Changes of error-related ERPs with age

Errors in reaction tasks are followed by a negative component of the event-related brain potential (ERP), the error negativity (Ne), which is thought to be a correlate of error detection. In the present study we show that, in tasks that induce different types of errors, the amplitude of the Ne was reduced in elderly (54-65 years old) compared with young subjects (19-25 years old). This reduction was also seen in single trials, as were computed for one of the visual tasks. Moreover, in this data set, the single-trial Ne was also delayed for the elderly compared with the young. These data suggest an alteration of error detection in the elderly, which is only marginally reflected in performance.     

Grapheme monitoring in picture naming: an electrophysiological study of language production

Electrocortical correlates of language production were examined in two picture naming tasks that involved grapheme monitoring. In both tasks subjects (N=12) had to detect target letters in picture names, the target letter being positioned either at the beginning or at the end of the picture name. Between tasks, the target letter was shown either before (target-picture, TP) or after (picture-target, PT) the presentation of the object pictures. In both tasks, subjects responded faster, whenever the target letter appeared at the beginning of the picture name than at its end. The EEG, recorded from 64 electrodes, was analyzed in the signal and in the source space (using the Minimum Norm estimate). Differences in the event-related potential (ERP) following the second stimulus became evident earlier in the PT (at 320 ms) than the TP (456 ms) task. This onset of diverging ERPs was called the "point of divergence" (POD). The ERP following the POD was characterized by a positive deflection in the "begin" condition in both tasks. In the "end" condition, the sources of brain activity were focused over the left hemisphere in the TP, while a bilateral distribution characterized the PT task. Performance and electrocortical indices support the hypothesis of serial "left-to-right" processing of a representation of the picture name. The left-hemispheric activity focus in the TP task is assumed to indicate the encoding of the picture name, while frontal symmetrical activity in the PT task might indicate the involvement of working memory processes.     

Action monitoring in motor control: ERPs following selection and execution errors in a force production task

Action monitoring has been studied in many tasks by means of measuring the error-related negativity (Ne/ERN), but never in a motor control task requiring precise force production. Errors in discrete choice reaction tasks are the result of incorrect selections, but errors in force production can also arise from incorrect executions. ERPs were obtained while participants produced low or high isometric forces with their left or right hand. As expected, incorrect choices of hand elicited an Ne/ERN. Interestingly, Ne/ERNs were also present in the less discrete selection error of an incorrect choice of force, but only when erroneously a low instead of a high force was chosen. In both force ranges, no Ne/ERNs were found after errors in execution. These errors showed a large positivity in feedback ERPs and, similar to correct responses, a prolonged negativity in response ERPs. We propose that, compared to selection errors, the time uncertainty aspects of execution errors and the resulting changing response representations prohibit error detection by the internal monitoring system responsible for generating the Ne/ERN.     

Error-related processing during a period of extended wakefulness

The nature of error detection as manifested by the error-related negativity was examined in both a Sternberg memory search task and a visual search task. Both tasks were performed in conditions with consistent or varied stimulus-response mapping and loads of three or six letters. After subjects were trained extensively in all conditions, they performed the tasks throughout the night without sleeping. The data suggest that the effectiveness of error detection decreases over time because of a decrease in the quality of perceptual processing. Error detection also suffers when performance requires more search-related resources. In both cases, the representation of the correct response is compromised. These results indicate that error detection depends on the same perceptual and cognitive processes that are required for correct performance.     

Retest reliability of medial frontal negativities during performance monitoring

The error‐related negativity (ERN) and feedback‐related negativity (FRN) have been used as electrophysiological indices of performance monitoring produced in response to internally generated (errors) and externally generated (feedback) activations of the anterior cingulate cortex (ACC). No studies to date have systematically examined the measurement reliability of these components. In this article, we present the retest reliability of the ERN and FRN during response tasks designed to elicit errors or feedback responses on two occasions. Data from four experiments are presented in which participants performed tasks over various periods of time. Results indicate good retest reliability of the ERN and FRN amplitudes and source generation of these components. The present article provides important validation of the ERN and FRN as stable and trait‐like electrophysiological reflections of performance monitoring and ACC functional integrity.     

