Perturbing reach elicits anticipatory responses in transport and grasp

When the perturbation was expected, EMG activity of the <i>triceps</i> and <i>pectoralis major</i> muscles significantly increased about 50 - 200 ms before the perturbation onset. Peak acceleration of the reach was significantly higher and occurred earlier relative to control trials. Similar adjustments were observed in the grasp kinematics, reflected as significantly shorter time to peak aperture velocity and acceleration, as well as in increased activity of <i>flexor</i> and <i>extensor digitorum</i> 100-200 ms before perturbation onset. In summary, our data demonstrate that knowledge of an upcoming perturbation of reach during reach-to-grasp action triggers anticipatory adjustments not only in the muscles controlling the reach component, but also in those controlling grasp. Furthermore, our data revealed that the preparatory activations were generalized, rather than direction specific.