DISTRACTIBILITY IN AD/HD PREDOMINANTLY INATTENTIVE AND COMBINED SUBTYPES: THE P3a ERP COMPONENT, HEART RATE AND PERFORMANCE

The role of single trial variability in event related potentials in children with attention deficit hyperactivity disorder

OBJECTIVE

Children with attention deficit hyperactivity disorder (ADHD) show attenuated mean P3 component amplitudes compared to typically developing (TD) children. This finding may be the result of individual differences in P3 amplitudes, P3 latencies, and/or greater single trial variability (STV) in amplitude or latency, suggesting neural "noise."

METHODS

Event related potentials (ERPs) from 75 children with ADHD and 29 TD children were recorded with electroencephalography (EEG). Caregivers provided ratings on child ADHD symptoms. Single-trial ERP amplitudes and latencies were extracted from the P3 component time window during a visual oddball task. Additionally, we computed individual-centered and trial-centered P3 amplitudes to account for inter-individual and inter-trial variability in the timing of the P3 peak.

RESULTS

In line with prior research, greater ADHD symptom severity was associated with reduced mean P3 amplitude. This correlation was no longer significant after correcting for inter-trial differences in P3 latency. In contrast, greater ADHD symptom severity was associated with reduced STV in P3 amplitude.

CONCLUSIONS

Our results suggest that attenuated average P3 amplitude in ADHD samples is due to a consistent reduction in strength of the neurophysiological signal at the single trial level, as well as increased inter-trial variability in the timing of P3 peak amplitudes. The traditional method of extracting P3 amplitudes based on a single time window for all trials may not adequately capture variability in P3 latencies associated with ADHD.

SIGNIFICANCE

Inter- and intra-individual differences in brain signatures should be considered in models of neurobiological differences in neurodevelopmental samples.

Reduced Error Recognition Explains Post-Error Slowing Differences among Children with Attention Deficit Hyperactivity Disorder

OBJECTIVE

Youth with attention deficit hyperactivity disorder (ADHD) often show reduced post-error slowing (PES) compared to typically developing controls. This finding has been interpreted as evidence that children with ADHD have error recognition and adaptive control impairments. However, several studies report mixed results regarding PES differences in ADHD, and among healthy controls, there is considerable debate about the cognitive-behavioral origin of PES.

METHODS

We tested competing hypotheses aimed at clarifying whether reduced PES in children with ADHD is due to impaired error detection, deficits in adaptive control, and/or attention orienting to novelty. Children aged 7-11 years with a diagnosis of ADHD (n = 74) and controls (n = 30) completed four laboratory-based computer tasks with variable cognitive loads and error types.

RESULTS

ADHD diagnosis was associated with shorter PES only on a task with high cognitive load and low error-cuing, consistent with impaired error recognition. In contrast, there was no evidence of impaired adaptive control or heightened novelty orienting among children with ADHD.

CONCLUSIONS

The cognitive-behavioral origin of PES is multifactorial, but reduced PES among children with an ADHD diagnosis is due to impaired error recognition during cognitively demanding tasks. Behavioral interventions that scaffold error recognition may facilitate improved performance among children with ADHD.

Indices of Heart Rate Variability and Performance During a Response-Conflict Task Are Differently Associated With ADHD and Autism

We investigated autonomic arousal, attention and response conflict, in ADHD and autism. Heart rate variability (HRV), and behavioral/electrophysiological indices of performance, were recorded during a task with low and high levels of response conflict in 78 children/adolescents (7-15 years old) with ADHD, autism, comorbid ADHD+autism, or neurotypical. ANOVA models were used to investigate effects of ADHD and autism, while a mediation model was tested to clarify the relationship between ADHD and slower performance. Slower and less accurate performance characterized ADHD and autism; however, atypical electrophysiological indices differently characterized these conditions. The relationship between ADHD and slower task performance was mediated by reduced HRV in response to the cue stimulus. Autonomic hypo-arousal and difficulties in mobilizing energetic resources in response to sensory information (associated with ADHD), and atypical electrophysiological indices of information processing (associated with autism), might negatively affect cognitive performance in those with ADHD+autism.