Error-related negativity in individuals with obsessive-compulsive symptoms: toward an understanding of hoarding behaviors

The error-related negativity (ERN), an event-related potential component elicited by error responses in cognitive tasks, has been shown to be abnormal in most, but not all, studies of obsessive-compulsive disorder or obsessive-compulsive symptoms (OCD/S); these inconsistencies may be due to task selection, symptom subtype, or both. We used meta-analysis to further characterize the ERN in OCD/S, and pooled data across studies to examine the ERN in OCD/S with hoarding. We found an enhanced ERN in OCD/S relative to controls, as well as heterogeneity across tasks. When stratified, OCD/S showed a significantly enhanced ERN only in response conflict tasks. However, OCD/S + hoarding showed a marginally larger ERN than OCD/S-hoarding, but only for probabilistic learning tasks. These results suggest that abnormal ERN in OCD/S is task-dependent, and that OCD/S + hoarding show different ERN activity from OCD/S − hoarding perhaps suggesting different pathophysiological mechanisms of error monitoring.     

Real time monitoring and analysis via the medical information bus, Part II

The complexity of the monitored data available in modern intensive care units suggests that they may be best processed, for presentation to medical staff, by expert system techniques. However, standard expert system shells are ill-fitted to either the basic sequential monitoring tasks of data acquisition and storage, or to handling the temporal considerations inherent in monitoring and in the recognition and processing of sporadic alarm signals. A solution to this dilemma is described: an expert system that has an appropriately designed inference engine and manages data acquisition via a medical information bus (MIB). Use of this MIB standard allows great flexibility as regards the monitoring apparatuses employed; in particular, the connection or disconnection of any apparatus is recognised and triggers the automatic reconfiguration of the network.     

Electrocortical measures of performance monitoring from go/no-go and flanker tasks: Differential relations with trait dimensions of the triarchic model of psychopathy

This study examined associations of performance-monitoring event-related potentials (ERPs) from go/no-go and flanker tasks with one another, and with psychopathy-related traits of disinhibition, meanness, and boldness. A task-dependent relationship was evident between the error-related negativity (ERN) and trait disinhibition, with high-disinhibited participants showing reduced no-go ERN but not flanker ERN. Disinhibition was also inversely related to variants of the P3 and the error positivity (Pe) from these two tasks. A factor analysis of the ERPs revealed two distinct factors, one reflecting shared variance among the P3 and Pe measures from the two tasks, and the other covariance among the N2 and ERN measures. Scores on the P3/Pe factor, but not the N2/ERN factor, were inversely related to disinhibition, and accounted for associations of this trait with variants of the P3 and Pe across tasks. The implication is that high trait disinhibition relates mainly to reductions in brain responses associated with later elaborative stages in the processing of motivationally significant events across different tasks. Importantly, no-go ERN predicted disinhibition scores beyond N2/ERN factor scores, indicating that high disinhibition is not generally related to diminished early preresponse conflict and error processing, but rather to processing impairments in conditions calling for inhibition of prepotent response tendencies.     

Multimicroprocessor system for online monitoring in a CCU

A real-time monitoring system for physiological signals, developed for patients in coronary care units (CCUs), is described. This system monitors the signals that have the greatest clinical value in a CCU environment (ECG and cardiovascular pressures), taking charge of detecting dangerous situations and of extracting information significant to the correct monitoring of the patient. The information it extracts, mainly from the ECG, is presented to the user in an ergonomic way using written reports and graphs which collect and compile the information, facilitating its interpretation. Some utilities have been developed to allow the user to modify certain monitoring conditions as well as to correct results derived from them, thereby improving the reliability of the monitoring process. The system uses a multimicroprocessor architecture (imposed by the need to perform a large number of tasks in real time) with a block based on the VME bus, charged with acquiring and processing the monitored signals, and an IBM-compatible PC/XT which is used as a system user interface and a massive storage device in which the information resulting from the monitoring of signals is stored.     

