Age and medication effects on rhythmic responses in ADHD: possible oscillatory mechanisms?

Voluntary motor responses in children with attention-deficit hyperactivity disorder (ADHD) may reflect underlying neuronal oscillatory mechanisms. The aims of this study were: (1) to corroborate the presence of rhythmic motor abnormalities on tapping test in children with attention-deficit hyperactivity disorder, shown in previous studies; (2) to delineate the characteristics of ADHD children demonstrating these rhythmic abnormalities; (3) to assess the impact of methylphenidate (Ritalin) on this abnormal motor phenomenon. The study was designed in a double blind manner. Sixty-four ADHD children aged 6-12 years and 60 matched controls underwent a finger tapping test (1-5 Hz). We measured the abnormal rhythmic tapping with and without methylphenidate treatment in a double blind design. Conventional statistical analysis was used to assess the correlation of the presence of motor abnormality with various clinical characteristics (such as degree of hyperactivity/impulsivity). Fifty-six percent of children with ADHD compared to 8% of controls demonstrated abnormal rhythmic responses at a mean frequency of 3.1+/-0.9 Hz. These erroneous voluntary movements were more common in children with a greater degree of hyperactivity, in younger children but not significantly altered by methylphenidate treatment. Surprisingly, abnormal rhythmic responses showed less variability than found for responses for which the tapping was adequately paced, suggesting different motor control processes for normal and abnormal paced tapping. We speculate that rhythmic tapping responses reflect abnormal oscillatory mechanisms involved in ADHD, exacerbated in younger children with ADHD and in those in whom the hyperactivity/impulsivity is more pronounced.     

Psychostimulant augmentation during treatment with selective serotonin reuptake inhibitors in men with paraphilias and paraphilia-related disorders: a case series

BACKGROUND: We describe an open trial of psychostimulants (primarily methylphenidate sustained release [SR]) added to selective serotonin reuptake inhibitors (SSRIs; primarily fluoxetine) during the course of pharmacologic treatment of men with paraphilias and paraphilia-related disorders (PRDs). METHOD: Twenty-six men with paraphilias (N = 14) or PRDs (N = 12) were assessed for life-time mood disorders and attention-deficit/hyperactivity disorder (ADHD) as defined by DSM-IV. All men were assessed at baseline for total sexual outlet and average time per day associated with paraphilia/PRD sexual behaviors. The indications for the addition of a psychostimulant to a stable dose of SSRI included the retrospective diagnosis of ADHD with persistent adult symptoms despite pharmacotherapy with an SSRI (N = 17); residual paraphilia/PRD fantasies, urges, and activities despite SSRI pharmacotherapy (N = 16); the persistence or presence of residual depressive symptoms despite SSRI pharmacotherapy (N = 6); relapse or loss of SSRI efficacy during the treatment of sexual impulsivity disorders (N = 4); and treatment of SSRI-induced side effects (N = 4). RESULTS: SSRI pharmacotherapy (mean +/- SD duration = 8.8+/-11.1 months) had statistically significant effects in diminishing paraphilia/PRD-related total sexual outlet (p < .001) and average time/day spent in paraphilia/PRD sexual behavior (p < .001). Addition of methylphenidate SR (mean dose = 40 mg/day; mean +/- SD duration = 9.6+/-8.2 months) was associated with additional statistically significant effects on paraphilia/PRD-related total sexual outlet (p = .003) and average time per day (p = .04) in addition to improvement of putative residual ADHD and depressive symptoms. CONCLUSION: Methylphenidate SR can be cautiously and effectively combined with SSRI antidepressants to ameliorate paraphilias and paraphilia-related disorders for the indications listed above.     

