Time Estimation and Performance on Reproduction Tasks in Subtypes of Children With Attention Deficit Hyperactivity Disorder

This study compared Hispanic children (ages 7 to 11) with combined type (CT, n = 33) and inattentive type (IT, n = 21) attention deficit hyperactivity disorder (ADHD) and a control group (n = 25) on time-estimation and time-reproduction tasks. The ADHD groups showed larger errors in time reproduction but not in time estimation than the control group, and the groups did not differ from each other on their performance on this task. Individual differences could not be accounted for by oppositional-defiance ratings and low math or reading scores. Although various measures of executive functioning did not make significant unique contributions to time estimation performance, those of interference control and nonverbal working memory did so to the time-reproduction task. Findings suggest that ADHD is associated with a specific impairment in the capacity to reproduce rather than estimate time durations and that this may be related to the children's deficits in inhibition and working memory.     

Assessing multitasking in children with ADHD using a modified Six Elements Test.

The study was designed to investigate whether children with Attention Deficit Hyperactivity Disorder (ADHD) demonstrate a deficit in multitasking, measured by their performance on a modified Six Elements Test designed for use with children (C-SET). The C-SET was administered to 38 children, aged 7-13. The subjects comprised two groups: an ADHD sample (n = 19) and a community control sample (n = 19). The results show that the ADHD group performed significantly worse on the C-SET, in that they attempted fewer tasks than the control group. However, they did not commit more rule breaks. These findings suggest that children with ADHD did not have problems with retrospective memory, as they were as able to remember the rules as the control group. Rather, the ADHD children appeared to have a specific deficit in monitoring their ongoing behaviors and generating useful strategies for task completion, as indicated by the decreased number of tasks attempted compared to the control group. The number of tasks tried on the C-SET correlated significantly with a measure of working memory, but not with a measure of response inhibition. C-SET total tasks tried also correlated with all subscales of the Conner's Parent Rating Scale-Revised (Short Version). The C-SET appears to be a useful measure of rule-governed multitasking behavior in children.     

Abnormal executive function in attention deficit hyperactivity disorder: the effect of stimulant medication and age on spatial working memory

OBJECTIVE: This study sought to examine the factors associated with spatial working memory and the use of strategies to impairments in spatial working memory in children with attention deficit hyperactivity disorder (ADHD). The developmental trajectories for spatial working memory in medicated and medication na?ve children with ADHD were investigated. In addition, the effect of psychostimulant medication on deficits in spatial working memory was examined. METHOD: A cross-sectional study compared performance between 21 psychostimulant medicated children with ADHD, 27 medication na?ve children with ADHD and 26 matched control subjects on computerized tests of spatial memory and spatial working memory. RESULTS: Compared with the controls, performance in medication na?ve children with ADHD was significantly worse on the spatial working memory task. There was no difference in performance between the medicated children with ADHD and the control subjects on this same task, despite the ongoing symptoms of ADHD in the former group. The pattern of normal and abnormal performance in the ADHD groups was age-independent. CONCLUSIONS: Deficits in executive functions related to spatial working memory do occur in children with ADHD, although the magnitude of these deficits is not related to the child's age or the level of ADHD symptoms. These deficits were not present in the current sample of children who were receiving psychostimulant medication.     

注意缺陷多动障碍儿童记忆和学习的研究

目的：探讨注意缺陷多动障碍DSM－Ⅳ亚型记忆学习功能及与持续性注意的关系。方法：对113名8－12岁注意缺陷我动障碍男童与83名正常儿童对照研究，并与持续性注意测验进行相关分析。结果：ADHD各亚型图案记忆成绩均较对照组差；混合型儿童的图片记忆，言语记忆和故事记忆成绩较对照组差。持续性注意测验的击中度，虚报数，d‘值与记忆和学习相关。结论：注意缺陷多动障碍儿童存在记忆与学习功能损害，与注意障碍明显相关。     

