Figure 1. Experimental setup.

(A) Change in primary motor cortex (M1) excitability for agonist and antagonist muscles during probabilistic reward tasks was investigated. Subjects were seated comfortably in a chair. The right arm hung to the side in a relaxed posture, with the palm and forearm placed on the equipment. (B) Schematic of a head with a grid showing the stimulated scalp sites. Cz represents the intersection of nasion-inion and the interaural lines. (C) Experimental design in probabilistic reward task. Probabilistic reward tasks comprised 3 conditions of 30 trials: 30 trials contained 10% reward stimulus and the remaining trials contained a non-target stimulus, 30 trials contained 50% reward stimulus, and 30 trials contained 90% reward stimulus. The inter-trial interval was randomized between 7–8 s. Single-pulse transcranial magnetic stimulation (TMS) was delivered at 2 s after appearance of the red fixation cross and 1 s after appearance of the reward/non-reward stimuli.