Disturbed structural connectivity is related to inattention and impulsivity in adult attention deficit hyperactivity disorder

Inattention and impulsivity are the most prominent clinical features of attention deficit hyperactivity disorder (ADHD) in adulthood. Structural and functional neuroimaging studies of subjects with ADHD have demonstrated abnormalities in several brain areas, including fronto‐striatal and fronto‐cerebellar networks. Mostly, these studies were based on volumetric measurements and have been conducted in children. We investigated white matter (WM) integrity and correlation with measures of attention and impulsivity in adult patients with ADHD adopting diffusion tensor imaging (DTI). N = 37 (21 males) never‐medicated adult patients with ADHD combined subtype and N = 34 (16 males) healthy controls were investigated. ADHD diagnosis (DSM‐IV) was assessed with clinical interviews and rating scales, subjects also underwent a large neuropsychological test battery including tests of attention and impulsivity. DTI was acquired, and group differences of fractional anisotropy (FA) and mean diffusivity (MD) as well as correlation analyses with measures of attentional performance and impulsivity were calculated using voxel‐based analyses. In adult patients with ADHD, we found reduced FA as well as higher MD bilaterally in orbitomedial prefrontal WM and in the right anterior cingulate bundle, while elevated FA was present bilaterally in temporal WM structures. Measures of attention were correlated with DTI parameters in the right superior longitudinal fasciculus, whereas measures of impulsivity were correlated with FA in right orbitofrontal fibre tracts. This is the first DTI study demonstrating disturbed structural connectivity of the frontal‐striatal circuitry in adult patients with ADHD. Moreover, a direct correlation between WM integrity and measures of attention and impulsivity is shown.     

Characterizing impaired driving in adults with attention-deficit/hyperactivity disorder: A controlled study

OBJECTIVE: We sought to confirm previously documented findings that individuals with attention-deficit/hyperactivity disorder (ADHD) demonstrate impaired driving behavior when compared with controls. METHOD: Subjects were adults with (N = 26) and without (N = 23) DSM-IV ADHD ascertained through clinical referrals to an adult ADHD program and through advertisements in the local media. Driving behavior was assessed using the Manchester Driving Behavior Questionnaire (DBQ) and 10 questions from a driving history questionnaire. Neuropsychological testing and structured interviews were also administered to all subjects. RESULTS: Substantially more ADHD subjects had been in an accident on the highway (35% vs. 9%, p = .03) or had been rear-ended (50% vs. 17%, p = .02) compared with controls. Analysis of the DBQ findings showed that ADHD subjects had significantly higher mean +/- SD scores than control subjects on the total DBQ (34.1 +/- 15.2 vs. 18.0 +/- 8.6, p < .001) and in all 3 subscales of the DBQ: errors (9.3 +/- 5.4 vs. 4.6 +/- 3.5, p < .001), lapses (12.4 +/- 6.2 vs. 6.1 +/- 3.5, p < .001), and violations (12.4 +/- 5.2 vs. 7.4 +/- 4.1, p < .001). Using the score that separated ADHD from control drivers on the DBQ as a cutoff, ADHD drivers at high risk for poor driving outcomes had more severe rates of comorbidity and exhibited more impaired scores on neuropsychological testing. CONCLUSIONS: Our results confirm and extend previous work documenting impaired driving behavior in subjects with ADHD. Results also suggest that ADHD individuals at high risk for poor driving behavior might be distinguishable from other ADHD individuals on DBQ scores, neuropsychological deficits, and patterns of comorbidities.     

The effect of stimulants on nocturnal motor activity and sleep quality in adults with ADHD: an open-label case-control study.

OBJECTIVE: Sleep disturbances are common in adults with attention-deficit/hyperactivity disorder (ADHD). In a case-control study, adult ADHD was associated with increased nocturnal motor activity and reduced self-perceived quality of sleep. METHOD: Eight adults with DSM-IV-diagnosed ADHD (combined type, N = 7; inattentive type, N = 1) were treated with stimulants in open-label form at 8:00 a.m., 12:00 noon, and 4:00 p.m. The mean daily dose was 51 mg of methylphenidate (range, 30-90 mg) in 7 subjects and 30 mg of dextroamphetamine in 1 subject. Actimeters were used to assess nocturnal motor activity during 6 consecutive nights both at baseline and after 3 weeks of treatment. The data were compared with those of 8 matched normal controls. RESULTS: ADHD patients slept worse and showed significantly higher nocturnal motor activity at baseline compared with controls. No baseline differences between patients and controls were found in sleep latency, number of awakenings, and total time in bed. Changes from baseline to week 3 within the ADHD patients indicated improvement of sleep quality (p = .05) and reduction of Activity Level (p = .10) and Movement Index (p = .07) scores. When within-group changes were compared between ADHD subjects and controls, treatment with stimulants tended to be associated with a reduction of Activity Level (p < .01) and Movement Index (p = .04) scores and improved sleep quality (p = .02) in ADHD patients. Sleep latency, number of awakenings, and total time in bed were unaffected in within-group and between-group analyses. CONCLUSION: The results should be interpreted cautiously given the open-label design and small sample size. Further study is warranted into the influence of stimulants on sleep in larger samples of ADHD patients by using controlled designs, multiple dose levels, and polysomnographic measures.     