Interference control, working memory, concept shifting, and verbal fluency in adults with attention-deficit/hyperactivity disorder (ADHD)

In this study, the authors aimed to examine 4 domains of executive functioning in adults with attention-deficit/hyperactivity disorder (ADHD)--namely interference control, concept shifting, verbal fluency, and verbal working memory. Four groups of participants were included: (a) adults diagnosed with ADHD (ADHD-super(-); n = 20), (b) adults diagnosed with both ADHD and 1 or more comorbid disorder(s) (ADHD-super(+); n = 22), (c) adults referred for ADHD because of ADHD symptomatology but not diagnosed as such (non-ADHD; n = 34), and (d) healthy controls (n = 136). ADHD-related deficits (independent of comorbidity) were revealed for concept shifting and verbal working memory. In addition, the ADHD-super(+) and non-ADHD groups displayed deficits in terms of general processing speed. Given that these deficits were not found in the ADHD-super(-) group, the authors contend that these deficits are likely attributable to comorbidity rather than ADHD itself. Contrary to the authors' expectations, these findings do not correspond with the cognitive subtype hypothesis.     

Contextual abnormalities of saccadic inhibition in children with attention deficit hyperactivity disorder

Abnormalities of executive function are observed consistently in children with attention-deficit hyperactivity disorder (ADHD), and it is hypothesised that these arise because of disruption to a behavioural inhibition system. Executive and inhibitory functions were compared between unmedicated and medicated children with ADHD (combined type), age-matched healthy children and healthy adults. Executive functions were measured using a test of spatial working memory shown previously to be sensitive to ADHD and to stimulant medication. Inhibitory functions were measured using an ocular motor paradigm that required individuals to use task context to control the release of fixation. Context was set according to the probability that a target would appear at either of the two locations. In one block, targets appeared on 80% of trials. In the other block, targets appeared on 20% of trials. The ability to control the release of fixation was inferred from the fixation offset effect (FOE), or the difference in saccade latency when the current fixation is offset 200 ms prior to the onset of the saccade target (gap condition), compared with when there is no offset (overlap condition). Although the healthy children made more errors on the spatial working memory task than the healthy adults, there was no difference between the two groups in their ability to control fixation using context. Both showed a larger FOE when target probability was low. As expected, the unmedicated ADHD group made more errors on the spatial working memory test than the healthy children, although spatial working memory performance was normal in the medicated ADHD group. However, both the unmedicated and medicated ADHD groups were unable to modulate the FOE according to context, and this was due to their inability to voluntarily inhibit saccades when there was a low target probability. These data suggest that the context-based modulation of fixation release is not controlled by the same systems that control executive function. Furthermore, deficits in executive function and inhibitory control appear independent in children with ADHD.     

The cognitive structure of time estimation impairments in adults with attention deficit hyperactivity disorder

We compared the performance of 15 adults with attention deficit hyperactivity disorder (ADHD) and a group of 16 control adults on a temporal bisection task in auditory and visual modalities. The point of subjective equality (PSE) and the difference limen (DL) were computed to analyse performance. The main findings were that (a) individuals with ADHD overestimated the duration of both the auditory and visual stimuli in comparison to the control group, as evidenced by a shift in their mean PSE; (b) individuals with ADHD also showed less precision in their estimates than did the control group as evidenced by flatter psychometric functions; and (c) the degrees of overestimation and imprecision in subjects with ADHD were comparable across modalities. These results, discussed in the framework of the pacemaker–counter clock model of time estimation, suggest that temporal difficulties encountered by ADHD patients might be explained both by an alertness effect at the level of the switch that directs pulses into the accumulator and also by distortions of durations stored in reference memory.     

