Error monitoring in children with ADHD or reading disorder: An event-related potential study

This study compared children with ADHD, reading disorder (RD), ADHD + RD, and control children on behavioural (post-error slowing and post-error accuracy) and event-related potential (Ne and Pe) measures of error monitoring. Children with ADHD did not differ from children without ADHD in post-error slowing but showed less post-error accuracy enhancement, as evidenced by a higher proportion of double-errors. We found a smaller Ne but normal Pe amplitude in children with RD, and a smaller Pe but normal Ne amplitude in children with ADHD. Children from the comorbid group showed both a smaller Ne and a smaller Pe amplitude, which suggests that they showed the additive combination of the deficits found in both separate disorders. The results of the present study suggest that it might be important to control for the presence of comorbid RD when examining error monitoring in ADHD and that various measures of post-error adaptation should be included.     

Brain bases of error-related ERPs as influenced by age and task

Age effects in the error negativity (Ne) and error positivity (Pe) were examined in a standard letter flanker task and an age-sensitive source memory exclusion task. Older adults made more errors and produced Ne and Pe components of lower amplitude in both tasks. The Ne was insensitive to task and error rate. The Pe, however, was reduced in the source memory relative to the flanker task and was correlated with error rate in both tasks. Ne and Pe dipoles were generally localized to anterior cingulate cortex, but dipoles associated with the Pe were more frontal for flanker errors and, for young adults, more posterior for source errors. These data suggest that the Ne reflects an automatic response to error as it occurs whereas the Pe, being more sensitive to age and task demands, and more closely linked to accuracy, reflects the allocation of attention to an error that has been made.     

To err is autonomic: error-related brain potentials, ANS activity, and post-error compensatory behavior

A two-component event-related brain potential consisting of an error-related negativity (ERN/Ne) and positivity (Pe) has been associated with response monitoring and error detection. Both the ERN and Pe have been source-localized to the anterior cingulate cortex (ACC)--a frontal structure implicated in both cognitive and affective processing, as well as autonomic nervous system (ANS) modulation. The current study sought to examine the relationships among the ERN, the Pe, two autonomic measures, and behavior. Electroencephalogram (EEG), heart rate (HR), and skin conductance (SC) were recorded while subjects performed a two-choice reaction-time task. In addition to the characteristic ERN-Pe complex, errors were associated with larger SCRs and greater HR deceleration. The ERN correlated with the number of errors, but was unrelated to ANS activity and compensatory behavior. Pe, on the other hand, was correlated significantly with SCR, and both SCR and Pe were significantly correlated with post-error slowing.     

Error processing in patients with Alzheimer's disease.

Patients with dementia are prone to make errors while they perform a task. To evaluate error detection and action monitoring in patients with dementia of the Alzheimer type (DAT) at a relatively early stage of the illness, error negativity (Ne) and error positivity (Pe) of event-related potentials (ERPs) obtained by averages time-locked to error response were studied using a lexical recognition paradigm composed of Japanese 'kanji' ideogram characters. In the DAT patients, reaction times were significantly slower and error rates were higher. Not only in healthy elderly subjects but also in the DAT patients, the Ne component obtained by averages time-locked to error response showed a larger amplitude than negativity for correct response (Nc). The Ne and Pe amplitudes were significantly smaller for the DAT patients than for the healthy elderly subjects, whereas there were no significant differences in the Nc amplitude between the two subject groups. Latencies of the Ne, Pe and positivity for correct response (Pc) were prolonged in the DAT patients. These findings suggest that information processing and error detection are slower and somewhat impaired at a relatively early stage of DAT, although error detection and awareness are still preserved.     

