Spatial deficits in ideomotor limb apraxia - A kinematic analysis of aiming movements

Ideomotor limb apraxia is a classic neurological disorder manifesting as a breakdown in co-ordinated limb control with spatiotemporal deficits. We emp loyed kinematic analyses of simple aiming movements in left hemisphere-dama ged patients with and without limb apraxia and a normal control group to ex amine preprogramming and response implementation deficits in apraxia. Damag e to the frontal and parietal lobes was more common in apraxics, but neithe r frontal nor parietal damage was associated with different arm movement de ficits, Limb apraxia was associated with intact preprogramming but impaired response implementation. The response implementation deficits were charact erized by spatial but not temporal deficits, consistent with decoupling of spatial and temporal features of movement in limb apraxia, While the apraxi cs' accuracy was normal when visual feedback was available, it was impaired when visual feedback of either target location or hand position was unavai lable. This finding suggests that ideomotor limb apraxia is associated with disruption of the neural representations for the extrapersonal (spatial lo cation) and intrapersonal (hand position) features of movement, The non-apr axic group's normal kinematic performance demonstrates that the deficits de monstrated in the apraxic group are not simply a reflection of left hemisph ere damage per se.