Time perception and reproduction in young adults with attention deficit hyperactivity disorder

Adults with attention deficit hyperactivity disorder (ADHD; n = 104) were compared with a control group (n = 64) on time estimation and reproduction tasks. Results were unaffected by ADHD subtype or gender. The ADHD group provided larger time estimations than the control group, particularly at long intervals. This became nonsignificant after controlling for IQ. The ADHD group made shorter reproductions than did the control group (15- and 60-s intervals) and greater reproduction errors (12-, 45-, 60-s durations). These differences remained after controlling for IQ and comorbid oppositional defiant disorder, depression, and anxiety. Only the level of anxiety contributed to errors (at 12-s duration) beyond the level of ADHD. Results extended findings on time perception in ADHD children to adults and ruled out comorbidity as the basis of the errors.     

Delayed-execute prospective memory performance: the effects of age and working memory

This study follows the novel delayed-execute prospective memory paradigm, which involves briefly delaying the execution of an intended action, a task that has been shown to produce substantial age effects. During the ongoing task, sentences were presented, and participants had to answer reading-comprehension questions and general knowledge questions. In the prospective memory task, the participant was to press a key after the presentation of a specific cue in the sentences—but not before a subsequent phase of the ongoing task was reached. In contrast to previous studies using older participants taken from very broadly defined age ranges, this study examines development of delayed-execute prospective memory more precisely by examining a total of 4 age groups: a younger age group (age range = 22-31; n = 27), a young-old age group (age range = 60-69; n = 34), a middle-old age group (age range = 70-79; n = 31), and an old-old age group (age range = 80-91; n = 35). This study investigates the dependence of (age-related) delayed-execute prospective memory performance on working memory capacity by disrupting the phonological loop during the delay period as well as its dependence on neuropsychological processes such as inhibitory control and processing speed. The results show that (a) delayed-execute prospective memory particularly declines within the group of older participants, (b) delayed-execute prospective memory is diminished when working memory load is high during the delay period, and (c) age-related performance in delayed-execute prospective memory may be mediated by inhibitory control. The findings are discussed in the context of the frontal lobe hypothesis of cognitive aging.     

Delayed–Execute Prospective Memory Performance: The Effects of Age and Working Memory

This study follows the novel delayed-execute prospective memory paradigm, which involves briefly delaying the execution of an intended action, a task that has been shown to produce substantial age effects. During the ongoing task, sentences were presented, and participants had to answer reading-comprehension questions and general knowledge questions. In the prospective memory task, the participant was to press a key after the presentation of a specific cue in the sentences—but not before a subsequent phase of the ongoing task was reached. In contrast to previous studies using older participants taken from very broadly defined age ranges, this study examines development of delayed-execute prospective memory more precisely by examining a total of 4 age groups: a younger age group (age range = 22–31; n = 27), a young-old age group (age range = 60–69; n = 34), a middle-old age group (age range = 70–79; n = 31), and an old-old age group (age range = 80–91; n = 35). This study investigates the dependence of (age-related) delayed-execute prospective memory performance on working memory capacity by disrupting the phonological loop during the delay period as well as its dependence on neuropsychological processes such as inhibitory control and processing speed. The results show that (a) delayed-execute prospective memory particularly declines within the group of older participants, (b) delayed-execute prospective memory is diminished when working memory load is high during the delay period, and (c) age-related performance in delayed-execute prospective memory may be mediated by inhibitory control. The findings are discussed in the context of the frontal lobe hypothesis of cognitive aging.     

Perceptual and response interference in children with attention-deficit hyperactivity disorder, and the effects of methylphenidate.

Fourteen children with attention-deficit hyperactivity disorder (ADHD) and 14 normal control children were compared with respect to stimulus- and response-related processes. Subjects with ADHD took part in two additional sessions under methylphenidate or placebo. In both experiments, performance and electrophysiological measures such as the P2, N2, and P3 components of event-related potential and electromyogram (EMG) activity were measured during an Eriksen flanker task. In both groups of children, reaction times (RTs) to arrow stimuli incongruent with the target were longer than those to neutral stimuli (response interference), which were again slower than RTs to target-alone stimuli (perceptual interference). Children with ADHD made more errors to incongruent stimuli and showed more response interference. For correct responses, no differences between the groups in response interference effects on reaction time, P2, N2, and P3 latency, or EMG onset were found. Methylphenidate had a general enhancing effect on accuracy but did not specifically reduce interference from the flanking stimuli. Methylphenidate had no effects on RT, N2 and P2 latency, P3 amplitude or latency, or EMG activity. The conclusion that methylphenidate did not influence response processes contrasts sharply with findings reported by authors using the Sternberg memory search task.     

