Research on motor imagery proposes that overt actions during motor imagery can be avoided by proactively signaling subthreshold motor commands to the effectors and by invoking motor-command inhibition. A recent study by Rieger, Dahm, and Koch (2017) found evidence in support of motor command inhibition, which indicates that MI cannot be completed on the sole basis of subthreshold motor commands. However, during motor imagery, participants know in advance when a covert response is to be made and it is thus surprising such additional motor-command inhibition is needed. Accordingly, the present study tested whether the demand to perform an action covertly can be proactively integrated by investigating the formation of task-specific action rules during motor imagery. These task-specific action rules relate the decision rules of a task to the mode in which these rules need to be applied (e.g., if smaller than 5, press the left key covertly). To this end, an experiment was designed in which participants had to switch between two numerical judgement tasks and two response modes: covert responding and overt responding. First, we observed markers of motor command inhibition and replicated the findings of Rieger and colleagues. Second, we observed evidence suggesting that task-specific action rules are created for the overt response mode (e.g., if smaller than 5, press the left key). In contrast, for the covert response mode, no task-specific action rules are formed and decision rules do not include mode-specific information (e.g., if smaller than 5, left).

In two experiments, using a modified task-cueing paradigm, participants switched among a set of four tasks that was on some trials reduced to two by a pre-cue preceding the task cue. A pre-cue temporarily restricting the options to two candidate tasks facilitated performance on switch trials to a much larger extent than on repeat trials. This observation is interpreted as an indication of a short-term restructuring of a global task representation by implementing antagonistic constraints among the representations of the two remaining candidate tasks.

In task switching, a common result supporting the notion of inhibitory processes as a determinant of switch costs is the occurrence of n - 2 repetition costs. Evidence suggests that this effect is not affected by preparation. However, the role of preparation on preceding trials has been neglected so far. In this study, evidence for an influence of preparatory processes on n - 2 repetition costs is provided by focusing on the cue-target interval on trials n - 1 and n - 2. N - 2 repetition costs were affected by an interaction of both n - 1 and n - 2 preparation time, being more pronounced when both preparatory intervals were long. The results provide support for the notion of active preparation processes involved in backward inhibition.

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In task switching research, one of the most straightforward indications for the involvement of inhibitory processes are n - 2 repetition costs. The present study aimed at investigating effects of different types of repetition proportion on n - 2 repetition costs. In Experiments 1 and 2, repetition proportion was varied globally (i.e., equally for all tasks). The occurrence of 33% task repetitions reduced n - 2 repetition costs when varied within as well as between subjects, but no further decline was visible from 33% to 50% task repetitions. This result is interpreted in terms of a shift of balance between task inhibition and task activation due to the occurrence of task repetitions that is independent of the specific repetition proportion. In contrast, when repetition proportion was varied locally (i.e., by differentially manipulating the occurrence of task repetitions for the three tasks involved), n - 2 repetition costs were reduced monotonically from 0% to 50% task repetitions. This result indicates that when the utility inhibition is tied to individual tasks, the cognitive system is able to adjust the deployment of inhibition accordingly, possibly by modulating processes of overcoming inhibition, not releasing it.