Contributions to the study of "blindsight"--II. The role of specific practice for saccadic localization in patients with postgeniculate visual field defects.

This study investigated the effect of practice on saccadic localization in the perimetrically blind field region by patients with postgeniculate brain damage. The analysis of the saccadic responses of three patients with homonymous visual field defects showed that in the first test sessions they did not choose between different locations but, rather, preferred a consistent magnitude of eye movements. In these sessions no correspondence between target and mean eye position was found. After the patients were forced to change final eye position in each trial, a significant localization performance was observed. It seems, therefore, that the choice between different locations is a necessary, but obviously not a sufficient, prerequisite for the ability to locate targets within the perimetrically blind hemifield. Forcing the patient to frequently choose between different locations within his perimetrically blind hemifield may help him to use his spared localization ability even though he can never see the target.