Parametric modulation of error-related ERP components by the magnitude of visuo-motor mismatch

Abstract

a b s t r a c tErrors generate typical brain responses, characterized by two successive event-related potentials (ERP) following incorrect action: the error-related negativity (ERN) and the positivity error (Pe). However, it is unclear whether these error-related responses are sensitive to the magnitude of the error, or instead show all-or-none effects. We studied error-monitoring with ERPs while healthy adult participants performed ballistic pointing movements towards a visual target with or without optical prisms, in alternating runs. This allowed us to record variable pointing errors, ranging from slight to large deviations relative to the visual target. Behavioural results demonstrated a classic effect of prisms on pointing (i.e. initial shifts away from targets, with rapidly improving performance), as well as robust prismatic after-effects (i.e. deviations in the opposite direction when removing the prisms after successful adaptation). Critically, the amplitude of both ERN and Pe were strongly influenced by the magnitude of errors. Error-related ERPs were observed for large deviations, but their amplitudes decreased monotonically when pointing accuracy increased, revealing a parametric modulation of monitoring systems as a function of the severity of errors. These results indicate that early error detection mechanisms do not represent failures in an allor-none manner, but rather encode the degree of mismatch between the actual and expected motor outcome, providing a flexible cognitive control process that can discriminate between different degrees of mismatch between intentions and outcomes.

Delayed monitoring of accuracy errors compared to commission errors in ACC

“…Hence, in this condition (accuracy errors), a FRN component should be elicited as the participant presumably needs to process feedback information in order to detect whether his action is correct or not. In addition, we predicted that the amplitude of this FRN component generated following accuracy errors could actually vary with the magnitude of the perceived discrepancy between the spatial position of the shot on the screen and the location of the actual target (i.e., the larger this spatial deviation, the larger the amplitude of this error-related activity), in keeping with previous ERP results that already reported such parametric association for the ERN component during a simple visuo-motor pointing task (Vocat et al, 2011).…”

“…RCZ) to those reported in previous EEG studies which used GO-NOGO tasks, the same head model and the same source localization algorithm (Vocat et al, 2008;Koban et al, 2010;Vocat et al, 2011). Moreover, this region of the posterior medial frontal cortex (as evidenced with our source localization method) is also usually found in previous imaging studies focused on performance monitoring brain processes (Klein et al, 2007).…”

“…Consistent with previous studies focused on these error-related ERP components (Overbeek et al, 2005;Vocat et al, 2011), we primarily focused on the electrode FCz, where these components were found to be maximal (see topographic maps in Figure 5B). We first searched for the latency of maximum amplitude (either negative or positive depending on the component of interest) at electrode FCz during each time interval, for each condition and each subject separately, using the difference waveforms.…”

“…Bernstein and colleagues (Bernstein et al, 1995) already provided evidence for a parametric scaling of the amplitude of the ERN with the degree of error (see also Vocat et al, 2011). To the best of our knowledge, our study provides however the first evidence for a similar modulation of the FRN (hence not the ERN) with individual differences in spatial error magnitude.…”

“…This observation is consistent with the first indicator hypothesis of the RL theory Nieuwenhuis et al, 2004), showing that rapid activation of a prediction error signal depends upon the type of errors made by the participants. Because commission errors can be detected on a first indicator made readily accessible through the internal monitoring of motor representations, the detection of accuracy errors is likely based on the rapid monitoring of external feedback information (Heldmann et al, 2008;Gentsch et al, 2009;Vocat et al, 2011). The selectivity of a Pe effect for commission errors might also hint at differences in error evaluation, and in subsequent adjustments in cognitive control, which might be more needed following failures of response inhibition (i.e., Commission errors).…”