Fronto-central P3a to distracting sounds: An index of their arousing properties

The P3a observed after novel events is an event-related potential comprising an early fronto-central phase and a late fronto-parietal phase. It has classically been considered to reflect the attention processing of distracting stimuli. However, novel sounds can lead to behavioral facilitation as much as behavioral distraction. This illustrates the duality of the orienting response which includes both an attentional and an arousal component. Using a paradigm with visual or auditory targets to detect and irrelevant unexpected distracting sounds to ignore, we showed that the facilitation effect by distracting sounds is independent of the target modality and endures more than 1500 ms. These results confirm that the behavioral facilitation observed after distracting sounds is related to an increase in unspecific phasic arousal on top of the attentional capture. Moreover, the amplitude of the early phase of the P3a to distracting sounds positively correlated with subjective arousal ratings, contrary to other event-related potentials. We propose that the fronto-central early phase of the P3a would index the arousing properties of distracting sounds and would be linked to the arousal component of the orienting response. Finally, we discuss the relevance of the P3a as a marker of distraction.

One-year developmental stability and covariance among oddball, novelty, go/no-go, and flanker event-related potentials in adolescence: A monozygotic twin study

ERP measures may index genetic risk for psychopathology before disorder onset in adolescence, but little is known about their developmental rank-order stability during this period of significant brain maturation. We studied ERP stability in 48 pairs of identical twins (age 14-16 years) tested 1 year apart. Trial-averaged voltage waveforms were extracted from electroencephalographic recordings from oddball/novelty, go/no-go, and flanker tasks, and 16 amplitude measures were examined. Members of twin pairs were highly similar, whether based on ERP amplitude measures (intraclass correlation [ICC] median = .64, range = .44-.86) or three factor scores (all ICCs ≥ .69) derived from them. Stability was high overall, with 69% of the 16 individual measures generating stability coefficients exceeding .70 and all factor scores showing stability above .75. Measures from 10 difference waveforms calculated from paired conditions within tasks were also examined, and were associated with lower twin similarity (ICC median = .52, .38-.64) and developmental stability (only 30% exceeding .70). In a supplemental analysis, we found significant developmental stability for error-related negativity (range = .45-.55) and positivity (.56-.70) measures when average waveforms were based on one or more trials, and that these values were equivalent to those derived from averages using the current field recommendation, which requires six or more trials. Overall, we conclude that the studied brain measures are largely stable over 1 year of mid- to late adolescence, likely reflecting familial etiologic influences on brain functions pertaining to cognitive control and salience recognition.

Early Gamma-Band Activity During Interference Predicts Working Memory Distractibility in ADHD

OBJECTIVES

Patients with attention-deficit/hyperactivity disorder (ADHD) display deficits in working memory (WM) and enhanced distractibility.

METHODS

Evoked gamma-band response (GBR) occurs already 50 ms after stimulus onset and is modulated by attention. 16 boys with ADHD and 20 healthy controls (10-14 years) completed a WM task with distraction.

RESULTS

Occipitally evoked 40 Hz-GBR was higher during distraction in ADHD than controls. GBR correlated negatively with interference control.

CONCLUSION

These data suggest that ADHD patients are disturbed by interference on an early level of perception.

Predictive coding in autism spectrum disorder and attention deficit hyperactivity disorder

Predictive coding has been proposed as a framework to understand neural processes in neuropsychiatric disorders. We used this approach to describe mechanisms responsible for attentional abnormalities in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). We monitored brain dynamics of 59 children (8-15 yr old) who had ASD or ADHD or who were control participants via high-density electroencephalography. We performed analysis at the scalp and source-space levels while participants listened to standard and deviant tone sequences. Through task instructions, we manipulated top-down expectation by presenting expected and unexpected deviant sequences. Children with ASD showed reduced superior frontal cortex (FC) responses to unexpected events but increased dorsolateral prefrontal cortex (PFC) activation to expected events. In contrast, children with ADHD exhibited reduced cortical responses in superior FC to expected events but strong PFC activation to unexpected events. Moreover, neural abnormalities were associated with specific control mechanisms, namely, inhibitory control in ASD and set-shifting in ADHD. Based on the predictive coding account, top-down expectation abnormalities could be attributed to a disproportionate reliance (precision) allocated to prior beliefs in ASD and to sensory input in ADHD.