A functional classification of medial frontal negativity ERPs: Theta oscillations and single subject effects

Theta oscillations in the EEG have been linked to several ERPs that are elicited during performance‐monitoring tasks, including the error‐related negativity (ERN), no‐go N2, and the feedback‐related negativity (FRN). We used a novel paradigm to isolate independent components (ICs) in single subjects' (n = 27) EEG accounting for a medial frontal negativity (MFN) to response cue stimuli that signal a potential change in future response demands. Medial frontal projecting ICs that were sensitive to these response cues also described the ERNs, no‐go N2s, and, to a lesser extent, the FRNs, that were elicited in letter flanker, go/no‐go, and time‐estimation tasks, respectively. In addition, percentile bootstrap tests using trimmed means indicated that the medial frontal ICs show an increase in theta activity during the ERN, no‐go N2, and FRN across tasks and within individuals. Our results provide an important validation of previous studies by showing that increases in medial frontal theta to cognitively challenging events in multiple paradigms is a reliable effect within individuals and can be elicited by basic stimulus cues that signal the potential need to adjust response control. Thus, medial frontal theta reflects a neural response common to all MFN paradigms and characterizes the general process of controlling attention without the need to induce error commission, inhibited responses, or to present negative feedback.     

The Standardized Mental Stress Test Protocol: Test-Retest Reliability and Comparison with Ambulatory Blood Pressure Monitoring

The mental stress test protocol is used extensively in research, but different laboratories often employ different stress tasks, utilize different dependent variables to index the stress response, and perform different transformations on the gathered data. The present study determined the test-retest reliability of 11 cardiovascular dependent variables during a resting baseline and three common stress tasks: playing a video game, performing a choice reaction-time test, and performing a cold-pressor test. Sixty healthy, middle-aged males underwent testing twice, approximately three months apart. Instructions were delivered via videotape and data were gathered on-line by computer to ensure a standard laboratory environment. Each task elicited significant increases in blood pressure, vascular rigidity, LVET, heart rate, and stroke volume. In addition, the cold-pressor test led to increases in total systemic resistance and mean systolic ejection rate. The absolute levels of the 11 dependent variables were correlated across tasks (partial r, baseline removed, = .06 to .69, 32 of 33 comparisons significant at p<.05), indicating that reactivity to stress generalizes across alternate test forms. The absolute levels also showed significant test-retest reliability (r= .32 to .82; 40 of 44 comparisons significant at p<.05). In addition, for 19 of 33 comparisons, absolute levels showed greater test-retest reliability than change scores derived by subtracting the initial resting baseline value from the stress-task value. Finally, blood pressures taken during the stress tests were more highly correlated with the average blood pressures measured via ambulatory monitoring than casual office pressures, suggesting that such stress values may more accurately reflect average blood pressure.     

Age effects in dynamic vision based on orientation identification

Dynamic vision considers the time domain of visual processing, presumably a function of the magnocellular system. The temporal visual component is not completely developed at the beginning of school age. The effects of age on a certain aspect of dynamic visual perception are reported in this study of 286 subjects in the age range of 7-68 years. Three simple orientation identification tasks were used: a fixation, a saccade, and an anti task. In each case the subjects had to identify the last of a series of fast changing orientations of a T-symbol before it disappeared after a random time period. The percentage of correct identifications in 50-100 trials was measured for each of the three tasks. In the age range of about 14 to about 28 years the subjects could perform the tasks at 90% correct or better. At younger and at older ages the mean values of the scores are considerably lower due to a higher percentage of subjects with difficulties in the performance of the tasks. It is discussed whether it is the magnocellular system which mediates the dynamic orientation identification in these tasks and which begins to decline relatively early in life in parallel with a relative loss of saccade control.     

Selection and preparation of hand and foot movements: Cz activity as a marker of limb system preparation

Event-related potentials were used to examine the preparation of hand and foot responses in tasks using both limb systems. As in tasks using only one system, opposite lateralized readiness potentials were observed for hand and foot responses (Experiment 1). Furthermore, movement-related activity at Cz was more positive prior to hand than foot responses, revealing that Cz activity can be used to index selective movement preparation by one limb system. In Experiment 2, two responses were cued prior to stimulus onset. Cue-related activity at Cz was more positive with hand than foot cuing, reinforcing the conclusion that Cz activity is sensitive to selective preparation for one of these limb systems. Overall, the results show that it is possible to carry out motor preparation of two responses within the same limb system and that differential Cz activity is a useful index of this preparation in tasks with hand versus foot movements.     

