- [Show abstract] [Hide abstract] ABSTRACT: The event-related potential called "Error Negativity" (Ne, ERN), which appears when subjects commit errors in choice reaction time tasks, is a marker of response monitoring. By introducing a response probability bias, we show that the Ne is sensitive to response expectancy. We further show that the small negativity evoked by correct responses (Ne-like, CRN) is also sensitive to response expectancy: On unexpected responses, the former decreases while the latter increases to such an extent that the amplitudes of the two components are in the same range of magnitude. Although the sensitivity of the Ne to response expectancy is compatible with the current models accounting for the Ne, the common sensitivity of the Ne and the Ne-like supports the idea that they reflect functionally similar monitoring processes.
- [Show abstract] [Hide abstract] ABSTRACT: In between-hand choice reaction time tasks, the motor cortex involved in the required response (contralateral) has been shown to be activated while the motor cortex involved in the non-required response (ipsilateral) has been shown to be inhibited. The aim of the present study was to test the hypothesis that ipsilateral inhibition reflects an active mechanism aimed at preventing errors. To this end, the risk of committing errors in between-hand choice reaction time tasks was manipulated by introducing a response probability bias. The surface Laplacian transforms of electroencephalographic waves recorded over the motor cortices, contralateral and ipsilateral to the responding hand were compared. Results showed that contralateral activation was not modulated by the risk of committing errors while ipsilateral inhibition was sensitive to this risk in a gradual manner: the higher the risk, the stronger the inhibition.
- [Show abstract] [Hide abstract] ABSTRACT: In choice reaction time tasks, subjects speed up before making an error, but slow down afterward to prevent the occurrence of a new error. In some trials, the correct response is preceded by an incorrect electromyographic (EMG) activation too small to reach the response threshold. In this article, we show that these incorrect EMG activations give rise to the same sequential effects as overt errors: Before a trial containing an incorrect EMG activation, subjects speed up, whereas after that trial, they slow down. These activations reflect errors that have been detected, inhibited, and corrected in time. As such, they index the involvement of online executive control.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: Although it is widely accepted that control mechanisms are necessary for human behavior to be adapted, very little is known about how such mechanisms are recruited. A suggestion to fill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, and J. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successful in accounting for the reduction of compatibility effects after an incompatible trial: The level of conflict being, on average, higher during an incompatible trial, more control occurs after such a trial. The authors have tested this prediction by sorting the trials on the basis of amount of conflict (quantified by the electromyographic activity) they presented. A reduction of the compatibility effect was observed after incompatible trials, but it was independent of the level of conflict on previous trials, suggesting that the conflict does not trigger changes in executive control. Consequences for the conflict monitoring model are discussed.
- [Show abstract] [Hide abstract] ABSTRACT: The present study aims at developing a method to extract single sweep evoked potentials. It is based on the wavelets decomposition of the individual signals. Contrary to previous methods, no a priori assumptions on the signal are necessary. A thresholding based on the coefficient of variation is applied to the wavelets coefficients in order to extract the evoked potential from the background noise. This method is compared to the classical method of low-pass filtering
- [Show abstract] [Hide abstract] ABSTRACT: In reaction time (RT) tasks, event-related potentials (ERPs) reveal a response-locked negative wave when subjects commit errors. This wave, termed "error negativity" (Ne) or "error-related negativity" (ERN), is thought to index response-monitoring processes. With conventional monopolar recordings, this negativity is hardly seen on correct responses, likely overlapped by a large positive wave. Indeed, after Laplacian transformation (a spatial high-pass filter), a small Ne-like wave is unmasked. Recently, it has been shown that the positivity on monopolar recordings was larger for correct responses preceding an error than for correct responses preceding a correct trial. After Laplacian transformation, it appears that this effect is due, at least in part, to a decrease of the Ne-like wave on correct responses preceding an error. This result indicates that, as the Ne on errors, the Ne-like wave on correct responses is sensitive to performance and hence is likely related to response-monitoring processes.
- [Show abstract] [Hide abstract] ABSTRACT: The elicitation of an evoked potential, the 'error negativity' (Ne) when subjects commit errors in speeded tasks, is often taken as an index of response monitoring processes. The presence of a Ne-like wave on purely correct trials challenges the current conceptions about the nature of such a monitoring system. Here, we evaluate the possibility that the Ne-like wave on correct trials is merely due to reafferences, and at the same time, we test directly the general opinion according to which the Ne is generated by an internal signal. We studied the presence of a Ne-like wave in a completely deafferented patient. The patient performed two reaction time (RT) tasks: a two-responses RT task and a go/no-go task. In this patient, a Ne occurs on errors, on incorrect EMG activations, and on purely correct responses. On errors, the Ne was clearly followed by an error positivity (Pe). The Ne and the Ne-like wave are not generated by reafferences. This similarity is a further argument to consider that these two waves are of same nature. The present data demonstrate that sensory information is not mandatory for the brain to monitor and correct ongoing responses.
- [Show abstract] [Hide abstract] ABSTRACT: In a choice reaction time (RT) task, electromyographic (EMG) recordings allowed us to fractionate RT into two subcomponents, namely premotor time and motor time. This has been done for correct trials and errors. The analysis of the EMG burst and motor time (between EMG onset and overt response) showed that the EMG burst amplitude was reduced and the motor time was longer for errors than for correct responses. In the same way as posterror slowing on the RT was interpreted as revealing between-trials changes in executive control, the present data provide direct evidence for an on-line, within-trial, executive control.