The effect of environmental distractors incorporation into a CPT on sustained attention and ADHD diagnosis among adolescents

BACKGROUND

Diagnosis of ADHD in adolescents involves specific challenges. Conventional CPT's may fail to consistently distinguish ADHD from non-ADHD due to insufficient cognitive demands. The aim of this study was to explore whether the incorporation of environmental distractors into a CPT would increase its ability to distinguish ADHD from non-ADHD adolescents.

NEW METHOD

Using the rate of omission errors as a measure of difficulty in sustained attention, this study examined whether ADHD adolescents are more distracted than controls and which type of distractors is more effective in terms of ADHD diagnosis. The study employed the MOXO-CPT version which includes visual and auditory stimuli serving as distractors. Participants were 176 adolescents aged 13-18 years, 133 diagnosed with ADHD and 43 without ADHD.

RESULTS AND COMPARISON WITH EXISTING METHODS

Results showed that ADHD adolescents produced significantly more omission errors in the presence of pure visual distractors and the combination of visual and auditory distractors than in no-distractors conditions. Distracting stimuli had no effect on CPT performance of non-ADHD adolescents. ROC analysis further demonstrated that the mere presence of distractors improved the utility of the test.

CONCLUSIONS

This study provides evidence that incorporation of environmental distractors into a CPT is useful in term of ADHD diagnosis. ADHD adolescents were more distracted than controls by all types of environmental distractors. ADHD adolescents were more distracted by pure visual distractors and by the combination of distractors than by pure auditory ones.

Atypical mismatch negativity to distressful voices associated with conduct disorder symptoms

BACKGROUND

Although a general consensus holds that emotional reactivity in youth with conduct disorder (CD) symptoms arises as one of the main causes of successive aggression, it remains to be determined whether automatic emotional processing is altered in this population.

METHODS

We measured auditory event-related potentials (ERP) in 20 young offenders and 20 controls, screened for DSM-IV criteria of CD and evaluated using the youth version of Hare Psychopathy Checklist (PCL:YV), State-Trait Anxiety Inventory (STAI) and Barrett Impulsiveness Scale (BIS-11). In an oddball design, sadly or fearfully spoken 'deviant' syllables were randomly presented within a train of emotionally neutral 'standard' syllables.

RESULTS

In young offenders meeting with CD criteria, the ERP component mismatch negativity (MMN), presumed to reflect preattentive auditory change detection, was significantly stronger for fearful than sad syllables. No MMN differences for fearful versus sad syllables were observed in controls. Analyses of nonvocal deviants, matched spectrally with the fearful and sad sounds, supported our interpretation that the MMN abnormalities in juvenile offenders were related to the emotional content of sounds, instead of purely acoustic factors. Further, in the young offenders with CD symptoms, strong MMN amplitudes to fearful syllables were associated with high impulsive tendencies (PCL:YV, Factor 2). Higher trait and state anxiety, assessed by STAI, were positively correlated with P3a amplitudes to fearful and sad syllables, respectively. The differences in group-interaction MMN/P3a patterns to emotional syllables and nonvocal sounds could be speculated to suggest that there is a distinct processing route for preattentive processing of species-specific emotional information in human auditory cortices.

CONCLUSIONS

Our results suggest that youths with CD symptoms may process distressful voices in an atypical fashion already at the preattentive level. This auditory processing abnormality correlated with increased impulsivity and anxiety. Our results may help to shed light on the neural mechanisms of aggression.

Ten years on: a follow-up review of ERP research in attention-deficit/hyperactivity disorder

This article reviews the event-related potential (ERP) literature in relation to attention-deficit/hyperactivity disorder (AD/HD) over the years 2002-2012. ERP studies exploring various aspects of brain functioning in children and adolescents with AD/HD are reviewed, with a focus on group effects and interpretations in the domains of attention, inhibitory control, performance monitoring, non-pharmacological treatments, and ERP/energetics interactions. There has been a distinct shift in research intensity over the past 10 years, with a large increase in ERP studies conducted in the areas of inhibitory control and performance monitoring. Overall, the research has identified a substantial number of ERP correlates of AD/HD. Robust differences from healthy controls have been reported in early orienting, inhibitory control, and error-processing components. These data offer potential to improve our understanding of the specific brain dysfunction(s) which contribute to the disorder. The literature would benefit from a more rigorous approach to clinical group composition and consideration of age effects, as well as increased emphasis on replication and extension studies using exacting participant, task, and analysis parameters.