Medial prefrontal cortex and precision of temporal discrimination: a lesion, microinjection, and microdialysis study

In this paper, we examined the role of the medial prefrontal cortex in temporal discrimination in three experiments using rats. Experiment 1 attempted to dissociate the roles of the medial precentral (PrCm) area from the prelimbic and infralimbic (PL-IL) area in temporal discrimination using fixed-interval (FI) schedule. The gradient of response rate distribution became more moderate by a lesion of the PrCm, but not by a lesion of the PL-IL. In experiment 2, the efflux of acetylcholine (ACh) in the PrCm area during temporal discrimination tasks was compared to that during non-temporal discrimination tasks. ACh efflux was not different between these two tasks. In experiment 3, microinjection of the anticholinergic drug scopolamine (10 microg) into the PrCm area made the gradient of response rate distribution moderate. These findings suggest that reduced activity of the ACh system within the PrCm area impairs the precision of temporal discrimination, even though enhancement of this system is not indispensable for performing temporal discrimination.     

Cognitive task fulfilment may decrease gaze control performances

Human cognitive processing limits can lead to difficulties in performing two tasks simultaneously. In this respect, the mobilization of attentional resources seems to be more important in voluntary than in reflexive visuo-oculomotor movements. With this in mind, this study aimed to determine the differentiated effects of carrying out cognitive tasks on reflexive and voluntary movements generated by the visuo-oculomotor system. Eye movements were recorded with a videonystagmography system in 20 healthy adults. Prosaccade and antisaccade latency and accuracy were determined, as was the gain of regular smooth pursuit. The cognitive tasks comprised a backward counting task in steps of seven or thirteen and were carried out during the three oculomotor tasks. Whatever the backward counting, the cognitive tasks caused an increase in latency and a decrease in accuracy in the prosaccades and antisaccades as well as a drop in smooth pursuit gain. Despite a high degree of prosaccade, antisaccade and pursuit predictability, the oculomotor parameters were altered during dual-task fulfilment, and voluntary movements were more vulnerable than reflexive movements. Cognitive task achievement during oculomotor tasks requires greater attentional resource mobilization, and the reduction in visuo-oculomotor performance is even greater since the oculomotor task places more demand on the cognitive resources. Attention is thus a crucial cognitive process for the maintenance of adequate reflexive and voluntary oculomotor performance. Concurrently performing tasks have broader implications in motor coordination degradation understanding in situations like handheld phone when driving or in management of organisational and environmental constraints in occupational activities.     

The ambulatory measurement of posture, thigh acceleration, and muscle tension and their relationship to heart rate

We compared the relative ability of continuous accelerometric, electromyographic (EMG), and hydrostatic posture measurements to diseriminate tasks involving variations in motor activity and posture and to predict heart rate (HR) variability. EMG was a more sensitive measure than accelerometry in differentiating the tasks. How-ever, accelerometry and EMG explained comparable amounts of HR variance. The hydrostatic posture was a stable measure that elearly differentiated postures and explained a significant amount of HR variance but less than accelerometry or EMG. Accelerometric and EMG measures of motor activity used either alone or in combination with the hydrostatic posture are valuable in discriminating activities and in controlling for the effects of motor activity and posture on HR during ambulatory measurement.     

