Fig. 1

Experimental set-up, test protocol and representative signals of the reach-to-grasp performance. a A spherical retro-reflective marker placed a custom stand as the target for the reach-to-grasp kinematic task. b The mirror system for reach-to-grasp kinematic test. The reflective side of the mirror was facing the left alley and the grasping hand was behand the mirror in the right alley. c Protocol of reach-to-grasp kinematic test. d, e Trajectories in the horizontal plane (x–z plane) during reaching, grasping and returning under VF (d) and NVF (e) conditions from a representative AD patient. f The apparatus for reach-to-grasp kinetics. g The mirror system for reach-to-grasp kinetic test. h Protocol of reach-to-grasp kinetic test. i, j Grip force, load force and vertical position of the apparatus during precision grip under VF (i) and NVF(j) conditions from a representative AD patient