Inhibitory control mechanisms are important in a range of behaviors to prevent execution of motor acts which, having been planned, are no longer necessary. Ready examples of this can be seen in a range of sports, such as cricket and baseball, where the choice between execution or inhibition of a bat swing must be made in a brief time interval. The role of the FEFs, an area typically described in relation to eye movement functions but also involved in visual processes, was investigated in an inhibitory control task using transcranial magnetic stimulation (TMS). A stop signal task with manual responses was used, providing measures of impulsivity and inhibitory control. TMS over FEF had no effect on response generation (impulsivity, indexed by go signal RT) but disrupted inhibitory control (indexed by stop signal RT). This is the first demonstration of a role for FEF in this type of task in normal subjects in a task which did not require eye movements and complements previous TMS findings of roles for pre-SMA and inferior frontal gyrus (IFG) in inhibitory control.

The present study attempts to explore the process by which knowledge of another's intentional behavior in a joint-action scenario is represented through the action observation and execution network—also known as the common coding system. Participants ( n = 18) were instructed to perform the complementary social Simon task under the implemented belief of interaction with either an unseen human (biological agent) or a computer program, where in fact, all response sequences from either “partner” were generated by computer. Results provide behavioral and neurophysiological evidence (P3 and S-LRP) that the believed intentionality of another person's actions is sufficient to facilitate a strong-enough agency-dependent social Simon effect to modulate action planning and anticipation. We suggest that the co-representation of human action may be an evolved biologically tuned default of the human motor system.