What's an internal clock for? From temporal information processing to temporal processing of information

International audienceThe existence of an internal clock and its involvement in information processing has been investigated in humans using the experimental protocol of Treisman et al. (1990) [Treisman et al., 1990. Perception, 19, 705 – 743]. In this protocol, a periodical stimulation, which is assumed to drive an internal clock, is delivered during a reaction time (RT) task. The accelerating or slowing down effects of the periodical stimulation, according to its frequency, allowed an estimate to be made of a simple harmonic of the frequency of the internal clock. The estimate was close to 21 Hz. In the framework of the serial model of information processing, the present work investigates the involvement of the internal clock in the transmission of information between processing stages during RT. The data tend to support the idea that the internal clock allows the transfer of information from one stage to the next one at definite moments only, periodically distributed in time. According to our results, and recent data from the literature on electric cortical oscillations, we propose a model of an internal clock sending periodic inhibition, which would permit an increased signal/noise ratio in the processing and the transmission of information in the central nervous system

The costs and benefits of temporal predictability: impaired inhibition of prepotent responses accompanies increased activation of task-relevant responses

International audienceWhile the benefit of temporal predictability on sensorimotor processing is well established, it is still unknown whether this is due to efficient execution of an appropriate response and/or inhibition of an inappropriate one. To answer this question, we examined the effects of temporal predictability in tasks that required selective (Simon task) or global (Stop-signal task) inhibitory control of prepotent responses. We manipulated temporal expectation by presenting cues that either predicted (temporal cues) or not (neutral cues) when the target would appear. In the Simon task, performance was better when target location (left/right) was compatible with the hand of response and performance was improved further still if targets were temporally cued. However, Conditional Accuracy Functions revealed that temporal predictability selectively increased the number of fast, impulsive errors. Temporal cueing had no effect on selective response inhibition, as measured by the dynamics of the interference effect (delta plots) in the Simon task. By contrast, in the Stop-signal task, Stop-signal reaction time, a covert measure of a more global form of response inhibition, was significantly longer in temporally predictive trials. Therefore, when the time of target onset could be predicted in advance, it was harder to stop the impulse to respond to the target. Collectively, our results indicate that temporal cueing compounded the interfering effects of a prepotent response on task performance. We suggest that although temporal predictability enhances activation of task-relevant responses, it impairs inhibition of prepotent responses

Estimation of individual evoked potential by wavelet transform

ISBN : 978-2-9532965-0-1A new method to improve the signal-to-noise ratio of single evoked potentials (EP) measurements is presented, in which, contrary to previous methods, no a priori assumptions on the signal are necessary. This method is based on the wavelets decomposition of the individual signals. A statistical thresholding is applied on the coefficients of the decomposition: we estimate whether the mean value of the coefficients across trials and for each time point is significantly different from a random estimate. The performance of the method is evaluated with simulation and the method is applied to real dat

Sequential Compatibility Effects and Cognitive Control: Does Conflict Really Matter?

International audienceAlthough it is widely accepted that control mechanisms are necessary for human behavior tobe adapted, very little is known about how such mechanisms are recruited. A suggestion tofill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, andJ. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successfulin accounting for the reduction of compatibility effects after an incompatible trial: The levelof conflict being, on average, higher during an incompatible trial, more control occurs aftersuch a trial. The authors have tested this prediction by sorting the trials on the basis of amountof conflict (quantified by the electromyographic activity) they presented. A reduction of thecompatibility effect was observed after incompatible trials, but it was independent of the levelof conflict on previous trials, suggesting that the conflict does not trigger changes in executivecontrol. Consequences for the conflict monitoring model are discussed

Inhibiting errors while they are produced: direct evidence for error monitoring and inhibitory control in children

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Online Extraction and Single Trial Analysis of Regions Contributing to Erroneous Feedback Detection

International audienceUnderstanding how the brain processes errors is an essential and active field of neuroscience. Real time extraction and analysis of error signals provide an innovative method of assessing how individuals perceive ongoing interactions without recourse to overt behaviour. This area of research is critical in modern Brain–Computer Interface (BCI) design, but may also open fruitful perspectives in cognitive neuroscience research. In this context, we sought to determine whether we can extract discriminatory error-related activity in the source space, online, and on a trial by trial basis from electroencephalography data recorded during motor imagery. Using a data driven approach, based on interpretable inverse solution algorithms, we assessed the extent to which automatically extracted error-related activity was physiologically and functionally interpretable according to performance monitoring literature. The applicability of inverse solution based methods for automatically extracting error signals, in the presence of noise generated by motor imagery, was validated by simulation. Representative regions of interest, outlining the primary generators contributing to classification, were found to correspond closely to networks involved in error detection and performance monitoring. We observed discriminative activity in non-frontal areas, demonstrating that areas outside of the medial frontal cortex can contribute to the classification of error feedback activity