Regional cerebral blood flow in children with ADHD: changes with age

The aim of this study was to investigate the changes in regional cerebral blood flow (rCBF) with age in patients with attention deficit hyperactivity disorder (ADHD). Twenty-nine drug-naive ADHD subjects (24 boys, 5 girls; age 7-13; mean+/-SD=age 9.2+/-2.1) and 12 subjects with epilepsy (all diagnosed as having complex partial seizure, 6 boys, 6 girls; age 7-14; mean+/-SD=8.5+/-2.1) were included in the study. All cases of ADHD were diagnosed according to DSM-IV criteria. Cerebral blood flow was evaluated with Tc-99m-hexamethylpropyleneamine oxime (Tc99m HMPAO) brain single photon emission tomography (SPECT) during standard resting condition in all of the cases. Asymmetry indices for each region of interest were calculated. Absolute rCBF values were normalized as the absolute rCBF values divided by the whole brain absolute value. The prefrontal lobe asymmetry indices were significantly negatively correlated with age in ADHD cases (r=-0.408, P=0.025), which indicated the increased prefrontal rCBF lateralization from the right to the left side with age. When ADHD cases older than 7 years of age were compared with those with epilepsy, the ADHD cases had lower right prefrontal and frontal rCBF and higher left parietal rCBF. The epilepsy group showed no significant correlations between age and asymmetry indices and showed a different developmental trajectory for prefrontal asymmetry and right prefrontal rCBF values. The results indicated that the left hemisphere dominance in the prefrontal cortex significantly increases with age in ADHD cases.     

Gender difference in the association between adult attention deficit hyperactivity disorder symptoms and morningness–eveningness

We aimed to investigate the association between attention deficit hyperactivity disorder (ADHD) and morningness–eveningness in adulthood. Subjects without psychiatric comorbidity on the Structured Clinical Interview for DSM-IV Axis I Disorders (n = 344) completed the Morningness–Eveningness Questionnaire (MEQ) and the Adult Self-Report Scale for ADHD. MEQ showed an independent and negative association with ADHD symptoms (P < 0.0001). In male subjects, both inattention (P < 0.0001) and hyperactivity–impulsivity were associated with MEQ (P = 0.01). In female subjects, only inattention was associated with MEQ (P < 0.001). Our findings suggest that eveningness may be strongly associated with inattention of adult ADHD and that it may be associated with hyperactivity–impulsivity of adult ADHD in male subjects only.     

Impaired transcallosally mediated motor inhibition in adults with attention-deficit/hyperactivity disorder is modulated by methylphenidate

Using transcranial magnetic stimulation (TMS) in children with ADHD, an impaired transcallosally mediated motor inhibition (ipsilateral silent period, iSP) was found, and its restoration was correlated with improvement of hyperactivity under medication with methylphenidate (MPH). Hyperactivity has been reported to decrease during transition into adulthood, although some motor dysfunction might persist. As one underlying neurophysiological process, a development-dependent normalization of motor cortical excitability might be postulated. In order to test this hypothesis, we measured the iSP in 21 adult ADHD patients and twenty-one sex- and age-matched healthy controls. In 16 of these patients, a second TMS was performed under treatment with MPH. Our results indicate a persistence of impaired transcallosally mediated motor cortical inhibition (shortened duration) in ADHD adults, which was correlated with clinical characteristics of hyperactivity and restlessness, and was restored by MPH. In contrast to ADHD in childhood, the iSP latency was not impaired, suggesting a partial development-dependent normalization of motor cortical excitability in ADHD adults. ISP duration appears to be a sensitive parameter for the assessment of disturbed intercortical inhibition in adults with ADHD.     