Obligatory adaptation of saccade gains

We tested the hypothesis that saccade gains adapt to minimize error between the visual target and the saccade endpoint of every saccade we make even when the errors on sequential saccades are not directionally consistent. We utilized a state-space model that estimated the degree to which saccade gains were modified by the magnitude and direction of errors made on the previous trial. Importantly, to show that learning did not depend on the accumulation of directionally consistent errors, we fit the model to saccades made to targets that were displaced in a random direction during the saccade, thereby inducing errors with directions that were not sequentially the same. Saccade gains clearly adapted on a trial-by-trial basis despite that the perturbations were random, and the average amount of learning per trial was of similar magnitude as that found in a constant displacement of the target. These results indicate that saccade adaptation is a rapid and obligatory process that does not require conscious awareness.     

Methylphenidate improves deficient error evaluation in children with ADHD: an event-related brain potential study

Children with ADHD make more errors than control children in response-conflict tasks. To explore whether this is mediated by enhanced sensitivity to conflict or reduced error-processing, task-related brain activity (N2, Ne/ERN, Pe) was compared between 8- to 12-year-old children with ADHD and healthy controls during performance of a flanker task. Furthermore, effects of methylphenidate were investigated in ADHD children in a second study. ADHD children made more errors, especially in high-response-conflict conditions, without showing post-error slowing. N2 amplitudes were enhanced on trials resulting in an error response, Ne/ERN amplitude was unaffected and Pe amplitude was reduced in the ADHD group. Methylphenidate reduced errors in both low- and high-conflict conditions and normalized Pe amplitudes in children with ADHD. It was concluded that the inaccurate behaviour of ADHD children in conflict tasks might be related to reduced error-awareness and higher sensitivity to response conflict. Methylphenidate's ameliorating effects might be established through its influence on brain networks including posterior (parietal) cortex, enabling children with ADHD to allocate more attention to significant events.     

Secondary adaptation of memory-guided saccades

Adaptation of saccade gains in response to errors keeps vision and action co-registered in the absence of awareness or effort. Timing is key, as the visual error must be available shortly after the saccade is generated or adaptation does not occur. Here, we tested the hypothesis that when feedback is delayed, learning still occurs, but does so through small secondary corrective saccades. Using a memory-guided saccade task, we gave feedback about the accuracy of saccades that was falsely displaced by a consistent amount, but only after long delays. Despite the delayed feedback, over time subjects improved in accuracy toward the false feedback. They did so not by adjusting their primary saccades, but via directed corrective saccades made before feedback was given. We propose that saccade learning may be driven by different types of feedback teaching signals. One teaching signal relies upon a tight temporal relation with the saccade and contributes to obligatory learning independent of awareness. When this signal is ineffective due to delayed error feedback, a second compensatory teaching signal enables flexible adjustments to the spatial goal of saccades and helps maintain sensorimotor accuracy.     

Performance monitoring during sleep inertia after a 1‐h daytime nap

Performance monitoring is an essential function involved in the correction of errors. Deterioration of this function may result in serious accidents. This function is reflected in two event‐related potential (ERP) components that occur after erroneous responses, specifically the error‐related negativity/error negativity (ERN/Ne) and error positivity (Pe). The ERN/Ne is thought to be associated with error detection, while the Pe is thought to reflect motivational significance or recognition of errors. Using these ERP components, some studies have shown that sleepiness resulting from extended wakefulness may cause a decline in error‐monitoring function. However, the effects of sleep inertia have not yet been explored. In this study, we examined the effects of sleep inertia immediately after a 1‐h daytime nap on error‐monitoring function as expressed through the ERN/Ne and Pe. Nine healthy young adults participated in two different experimental conditions (nap and rest). Participants performed the arrow‐orientation task before and immediately after a 1‐h nap or rest period. Immediately after the nap, participants reported an increased effort to perform the task and tended to estimate their performance as better, despite no objective difference in actual performance between the two conditions. ERN/Ne amplitude showed no difference between the conditions; however, the amplitude of the Pe was reduced following the nap. These results suggest that individuals can detect their own error responses, but the motivational significance ascribed to these errors might be diminished during the sleep inertia experienced after a 1‐h nap. This decline might lead to overestimation of their performance.     