Executive Functioning in Hyperactive Children as Young Adults: Attention,Inhibition, Response Perseveration,and the Impact of Comorbidity

Tests of several executive functions (EFs) as well as direct observations of symptoms of attention deficit hyperactivity disorder (ADHD) during testing were collected at the young adult follow-up (M = 20 years) on a large sample of hyperactive (H; N = 147) and community control (CC; N = 71) children. The EF tasks included tests of attention, inhibition, and response perseveration. The H group was subdivided into those with and without ADHD (+ or w/o) at follow-up. The H+ADHD group made significantly more inhibition errors than the CC group on a Continuous Performance Test (CPT) and showed more ADHD symptoms while performing the CPT. The H+ADHD group also displayed more ADHD symptoms during a letter cancellation task than did both the hyperactive w/o ADHD and CC groups. Both H groups showed slower reaction times during a Card Playing Task. That subset of hyperactive probands with Conduct Disorder (CD) displayed significantly more perseverative responding on that task than did those without CD, but otherwise it did not differ on any other measures. Current level of anxiety contributed adversely to both CPT commission errors and ADHD behavior during the CPT. Comorbid depression did not contribute to any group differences on these tests. Although developmental improvements were found in both the H and the CC groups in their CPT inattention and inhibition scores since adolescence, the H groups remained distinguishable from the CC groups over this period. We conclude that formerly hyperactive children manifest greater EF deficits at follow-up in the areas of inattention, disinhibition, and slowed reaction time and greater ADHD behavior during testing, but these problems are mostly confined to those with current ADHD. Response perseveration, however, was limited to those hyperactive children with CD by follow-up, consistent with Quay's theory of these two disorders.     

N-acetyl cysteine supplementation prevents impairment of spatial working memory functions in rats following exposure to hypobaric hypoxia

Exposure to high altitude (HA), especially extreme altitude, is associated with impairment of cognitive functions including memory and increased oxidative stress. However, the underlying mechanisms involved are not well understood. It is hypothesized that HA induced oxidative stress may be one of the factors underlying hypoxia induced memory impairment. The aim of the present study was to investigate the effect of hypobaric hypoxia (HH) on spatial working and reference memory functions, oxidative stress markers in rats and effect of supplementation of N-acetyl cysteine (NAC). The rats were divided into four groups. Group I served as normoxic (n=6), Group II served as hypoxic (n=6), Group III as hypoxia group treated with NAC (n=6) and Group IV served as normoxic group treated with NAC (n=6). Group II & III were exposed to HH for 3 days equivalent to 6100 m and received oral NAC supplementation (750 mg/kg) daily. Rats from all the groups were trained in Morris Water Maze (MWM) task for 8 consecutive days. Spatial working and reference memory were tested immediately after the termination of HH and then the rats were sacrificed for estimation of oxidative stress markers in hippocampus. Rats displayed significant deficits in spatial working memory, and increased oxidative stress along with decrease in antioxidant status on hypoxic exposure. Supplementation with NAC in hypoxia-exposed group improved spatial memory performance, and decreased oxidative stress. These findings indicate that hypoxic exposure is associated with increased oxidative stress, which may have caused memory deficit in rats exposed to simulated HA.     