Methylphenidate does not improve interference control during a working memory task in young patients with attention-deficit hyperactivity disorder

Patients with attention-deficit/hyperactivity disorder (ADHD) show deficits in working memory (WM) which may be related to prefrontal dysfunction. Methylphenidate (MPH) can restore WM deficits in ADHD by enhancing prefrontal activity. At the same time, changes in striatal activation could cause ADHD patients to be more interference-sensitive during working memory tasks. However, it is unclear whether MPH reduces WM distractibility in ADHD. In this fMRI study, 12 ADHD patients and 12 healthy controls participated on two separate days in a delayed-match-to-sample test. During the delay interval, a distractor stimulus was presented in half of the trials. Children and adolescents with ADHD received MPH only on one of the two sessions. Behavioral data analyses revealed that MPH normalized WM in ADHD. However, MPH did not improve WM performance when a distractor was presented during the delay interval. Functional images showed that MPH enhanced prefrontal activity during the delay in ADHD patients when no distractor was present. If the delay was interrupted by a distractor, only healthy controls showed activation of the caudate. In patients with ADHD, however, in line with behavioral data, MPH did not enhance caudate activity. In healthy youth, caudate activity is involved in interference control allowing the successful maintenance of information in working memory even in the presence of distraction. Our findings suggest that interference control, linked to caudate activity, is not adequately enhanced by MPH in ADHD.

Maturation of response time and attentional control in ADHD: evidence from an attentional capture paradigm

Inattention and hyperactivity/impulsivity are the core symptoms of Attention Deficit/Hyperactivity Disorder (ADHD). Slowness, although less known, has been also recently reported in children with ADHD and may contribute to their learning difficulties. Slow response time and greater response time variability have been highlighted by several computerized tasks. The goal of the present work was to evaluate the age-related response time in ADHD children and in a group of matched control children during an attentional capture paradigm. The study population included 75 children with ADHD (aged between 6 and 13) and 75 age- and gender-matched typical developing children (Control group). The children with ADHD made more errors than children on the control group. The response times and the response time variability decreased with age in both groups and were significantly greater in ADHD than in controls. The distractor effect was similar in both groups. The maturation of response times and response time variability with age is quite similar in children with ADHD and typical developing children but whatever the age-class, children with ADHD were slower and exhibited greater response time variability than control children that could explain the variation during day-time of attention capacities in ADHD.

Impaired MMN/P3a complex in first-episode psychosis: cognitive and psychosocial associations

Mismatch negativity (MMN) is a neurophysiological indicator of the brain's ability to extract relevant information from an irrelevant background. The P3a orienting response often accompanies MMN in deviance detection paradigms. Both MMN and P3a have been described as reliable biomarkers of schizophrenia. MMN/P3a impairments are associated with deficits in verbal memory and attentional switching, reflecting dysfunctions in the temporal and frontal systems, respectively. It remains unresolved whether MMN/P3a are robust biomarkers of psychosis in first-episode patients. Thirty-four young people (18 to 30years) were assessed in this study; 17 first-episode psychosis (FEP) patients were compared to 17 healthy controls. To elicit MMN/P3a, a two-tone passive auditory oddball paradigm with 8% duration deviants was used; event-related potentials were recorded at frontal, central and temporal (mastoid) sites. Neuropsychological assessments included processing speed, attentional switching, simple attention, and verbal learning and memory. Social functioning and quality of life measures were also obtained. The FEP group showed significantly reduced MMN amplitudes compared to controls. The FEP group also showed significantly reduced P3a amplitudes at frontal and central sites compared with controls. As expected, the FEP group also showed significant deficits in attention and verbal learning/memory. Correlational analyses found strong associations between fronto-central MMN/P3a peak amplitude and cognitive/psychosocial functioning. This study provides evidence of early neurobiological markers in young people with FEP. These findings suggest that MMN/P3a impairments are present at early stages of psychosis and that fundamental pre-attentive/deviance detection deficits may mark the beginning of progressive underlying changes with illness onset. Such deficits in FEP appear to have important links with higher-order cognitive and psychosocial functioning.