FINDING EEG SPACE-TIME-SCALE LOCALIZED FEATURES USING MATRIX-BASED PENALIZED DISCRIMINANT ANALYSIS

International audienceThis paper proposes a new method for constructing and selecting of discriminant space-time-scale features for electroencephalogram (EEG) signal classification, suitable for Error Related Potentials (ErrP)detection in brain-computer interface (BCI). The method rests on a new variant of matrix-variate Linear Discriminant Analysis (LDA), and differs from previously proposed approaches in mainly three ways. First, a discrete wavelet expansion is introduced for mapping time-courses to time-scale coefficients, yielding time-scale localized features. Second, the matrix-variate LDA is modified in such a way that it yields an interesting duality property, that makes interpretation easier. Third, a space penalization is introduced using a surface Laplacian, so as to enforce spatial smoothness. The proposed approaches, termed D-MLDA and D-MPDA are tested on EEG signals, with the goal of detecting ErrP. Numerical results show that D-MPDA outperforms D-MLDA and other matrix-variate LDA techniques. In addition this method produces relevant features for interpretation in ErrP signals

Response-Locked Brain Dynamics of Word Production

International audienceThe cortical regions involved in the different stages of speech production are relatively well-established, but their spatio-temporal dynamics remain poorly understood. In particular, the available studies have characterized neural events with respect to the onset of the stimulus triggering a verbal response. The core aspect of language production, however, is not perception but action. In this context, the most relevant question may not be how long after a stimulus brain events happen, but rather how long before the production act do they occur. We investigated speech production-related brain activity time-locked to vocal onset, in addition to the common stimulus-locked approach. We report the detailed temporal interplay between medial and left frontal activities occurring shortly before vocal onset. We interpret those as reflections of, respectively, word selection and word production processes. This medial-lateral organization is in line with that described in non-linguistic action control, suggesting that similar processes are at play in word production and non-linguistic action production. This novel view of the brain dynamics underlying word production provides a useful background for future investigations of the spatio-temporal brain dynamics that lead to the production of verbal responses. Citation: Riès S, Janssen N, Burle B, Alario F-X (2013) Response-Locked Brain Dynamics of Word Production. PLoS ONE 8(3): e58197

Errors Disrupt Subsequent Early Attentional Processes

International audienceIt has been demonstrated that target detection is impaired following an error in an unrelatedflanker task. These findings support the idea that the occurrence or processing of unex-pected error-like events interfere with subsequent information processing. In the presentstudy, we investigated the effect of errors on early visual ERP components. We thereforecombined a flanker task and a visual discrimination task. Additionally, the intertrial intervalbetween both tasks was manipulated in order to investigate the duration of these negativeafter-effects. The results of the visual discrimination task indicated that the amplitude of theN1 component, which is related to endogenous attention, was significantly decreased fol-lowing an error, irrespective of the intertrial interval. Additionally, P3 amplitude was attenu-ated after an erroneous trial, but only in the long-interval condition. These results indicatethat low-level attentional processes are impaired after errors

Error Negativity Does Not Reflect Conflict: A Reappraisal of Conflict Monitoring and Anterior Cingulate Cortex Activity

Our ability to detect and correct errors is essential for our adaptive behavior. The conflict-loop theory states that the anterior cingulate cortex (ACC) plays a key role in detecting the need to increase control through conflict monitoring. Such monitoring is assumed to manifest itself in an electroencephalographic (EEG) component, the "error negativity" (Ne or "error-related negativity" [ERN]). We have directly tested the hypothesis that the ACC monitors conflict through simulation and experimental studies. Both the simulated and EEG traces were sorted, on a trial-by-trial basis, as a function of the degree of conflict, measured as the temporal overlap between incorrect and correct response activations. The simulations clearly show that conflict increases as temporal overlap between response activation increases, whereas the experimental results demonstrate that the amplitude of the Ne decreases as temporal overlap increases, suggesting that the ACC does not monitor conflict. At a functional level, the results show that the duration of the Ne depends on the time needed to correct (partial) errors, revealing an "on-line" modulation of control on a very short time scale