Behavioral inhibition,self-regulation of motivation,and working memory in children with attention deficit hyperactivity disorder

We examined 3 aspects of Barkley's (1997) recent model of Attention Deficit Hyperactivity Disorder (ADHD)-behavioral inhibition, self-regulation of motivation, and working memory utilizing 152 elementary school children ages 7 to 12. Seventy-six children with ADHD and 76 children without a psychiatric diagnosis completed the stop-signal task, a computerized Digit Span Task requiring concurrent storage and processing, and the Kaufman Brief Intelligence Test during a 1-hr testing session. Parent and teacher ratings were also obtained on the Conners Parent Rating Scale-Revised: Long Version (Conners, 1997), and the Conners Teacher Rating Scale-Revised: Long Version (Conners, 1997), respectively. Results indicated that children with ADHD had deficits in inhibitory control, working memory, and short-term memory relative to children without the disorder. Contrary to our prediction, the groups did not differ in their responsiveness to external reinforcement. In addition, children with and without ADHD had similar self-perceptions of their performances during the experimental session. Future directions for specifying childhood difficulties in inhibitory control and memory processes are discussed.     

Neuropsychological analyses of comorbidity between reading disability and attention deficit hyperactivity disorder: in search of the common deficit

Measures of component reading and language skills, executive functions, and processing speed were administered to groups of children with attention deficit hyperactivity disorder (ADHD; n = 113), reading disability (RD; n = 109), both RD and ADHD (n = 64), and neither RD nor ADHD (n = 151). Groups with RD exhibited pronounced deficits on all measures of component reading and language skills, as well as significant weaknesses on measures of verbal working memory, processing speed, and response inhibition. Groups with ADHD exhibited weaknesses on all response-inhibition and processing speed tasks and were impaired on some measures of component reading skills and verbal working memory. The group with comorbid RD and ADHD exhibited the combination of the deficits in the RD-only and ADHD-only groups, providing evidence against the phenocopy and cognitive subtype hypotheses as explanations for the co-occurrence of RD and ADHD. Slow and variable processing speed was characteristic of all 3 clinical groups, suggesting that measures of this domain may be useful for future studies that search for the common genes that increase susceptibility to RD and ADHD.     

Time Reproduction Deficits at Young Adult Follow-Up in Childhood ADHD: The Role of Persistence of Disorder and Executive Functioning

No studies have examined if time reproduction deficits exist in children with attention deficit hyperactivity disorder (ADHD) by adulthood. We followed 131 ADHD and 71 community control (CC) cases for 20+ years to young adulthood at which time they were given a time reproduction task. The ADHD group made smaller time reproductions and showed greater variability of errors at the longer durations compared to CC cases, whether ADHD was still present or not at follow-up. Nonverbal working memory and design fluency tests were related to timing errors while anxiety and depression were not. Childhood ADHD is associated with timing deficits at adult follow-up.     

Neuropsychological and behavioural disinhibition in adult ADHD compared to borderline personality disorder

BACKGROUND: Although attention-deficit/hyperactivity disorder (ADHD) is thought to be an inhibitory disorder, the question remains of how specific the inhibitory deficit is in adults and whether it distinguishes ADHD from borderline personality disorder (BPD), with which it shares several clinical features, particularly impulsiveness. METHOD: The study assessed various motor and cognitive inhibitory functions (inhibition of prepotent, ongoing and interfering responses) in addition to working memory in adult ADHD patients with and without BPD, compared to subjects with BPD alone and controls. In addition, questionnaire data on various aspects of impulsiveness and anger regulation were assessed in all groups. RESULTS: ADHD patients performed worse than BPD individuals and controls in two inhibitory tasks: the stop signal task and the conflict module of the Attentional Network Task (ANT). In addition, they exhibited longer reaction times (RTs) and higher intra-individual variance in nearly all attentional tasks. The co-morbid group exhibited poor performance on the stop signal task but not on the conflict task. The BPD group barely differed from controls in neuropsychological performance but overlapped with ADHD in some behavioural problems, although they were less severe on the whole. CONCLUSIONS: Impaired inhibition is a core feature in adults with ADHD. In addition, slow RTs and high intra-individual variance in performance may reflect deficits in the regulation of activation and effort in ADHD patients. ADHD and BPD share some symptoms of behavioural dysregulation without common cognitive deficits, at least in the attentional realm.     