Classification of ADHD patients on the basis of independent ERP components using a machine learning system

BACKGROUND

In the context of sensory and cognitive-processing deficits in ADHD patients, there is considerable evidence of altered event related potentials (ERP). Most of the studies, however, were done on ADHD children. Using the independent component analysis (ICA) method, ERPs can be decomposed into functionally different components. Using the classification method of support vector machine, this study investigated whether features of independent ERP components can be used for discrimination of ADHD adults from healthy subjects.

METHODS

Two groups of age- and sex-matched adults (74 ADHD, 74 controls) performed a visual two stimulus GO/NOGO task. ERP responses were decomposed into independent components by means of ICA. A feature selection algorithm defined a set of independent component features which was entered into a support vector machine.

RESULTS

The feature set consisted of five latency measures in specific time windows, which were collected from four different independent components. The independent components involved were a novelty component, a sensory related and two executive function related components. Using a 10-fold cross-validation approach, classification accuracy was 92%.

CONCLUSIONS

This study was a first attempt to classify ADHD adults by means of support vector machine which indicates that classification by means of non-linear methods is feasible in the context of clinical groups. Further, independent ERP components have been shown to provide features that can be used for characterizing clinical populations.

Cognitive and electroencephalographic disturbances in children with attention-deficit/hyperactivity disorder and sleep problems: new insights

There is overlap between the behavioural symptoms and disturbances associated with Attention-Deficit/Hyperactivity Disorder (AD/HD) and sleep problems. The aim of this study was to examine the extent of overlap in cognitive and electrophysiological disturbances identified in children experiencing sleep problems and children with AD/HD or both. Four groups (aged 7-18) were compared: children with combined AD/HD and sleep problems (n=32), children with AD/HD (n=52) or sleep problems (n=36) only, and children with neither disorder (n=119). Electrophysiological and cognitive function measures included: absolute EEG power during eyes open and eyes closed, event-related potential (ERP) components indexing attention and working memory processes (P3), and a number of standard neuropsychological tests. Children with symptoms of both AD/HD and sleep problems had a different profile from those of children with either AD/HD or sleep problems only. These findings suggest it is unlikely that disturbances in brain and cognitive functioning associated with sleep problems also give rise to AD/HD symptomatology and consequent diagnosis. Furthermore, findings suggest that children with symptoms of both AD/HD and sleep problems may have a different underlying aetiology than children with AD/HD-only or sleep problems-only, perhaps requiring unique treatment interventions.

Distinct response time distributions in attention deficit hyperactivity disorder subtypes

OBJECTIVE

To address the issue of response time (RT) profiles in hyperactive-impulsive (ADHD-HI), inattentive (ADHD-IA), and combined (ADHD-C) subtypes of ADHD. We hypothesized that children with ADHD-HI should respond more rapidly than children without ADHD and children with ADHD-IA and ADHD-C should respond more slowly than children without ADHD.

METHOD

Four groups (3 ADHD groups and 1 non-ADHD group) each composed of 16 children (7-13 years old) performed a visuospatial choice task.

RESULTS

ANOVA indicated very variable RTs for each ADHD subtype when controlling for individual RT. ANOVA performed on RT distribution showed significant differences between the ADHD and non-ADHD groups: biased to fast responses in ADHD-HI and biased to slow responses in ADHD-IA and ADHD-C.

CONCLUSION

The results suggest that response time profiles were abnormal in all ADHD subtypes and were markedly different between children meeting criteria for ADHD-HI and those meeting criteria for ADHD-IA or ADHD-C.

ERP indices of working memory updating in AD/HD: differential aspects of development, subtype, and medication

This study investigated whether children and adolescents diagnosed with the predominantly inattentive and combined subtypes of attention deficit/hyperactivity disorder (AD/HD-in and AD/HD-com, respectively) differed on psychophysiological indices of working memory updating off- and on-stimulant medication, as compared with control subjects and each other. ERPs were recorded in AD/HD and control participants during a one-back working memory task. The N100 (discrimination), P150 (selection), N300 (memory retrieval), and P450wm (updating) components after nontarget stimuli, which served to update working memory with target identity, were assessed. Premedication abnormalities were obtained for the N300 component, delayed in the child AD/HD-com group, and attenuated in the adolescent AD/HD-in group and P450wm component for all AD/HD groups, expressed as either delayed latency and/or attenuated amplitude. ERP abnormalities were predominantly ameliorated after stimulant medication. There were no psychophysiological differences between the subtypes. A general feature of the disorder relates to a deficit in the conscious updating of working memory systems with newly relevant information (P450wm), which varies with age and subtype. Children with AD/HD-com and adolescents with AD/HD-in also exhibit abnormalities in the retrieval of relevant prior memories (N300). This study indicates that AD/HD is related to abnormalities in the capacity to modulate the content of working memory stores.

