abstract Clémence Roger

Clémence Roger (Department of Experimental Psychology, Ghent University)

Succeeding in stopping wrong actions: Electrophysiological evidence for an internal on-line inhibition mechanism

Daily life requires constantly adjusting our behaviours to being adapted to the environment. This flexibility involves monitoring our actions but also requires the capacity to inhibit them rapidly when these actions need to be stopped. Many studies have investigated the mechanisms acting after the commission of errors in order to avoid making new errors. However, little is known about the capacity to inhibit on-line wrong actions during its course.

The goal of our study was to investigate the electroencephalographic (EEG) correlates of on-line inhibition of wrong actions. Because inhibition is a covert process, the measurement of electromyographic (EMG) activity of the muscles involved in the response is necessary to reveal indices of inhibition. For instance, in some correct trials partial errors were executed, detected and stopped before becoming over errors. Their presence provides evidence of the existence of successful on-line inhibition mechanisms. Interestingly, EMG recording showed that inhibitory mechanisms are also present in full errors but fail to interrupt the wrong response.

In our study, participants performed an Eriksen Flanker task known to induce many errors. EMG was recorded to track the trials were inhibition was engaged. The spatial resolution of EEG was enhanced by using Laplacian transform to be able to distinguish the contribution of different brain structures engaged in inhibitory processes.

Results showed that the primary motor cortex (M1) is involved in the on-line inhibition of incorrect responses. The decrease in the M1 activity accounts for the success and the speed of the inhibition of the wrong action. We further investigated the frontal activities supposed to be involved in monitoring and triggering inhibitory mechanisms. Our results showed that (i) the ERN coming from the anterior cingulate cortex cannot be responsible for triggering inhibitory mechanisms, (ii) instead, an activity observed over the supplementary motor area (SMA) or pre-SMA can account for it. The latter finding is in line with the results of an influential single-cell study in monkeys, which has also shown that pre-SMA is involved in the suppression of unwanted actions (Isoda and Hikosaka, 2007). To conclude, we identified a frontal component in humans which is likely involved similarly as in monkeys in the suppression of undesired actions.