Modulation of attention-deficit/hyperactivity disorder symptoms by short- and long-acting methylphenidate over the course of a day

The purpose of this study was to investigate whether a long-acting methylphenidate formulation (MPH-ret) is as effective as two doses of immediate-release methylphenidate (MPH-IR) in reducing attention-deficit/hyperactivity disorder (ADHD) symptoms including inattention, impulsivity, and hyperactivity during the course of the day. Two groups of children (n=18 each) with ADHD aged between 8 and 12 years completed a continuous performance test in combination with a motion-tracking system four times a day within 8 hours. Inattention (standard deviation of reaction time), impulsivity (commission error rate), and hyperactivity (path length of the headband) were simultaneously measured. We included a control group (n=20) to rule out circadian fluctuations of attentional performance and motor activity. We observed a postlunch dip in attentional performance and an increasing trend of motor activity throughout the day whereas impulsivity remained stable in controls. The MPH-ret and MPH-IR groups had comparable treatment effects on measures of hyperactivity and inattention and normalized participant performance to control levels. In contrast, MPH-IR seems to have an advantage over MPH-ret in impulsivity treatments. Thus, our data suggest that it is crucial to assess the different domains of ADHD symptoms precisely over the course of a day to determine the optimal titration and stimulant formulation for a person with ADHD.     

Speed of performance of children with developmental right hemisphere syndrome and with attention-deficit hyperactivity disorder

Slowness is a common complaint in children with attention-deficit hyperactivity disorder (ADHD) and with developmental right hemisphere syndrome. However, it was our clinical impression that slowness in developmental right hemisphere syndrome was more prominent than in ADHD. Our objective was to assess slowness as operationalized by speed of performance in children with developmental right hemisphere syndrome, children with ADHD, and controls. The research sample comprised 19 children in each group, matched for age, gender, socioeconomic status, IQ, and handedness. The subjects were administered a reaction time battery assessing speed of performance. Overall, the average performance differed among the three study groups (F(2,53) = 2.40, P < .01). Children with developmental right hemisphere syndrome were slower than their peers with ADHD (t(35) = 1.99, P < .05) and slower than controls (t(35) = 4.55, P < .001). Children with ADHD performed more slowly than controls, although for the majority of tasks, this was nonsignificant. We conclude that slowness is an integral and consistent component of developmental right hemisphere syndrome and cannot be attributed only to the ADHD symptomatology.     

A randomized, double-blind, placebo-controlled study of modafinil film-coated tablets in children and adolescents with attention-deficit/hyperactivity disorder

OBJECTIVE: To evaluate the efficacy and tolerability of modafinil in children and adolescents, ages 7 to 17, with attention-deficit/hyperactivity disorder (ADHD). METHOD: In this 9-week, double-blind, flexible-dose study, patients were randomized to once-daily modafinil (170-425 mg) or placebo. Assessments included ADHD Rating Scale-IV (ADHD-RS-IV) School and Home Versions and Clinical Global Impression of Improvement (CGI-I) scale. RESULTS: Two hundred patients were randomized. Modafinil produced significant reductions in ADHD-RS-IV total scores at school (n = 128; mean change +/- SD: -17.5 +/- 13.1 points) compared with placebo (n = 66; -9.7 +/- 10.3 points; p < .0001). Similarly, modafinil reduced ADHD-RS-IV total scores at home compared with placebo (-17.6 +/- 13.3 versus -7.5 +/- 11.8 points; p < .0001). Fifty-two percent of patients randomized to modafinil and 18% of those randomized to placebo met prestudy criteria for responder on the CGI-I (p < .0001). Randomization to modafinil was associated with significantly more insomnia, headache, decreased appetite, and weight loss than randomization to placebo, but discontinuation attributed to adverse events did not differ statistically between treatment groups (modafinil, 5%; placebo, 6%). CONCLUSION: Modafinil was well tolerated and reduced ADHD symptoms at school and home compared with placebo.     

