Figure 6
Hypothetical representation of the cortical microcircuits producing bursting activity of corticospinal cells at 667 and 333-Hz. Based on the results of this study, we speculate that the bursting of corticospinal cells is produced by two different mechanisms acting on different corticospinal cells. 1) Left: activation of chattering interneurons discharging at 667 Hz connected to the corticospinal cells. These elements are activated by monophasic magnetic stimulation with posterior-to-anterior (PA) current flowing across the central sulcus. 2) Right: activation of an oscillatory circuit with a native frequency of 333 Hz connected to the corticospinal cells. These elements are supposed to be activated by biphasic magnetic stimulation with posterior-to-anterior followed by anterior-to-posterior (PA-AP) current flowing across the central sulcus and by monophasic magnetic stimulation with anterior-to-posterior (AP) current flowing across the central sulcus. This oscillatory circuit is entrained by 333 Hz tACS.
