P240 Neural and functional bases of error monitoring: A TMS study

Abstract

Error monitoring is essential both to detect when an action deviates from a goal and to implement post-error adjustments. In speeded response tasks, individuals typically slow down following errors, probably to prevent future errors. This slowing is called post error slowing (PES) and it is one of the main behavioural measures of error monitoring. According to the cognitive control theory (Botvinick et al., 2001), PES reflects a measure of how well individuals can learn from own errors in order to adjust cognitive resource allocation. In the present study, we investigate the neural bases of error monitoring, studying in detail the role of the right and left dorsolateral prefrontal cortex (DLPFC) in PES manifestation. In a first pilot study, seven young adults (mean age: 25.8 years) were assessed with a modified version of the error awareness task (EAT, Hester et al., 2005). A single-pulse transcranial magnetic stimulation (spTMS) was applied on both the right and left DLPFC, and on a control area (vertex), during task execution. Pulses were delivered at different times after an error commission (50 or 200 ms). Moreover, after some errors no TMS pulse were delivered (TMS-off condition). Results show that PES was present in both the TMS-off condition and when the TMS pulse was delivered after 200 ms. Interestingly, when TMS pulse was delivered on the left DLPFC after 50 ms from the error commission, PES disappeared. This time-based effect of TMS is in line with the electrophysiological literature, in which error monitoring is associated with the error related negativity (ERN), a fronto-central component that appears after 50–100 ms after an error, and that is considered a first physiological manifestation of error-related processing. In our study, the TMS pulse delivered at 50 ms on the prefrontal areas might have selectively impaired the post-error adjustment processes associated with the ERN. Finally, our results seem also in line with some clinical evidences in which patients with frontal brain lesions present reduced PES (Molenberghs et al., 2009).