controls, children with ADHD were slower, were more inaccurate, were more impulsive, were less responsive to feedback, and showed less perceptual sensitivity and stability of performance, resulting in a marked decrease in vigilance over time. Unresponsiveness to feedback and the extent of the decrease in vigilance during time on task were found to be the only factors that distinguished children with ADHD from children with other diagnoses.

CONCLUSION

Although only children with ADHD are characterized primarily by "attention deficit," sustained attention deficit is common to a certain extent to all children with psychiatric disorders.

Differential measures of 'sustained attention' in children with attention-deficit/hyperactivity or tic disorders: relations to monoamine metabolism

Controversy exists on whether the constructs tested by paper/pencil and computerized continuous-performance tests (CPT) are similar, and the deficits recorded in children with attention-deficit/hyperactivity symptoms (ADHD) are comparable. Signal-detection measures were recorded on four such tests of 'sustained attention', with increasing working-memory requirements in healthy children (14; mean 10 years), and those with ADHD (14; mean 10 years) or a tic syndrome (TS, 11; mean 11 years). Clinical associations were sought from 24-h urinary measures of monoamine activity. The cancellation paper/pencil test revealed no group differences for errors or signal detection measures. On the CPT, ADHD children made more omission and commission errors than control subjects, but TS children made mostly omissions. This reflected the poor perceptual sensitivity (d-prime, d') for ADHD and conservative response criteria (beta) for TS children. This group difference extended to the CPTax, which was shown on a regression analysis to test for putative working-memory-related abilities as well as concentration. In all children, immediate response-feedback reduced omissions, and modestly improved d'. CPTax performance related negatively to dopamine metabolism in control subjects and to serotonin metabolism in the ADHD group. But comparisons between the metabolites in the ADHD group suggest that increased serotonin and decreased noradrenaline, with respect to dopamine metabolism, may detract from CPT performance in terms of d'. CPT tasks demonstrated a perceptual-based impairment in ADHD and response conservatism in TS patients independent of difficulty. Catecholamine activity was implicated in the promotion of perceptual processing in normal and ADHD children, but serotonin activity may contribute to poor CPTax (working-memory) performance in ADHD patients.

Development of sustained attention assessed using the continuous performance test among children 6-15 years of age

The Continuous Performance Test (CPT) is a widely used measure of sustained attention, which may rely on the efficiency of cognitive inhibition. We examined the relationships of age and sex with CPT performance among 341 randomly selected school children 6-15 years of age. Multiple regression analyses revealed that the hit rate, false alarm rate, and sensitivity of both the undegraded and the degraded CPT were associated with age by a quadratic relationship. The age-development curves for the hit rate and sensitivity were convex, whereas that for the false alarm rate was concave. Sex was associated with the hit rate and sensitivity on the degraded CPT only. Our findings are consistent with the hypothesis that sustained attention develops during the primary school ages. The data reported are essential for identifying children with conditions associated with sustained attention deficit, such as attention-deficit hyperactivity disorder, as well as those at an increased risk for developing schizophrenia.

Methylphenidate versus dexamphetamine in children with attention deficit hyperactivity disorder: A double-blind, crossover trial

OBJECTIVE

To compare methylphenidate (MPH) and dexamphetamine (DEX) in a sample of children with attention deficit hyperactivity disorder (ADHD).

METHOD

A total of 125 children with ADHD received both MPH (0.3 mg/kg twice daily) and DEX (0.15 mg/kg twice daily) for 2 weeks a double-blind, crossover study. Outcome measures were Conners' Parent Rating Scale-Revised, Conners' Teacher Rating Scale-Revised, a Parent Global Perceptions questionnaire, the Continuous Performance Test, and the Barkley Side Effects Rating Scale.

RESULTS

There were significant group mean improvements from baseline score on all measures for both stimulants. On the Conners' Teacher Rating Scale-Revised, response was greater on MPH than DEX on the conduct problems and hyperactivity factors, as well as on the hyperactivity index. On the Conners' Parent Rating Scale-Revised, anxiety was the only factor to differ significantly, in favor of MPH. Parents rated 73% of subjects as globally improved on MPH and 69% improved on DEX, compared with baseline. Overall, 46% of parents chose MPH as the preferred drug, compared with 37% who chose DEX. On the Continuous Performance Test, there was no difference in the number of correct responses or errors between the two drugs.

CONCLUSIONS

Most children with ADHD improve significantly on both MPH and DEX. There was a slight advantage to MPH on most measures.

A pilot study of neuropsychological function in girls with ADHD

OBJECTIVE

Attention-deficit hyperactivity disorder (ADHD) is known to have neuropsychological consequences that are evident from psychological tests and from measures of school failure. However, most available data are based on studies of boys. Our goal was to assess, in this pilot study, whether ADHD in girls expressed neuropsychological features similar to those found in boys.

METHOD

Subjects were 43 girls, aged 6 to 17 years, with DSM-III-R ADHD and 36 comparison girls without ADHD. Information on neuropsychological performance was obtained in a standardized manner blind to clinical status.

RESULTS

Girls with ADHD were significantly more impaired on estimated IQ than comparison girls despite being matched on other demographic variables. Relative to comparison girls, the girls with ADHD were also significantly more impaired on the Freedom From Distractibility subtests of the WISC-R and on arithmetic and reading achievement scores. Although their mean performance on executive function tests was generally poorer than that of control girls, there were no statistically significant differences on these measures.

CONCLUSIONS

Girls with ADHD have impairments in some tests of attention and achievement. However, neuropsychological performance on tests of executive function was less impaired than that previously documented in boys with ADHD. If confirmed in a larger sample, these findings suggest that girls with ADHD may be less vulnerable to executive function deficits than boys.

Computerized assessment of sustained attention: a review of factors affecting vigilance performance

Results of empirical studies using computerized tests of sustained attention are summarized. Factors that affect vigilance performance fall into three broad categories: task parameters, environmental or situational factors, and subject characteristics. Complex interactions of factors from each category affect performance further. Such interactions may help to explain inconsistencies in the literature regarding effects on vigilance. Implications for both research and clinical practice are discussed.

Continuous-processing--related event-related potentials in children with attention deficit hyperactivity disorder

Visual information processing in children with attention deficit hyperactivity disorder (ADHD) was studied using event-related potentials recorded during two versions of the Continuous Performance Task (CPT). ADHD children made more errors, and had longer reaction times than normal children on both the single- and dual-target CPT. Event-related potential waveforms were normal in the ADHD children with reference to early processing stages, i.e., contingent negative variation, P1-N1 laterality, and processing negativities, suggesting that ADHD children did not differ in their level of preparedness or their ability to mobilize resources for target identification and categorization. With respect to later processing, P3 amplitude was reduced in the ADHD group, whereas P3 latency was longer than normal. ADHD children had a diminished late frontal negative component, suggestive of reduced involvement in postdecisional processing.