A tridimensional study of lateral grasping and pointing in spatial neglect.

The aim of this study was to analyze the ipsilateral upper limb and head ki nematics in patients presenting with spatial neglect using pointing and gra sping to object Four patients were included and compared to an equivalent n umber of normal subjects. Head, shoulder, and wrist movements were recorded using a three-dimensional VICON system. Objects to be pointed or grasped w ere localized in the right or left space facing the subject Patients presen ted with a reduction in the mean wrist velocity, which was more obvious whe n directed to the left side. reduction in the peak velocity, and a severe i ncrease of the time between the peak velocity and the end of the movement. The amplitude and mean velocity of left head movements were comparable in b oth groups. The analysis of the intersegmental cc-ordination showed that th e sequence of activation of corporeal segments was similar in patients and controls: head movement, shoulders rotation, upper limb extension. Go-ordin ation between head and wrist movements was assessed using the cross-correla tion method. An increase in time lag and a reduction in crossed correlation s between the head and wrist movements was observed in leftward movements o f neglect patients, but the co-ordination between the shoulder and wrist mo vements was preserved Thus, we demonstrated a global disorder of intentiona l movements in patients, which was relatively similar in pointing and grasp ing to object, and predominated on the approach phase, which is associated to important visuo-motor adjustments. This study also demonstrated desynchr onization of head and wrist movements, which can be an important problem in neglect patients.