When distraction is not distracting: A behavioral and ERP study on distraction in ADHD

OBJECTIVE

Although an increased distractibility is one of the behavioral criteria of Attention Deficit Hyperactivity Disorder (ADHD), there is little empirical evidence that children with ADHD are in fact more distractible than their normal peers.

METHODS

We recorded event-related potentials (ERPs) to distracting novel sounds (novels) and standard sounds, (standards) while children performed a visual two-choice reaction time task. Twenty-five children with ADHD were compared with eighteen normal controls (aged 8-12 years).

RESULTS

Children with ADHD showed a larger early P3a (150-250 ms), both in response to the standard and in response to the novel. The late phase of the P3a had a larger amplitude in the ADHD group in the 250-300 ms window compared to the control group, which was only present in response to the novel. Interestingly, the novel reduced the errors of omission in the ADHD group to a greater extent than in the normal control group.

CONCLUSIONS

Although children with ADHD show an increased orienting response to novels, this distracting information can enhance their performance temporarily, possibly by increasing their arousal to an optimal level, as indicated by the reduced omission rate.

SIGNIFICANCE

These data indicate that distraction is not always distracting in children with ADHD and that distraction can also have beneficial effects.

BRAIN STRUCTURE AND FUNCTION CORRELATES OF GENERAL AND SOCIAL COGNITION

AIMS

To examine how general (e.g., memory, attention) and social (emotional and interpersonal processes) cognition relate to measures of brain function and structure.

METHODS

PCA was used to identify general and social cognitive factors from Brain Resource International Database in 1,316 subjects. The identified factors were correlated with each subject's corresponding brain structure (MRI) and function (EEG/ERP) data.

RESULTS

Seven core cognitive factors were identified for general and three for social. General cognition was correlated with global grey matter, while social cognition was negatively correlated with grey matter in fronto-temporal-somatosensory regions. Executive function, information processing speed and verbal memory performance were correlated with delta-theta qEEG, while most general cognitive factors negatively correlated with beta qEEG. Faster information processing speed was correlated with alpha qEEG. Executive function and information processing speed was correlated with negative-going ERP amplitude and slower ERP latency at frontal sites, but at posterior sites negative correlations were found.

DISCUSSION

In contrast to general cognition, social cognition is identified by different functional (automated) activity and more localized neural structures. Only general cognition, requiring more effortful, controlled processing is related to brain function measures, particularly in frontal cortices.

INTEGRATIVE SIGNIFICANCE

Recording measures from multiple modalities including MRI, EEG/ERP, social and general cognition within the same subject provides a method of brain profiling for use in cognitive-neurotherapy and pharmacological studies.

INTEGRATING OBJECTIVE GENE-BRAIN-BEHAVIOR MARKERS OF PSYCHIATRIC DISORDERS

There is little consensus about which objective markers should be used to assess major psychiatric disorders, and predict/evaluate treatment response for these disorders. Clinical practice relies instead on subjective signs and symptoms, such that there is a "translational gap" between research findings and clinical practice. This gap arises from: a) a lack of integrative theoretical models which provide a basis for understanding links between gene-brain-behavior mechanisms and clinical entities; b) the reliance on studying one measure at a time so that linkages between markers are their specificity are not established; and c) the lack of a definitive understanding of what constitutes normative function. Here, we draw on a standardized methodology for acquiring multiple sources of genomic, brain and behavioral data in the same subjects, to propose candidate markers of selected psychiatric disorders: depression, post-traumatic stress disorder, schizophrenia, attention-deficit/hyperactivity disorder and dementia disorders. This methodology has been used to establish a standardized international database which provides a comprehensive framework and the basis for testing hypotheses derived from an integrative theoretical model of the brain. Using this normative base, we present preliminary findings for a number of disorders in relation to the proposed markers. Establishing these objective markers will be the first step towards determining their sensitivity, specificity and treatment prediction in individual patients.