Absence of visual feedback abolishes expression of hemispatial neglect in self-guided spatial completion.

BACKGROUND

Patients with left neglect direct their attention too strongly to the right. Hypotheses hold that this is due to a failure to disengage attention from right-sided stimuli or to a directional bias of attention into right space.

OBJECTIVE

To test how persistence versus absence of visual distracters, which the patients themselves placed on a screen, influenced the expression of neglect.

METHODS

13 patients with left neglect and six right-hemisphere-damaged control patients without neglect were asked to evenly distribute 120 dots on a screen by clicking the computer mouse. In the Feedback condition, dots remained visible; in the No-feedback condition, the screen remained blank throughout the task.

RESULTS

The two conditions strikingly dissociated from each other in neglect patients but not in controls. In the Feedback condition, neglect patients placed initial dots with a rightward shift and then maintained this spatial bias till the end of the task. In the No-feedback condition, by contrast, they placed dots much more evenly over the whole screen; indeed, the right spatial bias typical of hemispatial neglect virtually disappeared when there was no visual feedback about the dot placements.

CONCLUSION

Absence of visual feedback about the location of self-placed stimuli markedly attenuated hemispatial neglect. The finding is compatible with impaired disengagement as the prevailing factor of visual neglect and may have therapeutic consequences.