Can allocentric neglect be treated by functional training and by stimulating bottom-up neuroplasticity?

Visuospatial neglect can be described as unilateral inattention to egocentric or allocentric positions in the environment or to objects. It is unknown how to treat allocentric neglect nor if a successful treatment will also reduce egocentric neglect. We used a randomized cross-over design to treat 13 patients aiming to improve allocentric neglect. The intervention concerned manipulations of left sided features of everyday objects, active segmentation of a surface in parts and wholes and, active synthesis of parts into whole visual objects. The allocentric asymmetry scores of the Apples cancellation test and of the Line-bisection test were used as the primary outcome parameter, whereas other tests and functional behavioral scores were used as secondary outcome measures. Functional electrical stimulation was applied to boost neuroplasticity during the verum and active control treatment. The intragroup comparison showed no improvement for allocentric measures and the patients improved only in one of the egocentric measures. Moreover, the intergroup comparison revealed no significant advantage for the allocentric intervention compared to the active control intervention. Allocentric measures correlated with behavioral scores, but in different ways before and after the intervention. Consequently, our treatment failed to show any effect on allocentric visual inattention. The nature and treatment of allocentric neglect remain a problem for neuropsychological rehabilitation. Key words: allocentric neglect, egocentric neglect, stroke, neuropsychological treatment, randomised control cross-over design