Contrast sensitivity loss in the neglected hemifield

Contrast sensitivity to gratings of various spatial frequencies displayed in the left and right visual hemifield was measured in a group of ten right brain-damaged patients with unilateral visuospatial neglect. Two groups of ten left brain-damaged (LED) and ten right brain-damaged (RED) patients without neglect served as controls. All patients had normal visual fields according to standard clinical procedure. Stimuli were patches of sinusoidal gratings of 1, 2, 4 and 8 c/deg spatial frequency. The patches subtended 6 deg and were displayed at 3 deg of eccentricity. A two-alternative forced-choice technique was employed. Results showed a reduction in contrast sensitivity for stimuli presented to the contralesional hemifield with respect to the ipsilesional hemifield in patients with neglect. No difference in contrast sensitivity between hemifields was found for LED and RED groups. These findings indicate a basic visual impairment in the contralesional hemifield in patients with neglect.