(2009). Participants performed one block of 60 trials, comprising 40 ‘money trials’ and 20 ‘blank trials’, presented in randomized order. Money trials included 20 repetitions of a $5 bill and 20 repetitions of a 10 cents coin. Each trial began with a cue (a picture of a $5 bill or a 10 cents coin within a white rectangle; or an empty rectangle for blank trials) for 2 s, followed by a blank screen for 1 s (Fig. 2A). TMS was delivered

at only one time-point – this was 500 ms before the choice screen (like the ‘late’ period of Experiment 1). This was motivated by the finding in Experiment 1 (see below) that this time-point was the optimal one for eliciting an effect. After this, a choice screen appeared (as for Experiment 1) learn more and the participant selected the response. Some trials included a yellow border around the white rectangle during money stimulus presentation; on these trials, the participant was required

to say ‘yellow’ (see Experiment 2b below). Participants were informed that, at the end of the experiment, one of the money trials would be randomly selected and honored (i.e. participants get the money if they selected Yes). Participants were instructed to select Yes on both types of find more money trials (optimal choice for participants), as well as on the blank trials. Having the same response on all three types of trials ensured that any resulting differences in motor-evoked Rho potentials (MEPs) across these trials were dependent only on the monetary value of the trials, and not independently driven by differences in the required responses. The task structure was similar to

Experiment 2a (Fig. 2A), the only differences being that the choice screen was not presented and the participants did not have to move their fingers to press keys. To minimize the possibility of participants not paying attention to the screen (as no hand responses were required in this experiment), each trial included, with a 10% probability, a yellow border on the white rectangle containing the money cue. On these trials, the participants had to say the word ‘yellow’ as soon as they saw the border; they were instructed that failure to do so more than once would result in the cancellation of any monetary rewards they might otherwise receive from the experiment. To keep Experiments 2a and 2b similar, this additional feature and requirement was also included in Experiment 2a. Note that Experiment 2b did not have any manual response requirement. The only motor requirement was to report the occurrence of the yellow border on the 10% of trials in which this occurred. Participants were seated 50 cm in front of an iMac (19-inch monitor). The experiments were run using Matlab (MathWorks, Natick, MA, USA) and the PsychToolBox3 (http://www.psychtoolbox.org).