Impulsive behavior in adults with attention deficit/ hyperactivity disorder: characterization of attentional, motor and cognitive impulsiveness.

Attention-deficit/hyperactivity disorder (ADHD) is characterized by inattention and/or hyperactivity/impulsivity. Impulsivity persists in adults with ADHD and might be the basis of much of the impairment observed in the daily lives of such individuals. The objective of this study was to address the presence, and more importantly, the three dimensions of impulsivity: attentional, non-planning and motor, in how they may relate to neuropsychological mechanisms of impulse control. We studied a sample of 50 adults with ADHD and 51 healthy comparison controls using the Barratt Impulsivity Scale Version 11 (BIS), and neuropsychological tasks, namely the Continuous Performance Task (CPT-II) and the Iowa Gambling Task (IGT). The ADHD group showed more signs of impulsivity on the three dimensions of BIS, committed more errors of omission and commission on the CPT-II, and made more disadvantageous choices on the IGT. These results support the existence of deficits related to three components of impulsivity: motor, cognitive, and attentional among adults with ADHD. Most importantly, this study also highlights the complementary nature of self-report questionnaires and neuropsychological tasks in the assessment of impulsivity in ADHD adults.     

Can adults with attention-deficit/hyperactivity disorder be distinguished from those with comorbid bipolar disorder? Findings from a sample of clinically referred adults.

BACKGROUND: Despite data describing the overlap of attention deficit hyperactivity disorder (ADHD) and bipolar disorder (BPD) in youth, little is known about adults with these co-occurring disorders. We now evaluate the clinical characteristics of referred adults with (n = 24) and without BPD (n = 27). METHODS: Referred adults to clinical trials of ADHD were evaluated by psychiatric evaluation using DSM-IV criteria. Structured psychiatric interviews were used to systematically assess adult and childhood disorders. RESULTS: The vast majority of patients with ADHD plus BPD had bipolar II disorder (88%). Adults with ADHD plus BPD had higher rates of the combined subtype of ADHD compared to ADHD without BPD (chi(2) = 8.7, p =.003), a greater number of DSM-IV ADHD symptoms (14.8 +/- 2.9 and 11.4 +/- 4.0; t = -3.4, p <.01), more attentional symptoms of ADHD (8.1 +/- 1.4 and 6.8 +/- 2.1; t = -2.5, p <.02; trend), poorer global functioning (47 +/- 5.9 and 52 +/- 7.4, t = 2.6, p <.02; trend), and additional comorbid psychiatric disorders (3.7 +/- 2.5 and 2.0 +/- 1.9; t = -2.9, p <.01). CONCLUSIONS: These results suggest that adults with ADHD plus BPD have prototypic symptoms of both disorders, suggesting that both disorders are present and are distinguishable clinically.     

Event-related potentials study in attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a childhood disorder characterized by lack of sustained attention, hyperactivity and impulsivity. Children with ADHD have functional impairment occurring at multiple levels. In the present study, cognitive status was assessed using auditory event-related potentials (ERPs). Twenty ADHD children and 20 controls were recruited for the study and ERPs were recorded on a computerized evoked potential recorder, using the international 10-20 system of electrode placement. The ADHD children showed a statistically significant N200 latency prolongation and amplitude decrease compared with the controls; the latencies of the other waves, i.e. N100, P200, P300, were prolonged in the ADHD children but the difference versus the controls was statistically insignificant. Reaction time was significantly longer in the ADHD subjects as compared with the controls. The above findings are suggestive of dysfunctions in the discrimination of task-relevant stimuli and a slower motor response in ADHD children.     

Cross-sectional study of abnormal amygdala development in adolescents and young adults with bipolar disorder.

