Timing the automatic activation and the early and late inhibition of the actions associated to a real object with event-related brain potentials
J. Bruno Debruille1, Molly Touzel2, Christine Snidal3, Julia Segal4; 1Dpt of Psychiatry, McGill University, 2Dpt of Neuroscience, McGill University, 3Dpt of Neuroscience, McGill University, 4Dpt of Neuroscience, McGill University
Stimuli of the environment automatically activate the actions they are associated to. These activations occur extremely fast, which might sometimes be critical to survival. Nevertheless, in most cases, these actions are then inhibited, as suggested by recent behavioral data showing that the inhibition could occur, as soon as 100 ms after the occurrence of the stimulus. We thus tested whether this inhibition could be indexed by the anterior N1 event-related brain potential (ERP). To achieve that goal, ERPs elicited by an object, that is, the occurrence of a real space bar of a keyboard out of the dark, were recorded in three block-conditions: a look-only task, a count-task and a press task. ERPs to the third of the trials with the fastest presses were isolated and compared a) with the ERPs to the third of the trials where presses were the slowest and b) with the ERPs of the two other block-conditions, where the space bar pressing had to be prevented. Fronto-central N1s (FC-N1s) were found to be minimal for the fastest presses, for which parieto-central P1s were greater. FC-N1 amplitudes were intermediate for slowest presses and maximal for the two no-press conditions. We thus conclude to the possibility that FC-N1s index the early, systematic and short lasting, inhibition of object-activated actions and that parieto-central P1s index the initial activation of these actions. On the other hand, consistent with the idea that N300s index late inhibition processes, they were quasi absent for fast presses trials and large in other conditions.
Topic Area: PERCEPTION & ACTION: Motor control