Executive functioning in hyperactive children as young adults: attention, inhibition, response perseveration, and the impact of comorbidity

Tests of several executive functions (EFs) as well as direct observations of symptoms of attention deficit hyperactivity disorder (ADHD) during testing were collected at the young adult follow-up (M = 20 years) on a large sample of hyperactive (H; N = 147) and community control (CC; N = 71) children. The EF tasks included tests of attention, inhibition, and response perseveration. The H group was subdivided into those with and without ADHD (+ or w/o) at follow-up. The H+ADHD group made significantly more inhibition errors than the CC group on a Continuous Performance Test (CPT) and showed more ADHD symptoms while performing the CPT. The H+ADHD group also displayed more ADHD symptoms during a letter cancellation task than did both the hyperactive w/o ADHD and CC groups. Both H groups showed slower reaction times during a Card Playing Task. That subset of hyperactive probands with Conduct Disorder (CD) displayed significantly more perseverative responding on that task than did those without CD, but otherwise it did not differ on any other measures. Current level of anxiety contributed adversely to both CPT commission errors and ADHD behavior during the CPT. Comorbid depression did not contribute to any group differences on these tests. Although developmental improvements were found in both the H and the CC groups in their CPT inattention and inhibition scores since adolescence, the H groups remained distinguishable from the CC groups over this period. We conclude that formerly hyperactive children manifest greater EF deficits at follow-up in the areas of inattention, disinhibition, and slowed reaction time and greater ADHD behavior during testing, but these problems are mostly confined to those with current ADHD. Response perseveration, however, was limited to those hyperactive children with CD by follow-up, consistent with Quay's theory of these two disorders.     

Baroreflex sensitivity during rest and executive functioning in attention-deficit/hyperactivity disorder. The TRAILS study

Children with attention-deficit/hyperactivity disorder (ADHD) often show executive function (EF) problems and neurophysiological hypoarousal. Baroreceptor activation, as part of the baroreflex short-term blood pressure regulatory mechanism, has been linked to cortical inhibition and attenuated cognitive-attentional functioning. We investigated the hypothesis that higher resting baroreflex sensitivity (BRS) predicts poorer EF performance in children with ADHD. EF measures of speed and accuracy were regressed upon resting BRS in 10-12-year-old children with ADHD from a clinic-referred sample (n=181) and healthy (n=194) and clinic-referred (n=260) comparison samples. Resting BRS was positively associated with poorer EF performance (e.g., response variability, working memory, response inhibition), especially in ADHD combined type, boys, and unmedicated children. Comparison samples partly suggested negative associations. We conclude that higher resting BRS is related to poorer cognitive performance in children with ADHD. Findings suggest afferent influences of the body's visceral state on higher-order cognitive functioning and imply energetic state dysregulation in ADHD.     

Executive functioning and olfactory identification in young adults with attention deficit-hyperactivity disorder

Young adults with attention deficit-hyperactivity disorder (ADHD; N = 105) were compared with a control group (N = 64) on 14 measures of executive function and olfactory identification using a 2 (group) X 2 (sex) design. The ADHD group performed significantly worse on 11 measures. No Group X Sex interaction was found on any measures. No differences were found in the ADHD group as a function of ADHD subtype or comorbid oppositional defiant disorder. Comorbid depression influenced the results of only 1 test (Digit Symbol). After IQ was controlled for, some group differences in verbal working memory, attention, and odor identification were no longer significant, whereas those in inhibition, interference control, nonverbal working memory, and other facets of attention remained so. Executive function deficits found in childhood ADHD exist in young adults with ADHD and are largely not influenced by comorbidity but may be partly a function of low intelligence.