Inhibition control and error processing in children with attention deficit/hyperactivity disorder: An event-related potentials study

We studied inhibitory control and error processing in a task requiring inhibition of a motor response. Behavioral and ERP indices were recorded in fourteen ADHD and fourteen healthy children aged between 6 and 10 years during the Stop signal task (SST). The ADHD group made more variable in RT and showed less accuracy, more omissions and choice errors. Also, the ADHD group had a tendency toward a lower probability of inhibition and a longer Stop signal reaction time. The ADHD group also displayed a flatter response inhibition slope compared to the control group. Smaller P1 in ADHD group reflected that the ADHD group has less efficient attention than the control group. Furthermore, the ADHD group showed normal ERN, reduced Pe (retrieved from response-locked epochs), and reduced LPW (retrieved from Stop signal-locked epochs), suggesting that they might be normal in early error monitoring process related to error detection, but show abnormal in later error monitoring process associated with a conscious evaluation of the error. Behavioral and ERP data of the present study show deficient selective attention, inhibitory control, and error processing in children of ADHD.     

Dissociation of Pe and ERN/Ne in the conscious recognition of an error

We evaluated the relationship between conscious awareness and the ERN/Ne and Pe in a digit entering task. On each trial, participants rated the accuracy of their responses on a three-point scale (incorrect, unsure, correct). The ERN/Ne was present on incorrect trials judged as incorrect. The Pe was evident on the same trials but also on correct and incorrect trials judged as unsure. We propose that the ERN/Ne occurs when there is an incorrect execution of a correct motor plan and the representation of the correct response is available for comparison with the actual response. The mismatch information that results from this comparison can be transferred to the Pe process and conscious awareness. However, the Pe process and conscious awareness do not only depend on this transfer of information from the ERN/Ne process. The Pe also occurs when there is uncertainty about the correctness of the motor plan, whether or not the plan is, in fact, correct.     

Neural correlates of error processing reflect individual differences in interoceptive sensitivity

Although self-monitoring is an important process for adaptive behaviors in multiple domains, the exact relationship among different internal monitoring systems is unclear. Here, we aimed to determine whether and how physiological monitoring (interoception) and behavioral monitoring (error processing) are related to each other. To this end we examined within-subject correlations among measures representing each function. Score on the heartbeat counting task (HCT) was used as a measure of interoceptive awareness. The amplitude of two event-related potentials (error-related negativity [ERN] and error-positivity [Pe]) elicited in error trials of a choice-reaction task (Simon task) were used as measures of error processing. The Simon task presented three types of stimuli (objects, faces showing disgust, and happy faces) to further examine how emotional context might affect inter-domain associations. Results showed that HCT score was robustly correlated with Pe amplitude (the later portion of error-related neural activity), irrespective of stimulus condition. In contrast, HCT score was correlated with ERN amplitude (the early component) only when participants were presented with disgust-faces as stimuli, which may have automatically elicited a physiological response. Behavioral data showed that HCT score was associated with the degree to which reaction times slowed after committing errors in the object condition. Cardiac activity measures indicated that vigilance level would not explain these correlations. These results suggest a relationship between physiological and behavioral monitoring. Furthermore, the degree to which behavioral monitoring relies on physiological monitoring appears to be flexible and depend on the situation.     

Error-processing deficits in patients with cocaine dependence

Cocaine abuse and addiction can be characterized by a persisting use of cocaine in the face of adverse consequences. In the present study we focus on one specific element of adverse consequences: the making of errors. The aim of this study was to determine whether cocaine-dependent persons have error-processing deficits as measured using error-related negativity (ERN) and error positivity (Pe). Event-related potentials (ERPs) during an Eriksen flanker task were recorded from cocaine-dependent patients and a control group. Cocaine-addicted patients showed reduced ERN and Pe components as compared to a control group. On the behavioral level, patients showed reduced post-error accuracy improvement. The present findings reveal that cocaine addiction is associated with reduced error processing and impaired behavioral correction of errors after an error is made. These deficits may be associated with a compromised dopamine system. It is argued that these cognitive deficits may contribute to the maintenance of the cocaine addiction.     

