The Role of Conjunctive Representations in Controlling Actions

Action selection appears to rely on conjunctive representations that nonlinearly integrate task-relevant features (Kikumoto & Mayr, 2020). We test here the corollary hypothesis that such representations are also intricately involved during attempts to stop an action--a key aspect of action regulation. We tracked both conjunctive representations and those of constituent rule, stimulus, or response features through trial-by-trial representational similarity analysis of the EEG signal in a combined, rule-selection and stop-signal paradigm. Across two experiments with student participants (N = 57), we found (a) that the strength of decoded conjunctive representations prior to the stop signal uniquely predicted trial-by-trial stopping success (Exp. 1) and (b) that these representations were selectively suppressed following the onset of the stop signal (Exp. 1 and 2). We conclude that conjunctive representations are key to successful action execution and therefore need to be suppressed when an intended action is no longer appropriate. Statement of RelevanceSome theorists have posited that as a necessary step during action selection, action-relevant features need to be combined within a conjunctive representation that is more than the sum if its basic features. Consequently, such representations should also play a critical role when trying to stop an intended action--a key aspect of self-regulation. However direct evidence of conjunctive representations has been elusive. Using a method for tracking both conjunctive and basic-feature representations on a trial-by-trial basis in the EEG signal, we show that the stronger the conjunctive representations, the harder it was to stop the intended action. Furthermore, the stopping process also selectively reduced the strength of conjunctive representations. These results further our knowledge about action regulation by showing that conjunctive representations are a necessary precursor for carrying out actions successfully and for that reason also need to be the target of self-regulatory stopping attempts.