BACKGROUND: In vivo imaging studies in adult bipolar patients have suggested enlargement of the amygdala. It is not known whether this abnormality is already present early in the illness course or whether it develops later in life. We conducted a morphometric MRI study to examine the size of specific temporal lobe structures in adolescents and young adults with bipolar disorder and healthy control subjects, as well as their relationship with age, to examine possible neurodevelopmental abnormalities. METHODS: Subjects included 16 DSM-IV bipolar patients (16 +/- 3 years) and 21 healthy controls (mean age +/- SD = 17 +/- 4 years). Measures of amygdala, hippocampus, temporal gray matter, temporal lobe, and intracranial volumes (ICV) were obtained. RESULTS: There was a trend to smaller left amygdala volumes in patients (mean volumes +/- SD = 1.58 +/- .42 mL) versus control subjects (1.83 +/- .4 mL; F = 3.87, df = 1,32, p = .06). Bipolar patients did not show significant differences in right or left hippocampus, temporal lobe gray matter, temporal lobe, or right amygdala volumes (analysis of covariance, age, gender, and ICV as covariates, p > .05) compared with healthy control subjects. Furthermore, there was a direct correlation between left amygdala volumes and age (r =. 50, p = .047) in patients, whereas in healthy controls there was an inverse correlation (r = -.48, p = .03). CONCLUSIONS: The direct correlation between left amygdala volumes and age in bipolar patients, not present in healthy control subjects, may reflect abnormal developmental mechanisms in bipolar disorder.     

Noninvasive in vivo assessment of cholinergic cortical circuits in AD using transcranial magnetic stimulation

BACKGROUND: A recently devised test of motor cortex excitability (short latency afferent inhibition) was shown to be sensitive to the blockade of muscarinic acetylcholine receptors in healthy subjects. The authors used this test to assess cholinergic transmission in the motor cortex of patients with AD. METHODS: The authors evaluated short latency afferent inhibition in 15 patients with AD and compared the data with those of 12 age-matched healthy controls. RESULTS: Afferent inhibition was reduced in the patients (mean responses +/- SD reduced to 85.7% +/- 15.8% of the test size) compared with controls (mean responses +/- SD reduced to 45.3% +/- 16.2% of the test size; p < 0.001, unpaired t-test). Administration of a single oral dose of rivastigmine improved afferent inhibition in a subgroup of six patients. CONCLUSIONS: The findings suggest that this method can be used as a noninvasive test of cholinergic pathways in AD. Future studies are required to evaluate whether short latency afferent inhibition measurements have any consistent clinical correlates.     

Neural circuitry engaged during unsuccessful motor inhibition in pediatric bipolar disorder

OBJECTIVE: Deficits in motor inhibition may contribute to impulsivity and irritability in children with bipolar disorder. Studies of the neural circuitry engaged during failed motor inhibition in pediatric bipolar disorder may increase our understanding of the pathophysiology of the illness. The authors tested the hypothesis that children with bipolar disorder and comparison subjects would differ in ventral prefrontal cortex, striatal, and anterior cingulate activation during unsuccessful motor inhibition. They also compared activation in medicated versus unmedicated children with bipolar disorder and in children with bipolar disorder and attention deficit hyperactivity disorder (ADHD) versus those with bipolar disorder without ADHD. METHOD: The authors conducted an event-related functional magnetic resonance imaging study comparing neural activation in children with bipolar disorder and healthy comparison subjects while they performed a motor inhibition task. The study group included 26 children with bipolar disorder (13 unmedicated and 15 with ADHD) and 17 comparison subjects matched by age, gender, and IQ. RESULTS: On failed inhibitory trials, comparison subjects showed greater bilateral striatal and right ventral prefrontal cortex activation than did patients. These deficits were present in unmedicated patients, but the role of ADHD in mediating them was unclear. CONCLUSIONS: In relation to comparison subjects, children with bipolar disorder may have deficits in their ability to engage striatal structures and the right ventral prefrontal cortex during unsuccessful inhibition. Further research should ascertain the contribution of ADHD to these deficits and the role that such deficits may play in the emotional and behavioral dysregulation characteristic of bipolar disorder.     