Error negativity and response control

Error trials are associated with faster responses than correct trials in simple discrimination tasks suggesting that errors result from impulsive responding. We investigated the relationship between error negativity (Ne/ERN), an event-related potential associated with error detection, and two behavioral indices of response control: response time (RT) differences between incorrect and correct trials (an index of impulsivity) and percentage of errors. Response-locked ERPs were collected from 17 young adults during a visual flanker task. Consistent with previous findings, participants were significantly faster on error trials. However, participants who exhibited larger Ne/ERN peak amplitudes had significantly smaller RT differences, suggesting a more controlled response strategy. Furthermore, Ne/ERN latencies were positively associated with percentage of errors. These findings are consistent with the view that the Ne/ERN reflects the activity of a monitoring system that is closely linked to remedial systems responsible for individual differences in response control or impulsive behavior.     

The brain regulation mechanism of error monitoring in impulsive children with ADHD—An analysis of error related potentials

The objective of this study was to investigate the brain mechanism involved in the regulation of impulsivity in children with Attention Deficit and Hyperactivity Disorder (ADHD) through error detection as well as error monitoring. The subjects in this study included 7–11-year-old impulsive ADHD children as well as normal children and adult controls. Error related negativity (ERN) and error positivity (Pe) were measured. ERN peak latency from the children groups was delayed significantly when compared with the adult group; however, no significant difference in ERN amplitude was found among the three groups. Impulsive ADHD children had the earliest peak latency of Pe. In addition, the average Pe amplitude in impulsive children was significantly smaller than in adults (Cz and Pz), and smaller than in normal children (Pz). Late conscious cognitive processing of error is significantly weaker in impulsive ADHD children, suggesting a serious deficit of late error monitoring, rather than error detection.     

Memory-guided saccade abnormalities in schizophrenic patients and their healthy, full biological siblings

BACKGROUND: Ocular-motor inhibition errors and saccadic hypometria occur at elevated rates in biological relatives of schizophrenic patients. The memory-guided saccade (MS) paradigm requires a subject to inhibit reflexive saccades (RSs) and to programme a delayed saccade towards a remembered target. METHOD: MS, RS, and central fixation (CF) tasks were administered to 16 patients who met the criteria for DSM-IV schizophrenia, 19 of their psychiatrically healthy siblings, and 18 controls. RESULTS: Patients and siblings showed elevated MS error rates reflecting a failure to inhibit RSs to a visible target, as required by the task. In contrast to controls, prior errors did not improve MS accuracy in patients and siblings. CONCLUSIONS: The specific characteristics of the elevated MS error rate help to clarify the nature of the disinhibition impairment found in schizophrenics and their healthy siblings. Failure to inhibit premature saccades and to improve the accuracy of subsequent volitional saccades implicates a deficit in spatial working-memory integration, mental representation and/or motor learning processes in schizophrenia.     

Adaptation of catch-up saccades during the initiation of smooth pursuit eye movements

Reduction of retinal speed and alignment of the line of sight are believed to be the respective primary functions of smooth pursuit and saccadic eye movements. As the eye muscles strength can change in the short-term, continuous adjustments of motor signals are required to achieve constant accuracy. While adaptation of saccade amplitude to systematic position errors has been extensively studied, we know less about the adaptive response to position errors during smooth pursuit initiation, when target motion has to be taken into account to program saccades, and when position errors at the saccade endpoint could also be corrected by increasing pursuit velocity. To study short-term adaptation (250 adaptation trials) of tracking eye movements, we introduced a position error during the first catch-up saccade made during the initiation of smooth pursuit—in a ramp-step-ramp paradigm. The target position was either shifted in the direction of the horizontally moving target (forward step), against it (backward step) or orthogonally to it (vertical step). Results indicate adaptation of catch-up saccade amplitude to back and forward steps. With vertical steps, saccades became oblique, by an inflexion of the early or late saccade trajectory. With a similar time course, post-saccadic pursuit velocity was increased in the step direction, adding further evidence that under some conditions pursuit and saccades can act synergistically to reduce position errors.     