Spectral EEG characteristics during increases in the complexity of the context of cognitive activity

The spatial and frequency characteristics of cortical electrical activity were studied in healthy human subjects in two series of experiments involving solution of sequentially presented visual tasks. The first task was to assess the relative sizes of two circles and was identical in both series. In the first series, this was supplemented by a task consisting of recognition of pseudowords/words, presumptively also requiring predominant involvement of the ventral “what?” visual system. In the second series, the additional task (spatial localization of a target stimulus in a matrix of letters) was associated with the predominant involvement of the dorsal “where?” visual system. Cortical electrical activity immediately before presentation of pairs of tasks was analyzed. Measures of EEG spectral power in the frontal, central, occipital, and temporal areas of the cortex was subjected to dispersion analysis. The power of electrical potentials in the delta and beta1 frequency ranges was greater when both tasks were associated predominantly with activation of the ventral visual system (first series of experiments). Power in the occipital alpha rhythm was lesser in the left hemisphere in both series of experiments. The interaction of the “experimental series” and “hemisphere” factors was significant in the temporal areas for EEG activity in the alpha2 range, where the predominant involvement of the ventral visual system on solution of both tasks corresponded to greater asymmetry in the electrical oscillations in the rapid alpha2 rhythm and its neighboring beta1 range with greater desynchronization (lesser power) on the left side. Thus, the nature of the ongoing activity is reflected in the spatial-frequency characteristics of the “background” electrical activity of the cortex.     

Incomplete inactivation and rapid recovery of voltage-dependent sodium channels during high-frequency firing in cerebellar Purkinje neurons

The ability of individuals to adapt locomotion to constraints associated with the complex environments normally encountered in everyday life is paramount for survival. Here, we tested the ability of 24 healthy young adults to adapt to a rightward prism shift (～11.3°) while either walking and stepping to targets (i.e., precision stepping task) or stepping over an obstacle (i.e., obstacle avoidance task). We subsequently tested for generalization to the other locomotor task. In the precision stepping task, we determined the lateral end-point error of foot placement from the targets. In the obstacle avoidance task, we determined toe clearance and lateral foot placement distance from the obstacle before and after stepping over the obstacle. We found large, rightward deviations in foot placement on initial exposure to prisms in both tasks. The majority of measures demonstrated adaptation over repeated trials, and adaptation rates were dependent mainly on the task. On removal of the prisms, we observed negative aftereffects for measures of both tasks. Additionally, we found a unilateral symmetric generalization pattern in that the left, but not the right, lower limb indicated generalization across the 2 locomotor tasks. These results indicate that the nervous system is capable of rapidly adapting to a visuomotor mismatch during visually demanding locomotor tasks and that the prism-induced adaptation can, at least partially, generalize across these tasks. The results also support the notion that the nervous system utilizes an internal model for the control of visually guided locomotion.     

A generalized physiological hyperreactivity to acute stressors in hypertensives

Hypertensives have consistently been found to have a more reactive cardiovascular system than normotensives. In the present study, it was examined whether this enhanced cardiovascular stress reactivity generalizes to the hypothalamus-pituitary-adrenal (HPA) axis and the immune system. Forty-two unmedicated hypertensives and 21 normotensive controls performed five passive coping and active coping stressful tasks in the laboratory. In addition to the expected greater mean diastolic blood pressure reactivity to the tasks, hypertensives exhibited enhanced (baseline corrected) task salivary cortisol and secretory immunoglobulin A (S-IgA) levels. Moreover, correlations were found between blood pressure responses and task related cortisol activity and between baseline blood pressure levels and task-induced S-IgA levels. These results indicate that hypertensives not only have a hyperreactive cardiovascular system, but also an enhanced HPA axis and immune system reactivity to stress. A central stress mechanism may be responsible for the heightened generalized stress response in hypertensives.     

Stability and reliability of error‐related electromyography over the corrugator supercilii with increasing trials

Electromyographic activity over the corrugator supercilii (cEMG), the primary facial muscle involved in negative emotions, is increased during the commission of errors on speeded reaction‐time tasks. In the present paper, data from two previously published studies were reanalyzed to investigate the reliability and stability of error‐related, correct‐related, and difference cEMG across increasing numbers of trials. For a modified go/no‐go and a flanker task, we found that error‐related cEMG was highly stable and reliable in 14 trials, and correct‐related cEMG between 56 and 82 trials, respectively. Given the typical number of trials used in studies of cognitive control, these findings suggest that many investigations of error monitoring are already sufficient to obtain acceptable error‐ and correct‐related cEMG signals. Error‐related cEMG activity is relatively easy to measure and, as such, it shows great promise for future research investigating the cognitive and affective mechanisms of error monitoring.