Figure 2.
Effect of Anterior Intraparietal Area cTBS on PMv-M1 Interactions and on the Muscle Pattern
(A) Relative amplitude of motor-evoked potentials (MEPs) (± standard deviation [SD]) recorded from the 1DI and ADM when preparing to grasp either the pen or the disc (left: before cTBS; right: after cTBS). y axis values represent the relative MEP amplitudes resulting from a suprathreshold test (T) stimulus applied over M1 preceded by a subthreshold conditioning (C) stimulus applied over PMv at different C-T intervals (x axis). Note that the facilitation of the 1DI when grasping the pen and of the ADM when grasping the disc (∗p < 0.05) decreased following cTBS (∗∗p < 0.05).
(B) Z score normalized electromyographic (EMG) activity (±SD) measured during grasp of the pen or the disc (left: before cTBS; right: after cTBS). EMG activity was measured between the time at which subjects left the hand pad and 100 ms before the object liftoff. The 1DI was more active when grasping the pen compared to the disc and, conversely, the ADM was more active when grasping the disc compared to the pen (∗p < 0.05). Note the less-selective muscle pattern following AIP cTBS (∗∗p < 0.05).
(C) Correlation between the effect of AIP cTBS on the MEP size and on the muscle pattern. The axes represent the effect of AIP cTBS in reducing the EMG activity (x axis) and the MEP facilitation (y axis) expressed in percent of values measured before the AIP cTBS. Left: 1DI values when grasping the pen; right: ADM values when grasping the disc. Note that the greater the disruptive effect of cTBS on MEP facilitation, the more the muscle pattern during grasp was disturbed.