Adaptive modification of saccade size produces correlated changes in the discharges of fastigial nucleus neurons

Saccade accuracy is known to be maintained by adaptive mechanisms that progressively reduce any visual error that consistently exists when the saccade ends. We used an experimental paradigm known to induce adaptation of saccade size while monitoring the neural correlates of this adaptation. In rhesus monkeys where the medial and lateral recti of one eye were surgically weakened, patching the unoperated eye and forcing the monkey to use the weakened eye induced a gradual increase in saccade size in both eyes until the viewing, weak eye almost acquired the target in one step. Subsequent patching of the weakened eye gradually reversed the situation, so that the saccades in the viewing, normal eye decreased from an initial overshooting to normal. In the caudal fastigial nuclei of unadapted monkeys, neurons typically exhibit an early burst of spikes that is correlated with the onset of contraversive saccades and a later burst of spikes that is correlated with the termination of ipsiversive saccades. Comparing the discharges of the same fastigial neurons recorded before and during adaptation, this basic pattern did not change, but some parameters of the discharges did. The most consistent changes were in the latency of the burst for ipsiversive saccades, which was positively correlated with saccade size (1.28 ms/deg), and in the number of spikes associated with contraversive saccades, which was also positively correlated (0.55 spikes/deg). The former was more important when saccade size was decreasing, and the latter was more important when saccade size was increasing. Based on current knowledge of the anatomical connections of fastigial neurons, as well as on the effects of cerebellar lesions and on recordings in other structures, we argue that these changes are appropriate for causing the associated changes in saccade size.     

Age effects on response monitoring in a mental-rotation task

A mental-rotation task was presented to young (18-28 years) and old (60-76 years) adults to simultaneously assess age-related changes in performance, response monitoring and adaptive behavior. Relative to young participants, older adults were less inclined to adjust their speed at the expense of accuracy. They displayed a larger number of slow errors, smaller error potentials (Ne and Pe), more immediate corrections of errors when detected, and a larger speed reduction on trials following an error. The data suggest that for older adults an increase of task complexity sometimes caused a radical failure in determining the correct response, rather than a gradual reduction of efficiency.     

Visual search of heading direction

When we move along we frequently look around. How quickly and accurately can we gaze in the direction of heading? We studied the temporal aspects of heading perception in expanding and contracting patterns simulating self-motion. Center of flow (CF) eccentricity was 15°. Subjects had to indicate the CF by making a saccade to it. A temporal constraint on the response time was introduced, because stimuli were presented briefly (1 s). On average, subjects needed two saccades to find the CF. Initial saccades covered about 50–60% of the distance between the fixation point and the CF. Subjects underestimated the eccentricity of the CF. The systematic radial error ranged from –2.4° to –4.9°. The systematic tangential error was small (about 0.5°). The variable radial error ranged from 2.7° to 4.6°. We found a relation between saccade onset time and saccade endpoint error. Saccade endpoint error decreased with increasing saccade onset time, suggesting that saccades were often fired before the heading processing had been completed. From the saccade onset times, saccade endpoint errors and an estimate for the saccadic dead time (interval prior to the saccade during which modification is impossible 70 ms), we estimated the heading processing time (HPT 0.43 s). In three out of four subjects, HPT was longer for trials simulating backward movement than for trials simulating forward movement. For each saccade we determined whether it reduced the distance error. The second saccade reduced the error more effectively per time unit than the initial saccade. On the basis of this finding, we suggest that visual processing that occurs during the saccadic dead time of the first saccade is used in the preparation of the second saccade.