Novel strategy for the analysis of CPT data provides new insight into the effects of methylphenidate on attentional states in children with ADHD

Continuous performance tasks (CPTs) provide a method for studying some components of attention, but do not take into account that attention fluctuates from moment to moment. To address this issue, CPT performance was classified into one of four states (on-task, impulsive, distracted, or randomly responding) every 30 seconds, based on commission and omission error rates. We evaluated this method on 60 boys (10.6 +/- 1.1 years) with attention-deficit hyperactivity disorder (ADHD)-Combined subtype, tested before and after a dose of methylphenidate (MPH, 0.4 mg/kg), and 8 unmedicated healthy control boys (11.3 +/- 2.0 years of age). Healthy controls were on-task during 82.4% of the 30-second epochs, and made an average of 5.4 attention shifts. In contrast, children with ADHD were only on-task during 42.6% of the epochs (p = 0.0006), and they made an average of 12.8 attention shifts (p = 0.00004). These state measures provided more robust indicators of the difference between children with ADHD and controls than did traditional CPT measures of error rates, latency, and variability. The new state measures were also more significantly affected by MPH. MPH produced a 77% increase in the percent of time children with ADHD spent on-task (p < 10(12)). Conversely, MPH reduced time spent in the distracted, impulsive, and random response states by 79%, 44.5%, and 69.2%, respectively (all p values < 0.0002). Unlike errors of omission and commission, which are highly correlated (r = 0.722, n = 60, p < 10(-11)), the percent of epochs spent in impulsive, distracted, and random response states were uncorrelated, and loaded onto discrete independent factors on principal component analysis. The level of activity during the CPT correlated with the degree of distraction, but not with the degree of impulsivity. Children with ADHD could be subtyped according to the nature of their attention performance problems, and these subtypes differed in levels of hyperactivity and degrees of response to MPH.     

Association between response inhibition and working memory in adult ADHD: a link to right frontal cortex pathology?

BACKGROUND: We sought to assess the relationship between response inhibition and working memory in adult patients with attention-deficit/hyperactivity disorder (ADHD) and neurosurgical patients with frontal lobe damage. METHODS: The stop-signal reaction time (SSRT) test and a spatial working memory (SWM) task were administered to 20 adult patients with ADHD and a group of matched controls. The same tasks were administered to 21 patients with lesions to right frontal cortex and 19 patients with left frontal lesions. RESULTS: The SSRT test, but not choice reaction time, was significantly associated with search errors on the SWM task in both the adult ADHD and right frontal patients. In the right frontal patients, impaired performance on both variables was correlated with the volume of damage to the inferior frontal gyrus. CONCLUSIONS: Response inhibition and working memory impairments in ADHD may stem from a common pathologic process rather than being distinct deficits. Such pathology could relate to right frontal-cortex abnormalities in ADHD, consistent with prior reports, as well as with the demonstration here of a significant association between SSRT and SWM in right frontal patients.     

Fine motor skills and effects of methylphenidate in children with attention-deficit-hyperactivity disorder and developmental coordination disorder

The aims of this study were to investigate fine motor skills of children with both attention-deficit-hyperactivity disorder (ADHD) and developmental coordination disorder (DCD) and those of a control group, and to examine the effects of methylphenidate on these skills. A group of 12 children with ADHD-DCD (11 males, one female; mean age 9y 8mo [SD 1y 7mo]) and 12 age- and sex-matched controls (mean age 9y 7mo [SD 1y 2 mo]) participated. The manual dexterity subtests of the Movement Assessment Battery for Children, the concise assessment method for children's handwriting, and a computerized graphomotor task were used. Results demonstrated that children with ADHD-DCD performed more poorly on the manual dexterity subtests, had poorer quality of handwriting, and drew more rapidly, more fluently, but less accurately than controls on the graphomotor task. On methylphenidate, manual dexterity and quality of handwriting improved, and strokes on the graphomotor task became less fluent but more accurate. ADHD is characterized by persistent symptoms of inattention, impulsivity, and hyperactivity, affecting 3 to 5% of school-age children. Up to 50% of children with ADHD also have motor coordination problems that are severe enough to meet criteria for DCD. In DCD, children demonstrate functional motor performance deficits not explained by the child's (chronological) age or intellect, or by other neurological or psychiatric disorders.