Figure 3.

Online and offline effects of tACS on action selection duration. A, B, Duration of action selection (z-scores) as a function of cylinder orientation for trials involving the right hand. Curves represent action selection duration during trials involving tACS to either the contralateral (pink) or the ipsilateral (blue) sensorimotor cortex, at 10 Hz (bold lines), 20 Hz (light lines), or without stimulation (dotted lines). Other conventions as in Figure 1D. It can be seen that the tACS intervention did not alter the dependency of action selection on biomechanical constraints, an indication that the faster response times following 10 Hz stimulation over the ipsilateral sensorimotor cortex during high-demand trials did not arise from a strategic shift toward the selection of a stereotypical grasping configuration. C, D, Same conventions as above, for trials involving the left hand, when no stimulation was applied. These curves were sorted according to the stimulation condition occurring in the preceding block, involving the right hand (see Fig. 1). This sorting procedure was applied to investigate potential offline effects induced by the tACS intervention. It can be seen that trials following tACS epochs had slower responses than trials following no-stimulation epochs (main effect of stimulation: F_(1,32) = 15.0, p < 0.0005), but these effects did not depend on the frequency or the site of stimulation, or on task demand.